Compression Ratio Chart - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wlee · 09-04-2002, 03:39 PM

Here's a quick easy way to figure compression ratio on small block Chevy engines

MandarinSixSeven · 09-04-2002, 04:00 PM

Man wlee, you are awesome, i was just looking for this exact thing last nite! i just got a copy of desktop dyno off a friend and was trying to figure out my numbers!

thank you very much
Benson

Beast388 · 09-04-2002, 07:03 PM

I would only use that to get a very very rough guestimate of comp. ratio. It doesn't take into account variences in valve relief volume, head gasket volume, true head cc, and deck height etc.

There are too many different gaskets, pistons, heads and deck heights for that to be very accurate.

*Fast68Chevy* · 09-05-2002, 10:33 PM

too many differences indeed, there were a couple different 305 engine pistons used, the L69 ones are alot different than the LG4 ones and then there were different CR;'s of 350's throughout the years, 8.5, 8.6 and 8.2 etc etc.

then the head gasket deal, some thinner some thicker, replacement composite ones being thicker than factory steel ones., and so forth,,

JimKshortstep4x4 · 09-06-2002, 09:00 AM

Thanks for posting this chart. It certainly is helpful for deciding basic head volumes needed for small block engines for particular compression ratios. Variances or other factors can be addressed
for the particular engine, but this gives a great starting point.

Jim

09-04-2002, 03:39 PM	#1
wlee Just an Old Mr Goodwrench Join Date: Feb 2002 Location: Green Ridge, MO USA Posts: 259	Compression Ratio Chart Here's a quick easy way to figure compression ratio on small block Chevy engines Attached Images __________________ 1969 CST 20 Longhorn 1970 CST 20 Fleetside 1991 Jaguar Sovereign 1992 Mazda Miata

09-04-2002, 04:00 PM	#2
MandarinSixSeven Seasonal Poster Join Date: Apr 2002 Location: Kelowna BC Canada Posts: 896	Man wlee, you are awesome, i was just looking for this exact thing last nite! i just got a copy of desktop dyno off a friend and was trying to figure out my numbers! thank you very much Benson __________________ 67 GMC Short Step 350/4-Speed/3.08 Posi Front/Rear Sway Bars Kelowna BC, Canada Member of DTPW

09-04-2002, 07:03 PM	#3
Beast388 Suburbans RULE! Join Date: Jan 2000 Location: Clinton, IA 52732 Posts: 689	I would only use that to get a very very rough guestimate of comp. ratio. It doesn't take into account variences in valve relief volume, head gasket volume, true head cc, and deck height etc. There are too many different gaskets, pistons, heads and deck heights for that to be very accurate. __________________ --Ben 71 GMC Suburban 4X4 The "Beast" 388 CID Stroker, TH350, NP205, 8-lug D44, 14BFF w/ Detroit, 4.10:1 gears, 4-Wheel Disks 4" Lift, 35" MT/R's.

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09-05-2002, 10:33 PM	#4
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	too many differences indeed, there were a couple different 305 engine pistons used, the L69 ones are alot different than the LG4 ones and then there were different CR;'s of 350's throughout the years, 8.5, 8.6 and 8.2 etc etc. then the head gasket deal, some thinner some thicker, replacement composite ones being thicker than factory steel ones., and so forth,,

09-06-2002, 09:00 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Thanks for posting this chart. It certainly is helpful for deciding basic head volumes needed for small block engines for particular compression ratios. Variances or other factors can be addressed for the particular engine, but this gives a great starting point. Jim



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