I'v gotten half the pistons in my L48. They are cast flattops that came with the motor, and should give me 9.5:1+ compression with 65cc heads. I am trying to get the recommended .040"-.050" quench distance to the heads, but the pistons are already .035-.037" in the hole. I didn't have the block decked to save the original vin stamping. I looked for the thinnest head gaskets out there and came up with these: I never had problems with the .039 or .041 composite gaskets, but these have me worried about longevity. Anybody use them or know about them?

Fel-Pro 1094 Embossed Shim with Precision Rubber Coating, .015 in. Thick, 4.100 in Bore, Iron or Aluminum Heads for use in some sportsman drag racing and flat top piston oval track classes. Can not be used on 400ci engines. Embossed shim with precision coating does not cause any brinneling on aluminum heads. Comment -are they meant for short drag strip passes, not continual highway use? Will it have to be re-torqued?

GMPP 10105117 This composition GM Performance Parts Head Gasket with stainless steel faces is recommended for stock and mildly modified engines with 4.00" cylinder bores. Its compressed thickness is .028".(Cast Iron or Aluminum Head) Comment - is this going to last? Will SS face require copper spray to seal?

GMPP 14096405 This composition GM Performance Parts Head Gasket has stainless steel on one side and graphite on the other side This gasket has a compressed thickness of .028". Comment - will SS seal OK with copper spray? What is graphite for?

As you can tell, I'm not up on head gasket technology. I usually put the blue ones in and forget about them. Thanks, Joe

edit, found two more:
Mr. Gasket 1134 Ultra-Seal Head Gasket, Composite Type, .028 in. Compressed Thickness Comment - is this a conventional gasket?

NAPA NGA1178SSB w/ Contoured Combustion Chamber .020" Compressed Operating Thickness Stainless Steel Comment what is a contoured combustion chamber? vortec style?

 

I use a MR. Gasket Ultra Seal (1034) gasket which is a graphite/steel compositition .028" compressed. I just put one set in and the other set was in for 30k miles with no problems.

I don't have any experience with the embossed shim gaskets, but I've read good things about them when I had an LT1.

 

I searched thru the chevyhiperformance.com site for info and came across this comment:
Fel-Pro makes a great rubber-embossed steel shim gasket that is only 0.015-inch thick, which increases the compression on engines like this one. This is a great gasket that seals well and also improves power by reducing the quench area above the piston.
I'd still like to hear anybody's experience with this gasket, or the others mentioned, but it looks promising. Joe

 

I'm pretty sure it was the Fel Pro 1094 gaskets that were on the engine that was in my 72. They were steel gaskets measuring 015. I don't know how many miles they had at that time, but I put 17,000 on it before changing out the block, and they had held up A-OK.

 

Flepro 7733 SH-1 ( Summit sells it ) steel shim head gasket used it on my 355ci with Sportsman II heads, worked great is about 18 thou compressed if I remember correctly, spray it with aluminum paint and slap it on

 

I am using the Felpro 1094 embossed shims. They are good for aluminum heads. No problems after 4 years & 20,000+ miles. I was going to retorque after the initial startup, but ended up doing the alternate method while the motor was still on the stand. After you fully torque down the head, go back the the #1 bolt & loosen it to zero torque, than smoothly bring it back up to full torque. Do this to the remainder of the head bolts in order. This was per Felpro's severe duty/racing instructions.

 

I use/like them but they cost a bit more than the cheapie gaskets that come with the kits. The most recent was in my Vette 350. Went from stock L-82 to Dart head L-46 specs. I like to use the copper spray head gasket sealer with them. I have no reason to think that they are less durable than any other steel shim gasket and they are highly recomended for improving the quench on matching number blocks or any other time you want to improve quench but want to avoid shaving the deck surface. Those things work for me.

10.4 C/R, stock 350 HP hydraulic cam and runs great on pump gas

-Mark.

 

And remember that many cast rebuilder pistons are made -0.20 to make up for the decking of the block that may have been done on a overhaul.

 

Do your pistons look like this? If so, GM used L82 TRW 464664 pistons in yours, they are forged

 

TT- no they are the cast 4-eyebrow pistons, .040 over.
Yellow 72 - that's probably why mine are so low.
Stingr69 - I'm not adverse to spending money where it is needed.
71 coupe - that answers my questions, thanks.
MotorHead - thanks for the suggestion.
Always Wave - it's good to know they last.



Now that I've put together the short block, it measures to 9.6:1 compression with Summit heads and .015 gaskets, and has .050-.055 quench. This should be a good street motor with a Crane 268 cam.
Joe