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· Registered
201 Posts
Discussion Starter · #1 ·
Is there any way to find out my real compression ratio? I think it's rated at 9.5:1 for my '69 spec 302 2v but are there any instruments to measure what the real compression is?
For the record, it runs well and pulls strong (certainly compared to my honda heheh) so it's not to fix anything, i'm just trying to learn more about my car.

Also, it's a rebuilt motor from Ford with a '77 block. I think the previous owner bought it in '92-'93 but it hasn't been driven much.

Thanks, guys/gals,


'69 coupe in the making

· Super Moderator
8,669 Posts
I don't think you could even hazard a real good guess without pulling the head off and taking some measurements. Even if you can figure the combustion chamber size based on the heads casting number, you still don't know if the cylinders have been bored, the block has been decked, does it have stock pistons, what the head gasket thickness is, what the head gasket bore diameter is, etc. etc. etc.


'65 Convertible (with many mods.)

· Premium Member
6,475 Posts
The compression ratio is the volume of the cylinder with the piston all the way down divided by the volume of the cylider with the piston all the way up. (The difference between the two numbers is the displacement.) The tough number to find is the volume with the piston at TDC. Off hand I can't think of any way to measure it easliy. Maybe somebody else has a trick. I would think that measuring the cylinder pressure would give you an idea.

67 Sports Sprint, Convert. Original C code, now 293 ci with Holley 450 and 295,000 miles
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