compression question
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Joined: Feb 2002
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From: bangor maine
compression question
I had a machine shop build me a 400. he used 351c pistions that wher 12:1 compression ratio im pretty sure nothing else was done shaving or anyhting like that i was woundering around what would my compression be. because im thinkin about swampin to aussie heads (i have 351 4v open chambers) now and the price are not bad on ebay so i was thinin about pickin up a set its in a mud truck so id want the torq off the line right but he told me that this motor will spin 7 thats a bit much for a big block so im not sure if i want off the line torq with aussie or stay with my 351c wich are better at the higher rpms
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Elder User
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From: Porterfield
compression question
OK first off yes get the Aussie heads, for a mud bogger you'll love them.
Now for the 351C 12.5 to 1 pistons your machinist put in there. With the open chamber 4V heads your lucky to putting out 9.4 to 1 with them. Unless your machinist went ahead and decked the block for you, if he didn't then the piston has about .075 to the deck plus the .045 for the gasket and 78cc for the open heads and you get 9.431 Comp.
Now if you put 58cc Closed chamber Aussie heads on there you'll bump up your comp. to 11.600 and you'll still be able to spin it to 6500 Rpm's.
Now for the 351C 12.5 to 1 pistons your machinist put in there. With the open chamber 4V heads your lucky to putting out 9.4 to 1 with them. Unless your machinist went ahead and decked the block for you, if he didn't then the piston has about .075 to the deck plus the .045 for the gasket and 78cc for the open heads and you get 9.431 Comp.
Now if you put 58cc Closed chamber Aussie heads on there you'll bump up your comp. to 11.600 and you'll still be able to spin it to 6500 Rpm's.
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Joined: Feb 2002
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From: bangor maine
compression question
shazam thanks for comming in to save me once agian your the man I still havnt even fired up the motor yet still waiting to see what it can do but Im deft going to have to order up a set of aussie I think the guy that built it wnated it to come alive late make it spin good cause the cam he got and all that dosnt come in till around 2200rpm and the intake is 1500-6000 so my low end torq will be crap till it starts spinning high but after i get teh motor broken in and see what it can spin ill deft order up a set of aussies 11.1 or so comp ratio with super gas would be awesome
thanks agian
nate
thanks agian
nate
