Inliners International Forums General Discussion Engines 261 chevy 848 porting

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!