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sgtsteve

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Discussion starter · #1 ·
Okay, I got a question on head gaskets. I just tore down my stock 350 down to bare block with intention of doing a relative stock rebuild. Now the question...what type of head gasket do I want to run on this? I've had a friend tell me that I want a all steel headgasket because it's thinner and will not lower my compression. On the other hand, I've heard from a somewhat knowledgable Chevy mechanic that no, I don't want to use steel gaskets without machining the block or else they'll leak. So should I go with a composite gasket, or stick with a steel gasket?

Sorry I'm not too much of a mechanical/engine person...just don't want to make any mistakes in rebuilding this engine.
 
#2 ·
Unless you are doing deck and head machining for the steel gaskets, I would stay with plain old Fel Pro replacement gaskets.
 
#3 ·
Shim or coated shim gaskets can be used to get a desirable compression ratio and quench, but they don't seal as easily and need to be retorqued.

If this is a basic, low compression deal your prolly better off sticking with a no retorque gasket. Like Ron said, the felpro permatorque gaskets that come with a basic rebuild set should be fine.
 
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#4 ·
I'll be the one to disagree.

Plain ol' steel shim gaskets--properly coated with sealant--should work fine unless there's obvious problems with surface finish or flatness of the block and head surfaces--which you should be checking for. The last steel shim gaskets I installed were coated top 'n' bottom with plain ol' ordinary DIRT CHEAP white "Teflon" pipe thread sealer; the kind you can buy at any home improvement center for about $6 per tub. Other folks seal them with aluminum paint; CopperKote, Indian Head shellac, Permatex #1 or #2...I think pretty much any sealer on Earth would work; possibly including mucus.

In addition, Fel-Pro makes a rubber-coated steel shim that would be perfect for you.

The LAST thing I'd do is install a .040 thick gasket on an engine that has the piston .020 or more down the hole. If you MUST use a thick head gasket--zero deck the block first.
 
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#5 ·
Install either Fel-pro's #1094's at .015" or the stock type .020" thick shims and go.

I have used aluminum paint, "Indianhead", and both spray and dauber bottle Copper-Cote but I always re-torque shims at least twice to be sure b/c I'm almost anal on this AND I have never had a problem w/ them.

And I have used a short, fine toothed triangle file to "dress" all the decks between head-bolt holes to true/clean them ALL up, BUT this is an old "pdq67" feelie thing here.

I go from bolt-hole to bolt-hole and spray w/ either Brake-Clean or WD-40...

You will see what I mean AND go EASY here b/c this is just a deck surface clean-up by me.. Don't remove MUCH deck metal!!

pdq67

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#6 ·
If this is your basic stock low compression 350, just go with the standard gaskets by fel-pro. You are not going to gain any noticeable hp increase that would warrant the extra work involved with steel gaskets.

If this is not a stock configuration, you need to post more of what is in the engine (cam, heads, pistons, etc) to get a better idea of what you are actually dealing with before anyone can give you advice on whether or not to use them.
 
Discussion starter · #7 ·
justkyle said:
If this is your basic stock low compression 350, just go with the standard gaskets by fel-pro. You are not going to gain any noticeable hp increase that would warrant the extra work involved with steel gaskets.

If this is not a stock configuration, you need to post more of what is in the engine (cam, heads, pistons, etc) to get a better idea of what you are actually dealing with before anyone can give you advice on whether or not to use them.
Click to expand...
I have not taken the block to the machine shop yet. If the bores are okay I plan on reusing the stock pistons and just changing the rings. Really the only things I plan to change from stock is the camshaft to a Comp Cams Xtreme Energy 262H-10, a crane roller timing set, intake to a Edelbrock performer, carb to a Carter AFB competition I think it's either 600 or 625 cfm. Also the heads will be swapped for a set of reworked 400 SBC heads cast # 493. Not sure what to do as far as exhaust yet.
 
#10 ·
IS your block deck stamped on the passenger side front? If so it has never been decked and is prolly +/- 9.025. Do U have any idea what pistons you have?
 
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Discussion starter · #11 ·
dirtrocker said:
IS your block deck stamped on the passenger side front? If so it has never been decked and is prolly +/- 9.025. Do U have any idea what pistons you have?
Click to expand...
I'll have to check on that, but so far I believe the mileage on the odometer to be accurate 68,000 miles. The block is original, the heads had never been removed, and the timing gears appeared to be original. Also everything was remarkably clean inside for a 37 year old engine.
Is there a number to look for on the pistons? They have the valve reliefs cut into the tops.
 
Discussion starter · #13 ·
pdq67 said:
Stock 4-notch flat-top pistons, you are at 10 to 1 CR.

Stay w/ your stock heads if they are double-humps, otherwise, you will lose compression w/ the 76 to almost 80 cc chamber sized 400 heads!

pdq67
Click to expand...
My original heads are 993 castings. My shop manuals say with original heads/pistons the compression ratio is 8.5 to 1.
I looked up the original cast # online and I believe that I read that the stock heads were 75cc chambers and the 400 heads (cast# 493) are 76cc chambers. I don't think that would be too much of a difference. Went by the machine shop today, and the owner told me no I want to stay away from steel headgaskets, it would require alot of unnecessary work and the deck would have to be decked. He said for a street engine the composite gaskets will be fine and it won't have a noticeable effect. If the block needs to be bored, then I will go with flat top pistons otherwise I plan on re-ringing the stock dished pistons.
 
#14 ·
I "Think" those stock 4 valve relief dish pistons will give you about 8.5:1 with a shim gasket, about 8.1:1 with a no retorque gasket.

If you wanted more compression and had a deck you didn't want to try shim gaskets with, something like a vortec head with 64cc should bump you to around 9.1:1
 
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#15 ·
"Went by the machine shop today, and the owner told me no I want to stay away from steel headgaskets, it would require alot of unnecessary work and the deck would have to be decked."

I call BS here! Read me again...

Oh, and btw, I installed .020" thick Mr G. 350 shims in my 406 so know all about this!! Had to mock her up and reach up inside and scribe the overhangs and then very carefully, hand remove, then drill them for steam holes and they worked great!

I'd install shims for no other reason than to hold what little quench you have tight to help her burn better!!

'72 engine, my bad on the 4-notch, flat-tops. Probably +12 cc dish w/ 4-notch and either 74 or 76 cc heads so it will be low compressioned vs like the old 295/300hp/350 L-48's at 10.+ to 1....

pdq67

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#16 ·
I used a set of these GM gaskets on a 305 recently. It says they are for a 350 too, but dia is 4.000. I wish I had thought to set one on a 350 block so I could tell you if they clear the bore or not, but I just stuck em on the 305 and didn't think. They are .028 and have a rubbery feel.

http://store.summitracing.com/partdetail.asp?part=NAL-10105117&autoview=sku

I wouldn't be afraid to use the shim on an un-decked block. I got a straightedge and a buffer says they'll seal. I also wouldn't be afraid to run a .040 gasket on a LCR engine where quench doesn't really count as much. Dets is why they worry about quench, and lowering the cr does more to get you out of det danger than quench ever will. That and heat.

permatorque,,,, ain't. imo. least not if abused adequately:). I usually find the center 2 or 3 bolts slightly loose.
 
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