Compression ratio 9.5 or 8.6 ???

canadianregal

Building from the grnd up
Joined
Jan 20, 2006
:confused: I looked at the NHRA engine specs on http://www.nhra.com/tech_specs/engine/blueprints/BUI-87.rtf
They list the NA 231 at 9.5 to one ratio --both the throttle body and the carb version but the carb has 42.7 cc heads and the throttle body has 36.5 cc heads
The turbo version has 8.6 ratio with 42.7 cc heads
Wheres the different ratios coming from :confused: :confused:
would it be the thicnkness of the head gaskets--i doubt it would change from 8.6 to 9.5 though
 
read on farther

sorry read on down further and the gaskets are different and so are the pistons--so i guess i wont use the forged version in my na after all
 
The difference is in the pistons. The NA 231 with a carb is the rear drive engine, I think the only TB non turbo 231 was in front wheel drive. The headgaskets are different but I think the turbo ones are actually thinner. Are you building this to class rules or are you just messing around with trying to get off the shelf parts for a turbo for your N/A motor?
 
re pistons

i am planning on using NOS on the motor and i thought forged would be better but i dont want to drop my compression ratio from 9.5 to 8.6 cuz i wont be using the spay alot just when i want to pi$$ off the v8 boys and the rice burners around here LOL
If i remember correctly the head cc are differentb on the throttle body so the diff between the turbo and na must be pistons
I may use the forged and have the heads plained and use the thin gaskets to keep up compression--if later i decide to supercharge i could put thicker gaskets to lower the compression and i also have 3 sets of 8445 heads--actually have 3 complete motors with all accesories.
 
canadianregal said:
i am planning on using NOS on the motor and i thought forged would be better but i dont want to drop my compression ratio from 9.5 to 8.6 cuz i wont be using the spay alot just when i want to pi$$ off the v8 boys and the rice burners around here LOL
If i remember correctly the head cc are differentb on the throttle body so the diff between the turbo and na must be pistons
I may use the forged and have the heads plained and use the thin gaskets to keep up compression--if later i decide to supercharge i could put thicker gaskets to lower the compression and i also have 3 sets of 8445 heads--actually have 3 complete motors with all accesories.
Ah... the TTA FWD heads have smaller chambers and thats there the 231 NA with TB came into play. I'm sure somewhere on here there is listed the compression with GN slugs and TTA heads. You can get them from Champion fully ported or look for a FWD car from that era and pull them yourself. I believe they might also have center bolt valve covers but I'm not sure on that.
 
Junk Yards

the junk yards here are just that--JUNK with emphasis on junk---i think i would rather buy new.
For now im gonna change to headers,cam 4 barrel intake and spray it till it explodes--hopefully in the meantime im gonna build an aluminum block with all the goodies and supercharger and all the toys---yep i know that putting a gn settup in my regal would be great but ya cant even find any car older than 1990 around here so i guess ill buy all new--LOL wife supports it so why not? :biggrin:
 
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