optimal dynamic compression
Thread Starter
Pro
Joined: Aug 2001
Posts: 724
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From: West Palm Beach FL
optimal dynamic compression
What would be the recommended dynamic compression ratio for a 427ci .....running on 92 octane pump gas?
How much cranking PSI would the optimal dynamic compression ratio have?
Tom
How much cranking PSI would the optimal dynamic compression ratio have?
Tom
Burning Brakes
Joined: May 1999
Posts: 760
Likes: 1
From: Greenwich, CT
This site http://cochise.uia.net/pkelley2/
mentions 7.5 - 8.5 for street engines.
I seem to recall Dave Vizzard had some discussion in one to his books.
I'd try the one on SB valve trains. If I run across my copy I'll see if that's right.
HTH
mentions 7.5 - 8.5 for street engines.
I seem to recall Dave Vizzard had some discussion in one to his books.
I'd try the one on SB valve trains. If I run across my copy I'll see if that's right.
HTH
Drifting
Joined: Aug 2001
Posts: 1,500
Likes: 0
From: Holliston MA
Cruise-In VII Veteran
A couple of years back I put together a 383 for my '90. Canfield 195 heads, 62 cc chambers, 6" connecting rods, hyper pistons, 11.2:1 static compression. Hydraulic roller cam 224/236, 110icl, 114 lsa, .502" i, .520" e. .041" compressed head gasket. Dynamic compression worked out to be 8.89:1. On 93 unleaded, the car didn't like more than 27 degrees of WOT timing in a 3500 car with 3.33 gears. Had to back out alot of part throttle timing also. I never ran the car with race gas, so I didn't get to see if it was a matter of the heads not wanting the timing or it was octane limited.
The car was crispy and didn't act like you'd expect with that little timing. Timing was verified to the balancer. Ran a best 1/4 mi mph of 118.2.
I think the 8.9 was pushing the limits, probably a little past really. With the larger bore of the 427 I'd go lower.
The car was crispy and didn't act like you'd expect with that little timing. Timing was verified to the balancer. Ran a best 1/4 mi mph of 118.2.
I think the 8.9 was pushing the limits, probably a little past really. With the larger bore of the 427 I'd go lower.
Racer
Joined: Nov 2001
Posts: 379
Likes: 0
From: Helsinki
Originally Posted by SloRvette
A couple of years back I put together a 383 for my '90. Canfield 195 heads, 62 cc chambers, 6" connecting rods, hyper pistons, 11.2:1 static compression. Hydraulic roller cam 224/236, 110icl, 114 lsa, .502" i, .520" e. .041" compressed head gasket. Dynamic compression worked out to be 8.89:1. On 93 unleaded, the car didn't like more than 27 degrees of WOT timing in a 3500 car with 3.33 gears. Had to back out alot of part throttle timing also. I never ran the car with race gas, so I didn't get to see if it was a matter of the heads not wanting the timing or it was octane limited.
The car was crispy and didn't act like you'd expect with that little timing. Timing was verified to the balancer. Ran a best 1/4 mi mph of 118.2.
I think the 8.9 was pushing the limits, probably a little past really. With the larger bore of the 427 I'd go lower.
The car was crispy and didn't act like you'd expect with that little timing. Timing was verified to the balancer. Ran a best 1/4 mi mph of 118.2.
I think the 8.9 was pushing the limits, probably a little past really. With the larger bore of the 427 I'd go lower.
Drifting
Joined: Aug 2001
Posts: 1,500
Likes: 0
From: Holliston MA
Cruise-In VII Veteran
Sorry I didn't. For what it's worth, the cam from that motor is now in a 398 sitting on a stand. Dynamic compression works out to be 9.3:1 now and cranking compression is 205 psi.
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