Head Gasket Thickness???

Hi I need some help. I am currently building a SBC TBI 383 Stroker and I am wondering what head gaskets to get. First off let me tell you what I am working with. I would like to keep this a daily driver so I am going to try to keep it TBI (my preferance). In doing so I have purchased the parts as far as cam and heads to do that. The heads are GM casting # 441 rebuilt with 2.02/1.60 valves 76 chamber size. I would like to know what head gaskets I need to get that will keep my compression ratio low enough to run on pump gas? Or should I not have a problem with that? I am not should what stock thickness is, nor do I know what I need. I would like to keep the compression ratio roughly 9.5 to 1 or lower. I am not even sure how high I can go on the ratio with 91-92 octane gas. So all you experts out there please help out this amateur. Thanks for you time. :banghead:

IMO there is not enough of a variance in gasket thickness to affect comp ratios in any appreciable way. If an engine pings with a thin gasket, it will ping with a thick one. It is more important to use a high quality gasket for max reliability than a thick one.

My half-assed calculation shows you will have a theoretical compression ratio of approximatly 10:1, which means you can use premium pump gas.

IMO there is not enough of a variance in gasket thickness to affect comp ratios in any appreciable way. If an engine pings with a thin gasket, it will ping with a thick one. It is more important to use a high quality gasket for max reliability than a thick one.

My half-assed calculation shows you will have a theoretical compression ratio of approximatly 10:1, which means you can use premium pump gas.


Thanks for the info. Like I said I am an amateur. (atleast I admit it lol) :iceslolan :licka:

by MagicRat, My half-assed calculation shows you will have a theoretical compression ratio of approximatly 10:1
MagicRat how can you figure that without knowing what kind of pistons 383 stroker is using? I have a 327 with 64cc chamber heads and stock flat top pistons that gives me 10:1. I aslo used GMs .020" high perf. metal(don't remember what alloy) head gasket.

Stroker with 93 octane you can go 10:1 with a well tuned engine. With 91-92 9.5:1 would be a safe bet. Gas costs enough you don't want to buy racing fuel to mix for higher octane.
Take care guys

According to Speed Pro, a "flat top" (with 4 valve reliefs) piston in a 383 CID engine, with 64 CC chambers, will yield 10.34:1. When doing the calculations, Speed Pro "assumes" a .040" thick gasket (about 1mm). This is the compressed thickness of Felpro "blues" and the standard issue Felpro Performance 1003. The Felpro Performance 1044 will gain you a little volume, at a thickness of .051".

One must actually measure the chamber volume if the heads are not brand new. It should also be done to the bargain-basement aftermarket heads, even IF new. Published data is "nominal", and may vary from one production run to another. In order to be certain, do the leg work. 9.5:1 is the PRACTICAL limit for iron heads and 93 octane. You can run a bit higher compression, but it won't gain anything, power-wise, as you'll need to retard the timing, richen the mixture, etc., to avoid detonation. Aluminum heads require about 1 full point higher ratio to achieve the same level of power, all other factors being equal.

Jim

According to Speed Pro, a "flat top" (with 4 valve reliefs) piston in a 383 CID engine, with 64 CC chambers, will yield 10.34:1. When doing the calculations, Speed Pro "assumes" a .040" thick gasket (about 1mm). This is the compressed thickness of Felpro "blues" and the standard issue Felpro Performance 1003. The Felpro Performance 1044 will gain you a little volume, at a thickness of .051".

One must actually measure the chamber volume if the heads are not brand new. It should also be done to the bargain-basement aftermarket heads, even IF new. Published data is "nominal", and may vary from one production run to another. In order to be certain, do the leg work. 9.5:1 is the PRACTICAL limit for iron heads and 93 octane. You can run a bit higher compression, but it won't gain anything, power-wise, as you'll need to retard the timing, richen the mixture, etc., to avoid detonation. Aluminum heads require about 1 full point higher ratio to achieve the same level of power, all other factors being equal.

Jim

I have speed pro flat top pistons with two valve relieves, running with iron heads 76 chamber size. I am looking to keep compression on the lower side towards 9.5 to 1. What is a good thickness for gaskets to go? What about the bore size does it have to match or how close do I need to be? I have not measured yet to get the exact bore size of my block, 350 bored 30 over. Thanks for all your help.

According to the same Speed Pro chart, that piston yields 8.88:1 at 4.030" bore. I would think, using the "shim" head gasket would bring you to about 9.4:1. Those gaskets are .017" when compressed. Felpro part number 7733SH-1.

Jim

i biult a 383 for my 67 camaro. i used a 12cc pop up piston. i had to have the head clayed for gasket thickness. in your case if your using a flat top piston. call jegs or summitt talk woth a tech. give them your engine specks and the will tell what gasket to use. along with what the compression ratio. keep it simple. good luck