Compresion readings

quickchange

quickchange

Well-known member
Took a stock engine out of the pile, fired it up & ran till warm, then tested compresion , 50 LBs on each pot. Question is what reading would one expect on a worn engine, A good working engine, then one with hi comp head, My delivery tested the same came in at 105 Ibs.:):):):o each pot. Tell us all your readings , Derek from a early spring day in NZ
 
My engine was last done in 1961 and registers 50# and it does not leak a drop of anything or use any oil.. I now drive this car almost every day in good weather.. That said, not all compression gauges are created equal, there will be a difference between each one..
 
Marco Tahtaras said:
I did a compression test on my original Fordor last week and got 65,66,68,66.
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;) So are you finally gonna give it that much needed, long overdue rebuild??
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My last compression values before rebuild, were in the low 70's with stock head. Perhaps aided by carbon buildup? :D

Have not checked compression since recent rebuild and HC head.
 
I have about 110 across all cylinders (bored +.40) with a Lyon 6 to 1 head, Jim Briely cam, over size intake valves ported intakes to match a "B" manifold and carb.
 
50-55 is probably ok for a stock engine with a stock head. It won't be fast but the babbit should last a long time. It's more important that they're all the same or very close.
 
There will be a big difference in readings if measured with a warm engine with wide open throttle and no filter-breather on the carb. I picked this up from Brumfield, years ago.
 
The coupe that I gave my daughter with an 18 year old overhaul, .080 pistons and my worse 5.9 Brumfield head measured around 65 lbs. With the engine warm and the throttle WIDE open the numbers jumped to 95 and a little better on some of the cylinders. Don't get me wrong, Brumfield heads are great. This was my first, They just got better and better each time he made a new batch.
 
Purdy Swoft said:
The coupe that I gave my daughter with an 18 year old overhaul, .080 pistons and my worse 5.9 Brumfield head measured around 65 lbs. With the engine warm and the throttle WIDE open the numbers jumped to 95 and a little better on some of the cylinders. Don't get me wrong, Brumfield heads are great. This was my first, They just got better and better each time he made a new batch.
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Checking the compression with the engine cold is improper and will not give a true indication. The engine should always be at normal operating temperature which in my opinion is about 30 minutes of run time.
 
Well worn engine with stock head that's a bit noisey, but doesn't leak a drop of oil has 50-50-50-50 when I checked it early this spring. Power is still fine.
 
Tom Wesenberg said:
Well worn engine with stock head that's a bit noisey, but doesn't leak a drop of oil has 50-50-50-50 when I checked it early this spring. Power is still fine.
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A stock worn engine with plenty of clearance will usually out run a tight stock engine. I know that my rusty 29 tudor that set up for 40 years is purdy swoft.
 
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