Head Gasket Thickness???

[383stroker_1]

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.

[MagicRat]

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.

[383stroker_1]

Originally Posted by MagicRat

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)

[66 chevelle]

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

[MrPbody]

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

[383stroker_1]

Originally Posted by MrPbody

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.

[MrPbody]

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

[hottievett]

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