Inliners International Forums General Discussion Blown and Injected Time to get building....

Well the time has come to do something to the 250 in my car. I am hoping to get an EFI turbo charged engine into it before the summer starts, but there are a few obstacles to overcome.
I do think the best way to start is a rock solid bottom end and then if the plans don't allow for turbo charging this year I can run with a hot cammed normally aspirated carbed combination.

So, the question is,
What is the best combination for a bottom end? I have read Leo's book and have some ideas but I would appreciate the input of those who have already been in this position.
My idea includes the original 250, .030 over, forged pistons (suggestions on this appreciated), new connecting rods, crank work as required, better than stock harmonic balancer, new oil pump, and let the machine shop have their way with the block as required. Balance the entire rotating assembly including flywheel and clutch.

What am I missing?

If I can swing the turbo and EFI this year that would be great, if not I'll top off the short block with a well built head and as much cam as I can tolerate weekend use and a few trips out of town.

The basic idea is to have a bottom end that will serve me for a few years regardless of what I add to it. does this seem reasonable?

Thanx in advance for your input.

Paul

Problems are compression on a N/A engine as compared to a turbo engine.

Cams differ considerably.

Need to stick w/one or the other or a have an engine that works Ok for both N/A or turbocharged.

What are your goals for HP, fuel economy etc?
Daily driver? Strip,street?

MBHD

Paul, you definately want to have some decent cylinder head work done, and even consider doing the lump porting thing to your head. Tlowe has also been the turbocharged route with his 292, and can prep your head as needed. How much power output are you looking for, and what kind of boost levels are you thinking of running.

Hank,
Can compression be controlled by the head? i.e. combustion chamber volume?

I know that cam profiles are very different, but the cost of cam swap v.s. EFI & turbo makes it a reasonable expense over a year or so.

HP gains? I am inspired by bosanova's engine for a turbo set up. For N/A I'll take as much as I can get.

Economy? Well I have a TKO 500 5 speed In the Camaro and 3.55 gears going in this spring. If I can hold 25 MPG on the highway that would be good. Right now I get about 28-30 MPG.

The car will not be a daily driver, but when I head out on the road trips of 500-1000 KM are not out of the question. I also enjoy Friday nights at the drag strip and a few hot laps on the road course.

I don't ask for much do I?

Paul

I have been following posts on this site for quite a while now, and there is no question that the head work is a major factor here.
In a boosted engine I would like to limit to 1 bar boost depending on how the whole package works out. as I mentioned to Hank, Bosanova's engine inspires me. I want to do it right, but I also have to do something to the short block right away. I have about 80 lbs compression in each cylinder right now so you can see why I need to start somewhere.

Paul

Paul,

that's not too much to ask for.

As far as Combustion chambers volume,,,

I would use the small chamber head ( N/A) as to bump up the compression since you will want to run a lower static compression ratio later w/the turbo.

Some people here does not recommend useing the small chamber head,,, ,but I do & so does Larry AKA Twisted 6. We have used them in the real world of racing & just plain driving on the street ;-) I was very,very happy w/my results using the small chambered 194 cyl head.

Bosanovas cyl head has minmal head work done & look @ his stats for HP & torque,,pretty nice!

Depending on what kind of gas you can use ,look for a compression ratio of 8.5:1 to 9.2:1 range for a turbo application.

If you are going to have E-85 fuel 8.75:1-9.5:1 range approx,,all depends on what fuel you will use or what is available.

There will ba a lot of choices of parts,cams,lobe centerline,,big turbo, medium sized turbo,desent sized all around turbo etc.

I think we can help you along the way.

My old combo was a 250 L6 ,TRW forged flat top pistons w/4 valve reliefs.
I had 12.0:1 compression,w/194 head 220 psi cranking ,then later switched to a larger chamber head,opened up the chamber,sunk the valves a bit,& ended up w/8.4:1 compression & a Paxton supercharger on it..

So basically let us know what fuel you will be able to use & we can start w/your compression ratio & pistons to use.

MBHD

Hank, just to update you on this matter. Tom had the 194 small chamber head casting with the 1.94" valves in it, and the big chamber head with the 1.94" valves in it, that were both used in the dyno testing, flow tested this week. The small chamber head was down on flow by over 20 CFM compared to the big chamber head. That is probably why the HP was also down when we tested that head. So, we have tested the small chamber head in 2 ways, both with flow testing and with a dyno, and have consistently seen that it is showing us, both less flow and HP compared to the big chamber head are lower on both counts. We will test it again on the 250 dyno test coming up, but if it still shows us the same results, I can only say that if you and others have experienced gains in using that head, it is more likely from something else you might have changed or done you haven't considered, instead of the head itself.
Its like the guy who makes one pass in his car at the track, and then decides to let 1/2 a pound of air out of his slicks, and when he makes another pass an hour or so later, he goes 2 tenths faster. Not knowing that the track officials sprayed VHT on the track since his last pass. So know he thinks he honestly picked up 2 tenths off his time by dropping his air pressure a 1/2 pound. Im just saying, that there are dozens of variables that could have lead to a better ET after your head swap that might lead you to think the head was the reason of the gain you experienced. You might have gotten better as a driver for instance, the track might have improved, the air might have been better, and on and on. Im sure you know, but others that race occassionally, might not realize that track temps, tire/slick temps from round to round, barometric pressure and air density and so many other factors will affect a cars performance one pass to the next. And if they dont know that any of these factors have changed, they will mistakenly think they did something to create the increase or decrease, when they actually had nothing at all to do with it. Thats how many "urban legends" in racing have started over the years.

My changes between the two heads were very different then Toms cylinder head swap. It was not just a point of compression it was over 2 points.

Plus like I stated earlier,I would never use a 1.94" valve in a 194 cyl head,it's too shorouded by the chamber.CFM drops dramatically!
Toms 194 head had a 1.94" valve.IIRC?
I have gotten more CFM out of my 1.85" intake valved 194 CI head over a 194CI head w/a 1.94" intake valve installed.

If you do not have a correct throat cut or correct angles cut on the valves,seat widths,etc,, you can loose serious cfm.
A poor valve job will kill,absolutely kill CFM flow.
I am not just talking about the valves sealing.

Tom stated he was going to get the heads flow tested over a week ago,,,what are the results? What are the numbers?

My open chamber head had about 10.1:1 compression,then the small chamber head was cut ,thus increasing compression,less chamber wall to impead airflow. Raiseing the compression to 12.0:1

I am not saying my combo made alot more HP,,,,I am stating it made A LOT more torque w/the 194 Head & torque is what you can really feel.


My comparisions are racing my friends cars before & after I do all my changes & swaps. Dead stops,roll ons,etc.

My car w/the 194 cylinder head consistantly pulled better everywhere over my friends cars. They did not do any changes to there cars for this reason,to make equal comparisions.
I was the only one making changes.

I am sticking to it. Sorry.Guess I'm stubborn

I do think quite honetly, Toms chambers were either not unshrouded enough,valve throats incorrect,angles off,something,, or something is amiss.

Thats my thoughts on that matter.
Lets not hijack this guys thread anymore.

Back to Time to get building.
MBHD

Thanx for the input guys. I am paying attention.

I am still torn on how far to take the engine this year, but I have to do something.. MBHB's comment on raising compression by two points with the 194 head makes sense to me. If I recall I can mill the heck out of the head to raise compression. Since I have a spare 250 head right now would it be worth it to use 194 valves and then cut the max off the head to raise compression for the N/A application?

My second head will be saved for the turbo application.

Hank, you mentioned TRW pistons in your 250 build. I have read that a piston made specifically for turbo applications is the best way to go, so I'm thinking that these will be custom slugs. JE, Weisco, TRW or???? I know that custom pistons are not cheap, but I don't want to buils two short blocks or have to rebuild one by next year if you know what I mean.

My fuel choice is pump premium. When I add the turbo I might rely on something better for track use, but I need to make this an affordable engine to run.

Cheers,

Paul

Figuring a .005 deck height and a .040 thick head gasket with a flat top piston with no valve reliefs, a large chamber head at 72cc's will give you 9.69:1 compression. So you might be at the upper limit even with the premium pump gas, but should be good for your N/A combo.

Thanx CNC

What sort of effect does milling the head have on the combustion chamber volume? Is 72 cc a stock volume without any milling?

I was thinking that 10:1 would be the limit, factor in my 3,300 foot elevation here too.

P

I've seen some charts for some SBC heads claim that a decking of around .007 will drop the chamber roughly 1cc. I dont know if that is a good reference for these heads, but I would guess it would be similar. And yes, your higher altitude might let you get away with a little higher compression. That 72cc is close for a stock big chamber uncut head with stock valves.

Ok, how about when he wants to lower the compression ratio w/the same pistons installed for the turbo application?

What are his options?

Scott -
I'm confused by your reply recommending the lump porting to the head. In one of your previous posts you stated that Darren
Davis's naturally aspirated engine had a significant power increase by removing the lumps from his cylinder head. Since this is eventually going to be a turbo charged fuel injected engine, wouldn't the port dividers be a better idea? Just curious.

Bob

Hank -
You and Larry shouldn't feel too bad. Having raced and been associated with Mike Kirby for over 15 years, I know for a fact his choice of cylinder heads is the 194. He has proven through years (not days) of dyno testing, flow testing and actual racing (not occasional) that the 194 cylinder head will outperform the others. There could be as many variables in cylinder head prep and dyno testing as there are in actual racing.

Bob

Bob,
I can answer for the port dividers, atleast my take on them. They worked well for me. I run a turbo system with multiport EFI. With them idle quality went way up and so did performance. It is more of a Multiport EFI thing, not so much for Carb.

You are also correct about variables with head work. But I have found for the average Joe, doing the same mods to a open chamber vs a "194" head, the open chamber wins.

Last I knew with Mike Kirby, he mainly reworks open chamber heads. Maybe someone should call him and get his 2 cents.

One part of the reason Mike uses the open chamber cyl head is because,if he is going to braze them ,he prefers a new casting,less chances of cracks.

Always better when using new or newer castings when you can.

Look how old the castings are for a small chamber head.
When was the last year they were made?

Anytime you are using used cylinder heads you are taking a risk that the casting is good still.

If it goes bad & or is bad & you have done a lot of work to the head,well you need to do some type of warranty?

GMCCORBETT ,
I do not feel bad @ all about my statements on the 194 cylinder head,I still stand by what I say about them.

Also, when Turbo 6 hear devided he intake ports on his 292
he stated he had to increase the boost pressure quite a bit to make the same HP as he did w/no deviders,but it helped w/the un even fueling from cylinder to cylinder.

MBHD

He will have to build his engine to start with, with that lower compression as an objective. He isn't going to be able to have both high and low compression with the same pistons or by swapping heads. Since the 194 head is going to put him over the top, compression wise for his N/A engine, it really isn't an option for him to even consider that head at all. He will have to use some sort of dish pistons, and maybe cut the large chamber head by some amount to get back into the mid 9's with compression. It all depends on what size dish he can find available to start with, and do some number crunching to see if he can find a happy medium to use for both engines.

Bob, I personally have never used the port divider idea, so I can't say from my experience that it would/will work for his application. Darren's story to me sounded good and convincing, but I have yet to try it myself to see if it has crossover potential for street type engines or not. I just think it shows how to not rule out any idea as being plausible. Darren had both Sissell and Headrick both tell him it absolutely would not work, don't even try it, your wasting your time, your engine wont even start and run....Thats how hard they tried to convince him it wouldn't work. Even though, they themselves never did it. I truly respect both Sissell and Hedarick, I worked for Headrick for over 15 years, but I think it shows that even some of the best engine builders can even get too focused on their agenda to not realize that there will always be something better and faster to come along. I know tlowe has done it with his turbo car and had good results from it. So maybe we can do some testing of this idea on some future dyno testing and either prove or disprove its potential as a viable modification.

I had used the standard 307 SBC TRW flat top pistons in my 250 ( still in there) w/4 valve reliefs.

I had used the 194 cyl head to get high compression 12.0:1

Then I swapped the cylinder head to the large chamber.

I dropped the compression down to 8.4:1 ,I did not change my pistons.
This set-up was for when I ran a Paxton supercharger, 12.0:1 was a little high for a supercharger on pump 91 octane.



They are diffferent compression ratios you can pick inbetween what I had choosen & had run.

I did not leave the combustion chambers to standard size.

But @ the time I felt I had the cheapest combo to use w/out changing the pistons.
12.0:1 small chamber head, then 8.4:1 w/the large chamber head.

IIRC, the cranking compression was around 150 psi w/the low compression set-up & 220 psi w/the high compression set-up.

Back then ,,pistons were not in my budget, so I had to improvise w/what I had..


MBHD

Gee, I'd hate to think what my CR is with 80 lbs. cranking pressure!
I am willing to use custom pistons so long as they are not $200 each. That being said, 12:1 is a bit much for my needs if I end up N/A this year.

Paul

I realize that this is a bit of a tall order, so I guess the best approach is to build a turbo engine that might have to get by in a N/A state for a while.
I just don't want to build two short blocks, but I need to do something with the current combo.

Using a custom piston is an option for me. I also have no problem having two different cylinder head combinations, one for N/A and one for Turbo.
I already have a Clifford intake and header to use for a N/A engine.

I really do appreciate all of this input, it is opening my eyes to the challenge at hand.

Paul

The 12:1 & 8.4:1 is just an extreem example I did.

Normally if you run the 307 pistons I have & a 194 head compression would be around 10.5:1
Open chamber head 9.5:1 Just an approximation.
It's been a long time guys when I put together this engine.
So the numbers are not right in front of me & I'm too busy baby sitting my kids all the time. They drive me crazy.

It's been so long when I checked last the cranking compression when I had 8.4:1 cranking compression was probably closer to 130 psi
But with the 12.0:1 I definatly remember checking a few times 220-225 PSI. Absolute torque monster ,3 Weber DCOE's helped out alot,really torqued & twisted my Camaro chassis pretty good w/that combo.


MBHD

Paul, you can use the 307 pistons like Hank said or go custom as you also mentioned. Just figure out what the compression needs to be for your Forced Induction motor and what head you will use on it, and work from that. You could pretty economically prep two seperate heads to allow one for a higher CR for your N/A setup, and a lower CR head for the turbo setup. I would also avoid cutting one of the heads excessively to achieve a real high compression, you might end up having to buy (2)different sets of pushrods, which could be an unexpected expense you might no have considered.

Tom -
With your turbo and fuel injection your idle quality went up. I can understand that, but, what amount of gain in performance did you experience?

I also agree that for the average Joe (myself and many others) the 194 head might be a challenge. Someone with many years of inline cylinder head experience might have a little more success. Sometimes cheaper is not better.

After speaking with Mike Kirby, he stands by what I said about the 194 head. He also stated availability and cost are the reasons he is doing mainly open-chambered heads.

Bob

I just don't believe that.
You guys are full of it. Sarcasium

MBHD

Bob,
The gain is a hard one to judge.
Idle quality went way up, there was a weird stutter at times and sometimes even a backfire when getting into low boost. Those cleaned up with the dividers. My track times improved. The startability and cleaner(brisker?) running engine were immediately noticed.

I did post about this, look under "292 turbo writeup"

Tom

Sorta like this?,so you guys can hear it & see it.
http://www.youtube.com/watch?v=q1TtDeFfzZs&feature=related


MBHD

I also agree that for the average Joe (myself and many others) the 194 head might be a challenge. Someone with many years of inline cylinder head experience might have a little more success. Sometimes cheaper is not better.

Bob

[/quote] Bob, that has been the viewpoint we have been trying to point out from the beginning. The dollar to dollar comparison between these two heads. These tests have been for the average Joe, and the average Joe comprises 99.9% of the enthusiasts that are only going to do the basic head prep work for their projects. And for each dollar spent on either style of head, the large chambers performance gains exceeds the small chamber heads gains. Its only after you spend an additional amount of $$$$'s to further relieve and reshape the chambers of the small chamber head, and do additional milling to further increase the compression, that the small chamber head finally begins to pull ahead of the large chamber, but again, its only that final one tenth of 1% of enthusuiasts that are going to even go to that extreme to do this. And these dyno tests were selected to benefit the 99.9% of average Joe's that are going to do these simple basic modifications to start with.

Hank,
That vid is after the port dividers were installed. Before that, the idle and reponse were much worse.
Try comparing the 2 different dash run vid's. In the 2nd one, the engine comes on much stronger, Mainly because the tune is better and more boost. Tom

Just out of curiosity (not on the prod here, just asking) was there a durability issue before the port dividers? Burning valves, detonation, backfire induced turbo failure, etc?

Asking as I don't have a frame of reference as to how bad the mixture distribution is (just a "performance" issue, or is it a durability issue with boost)?

Nex,
Here is the quick answer. It was a cylinder robbing fuel charge problem.
Read from the start here.
https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=41727#Post41727

Tom

My problem was definitely a durability issue, when it tried to make over 500 HP it would melt cly 1 and 6, it was a valve timming issue between intake 1&2 in the front port and intake 5&6 in the rear port. Dividing the ports fixed the problem.

Some time ago someone posted about a ford six that had a separate port for cly 1&6, the others were siamesed ports, the engineers probably did it for that reason.

Harry

[/quote] Bob, that has been the viewpoint we have been trying to point out from the beginning. The dollar to dollar comparison between these two heads. These tests have been for the average Joe, and the average Joe comprises 99.9% of the enthusiasts that are only going to do the basic head prep work for their projects. And for each dollar spent on either style of head, the large chambers performance gains exceeds the small chamber heads gains. Its only after you spend an additional amount of $$$$'s to further relieve and reshape the chambers of the small chamber head, and do additional milling to further increase the compression, that the small chamber head finally begins to pull ahead of the large chamber, but again, its only that final one tenth of 1% of enthusuiasts that are going to even go to that extreme to do this. And these dyno tests were selected to benefit the 99.9% of average Joe's that are going to do these simple basic modifications to start with.[/quote]

Scott -
You finally said what I wanted to hear, if you are admitting the 194 head is a very viable piece if properly prepared. There are some people on the bulletin board that have been very successful with this cylinder head. They have apparently put forth the effort or the money to make this head work for them.

I don't feel anyone should state they are wrong for what they believe and that this head isn't an excellent option for a more than average performance engine. If anyone is willing to do what it takes - more power to them.

If this is your opinion, and I have missed it somewhere in a post, I apologize. I agree there are many people on this board
that are looking for only moderate performance, however, there maybe more than 5 out of 5,000 that want something a little more extreme.

Bob

If you read through the posts I think it is pretty obvious, some people did not recommend the 194 cylinder head no matter what,,, & you people know who you are.

It seems now they are changing there tune. Maybe because they are getting info from some other people other than us BB members?

Who knows & who really cares.

Both cyl heads can be used w/good success, end of debate.
Lets move on/fwd!

MBHD

Yes, Bob, I absolutely think the 194 head is a very viable cylinder head. On all of Cotton's race engines, that is the only head we used. But, it is difficult to test and be objective when trying to compare engines and components that are being used on a scale smaller than what I am used to seeing. I think that its only when the 194 head is taken to the higher levels of modification, that it really starts to excel. And when used in the types of street engines that we tested, with only having modest and minimal tricks and bells and whistle done to both style heads, it shows to be fairly equal to the large chamber head, in comparison. But for a very serious high HP or all out race engine, I believe the 194 head would be the way to go hands down. We wanted to put a 9 to 9.5:1 compression limit on our testing to have a true pump gas style engine, I think that others are also having trouble putting this testing into perspective as well, and are thinking of the potential a highly modified 194 race head has, and not looking at one that is only mildly modified with basic procedures that the average Joe is going to do, and when the 194 head is used at this level of preparation, it has shown only to have nominal gains, if any compared to the large chamber head.

Been out of town for a bit.

Looks like I'm using a 250 head. Difficult to find any shops around here that can truly say they have experience with inlines so I might have the head done in the U.S.A. and ship it here. Anyone have a head that is already done and willing to sell?

As far as the bottom end goes, it looks like custom pistons are the only way to go. (man they are pricey little buggers though) How about connecting rods? Is it worth it to spend the $$ on some nice H beam rods or spend a little less reworking the stock ones?
Any machine work other than normal for the crank? And I am thinking of a Fluid Damper for the front of the crank I know they need to be modified a wee bit but I am open to suggestions.
I will have the whole rotating assembly (clutch included) balanced as well.

Oiling plans are for a melling pump and stock pan and pickup.

I am still considering the turbo this year, but if I do it will have to be blowing into a carb, not an EFI. Budget being consumed at a rapid rate. The car needs a new rear end also so that might mean the turbo waits 'till next season.

Camshaft will be the next issue. Turbo vs N/A influence this. Local guy suggested a custom grind when turbo is put on and an out of the box cam kit (Comp Cams or ???) for N/A. I don't mind having a spare cam kicking around if needed. I assume that Harland Sharp roller rockers are the best way to actuate the valves?

Target date to get it running is June 19th.

Paul