compression test

2

28 fast faton

Member
just tested the compression and they were all around 65 , 66 and one was at 58 or 59. What should they be at. What would a HC head be at. Thanks Guys
 
Depends on the altitude. In Albuquerque, a 6:1 Snyder's head will will yield about 72 to 75 psi. An original head will yield about 50 psi. Also a engine bored out to .125 over will yield higher pressures. In Texas, Louisiana, California (ie sea level) numbers would also be higher.
 
As long as all are within 10% they are good.. Not all compression gauges are created equal,, there can be quite a difference between them.. There are also a number of contributing factors such as how recent the engine has been run, whether done hot or cold,, whether throttle was open or closed,,etc.. Sounds like yours are OK.. Mine happen to be 45#..
 
If it's a stocker around 65 is good to go. Like Patrick said, best within 10lbs. Compression tests are best done with a warm or hot engine, or so I have been told.
 
You said it! Compression gauges are not the same! Some of them are even a little screwed up. My old Schauer (1960s vintage, but seldom used) for one! My new coupe was reading 30lbs and it scared m e. So I put it on my new rebuilt engine from Schwalms with a 5.5 HC head and it read 40lbs. That can't be right! I will take the back off the gauge and lubricate it and see if it make a difference.
Terry






Patrick L. said:
As long as all are within 10% they are good.. Not all compression gauges are created equal,, there can be quite a difference between them.. There are also a number of contributing factors such as how recent the engine has been run, whether done hot or cold,, whether throttle was open or closed,,etc.. Sounds like yours are OK.. Mine happen to be 45#..
Click to expand...
 
6:1 is claimed to add a couple hp over the 5.5:1. The 6:1 is still not available from the manufacturer but should be soon.
 
I am running a 'C' (Model B) head on a stock Model A engine that is bored .080 over. The compression tested 80 psi. I have no idea what the compression ratio is with the 'C' head.
 
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