Compression question...

[Bobert540]

I checked my compression tonight and it read 150psi in each cylinder cold. To me it seemed low since I have a Pro-Tec Rec. Head on it. Any thoughts??

 

[Matt_E]

There are many factors.
Gauge? Many are inaccurate.
What compression should the head give?
Are you using the right threaded attachment for the gauge?
Does the cylinder have porting?
Is the battery fully charged?
Is the starter spinning the engine fast like it should?

 

[Bobert540]

I was told 175-180. I may call Pro-Tec and see what they say.
I am using the correct attachment.
Cylinder is stock.
Battery was fully charged.
Starter was working like it should

 

[Matt_E]

Are both holes even in compression?

Try to measure a different motor with the same gauge, to get a comparison. (Or, use a different gauge on your motor).
I usually test my gauge by testing a motor with known good stock compression.

 

[Freakrider]

pro-tec rec heads are rated to elicit 175 psi...I have two of them...

 

[Duster8]

I just had a fresh rebuild and my compression is around 130 per cylinder. so if i put an aftermarket head on it, would that make it around 150 per cylinder?

 

[Freakrider]

cheap auto parts testers have given me low readings like these two have indicated...bought a craftsman's and it makes sense.

 

[Matt_E]

I just had a fresh rebuild and my compression is around 130 per cylinder. so if i put an aftermarket head on it, would that make it around 150 per cylinder?

Depends on what head and domes you buy.

 

[chattin]

I just built a brand new 701 with the ocean pro head.. and I am only pushing 150 psi... i checked it 5 times... all the same.. I am at 5000 feet though.. I could probobly mill the head a little but it is in a back up blaster I just picked up... so no biggie... it will be reliable..

 

[Matt_E]

The altitude does you in.