felpro permatorque head gaskets vis a vi compression ratio - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stknrdr · 12-04-2002, 05:45 PM

Putting some vortec heads on, and Im trying to calculate my new compression ratio, I am using felpro permatorque head gaskets, and am wondering does anyone know the compressed thickness of these?

crazy longhorn · 12-04-2002, 05:54 PM

They should be approx .038-.039 compressed.....

stknrdr · 12-04-2002, 05:57 PM

thank you! that was fast heheh

bigjimzlll · 12-04-2002, 06:42 PM

you might look into this a little first...you want to try to get you quench around .045..this is piston down from top of deck plus the head gasket thickness...when you pull the heads ..lay a flat edge across the cylinder and measure from the top of piston to flat edge..on a stock sbc thhis number is aroun .025..if yours is this number ..get a head gasket thickness as close to .020..if it has .015...try for .025..if you have the .025 and you but .039 gasket, it may lead to detonation problems.

crazy longhorn · 12-04-2002, 07:22 PM

Thats good advice Big Jim has on the quench, So I will add just a little info. If you havent cut the decks, & are unsure if they they are good & flat.....I would rather fight the quench issues than blown gaskets. As a rule, if you are under .060 quench on a 9 - 9.5 to1 eng you shouldnt have too much problem with detonation.......you may have to run a little less timing, & wont make max power tho..... My quench is a little wide at .056 on the 383, but I didnt want shim gaskets with alum heads. Still @ 9.8 on ratio, i run pump fuel without problems, & make good power(alum heads help). when she come down for a "freshen up", I will have the decks cut again to optimize the combo & run a couple more degrees of timing. calculating your combo on smokem up com, I come up with around 9.1 with the vortecs, .025 deck, .039 gasket, & a 12 cc dish......if you can go a little thinner on the gasket, you will be better off. Damn i talk too much! Good luck, Crazy AL

shadetree · 12-04-2002, 09:25 PM

Crazy, you do NOT talk too much (IMHO), excellent advice, good plan, but I keep hoping to read about how someone has come up with THE answer for quench & good gasket without milling decks.

stknrdr · 12-05-2002, 12:05 AM

thank you very much for the info guys, I will look into it - gotta love all this support!

12-04-2002, 05:45 PM	#1
stknrdr Registered User Join Date: Apr 2001 Location: Utah USA Posts: 27	felpro permatorque head gaskets vis a vi compression ratio Putting some vortec heads on, and Im trying to calculate my new compression ratio, I am using felpro permatorque head gaskets, and am wondering does anyone know the compressed thickness of these? __________________ 72 C/10 Fully Restored Hugger Orange - 355, 4" lift 35's Auburn limited slip diffs front and rear, 4.56 gears. Vortec Heads, 700r4/NP208 combo. On the burner: Roller Cam, Blower 77 Ford Bronco Rockcrawler 93 BMW 325IS Have-fun-on-the-way-to-work-car.

12-04-2002, 05:54 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	They should be approx .038-.039 compressed..... __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

12-04-2002, 05:57 PM	#3
stknrdr Registered User Join Date: Apr 2001 Location: Utah USA Posts: 27	thank you! that was fast heheh __________________ 72 C/10 Fully Restored Hugger Orange - 355, 4" lift 35's Auburn limited slip diffs front and rear, 4.56 gears. Vortec Heads, 700r4/NP208 combo. On the burner: Roller Cam, Blower 77 Ford Bronco Rockcrawler 93 BMW 325IS Have-fun-on-the-way-to-work-car.

12-04-2002, 06:42 PM	#4
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	you might look into this a little first...you want to try to get you quench around .045..this is piston down from top of deck plus the head gasket thickness...when you pull the heads ..lay a flat edge across the cylinder and measure from the top of piston to flat edge..on a stock sbc thhis number is aroun .025..if yours is this number ..get a head gasket thickness as close to .020..if it has .015...try for .025..if you have the .025 and you but .039 gasket, it may lead to detonation problems. __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

12-04-2002, 07:22 PM	#5
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Thats good advice Big Jim has on the quench, So I will add just a little info. If you havent cut the decks, & are unsure if they they are good & flat.....I would rather fight the quench issues than blown gaskets. As a rule, if you are under .060 quench on a 9 - 9.5 to1 eng you shouldnt have too much problem with detonation.......you may have to run a little less timing, & wont make max power tho..... My quench is a little wide at .056 on the 383, but I didnt want shim gaskets with alum heads. Still @ 9.8 on ratio, i run pump fuel without problems, & make good power(alum heads help). when she come down for a "freshen up", I will have the decks cut again to optimize the combo & run a couple more degrees of timing. calculating your combo on smokem up com, I come up with around 9.1 with the vortecs, .025 deck, .039 gasket, & a 12 cc dish......if you can go a little thinner on the gasket, you will be better off. Damn i talk too much! Good luck, Crazy AL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

12-04-2002, 09:25 PM	#6
shadetree Senior Member Join Date: Dec 1999 Location: Knightstown, in, usa Posts: 2,525	Crazy, you do NOT talk too much (IMHO), excellent advice, good plan, but I keep hoping to read about how someone has come up with THE answer for quench & good gasket without milling decks. __________________ 1970 long fleet, 355 4 speed, primer, walnut goodies

12-05-2002, 12:05 AM	#7
stknrdr Registered User Join Date: Apr 2001 Location: Utah USA Posts: 27	thank you very much for the info guys, I will look into it - gotta love all this support! __________________ 72 C/10 Fully Restored Hugger Orange - 355, 4" lift 35's Auburn limited slip diffs front and rear, 4.56 gears. Vortec Heads, 700r4/NP208 combo. On the burner: Roller Cam, Blower 77 Ford Bronco Rockcrawler 93 BMW 325IS Have-fun-on-the-way-to-work-car.



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