11.8:1 Compression?
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: 11.8:1 Compression?
Originally Posted by Mindgame
You talking about a mag base and dial indicator, deck-to-piston-@-TDC, measurement 'dude?
Yeah, I do that too. Even check it on all eight cylinders.
My problem with the "tight is right" arguement is this.... you can't calculate the dynamic clearance easily. Take into account some of the variables we'll need to do that and ask some questions....
How much does the rod stretch at peak rpm or at off-throttle?
How much does the crank flex?
How much does the piston expand (perpendicular to the pin bore)?
Piston rock?
Too many variables for a static check to be the end-all that determines where the piston and head won't touch.
And I'm sure many of you remember this discussion from Advanced Tech. Circle Track magazine did a test a number of years ago showing the effect of tighter quench and found a point of very diminishing returns. .025 vs .035-.040 power differences were less than a % in a 600 hp asphalt race motor.
Just my 2 cents.
-Mindgame
Yeah, I do that too. Even check it on all eight cylinders.
My problem with the "tight is right" arguement is this.... you can't calculate the dynamic clearance easily. Take into account some of the variables we'll need to do that and ask some questions....
How much does the rod stretch at peak rpm or at off-throttle?
How much does the crank flex?
How much does the piston expand (perpendicular to the pin bore)?
Piston rock?
Too many variables for a static check to be the end-all that determines where the piston and head won't touch.
And I'm sure many of you remember this discussion from Advanced Tech. Circle Track magazine did a test a number of years ago showing the effect of tighter quench and found a point of very diminishing returns. .025 vs .035-.040 power differences were less than a % in a 600 hp asphalt race motor.
Just my 2 cents.
-Mindgame
MG,
It's not so much for the HP gains as trying to keep detonation away and concentrate the burn.
I know ya can run .030 and have not tried less.
How many average guys have the tools to check or do any measuring past what a feeler guage will do,not many I'll bet.
Call any rod manufacturer and "try"to get a figure on rod stretch.They don't know or wont tell ya.
Ya certainly need to know the measurements on everything and thats what I said most don't have the tools to measure all that needs measuring.
I have not seen a need to go less than .030 but from .060 to .030 ya can tell a difference in the way it sounds and preforms.
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