LT1 head gaskets for boost

I would like to know what head gaskets are you guys using to run 15-18 psi

thanks for your time.

I am going with the Fel Pro 1074 gaskets.

I use the 1074 as well with ARP bolts.

I have used the FelPro without any problems. This year I am ging to try the Cometic, but you should be fine with the FelPro.

Rich Krause

I'm going to go with the Cometic gaskets on my build-up too. Heard great things about them, we shall see...

Marty

I am using the Cometics. I machined the block and heads to insure proper mating surfaces, put them on dry with studs, no problems so far.

However, I am told you will pop a piston before you blow these things. Kinda of gets rid of the fuse, make sure your tune is right on. Right Rich?

Wingnut

Originally posted by wingnut
I am using the Cometics. I machined the block and heads to insure proper mating surfaces, put them on dry with studs, no problems so far.

However, I am told you will pop a piston before you blow these things. Kinda of gets rid of the fuse, make sure your tune is right on. Right Rich?

Wingnut

Yes, I thought about that but there was no sign of detnation on teardown this year.

Rich Krause

Thanks guys,
Is there a part number for the Cometics? and where can I get them?

thanks again.

Never mind those questions, did a search and answered myself, sorry!

I think the cometics may have an advantage as you can get them in any thickness.
I was looking at the srp with -31cc dish, wich they say should give 9:1 cr with 58cc chambers,
From your experience, should i look for a lower c.r. ? different pistons? Could I use the cometics in a thicker size to lower the c.r. even more?
I want to run 15-18 psi, i have 94 octane gas available at the pump.

thanks for your input and time.

Since you are running a 383, I am pretty sure that you will need to change you heads to get a lower comp ratio. You can go with a thicker gasket, but experience has proven to me that 1) It does not lower your compression that much 2) better performance out of a better head.

I am running about 9.2 to 1 with my 355 and had to leave pump gas at around 15 pounds of boost. But if you have a set of good ported LT1 heads with big valves, good turbo or supercharger cam, and good exhaust with ported intake, you might start with 11 to 12 pounds of boost first. With that 383, I bet you will like it a lot. If you must turn up the fun factor, you are going to have to evaluate cost vs. pleasure. In other words, things get critical north of 16 to 17 pounds of boost. High oct # fuel becomes a necessity in stead of just insurance, and long stroke engines get pushed to their max. Big HP, Huge smiles, lots of girls, but all at a cost.

Rskrause and Engineermike both have a lot of experience in this area, I bet they could throw out some numbers that might make your decision a little easier.

Do you have an HP goal instead of a boost level goal to work with?

Wingnut
;)

Thanks for your input,
I didnt want to set a hp goal really because I didn't want to be disapointed once the dyno sheets print out... I do want this to be fun to drive and have a awesome seat-of-the-pants feel adn I am pretty sure 500rwhp will take care of pretty much anything I see on the street around here. I beleive that something north of 500 rwhp is realistic.

I would also like to know what kind of compression ratios guys around here run with at least 15 psi...also is my 9:1 a good start?

once again, thanks!

I am at ~8:1 to run 17psi on pump fuel. However, when really beating on it (at the track with nitrous plus boost) I run race unleaded (104 octane). Using a very thick gasket to lower CR is ultimately self defeating because it will prevent you from achieving an optimum "quench height". Optimum is ~0.035" to a max of 0.045". I am running 0.040" for this year (zero deck, 0.040" gasket).

Rich Krause

You've done your homework Rich. That is the correct range for proper quench. Don't listen to the guys who say that quench doesn't matter. By the way, isn't a Felpro 0.039? ;)

Originally posted by Wild1
You've done your homework Rich. That is the correct range for proper quench. Don't listen to the guys who say that quench doesn't matter. By the way, isn't a Felpro 0.039? ;)

I am using the Cometic 0.040" gasket this year.

Rich Krause

Correct the felpro 1074 has a crush thickness of .039.

Bill

ok, I have a question. let s say your goal is .040 for quench. What are the advantages/disadvantages (if any) to have the block zero decked and use a .040 gasket? Would having the block decked at .005 and use a .035 gasket have the same effect? Is one better than the other? and why?

From what I understand, the quench is important. I can't see any variance with a 0-Deck and 0.040 HG or a 0.050-Deck and a 0.035 HG.

The advantage of using a 0.035" gasket and an 0.005" deck is that there is still a little deck left for the next time you need to mill it for flatness or to remove scratches although 0.005" isn't much it might be just enough.

Tim, good to hear from you.... this is Greg from the SCCC. I can see you point about the 0.005 deck. Yes, it does leave some more meat for the next build. But, the 0.005 & 0.035 HG should not affect the quench "effect" differently than a 0.000 & 0.040 HG.

It would seem the safer bet to leave 0.005... I'd opt for that route.

Tangent - Tim, how is the build coming along? Will you be ready for the cruise tomorrow?

ok so logically thinking, the more metal you can leave on the block the more rebuilds it will last. the .005 and .035 were just examples I used. I was also wondering what would be the minimum head gasket thickness be? I guess at one point the gasket is too thin to compensate for block/head warp,shift caused be the heat up cool down cycles and the different expansion rates of aluminium and iron? What do you guys think?

No answers?
Ideas, maybe?

Those are great questions, I was waiting for some answers too. TTT for ya.

ok this may sound stupid but it has been bugging me for a while... what does " ttt" stand for ???

TTT is to the top.... to bring your post back to current.

As far as the thickness issue. A greater thickness will likely result in a weaker gasket as there is more surface area for the combustion pressure to press against. Remember a gasket of double the thickness also has double the force trying to push it out between the head/block.

A large deck/thin gasket combination will have more compression than a short deck/thick gasket combo as the gasket is larger than the bore adding combustion volume. This also has a drawback as some additional combustion residue (although small) remains in this area diluting the incoming charge.

Remember that you still have to achieve a suitable compression with a combination of heads, piston, gasket & deck height. Unless you are buying custom pistons, you will be limited to your choices.

For reference the stock LT1 gasket is not that strong & the 1074 has a copper fire ring which is also not severe duty but substantially stronger than the stock one.

Most severe duty gaskets have a stainless wire ring, but there is no direct LT1 gasket of this type that I am aware of (atleast in the FelPro catalog)...... although modifying the water passages in a standard small block gasket is a possibility.

An interesting side note is that a recent magazine article (I'll find & post the issue if anyone is interested... currently misplaced at the moment) using a Ford Turbo buildup from Bennett Racing. It said they routinely use large deck clearances to get compression down on their buildups. This contradicts most common thinking & honestly surprised me as well. They are one of the most desirable engine builders of Ford racing engines & have many winning engines in NMRA & Pro 5.0 classes so I'd hate to disagree with their philosophy. I'm sure this did not clear up the thread but is a reality that needs investigation.

thanks for your post.

I m still trying to figure this out, all help is welcome.

I looked into the cometic head gaskets and I believe that the part number is C5645 and was hoping that someone would verify this. I didn't find anyone that sells these for the LT1, were are you guys gettin um? Also, you stroker guys, what oil pan gasket are you using with a pan that has notches? Thanks

I went to the Cometic website and it was fairly sparse. I only saw two gaskets available for the LT1. Is there another place on their website to look? Neither gasket on their website mentioned the squish thickness.

Check with Sam at Combination Motorsports. That is where I got mine.

www.cmotorsports.com

Wingnut:D