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Old 01-28-2001, 09:08 AM
hey-you hey-you is offline
Join Date: Jan 2001
Location: Canada.
Age: 63
Posts: 116

I recently got some TRW pistons for a 73 440 part# L2388 .040 over. Does anyone know what compression ratio these would be. Heads are stock 906.
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Old 01-28-2001, 02:11 PM
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Locomotion Locomotion is offline
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Join Date: Jan 2001
Location: FL
Posts: 386

From a TRW catalog:

.123 deck clearance - 73.5cc chambers = 8.95
81.5cc " = 8.42
86.0cc " = 8.16

.051 deck clearance - 73.5cc chambers = 10.38
81.5cc " = 9.66
86.0cc " = 9.30

Production tolerences on the deck and chambers vary too much to give an exact figure, but your engine builder should be able to measure everything and tell you what you will be starting with and adjust the deck accordingly.

[This message has been edited by Locomotion (edited January 28, 2001).]
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Old 01-28-2001, 02:17 PM
cuda66 cuda66 is offline
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Location: Beaverton Oregon
Posts: 126

Sure....anywhere from 8:1 to 13:1
Huh? you say?
Well lets look at all the varibles for Compression ratio...
Whats the pin hieght? the lower the pin the higher the piston = more compression or vise versa..
How thick is the head gasket, the thickness of the head gasket changes the combustion chamber size therefore changing the CR
What is the CC measurement of the combustion chamber? have those 906's been cut? are the valves recessed in the head?? all these factors determine the CR.
Are they domed? remember a domed piston increases CR but decreases swept volume.
What about your deck hiegth...are they .030 in the hole or .010 out of the hole??? major differance...the only way to determine true compression ratio is to mock up the piston in the hole and CC it, then do the math, once you have determined what you have then you can machione the parts to get you where you want to be.
On a final note....TRW's are Heavy, have rough machine work but are pretty strong for the money.

Happiness is stomping a BBC with a 318 Mopar
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