Compression bump

[beanhead]

Just out of curiosity, how much would compression be raised by going from an open to a closed chamber head, roughly?
My engine is a 440 that was, according to builder, about 9.7 using 452 heads, which I later switched to 84cc edelbrocks..thanks

 

[Garys1969RR]

There is a C Ratio calculator on United Engine and Machine website. Just plug in all your info, and it will tell you your calculated C/R

 

[PurpleBeeper]

Hey bean, aren't the 452 heads about 80 cc's combustion chambers??? I'm not sure, but I was talking to a guy that cc'd some 452's I was looking at and he said his came in at 79 cc's

OK, I'm dreaming... I couldn't find an exact number for 452's, but 84cc-88cc seems to be the range I was finding in a quick search.

 

[beanhead]

Hey bean, aren't the 452 heads about 80 cc's combustion chambers??? I'm not sure, but I was talking to a guy that cc'd some 452's I was looking at and he said his came in at 79 cc's

Thanks, I'm not sure.. seems I've read they varied but were more like 88 and up? That could be wrong though. It was built about 17 years ago and I just don't have or remember the finer details of the build unfortunately..just looking to add to my own knowledge base

 

[gtxracer]

I would think piston configuration, whether flat top or dome affects over all compression ratio, no matter the heads.

 

[HT413]

Tough to say exactly without more detail. It went up to probably close to 10:1 but a lot depends on head gasket thickness. Meaning, if you had steel shims with the 452’s then switched to something like 0.040’s with the Ede’s, the thicker gaskets would have eaten into that CR increase a bit.

Play around with this...

http://www.wallaceracing.com/cr_test2.php

 

[beanhead]

Okay thanks guys... That Wallace calculator asks for some information that I don't have, but I just gave it an educated guess and used the same numbers for both head cc's... They show an increase of about .35, I was able to find some old faded paperwork that showed my iron heads at 88cc after a resurface

 

[Garys1969RR]

915 heads are supposed to be 73cc, 906 heads 79cc, 452s 82 I think. In reality, 915s are 79, 906 @86 to 88, 452s @ 88 to 90. Factory head [email protected] for the steel shim. Deck clearances all vary.

 

[wyrmrider]

the 73-75 cc for 915 is the NHRA minimum
mine come out low 80's with the chambers opened up a little
rest of the above post looks close
deck clearance can very greatly side to side and end to end
when you tear down a core measure deck at all four corners first

 

[lewtot184]

unmilled '452's are around 90cc. when you get into the 9-10:1 compression range each cc will change compression about one tenth of a point.