well I know I wont get much from these ideas of porting a head of this nature but i just cant leave well enough alone, and were off. I have read the framk mcgurk article and snooped through the archives here but what I am looking for just cant seem to be found. I was reading an online article about these 848 heads and what it said was that the valve port right above where the valve seats, that opening or the "throat?" is approximetly 1.44 inches wide and that they should be pushed up to 1.5 across and not to go any further than that because it can get into water if any more is removed. Now for the actual manifold port/runner, mcgurks article said they pushed those out 1/8 of an inch from 1.5 inch to 1.625 inches, and that other than these two things being done to the intakes, this is all that should be done, along with smoothing out rough spots and "clean up bad spots and smooth things out". A performance shop told me that the best thing to do is to "acid wash" the intakes to better atomize? They told me that I could port them, but should I make it a "rough port/polish"? As for the exhausts most people say dont bother cause they aint worth it and that they are long and curved which makes the job hard? and the benefits are not worth it in the long haul, but wouldn't polishing up the bowls really help that exhaust flow? McGurks article looks as if the porting got like 15-20 hp at some RPMS? and that does not sound terrific, but looking at the HP and Torque graph it looked like the porting and polishing helped the "under the curve power" fantastically. Any ideas/comments/advice is appreciated, I wish I could just ignore the trouble of porting and polishing, but I cant, I'll just think later "what if?", so I'm in quite the quandry.

Hello sir, I am fixing to recieve an 848 head that is going to be my "test bed" for just that very issue! I am currently looking at more modern approaches to an age old topic. These Stovebolts have untapped potential that just hasn't been realized by many in our generation. Most people are looking back to 1955, to try and revive these engines. When so much more advancement has been made in modern times concerning head porting and engine technology. I will be "sectioning" the 848 head for porting purposes, and putting together a photo journal step by step account of my findings to post and show others that might be contemplating mods just as you are. Hope this info will be helpful to you and others. Sometimes you just have to think outside the box. I also posted an intro in the "Bench Racing" forum giving some stats on myself titled "292 Speed Secrets". Hope to have some results to post soon.....Scott

As I understand it the theory of "rough/port polish" is to keep or create turbulence to atomize and move the the fuel load more efficiently. A too smooth entry can create static air cavitation on the port wall.Whether this theory holds true for 6 cylinder inlines I can't say. As to the exhaust ports, I've read that 6 cylinder inlines are notoriously poor in dumping exhausted fuel at the port opening and benefit from some smoothing and gasket matching.

The rough finish is typically beneficial on the intake ports, as you said earlier, to help atomize the fuel molecules more uniformly. This seems to be less critical on the exhaust ports floors and walls, and probably wouldn't fall into a category of being wrong or right if your were to do it. Gasket matching is often overlooked as being helpful, but it is always a good idea to do on intake and exhaust port entry and exits....

Most leave the intakes ruff(80 grit)I myself stay at 80 grit for the intake ports an 100-120 for the exhaust The smoother the exhaust the better. That will lessen the chance for exhaust carbon build up.Because carbon has a much harder time sticking to a Smooth surface.The ruffer it is the More likly it will build up and slow down the exhaust gases.Gasket Matching is also at the top of the list at the very least.It removes any lip between the intake and the port and the same goes for the exhaust.

dbane261 et al,

Have you seen the article in the Jan/Feb 2001 issue in the 12 Port News by Robert Duggan about his 261 build and 848 head work? if one wants to go back to what the racers were doing in the early fifties, there are the books by Roger Huntington and California Bill.

I'm very interested in seeing what you and the CNC-Dude (a great addition to our little band!) do with your heads, as I have an 848 and a couple of 850 heads with which to experiment in the near future for my next 261 build. One of the major problems with the stovebolt heads must be the sharp radius that the intake flow must negotiate as it turns 90 degrees to head towards the intake valve.

Hoyt

Thank you....

I'm not real old, but I'm old enough to remember the very basic rules to build the best, most powerful engine one can build is to do everything possible to the utmost to make the engine as perfect as one can make it. To me, this means polishing ALL ports. When I was a kid, polishing and relieving was a major step in building engines.....and the engines they were building then were 235's, 261's and flatties.
Why would the professional's rules change if the engine hasn't changed? I think the answer is in your thoughts. It needs to be done, THAN and only than you won't have to ask "what if?"
Joe

Hello sir, I don't believe that the rules have actually changed as much as its the "techniques" in how its done have become refined and improved. It's true that back before many hotrodders had access to flowbenchs, the popular thought of that time was that smoother was better when it came to relieving and porting. Probably because the only gage for this thinking was your index finger rubbing across the ports of a head or intake, and they just convinced themselves that a rougher finish had to create drag or some other unacceptable issue! True, even slick finishes on intake ports still produced more HP because the port was "ported" as well. The difference between a "polished" port and a "rough" finish in the intake tract probably is miniscule on a dyno. But the improvements in fuel atomization helps promote better and more complete and consistant burning of gases. If you don't burn 100%(or close to it) of the gas that enters the cylinders, then you begin to have a break down in efficiency. Fouled plugs, wash out cylinders....if you are racing, you find yourself following instead of leading the race! Head porting technology has probably improved at a faster rate than any other technology in the racing industry. Partly because so much gain can be gotten in terms of HP. And in 10 years, it will be so far advanced from where it is now....Just as in the day of polished ports, it still worked, you still could tell you made increases in power,technology improved and you moved forward and here we are 30 or 40 years later, still improving and advancing!

If you want to get the head to flow better.
There are epoxyies out there that you can fill the ports where you want to & remove it where you want to.
Devcon is a good product also a little more money for other types of different applications,Defcon w/aluminum,Devcon w/titanium etc..

The trick thing to do is use a mig welder(wire feed) & apply weld wire to the intake ports where you are going to apply the epoxy,basically you will be leaving short welded pieces of the wire that has welded to the cylinder head,make sense?
This will make it so the epoxy or JB weld will have something to attach to.
Thinking outside the normal Box.
Of course you need to freshen up the heads more often to reapply the epoxy,so it will not be much of a "street head" Then again it seems to work for a long period of time.

Porting into water chambers & applying epoxy is what Hendric did on the Famous L6 cylinder head that flowed over 320 CFM IIRC.According to Mike Kirby & he also has that famious cylinder head last I talked w/him about that.

It is what guys do also as I stated earlier in Super stock class,heads have to be stock cast iron & cannot be any larger than a stock port volume/cc's

If you looked at one of these heads you would not recognize the port if you saw them.

MBHD

but do those numbers sound about right? open the runners up an 1/8 of an inch to 1.625, and open the throats directly above the intake valves to 1.5 inch and rough polish up everything in the intakes and smooth out the exhausts as possible? is it worth it to really port out the exhausts? or just smooth them up real good? thanks in advance, Tye.

The stock valve sizes are escaping me at this moment, but a typical bowl cut below the valve seat area is usually between .75-.80 of the diameter of the valve. This will help maintain a venturi shape passage into or out of the port, helping to retain a relatively high air speed through it, and not having "dead air". Also, since much of those early concepts and ideas on air flow technology have been shown to now not be considered good practices,ie... (using a shell reamer to enlarge the port opening).First,nothing is wrong with a shell reamer to enlarge an opening. But, what is does to a 235 head is that it lowers the port floor,which has been proven in modern times to not be a wise move as far as air flow is concerned. My thoughts would be to either shift the port upward while at the same time enlarging it, or stretch it from side to side,forming an oval shape while keeping and maintaining the stock floor height! As soon as I recieve my 848 head for science purposes, I will be able to show and dispell many myths regarding these early mods and show that modern technology and concepts will be the way to progress with these engines.

One last thought, look at what similarities exist between the 216-235-261 heads and the 194-230-250-292 head! Many people might look at a side to side comparison, and see that they both have a siamese port configuration and say that perhaps the later L6 head evolved from the earlier 235. The newer L6 having an improved port design and other modern changes applied to it. Look at how much the "Lump Port" technology has raised the bar for the 250/292.......could "Lump Port" practices be applied to the 235 as well? I will explore that also. I bet it will!

actually the idea on lumps for this head sounds bloody brilliant, and I hope that you can do a test on this soon. This being said i have always wondered if something like this could be done for this motor given that it works for the 250/292 pursuation. the stock vavles on the intake side for the 235 measures 1.875 inches and standard small block chevy 1.50 inches for the exhaust. The exception for 235 would be the 1.94 intake valves for the power glide 235, wgich was like 50-52 right? but none the less your ideas are very exciting to hear, keep us posted.

Thanks, I thought that was pretty clever myself! But it just seemed natural for those same techniques to apply to any siamese port engine as well. The engine doesn't know if its a 292 or 235 or 4 cylinder. If it works for one, then similar results can be expected to cross over to any siamese engine! Same for the relieving and porting techniques you do to a Flathead Ford, its been proven to work on a Lincoln Zephyr v-12, Flat 6 Dodge, it doesn't know the difference! Im telling you, when I put on my "thinking cap"....I scare myself sometimes! Im excited also, I think this will open a new door for many to pass thru and explore, and possibly raise the bar as well for the 235 style engines performance without having to resort to a 12 port head! And thanks for the "bloody brilliant" tag, but I have to admit I've had some extraordinary mentors that have passed the torch to me and inspired my imagination.....If you think that idea was neat......hold on,i've got a million of 'em!

Oh yeah, dont forget you heard the "lump port" in a 235 head concept here first, on Inliners International....

Great stuff Dude. Do you believe this can be done without adding material and simply modifying the shape within the confines of what a shell reamer would remove? What about some type of helix in that area?

Curt B.

It could not be a bolt-in due to the way the water chamber is.
At least not from the cut up photos i have seen on these heads.
I have been trying to get my hands on a BAD head for a few yrs
now. Because so many guys have asked me if this could be done.
And from what i have seen those ports are small to start with,
an if they can not be opened up some adding a lump to those
ports may do more harm then good.Unless they could be made very short and Close to the short turn raduis.
But bottom line is If the ports can be opened up before hand i seen no reason why the lump wouldn't help that head.

We have done quite well at Bonneville with Gary Cope's XXO/VGCC with a Kirby/Sissell lump-ported GMC head. Kay Sissell set many drag records in the '70s when he introduced the lump ports in his roadster with a 7 port Jimmy.

Hi Curt, I believe that just by moving the port opening upward(and leaving the port floor unchanged) and either leaving it round or by reshaping it into some other shape will not only show promising improvements by itself, but also branch into many different ideas for others to explore for more radical concepts that could even end up with the "lump port" as being a final and conclusive goal! I am just opening the doors of possibilities for myself to explore and stimulate others into tapping into "unchartered territory" for the 235 style engines! And sure, any device or divider that can help generate swirl or enhance air movement can easily be implemented either by filling with epoxies or brazing into the ports. I kinda' look at this the same way California Bill and others did back in the day. We all are pioneers at this point, going into and trying new and untested ideas and concepts on this head. But one advantage we have that they didn't, is about 50 years worth of development in racing and other high tech fields to allow us to "revisit" and apply what we have learned in those 50 years....I dont think I or we, will be disappointed with the results!

I believe the "lump port" is by far the best mod for the siamese port head that has ever come our way so far! I also have had the priviledge of having much experience with working with and also meeting Kay Sissell personally in the summer of 1984, when he visited our race shop and to see first hand his handy work with the awesome cylinder head on Cotton's world record holding "Pocket Rocket" Chevy II. That has long been my inspiration for applying those "tricks of the trade" to these earlier heads!

Your probably right Larry, the intake ports are kinda' small and more concealed compared to the 250/292 L6 heads! I was thinking that to apply the "lump" concept to it would require more aggressive measures, such as brazing or epoxy to contour and reshape the inside of the intake port cavity. Once I recieve my test head, I can section apart the head and create a 3D drawing, and then make a test port with the modifications I need and CNC it out of aluminum, and then tweek the final shape and design after flow bench testing. Im also going to test different port opening shapes and sizes. I was fortunate and able sometime back to create some test orifices for a Winston cup engine builder friend of mine to evaluate. The premise was to test air flow changes in round vs. oval orifices of the same size in square inches. I was also able to get feedback on the results of their findings. Even though what their intended use of them was, was kept confidential. The results gave me ideas for throttle bodies and intake ports and other things that need to have enhanced airflow. So, im just going to try and apply those findings in some ideas I have with heads and other things and see what happens.....

Well as for welding I think?????(sometime's haha) anyway I think the best way to go about welding ,Is to try and do what is called Blow welding This should be Less stress On the Head and lowwer the risk Of cracking it.

Well when I think of welding, I usually think of some form of arc welding or mig and tig. Even though using an oxy/acetylene torch is still considered a form of welding(gas welding), it is a lot less thermally shocking to the parent metal because it involves a lot less temperature, and can be controlled more easily.I remember having to fix many of Cotton's heads after a combustion chamber was blown out, or dropping a valve, and using a gas torch and brazing rods to make to repairs. It sure beat scrapping a mega dollar "lump" head. The 250/292 L6 heads are a much lighter weight of a casting, than the earlier 235 heads, and are,as you pointed out more sensitive to welding and high heat. Im still in the beginning stages with this idea, and may find that some form of epoxy may be more practical as far as time and expense are concerned.

I was just looking at as Not to have to put it in a oven but Tig or miging something in for the epoxy to hold on to is not dout a fast way. and much easier to reshape.

Yeah, epoxy would be quick and easy compared to a big blob of brass to have to shape! But, the things we do to try and go fast.....

Any reason you couldn't make a "lump sleeve"? Open the runner 1/8. Take a piece of 1 5/8 od aluminum 18 or 20 gage and make a sleeve to fit in the head. You could dimple a lump in the area you want. Maybe put a lip on it so it wouldn't slide all the way in. The intake would press on the lip to hold it. If you had a flow bench you could pull it out and tweak the "lump" till you got the best shape. That make any sense?
Z

Kind of like an alignment sleeve that goes deeper into the head with a "lump" tapped in to create a better short turn radius.
Z

From what I see the lump on the port flow is too straighten the flow before it hits the valve head.So the port floor is raised by the lump.On a later L series head,once the divider between the ports is removed,you have room to work on the port floor.On a 235-261 with it's 3 intake ports there really isn't room to get in there very easily.
Modern porting theory is also concerned with port flow velocity,maybe more so than all out flow numbers.
For example with the Chevy V-8 guys it's the newer Vortec type head that pretty much is the best buy for the money.Not the biggest ports but better flow and velocity.
Buy a cracked Vortec head,they do crack,lol,and examine the port design,see if it can be applied to the 235 head.Or look at a late LS V-8 engine with it's goofy shaped intake ports.
Or perhaps a head swap,maybe like the welded together V-8 heads used on the L series engines.

Clay can also be used just for testing.And a mold can be made from that.

The problem with the port entry on these heads is that the port is roughly in the middle of the two valves! As the air/gas flow enters the port, it has to split and take an angled path to the right and to the left to even reach each of the valves. The thought of the "lump sleeve" is really a pretty good idea, but I think for it to be able to work at all, the port opening would have to be directly in front of the valve to direct the flow straight at it. As it stands, the sleeve would have to turn the air/gas mixture at roughly a 45 degree angle to the right and left after it passed the port entry wall to direct the mixture a each valve. This would probably make that end of the sleeve much wider than the port opening itself, and impossible to insert into the port. That was a good thought, keep it up....

What it you took something like a throttle body air foil, grind it to fit into the sleeve and tack it in with a tig. Maybe angle it to divert the flow down toward the valves?
Z

I think that for sure would get you a lot closer! Another good idea....keep it up!

Also, now that you have come up with the airfoil, that "lump" tube idea might be able to work better along with this as a pair and complement each other better!

Several types of airfoils like Thunder Racing and Holley have more material on the top and bottom. Seems that you could dremel (poor mans cnc mill) a lump shape to raise the runner floor for a better short turn radius. Which is what the normal lump is doing in a 250 l6.
Z

Do you have a 235 head or engine yourself to try that on!

A 216, should be the same theory. It is just being used as door stop.
Z

The ports of course are smaller, but the principle will apply just the same! I was thinking if you had an engine in running condition, you could get a more "realistic" demonstration. But it still will get the ball rolling if someone wants to try it out. Im dead in the water until my 848 head arrives, and I can begin my research more extensively!

I love the way you guys are thinking and all of this looks extremely promising, heck if the flow gets upped and these heads, the possibilities are not endless but we could come light years ahead of where we stand right now, that being said I have an old 3834850 head? anyway its from my 261 i know that it ends in 850, i have an 848 thats goin on the rebuilt 261, so this 850 is free to someone if they want to pursue this path, kind of a donation in the name of science if you will. heck i think its still good too, its a shame but its dismantled so its got no valves or rocker shaft assemblies. just a head, I might have an old 913 head lying around too, i know if its still here its cracked for sure, let me know if someone wants it......FREE, I just want in on the goods if this idea should work out and produce results. Let me know.

Well, all I can say is a FREE head casting will definately keep you in the loop for sure!LOL! I sent you a PM!

I’m in!

My spare 848 head has an appointment with a CMM on Saturday and a solid model of the “before” condition will be on it’s way to CNC Dude in the next week or 2.

Cool, I cant wait! I'm sure others are anxious as well....

This is a great thread. Ive been waiting for someone to put modern principles to use on these old heads. My own porting efforts have yielded noticeable changes on my cars. Mostly in midrange tourqe. The way I look at it anything helps on the old design ports.

Great! I hope that I have been able to "stir" peoples imagination with my comments and "advice"(if you can call it that). Maybe it will let you take your ride to a higher level....As you said,anything helps these heads,so maybe modern thinking applied to them will help as well, if not, its at least fun bench racing them into the winners circle(ha ha). Don't change that channel,I will soon be posting pics of my progress!

CNC dude, I will be following this as well with great interest. Also, I can furnish you with a 302 GMC head if you want to experiment with it as you go along. I too am in North Ga. and will deliver it if interested.

Keep it up, Eddie

Thanks Eddie,PM sent!

CNC-Dude I can't seem to send PM. Send me an e-mail address or phone number. Thanks, Eddie (littlejeep2) 706-835-5990

Update:

I got the head cleaned up for inspection and my programmer and I gave it a good look. We agree that standing it in a 4 axis horizontal machine should give access to get in from both sides in one setup. A 3 axis vertical could also be used but it would be quite a bit more time consuming. NOT requiring a 5 axis mill reduces the expense greatly at least in my case. Tomorrow we measure it with this:

http://us.romer.com/stinger-iii

Many thanks to littlejeep2(Eddie) for the GMC 302 cylinder head he donated to the cause.Few people would drive an hour and a half to contribute time,gas,and parts these days to help others in this way! Again, many thanks and I enjoyed our "bench racing" at Cracker Barrel this morning....I'm glad to have had the opportunity to meet you!

Thanks for the update Curt!

This is off topic.

But lets say a guy has a hand ported cylinder head that flows like nothing else.

What $$$$ figure would he be looking at to have this head measured and the data saved?

What $$$$ figure might be then expected, to have an untouched (stock) cylinder head duplicated?

Guess I should ask, what are the limitations of the CNC machines, could they duplicate what was originally done by hand?

Kinda like what powerheads has done.

Dont wanna screw up this thread, but this has been on my mind, so if anyone has some input, feel free to PM me. Thanks

Were still talking ported heads, so I think were on track here! And this is a good point that might need to be brought to others attention for explanation purposes! The potential for CNC is unlimited,considering you have the maximum number of axis' needed for head porting. Most companies that specialize in head porting, have equipment that can move the head(or part) in (5) different axis' to reach every concievable spot on all the surfaces of it. There are many neat videos on YouTube that people have posted showing heads and blocks being machined from a solid billet of aluminum. Just type in the words : 5 axis CNC, and you will be amazed at what is possible with this technology. Not all heads will need 5 axis' to be ported or be copied. As Curt mentioned, his 848 head only needed 4 axis' to have its ports scanned and probed. I personally have never had a head scanned or probed, so as far as cost to have that portion of the process done,I couldn't say. Maybe you could PM him, and he could give you some input on the process and whats involved in having it probed. The cost to actually reproduce the head once all the data is gathered is usually based on the machine "run time", plus any fixturing that needs to be made to attach the head into the machine. If it is a different type of head than they have done before, they might not have fixturing and will have to make it. Since aluminum is the most common material, and the fastest and easiest to machine, cast iron is going to be more costly, just from the simple fact that the speeds and feed rates in which your tooling operates will be slower, generating more machine "run time". I see your username, and figured that you are inquiring about a 300 Ford head. My friend Cotton Perry raced against another Comp racer that had an awesome 300 Ford in a roadster, and now that racer(Ambrose) has probably the fastest 300 Ford in NHRA. Those engines have great potential. Hope that answered your questions, and thanks for joining in on our discussion!

This is my friends cylinder head shop.
Click on the little pic of cylinder head & mill to see a video of CNC porting
http://www.proheads.com/services.html

MBHD

Its just amazing what we are capable of making and producing with the technology we have at our disposal today! I couldn't even begin to number the parts i've designed and made with CNC for different engines! If you can think it....you can make it!

I've sent dbane several PM's about his offer for the FREE 235 cylinder head, and have not gotten any response yet! I sent a PM to Curt today to see if he had any updates. Maybe we can soon see some action with all the interest that seems to be happening with this topic....

sorry about that lapse in responses there bud, been super bsuy with midterms and all, i havent even been sleeping really, couple hours a night, took my zoology test today, organic chemistry tomorrow and I have a physics midterm and art next week, super busy. None the less the head is up for grabs, we just got to figure out the shipping and all and we'll make this happen for sure, I have just been super busy this week and will be next week too. I will definetly try my best to get a shipping quote for ya next week if I cant get it tomorrow. So that was a lot of talking, anyway I did send you a response to the PM that you sent me, did you not receive that message? I will do my best to stay in contact with ya, talk to ya soon.

Thanks for the reply! No, I didn't receive any PM's from you. I also had others that had difficulty in sending PM's to me, but then there were several that were able to, leaving me to think that there was just probably work or something that had people busy. No problem or rush, thanks for the update, and good luck with your studies.

Delete.

BTTT....

Sorry for the delay but now the guy is swimming in an ISO audit and may not get to it for another week or two. I see him every day and the equipment is always available so it will get done. In the mean time I have put together a starting point for him to digitize from based on the following dimensions on the intake side which I would like someone to confirm on another 848 head.

Port center to center distance = 8.562”
Alignment ring bore diameter = 1.562”
I.D. of alignment ring installed = 1.414”
Alignment ring bore depth = .188”
Bore diameter @ .188” deep = 1.437”
(45 degree bevel transition from this point to cast bore)
Intake runner diameters:
Min. found = 1.340”
Max. found = 1.395”
Inconsistent all around but no more oval than .03” at any point.
Runner diameter continues in to a depth of 2 ¼” where it widens into bowl.



It would appear one would be able to generate a “hill” with the material available but where is the jacket and what kind of minimum wall thickness should there be?

If opened to 1.5” on the intake side the alignment rings would be eliminated. How to address this? Cut a bigger step in the head and intake for larger rings? Dowel the intake and head as an assembly? Ignore it and try to align by eye? How big is the hole in the gasket?

As far as opening up the area behind the valve what kind of radius into the bowl would be most beneficial? A lollipop cutter could do wonders there to generate a smooth curve from the valve seat into the bowl.

I know im probably beginning to sound like a broken record, But as soon as I can ever get my "test" head, I can begin to address and answer some of these questions. Since there is no alignment dowels for the intake, only the port rings. Then, the counterbore for larger rings will need to be machined into the head or possibly as you said, some dowels placed into the head and intake to locate them at each end! Still its a start,we will just be patient. You have gotten farther than I have so far....Thanks for the info and update!

My 848 head will ship on Mon. the 27th of Oct. so this coming week I should be able to dive into my research, and be able to soon give some details!

I received my 848 cylinder head on Saturday 11/01/08, now I have a 235 Chevy and a 302 GMC cylinder head to begin doing similar porting styles to each, and see how both engine families can benefit from the "lump port" technology that we have been discussing so far. I'll post pics as soon as I can begin to document my steps one by one. Curt told me he would try to have his 3D model completed this week as well. Also, special thanks to 6inarow and Patrick's antiques on the 848 head!

As far as im concerned, everyone here on Inliners is in the "loop". I appreciate everyones interest and support on this project. And will be glad to share my findings with everyone here. If anyone feels that certain issues might be overlooked or skipped over, just let me know, and I will be glad to address them. This project is for all us Inliners to benefit....

Glad to hear it. Looking forward to the results (and details along the way ).

The 848 head has an appointment with the flow bench this coming weekend to see what fixturing or adapters need to be made, if any, to bolt it onto the flowbench(Superflow 600). I know I will need to make a transition tube to bolt to the intake port entry with a radius to help stabilize air entry into the port. I will "bump" the valve seats, and establish a baseline of flow #'s(intake and exhaust) to have a starting point with a head in stock trim and condition. I will then systematically make changes that you would normally make in trying to increase performance and airflow, such as enlarge the bowl area(bowl cut)and radius the short side,step up the valve sizes, enlarge ports and entry,etc...checking each mod of the bench one at a time to see how each item helps or hurts the flow. Then I will move on to the "lump" port style mods that really got this topic "fired up".But not all at once, just preliminary setup this weekend. Also,pics will follow as well.....

YEAH!!!!!!!!

I cant tell you how good that last post is to read!!

It seems a huge waste that a tool with this ability lays around in the case for months on end waiting for an oversize part that requires a CMM report:

http://good-times.webshots.com/photo/2665966070023244788oQVBZl

http://good-times.webshots.com/photo/2160856010023244788yvMWRm

http://good-times.webshots.com/photo/2129548620023244788hVOGgy

http://good-times.webshots.com/photo/2644169740023244788KLmKum

This project has forced myself and a couple co workers to actually climb the steep learning curve on collecting surface data. The point cloud is quite disorganized on our first effort but hopefully enough of a platform to build from. We will make another effort using other more organized approaches soon. If anybody has a ported head that’s cracked don’t throw it away as the ultimate knowledge in all this will be to determine how close yesterday’s masters came to the flow geometry generated by today’s software.

Scott,
pm me a destination and I’ll forward you the data.

Also… Everybody remember or thank a veteran today.

Curt B

Curt, anytime we step into uncharted waters, delays and unexpected learning curves seem to be part of the journey. But, once we get there, it will be well worth it! Thanks for all your help. Its this type of comradery, that will make this project succeed,where others have not....TEAMWORK!

Okay, that's just impressive there. And you say that's your first attempt? You're doing better than I would.

You can tell the "Boss Man" that the head is a new "calibration tool" for the CMM, and must be used frequently to keep the CMM fine tuned for the tasks it needs to perform for the company(LOL),because if it sets idle it is not good for it, and therefore must be kept in ready to use condition at all times....

Wow you guys are making it happen! A digital model is on its way. Very cool, cant wait to see where the limits of the casting are. Keep up the great research.

I would venture to say that nowhere else on the internet will you find such a high tech approach applied to these Stovebolts and GMC's, definately making Inliners the place to be, and the standard for all others to follow! I also think it will rival any V8 websites by far, making them seem insignificant in comparison to our research and achievements. Where else on this planet can you get a 3D model of a 235 intake port....Inliners! Where are all the soon to be fastest and highest tech Stovebolts and GMC's....Inliners! Where are all the coolest Inline enthusiasts....Inliners! Inliners has got it goin' on, you dont need to go to any other website, its all right here! Don't change that dial....you might miss something!

Not to take you off in another direction, but, in 1969 Bud Moore had a port problem with the 351 Cleveland motor. The exhaust port had a terrible path even though it was very large. His solution was to mill a rectangular chunk off the entire length of the head down to the bottom of the port and replace it with an aluminum bar with his own high port design. As I recall it was held in place with head bolts.I dont know if it got into the water jacket but you might be able to furnace braze a steel piece to the CI head.
He got away with it by calling it part of the header.

The exhaust ports on a Cleveland extend outward from the head and do not get into the water jacket, and is a common mod still done today. I have a friend that I have made some port plates for on his race engine, and it does straighten the port out and really increases the flow substantially. A lot cheaper than a set of Yates heads....

Someone was selling 'header plates' (or port tounges) that did essentially the same thing without the machine work (sandwiched between the header and the head).

Don't know where you could apply that to our beloved inlines, but it's a good mental exercise.

Im hoping to have flowbench data this evening for both the 848 Chevy head and the 302 GMC head. I had to make some pieces for the intake ports to form a radiused entry for the air leading into it. This helps simulate a manifold being attached to the head, and gives a smoother,more consistent flow into the port,and is standard procedure for flowing intake ports,as is bolting a short piece of tubing to the exhaust port to simulate the transition from head to header....

CNC,

The results of your tests will be like an early Christmas present. I did some simple calculations for a stock 848 head using the methods we use at work for calculating pressure drop for aircraft engine components; for a valve opened to 0.500", the flow at 28" of H2O was 155 SCFM. This seems low; I've heard that it could be about 170 SCFM.

Your work and wisdom is really welcome here.

How does reversion/ engine pulse effect a siamesed port?

Its not as pronounced in an inline compared to a V-style engine such as a Flathead. Mostly because the cylinder firing is farther apart in degrees of rotation(90 degress for V,120 degrees for inline 6)and scavenging from the shared ports isn't as much of a problem in the inlines as the V engines that are siamesed. Putting exhaust dividers in the ports of a Flathead helps scavenging when real radical cams are used....

This may or may not be a fair comparison being it's a list of Chevy V-8 heads and it's hard to compare flow testing from different sources and different engine designs.That and actual wet flow when using carbs is different than dry flow with port fuel injection.The two lowest flowing SBC chevy heads are the so called smog heads found on pedestrian 350 engines.Generally,the unmodified smog head can support about 280-300 hp at 5000 rpm on a 350 Chevy that's quite streetable.Both a 261 and 350 V-8 have about 44 cubic inch cylinders.The higher flowing heads make a lots more power at 6000 rpm and higher.The V-8 heads were tested at 28 inches of vacuum.
Chevy V-8 head flow

28 inches is the recognized industry standard for flow comparison on cylinder heads, much like cam companies using the "@.050 lift" measuring to compare one companies camshaft against anothers. The previous question was asking what effects scavenging has on engines with siamese ports.And since SBC's dont have siamese ports, your post doesn't seem to follow any of the recent queries, maybe you can elaborate on what you are trying to say more clearly....

CNC Dude - you have a PM regarding hopping up these heads

Cheers

Mark

Thanks Mark, the more input the better! Welcome to the discussion.

PM'd you again

Hey its been to long. Whats happening???? 1 OL REDNECK I.I.#113

Having to make a dial indicator stand to place the dial indicator over the valves to open them. Since it is a rocker shaft engine, there is no way too place the indicator over the valves as in an individual rocker stud type head. Almost done!

Sorry for being impatient. I don't know how you do all you do and still have time for this, BUT I'm loving these imformative forums Thanks DARRELL

Since heads like this aren't the run of the mill cookie cutter design, sometimes you have to think outside the box to "gitter dun". Luckily,i've got access to a state of the art CNC machine shop, and can make anything I need with little effort, just time. Im anxious too, its getting closer every day!

This is cool. I volunteer the "test mule" if we need one for head and cam selection etc. after all this is done on paper.

Ok,great! That would be a good starting point....

Here are the details Frank McGurk published regarding modifying this head which could represent a benchmark:

“This latter operation was done on the intake ports by using a 1 1/2 inch diameter shell reamer piloted into the valve guide bores and enlarging the valve pockets to the point where the ports change direction. Next, a 1 9/16 inch diameter piloted shell reamer was inserted halfway into the valve pockets and the ridges between the two reamed diameters were removed by blending the surfaces together with a hand grinder. A 70 degree piloted hand reamer was then used to increase the minor diameter of the valve seat to 1 ¾ inches. The 1 ½ inch reamer was also used to enlarge the port openings on the side of the head to the point where the ports change direction. At the juncture, the hand grinder was again used to blend the surfaces together. The exhaust valve pockets were enlarged by using a 1 3/8 inch diameter piloted shell reamer. The exhaust port openings were not enlarged appreciably, but were merely cleaned up with the grinder. The 70 degree hand reamer was used to enlarge the minor diameters of the exhaust seats to a consistent 1 3/8 inches. Next the “barnacles” were removed from the surface of the combustion chambers which were then ground to a smooth finish, the hand grinder used for both operations. Finally the intake valve seats were ground to 30 degrees and were narrowed from the top to a width of 1/16 of an inch by using a 10 degree valve seat grinding stone. Similarly the exhaust valve seats were ground to an angle of 45 degrees and were also narrowed to a width of 1/16 inch.”

He goes on to say .030” was milled from the head and the same amount was removed from the top of the valve stems. These improvements were documented as providing a power increase of 8.9 percent and a torque increase of 4 percent. Compression improvement was 16.9 percent due to head milling. I would be curious to know if those values would be repeated based on the difference between the stock port configuration and what Mr. McGurk did and how much further performance improvement beyond that is possible with the tools and methods CNC Dude will use.

I intend to do this work on a basic 3 axis vertical CNC mill and plan on posting the toolpath so that other Inliners can get this done in most average machine shops and not just the few with 5 axis capability. That’s the beauty of CNC in that one tool can be made to behave like a whole collection of shell reamers and generate smooth transitions.

Digitizing determined that the intake valves are set in the head at an angle of 5 degrees so I needed to come up with a way to hold the head so that the valve guides would be parallel to the machine spindle. The valve cover bolt holes measured 12.766” front to back and 5.562” from side to side and I decided to use them to mount sine blocks. I drilled and counterbored a pair of 1” keystocks and milled them at 5 degrees with a difference of .450” in height. Now I’m ready when CNC Dude has data on where and how much to cut. Here’s a couple pic’s of the blocks:


http://s176.photobucket.com/albums/w186/curt160/848%20head/?action=view¤t=000_2420.jpg

http://s176.photobucket.com/albums/w186/curt160/848%20head/?action=view¤t=000_2421.jpg

Hey Curt, most valve bowl cutting today is done with a 85-90% size of the valve that is used. So if you are using a 1.94 intake valve, you would cut the bowl from 1.649"-1.746" . I would use a 3/4" ball mill to just touch where it meets the roof, and let that rad blend the pocket walls and roof. Heres a G13 to do it. G13 Z-x.xxx Dxx I.873 F5. You just need to add the Z depth to the actual amount of depth you need, and put the appropriate D# in it as well to match your tool #. Your X and Y would be the valve centerline. You can kinda' see how the thinking has changed since the 50's as far as bowl cutting goes. But the 85-90% rule of thumb is what all race stuff is today. That is the direction im heading, if you want to go ahead and do a test run with your head,it might reveal something. Also, I had planned to replace the guides, since a G13 starts at the XY centerline, adjust your feed so you don't crash your end mill into it.

Thanks Scott. On the subject of the guides have you investigated what the optimum geometry would be on the ends of them? Will a chamfer or radius be beneficial? While I’m there they could be shaped too.

Curt, I am going to taper the guides as it protrudes from the roof on both the intake and exhaust.

Also creating a vein on the leading edge of the guide on the roof of the port to help steer the airflow around the guide helps also. You might experiment with Bondo first to see about size and shape. But I would have the leading edge more blunted than sharp. After flow testing with Bondo, I would build-up with some brass brazing rods to make something more permanent, and do the same for the "lumps" on the floor of the port.

The more I look at those valve guides the bigger interference they seem to be. Once the ultimate flow geometry around the guide is determined why not make guides that incorporate those aerodynamic features and just orient and press them in?

You probably could,but most guides only have an OD of about .500, and whether you could create that significant of a change that close to the valve centerline or not, I don't know.Most race heads have a vein that starts about .750"-1.000" away from the valve centerline to give it a little lead-in transition and blending before it gets to the guide. You might take a new guide and stand it up in a vice and use your CAM software to create an ellipse shape around the circumferance of the guide that protrudes thru the roof. This should create less of a frontal area to obstruct the airflow around the guide, and im sure it will help the flow as well to some degree by creating a surface similar to an airplane wing leading edge with less turbulence than just a round obstruction.Something to try....have you tried a G13 for your bowl cutting yet!

I guess we’re not on the same page. I’m talking about completely new high tech guides installed from the bowl side with an integral vein, taper, slight helix, and shouldering up against the roof. The vein could start just slightly less than the opening behind the valve which was mentioned to be somewhere between 1 5/8” and 1 3/4”. This would allow for a vein of up to 7/8” from the valve centerline. As far as using G13 goes it will only generate a circle starting and ending at the center point and I plan to take full advantage of my software by generating point to point surface contours. The tool I have allows me to roll part way around the corner as shown here:

http://www.iscar.com/Ecat/familyHDR.asp/fnum/1614/app/71/mapp/ML/GFSTYP/I/type/1/lang/EN

Creating a helix will help promote swirl into the bowl area. Are you thinking of under cutting the valve seat with that cutter and creating a venturi shape above the seat in the bowl.

I cant wait to see the chips fly. And then get one of these on the flow bench! Who are these premade "aeroguides" made by?

I think that Curt is contemplating making them for his head to test....

It is this thread in particular that led me to this forum and made me join it. I have a strong interest in the subject that was being discussed. I appear to have started reading a great book. Not necessarily looking for the ending, but would like more to read. I am currently in the teardown stage of my 235 with an 848 head. Whats the next chapter?

The thing that this thread does for me is give me hope. I've got a 235 with an 848 in my 56 Chevy and although it will likely never be rebuilt to more than a stock specification, whatever results come from this thread will provide tantalizing "what ifs" for me to dwell on. I've always been a fan of applying new thinking and new technology to old stuff.

Thanks for all the R&D time you've spent on this topic.

holy moly its been so long ago that I started this thread I forgot that I started it lol, anyhow guys I still have an already bare head that I can donate to the project and research if needed, its not an 848 head but an 850-261 chevy head pretty close tho minus the combustion chamber being a tad larger. I already had my 848 head ported and polished but due to the strange port design I think that there is rom for improvement tho, let me know if ya guys want it

The 848 appears to be the best subject for development, because:
1. small chamber = best static CR in stock form
2. pretty common
3. fits all 1954-63 motors

Also: I'll bet that the compression bump on Ross etc. pistons will clear the exhaust pocket on the 848 better (viz. won't crash anything or require big chunks carved off) than a casting chosen at random.

Good afternoon, I just finished reading the entire thread and the more I read the more I think I understand about this fascinating topic and the more questions I have about Stovebolt engines.

I have a '54 850-261 that I want to start on this winter. I spent all of my son's youth working and didn't share time with him. Now we're going to re-work a 51 pickup to take to Reno next year. I want to put one of Tom Langdons Bulldog cams in it, dual Rochester BCs and headers.

If you guys were building this for the street what would the build be comprised of? Porting the head, domed pistons, cam
with solids, and??? This would be my second engine build and I have access to good machine work but don't know what to ask for or be concerned about.

I live outside Salt Lake City, Utah. Do any of you have a similar project going on that I could chat/visit with you about as the project goes along?

Thanks,

Ted #4730