Another CR ????
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Joined: Nov 2001
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Another CR ????
I am running a 460 with D3VE-A2A heads on a block with a 10.322 deck. I beleive the CR is 8.5/1 I know this has changed a little as the block is now .030 over now. I am wondering what a set of D0VE-C heads would do to the equation. D3VE-A2A @ 92CC's and D0VE-C at 75cc's. I have seen specs for 429 with D0VE-C's @ 10.5/1 but wouldn't it be lower with a 460 crank/piston combo???? Help!!!
Thanks,
Craig
Thanks,
Craig
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From: Nevada
Another CR ????
The only difference in the 429/460 is the longer stroke of the 460, and that doesn't affect compression ratio.
DOVE or any of the '68-71 75.8cc chambered heads and a 10.322 deck height block should provide about 9.5:1 c/r. That's a base; you need to factor in your overbore, gasket thickness and piston top volume.
This page has a calculator that will give the exact C/R based on your specs:
http://www.bgsoflex.com/auto.html
DOVE or any of the '68-71 75.8cc chambered heads and a 10.322 deck height block should provide about 9.5:1 c/r. That's a base; you need to factor in your overbore, gasket thickness and piston top volume.
This page has a calculator that will give the exact C/R based on your specs:
http://www.bgsoflex.com/auto.html
Senior User
Joined: Oct 2000
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From: arkansas
Another CR ????
Stroke doesnt affect c/r? Maybe I've been misled...
look at the formula:
c/r=swept volume (borexstroke) + total chamber volume [divided by] total chamber volume.
example 429 with 19cc dish pistons, dove heads (75cc chambers), piston is .020 in the hole, and the head gaskte is .040" thick.
658.6 swept volume, 86 cc chamber volume (included -.020 deck clearance) adds up to 8.65 compression.
same thing with a 460's longer 3.85 stroke is 9.21.
if you put dove heads on a .030 over 460, with stock dish pistons, it would end up near 9.5:1.
look at the formula:
c/r=swept volume (borexstroke) + total chamber volume [divided by] total chamber volume.
example 429 with 19cc dish pistons, dove heads (75cc chambers), piston is .020 in the hole, and the head gaskte is .040" thick.
658.6 swept volume, 86 cc chamber volume (included -.020 deck clearance) adds up to 8.65 compression.
same thing with a 460's longer 3.85 stroke is 9.21.
if you put dove heads on a .030 over 460, with stock dish pistons, it would end up near 9.5:1.
Senior User
Joined: Oct 2000
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From: arkansas
Another CR ????
I just tried that link to the comp. ratio calculator...
it's dead wrong, it says with dove-c heads, you will end up with 16.7 compression ratio. I know that's wrong. I have basically the same engine, makes 515 hp @ 5400, 505 lb-ft torque @3900. runs all day on 93 octane (will run on 87, but I like to advance the timing too much)
it's dead wrong, it says with dove-c heads, you will end up with 16.7 compression ratio. I know that's wrong. I have basically the same engine, makes 515 hp @ 5400, 505 lb-ft torque @3900. runs all day on 93 octane (will run on 87, but I like to advance the timing too much)
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Another CR ????
The compression ratio will change if you change 429/460 crankshafts without changing to the matching 429/460 pistons. The stock 460 pistons are shorter from the wrist pin to the piston top than the equivalent 429 piston by about the same distance as the stroke difference.
Just my humble opinion,
John
Just my humble opinion,
John
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From: Nevada
Another CR ????
John's correct - my error in that I didn't consider someone might change the crank without matching the pistons.
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Senior User
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Another CR ????
Car Craft magazine did a build up of a 460 using a '71 block, DOVE-C heads and the regular dished pistons that most 460 engine rebuilders have used, and they came up wih 8.8 to 1 C.R. (they also said using a thinner head gasket would bump up the C.R., they used .051" compressed thickness head gaskets). I used the same set up as they did but machined .012" off the block's deck height and just removed enough material off the heads to clean them up. I believe my comb has 9.25-9.5 to 1 C.R.
Todd
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Todd
BB79RANCH
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