72cc heads for 9.3 cr
10-13-2009, 02:29 PM
#1
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72cc heads for 9.3 cr ok i bought my car this way and what im wanting to do is up the cr a little bit but i am going to be replacing my paitriot heads with afr heads.
My ? is i have a ls6 382 with 72cc heads i dont no what cc's the pistons are but the shop my car was built at told me that the heads are 72cc heads and the cr is 9.3 i am looking to up the boost to around 9.5 to 9.7 is there a chart or something i could figureout this stuff. if i was to got to like a 66cc head could i figure out the cr without any other information? Any help would be great!
My ? is i have a ls6 382 with 72cc heads i dont no what cc's the pistons are but the shop my car was built at told me that the heads are 72cc heads and the cr is 9.3 i am looking to up the boost to around 9.5 to 9.7 is there a chart or something i could figureout this stuff. if i was to got to like a 66cc head could i figure out the cr without any other information? Any help would be great!
10-14-2009, 04:13 PM
#6
How is anyone else supposed to know then? Dude, these are things needed to know your compression ratio. And no, theres really not an exact way to measure the change in compression without knowing that either. Why not call the engine builder and see what parts are in there? If its a 382, its probably a 3.905 bore, 4.00 stroke, im guessing aftermarket rods, which is typically 6.125.. do a little research man. Hell, with that info, you can guess at the rest of the stuff and probably get pretty close on the spreadsheet.
10-14-2009, 05:32 PM
#7
your going to have to work the problem backwards and with multiple unknowns at that...
you need the following
bore size
Stroke
Piston dish/dome cc
deck height
head combustion chambers
head gaskets
=compression ratio
you have cr and head chamber volumes your not going to get very close
This is a big guess but assuming
3.905 bore
4" stroke
GM MLS head gaskets
72 cc heads
-12 cc dish pistons (this is what I manipulated to get in the 9.3cr range)
flat deck height (just for a control #)
If you indeed have GM MLS head gaskets then you can get into your cr range by just getting some cometic gaskets custom made with a compressed thickness of .040. Find that out and your piston dish and deck height don't really matter assuming your bore and stroke was inputted correctly.
http://www.csgnetwork.com/compcalc.html
your best bet is to do research track down the build sheet it's somewhere and get it right otherwise your going to have to pull the heads and measure it all yourself which would be a PITA with the engine in the car.
you need the following
bore size
Stroke
Piston dish/dome cc
deck height
head combustion chambers
head gaskets
=compression ratio
you have cr and head chamber volumes your not going to get very close
This is a big guess but assuming
3.905 bore
4" stroke
GM MLS head gaskets
72 cc heads
-12 cc dish pistons (this is what I manipulated to get in the 9.3cr range)
flat deck height (just for a control #)
If you indeed have GM MLS head gaskets then you can get into your cr range by just getting some cometic gaskets custom made with a compressed thickness of .040. Find that out and your piston dish and deck height don't really matter assuming your bore and stroke was inputted correctly.
http://www.csgnetwork.com/compcalc.html
your best bet is to do research track down the build sheet it's somewhere and get it right otherwise your going to have to pull the heads and measure it all yourself which would be a PITA with the engine in the car.
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10-15-2009, 12:11 AM
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guys i understand i need that stuff, i bought the car off of a guy that had this stuff done, i have all the paper work from the company that built the car but the motor its self was built by a company that built the motor and shipped it to the company that built the car and they installed it. i have contacted the company that built my car so i could get all this info and am waiting on a reply.
Also i have done my research and i know for a fact that the bore is a 3.905 and the stroke is a 4.00 wich means it has to be a 6.125 lenght of rod. I dont want to guess and get close i want to be exact if i was to do it i just did not no if there was any other possible way to meassure it and that is why i posted a thread on it.
I am planning on swaping the current heads out to an afr 225 with 66cc chambers i guess i will just have to run a thicker head gasket and go from there
Also i have done my research and i know for a fact that the bore is a 3.905 and the stroke is a 4.00 wich means it has to be a 6.125 lenght of rod. I dont want to guess and get close i want to be exact if i was to do it i just did not no if there was any other possible way to meassure it and that is why i posted a thread on it.
I am planning on swaping the current heads out to an afr 225 with 66cc chambers i guess i will just have to run a thicker head gasket and go from there
10-15-2009, 08:03 AM
#10
If you go to 66cc heads and your already running a GM MLS gasket your not going to be able to get your CR in your suggested range with gasket alone most likely. You need to know what gaskets you have now gaskets can have a huge impact on CR.
10-15-2009, 01:35 PM
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ok i talked with a guy that has done this and he said his started at a 9.3cr and he did the same thing with the same size head gasket and it put him at 9.85 so i think i will be able to get close to the 9.7 that im looking for with a little bit thinker head gaskets.
thanks everyone
thanks everyone
