90 compression on 135 hp

[WinnerCougar74]

I just ran a compression check on a 1974 Chrysler 135hp. It was about 45 degrees outside and the engine was completely cold and has not been run for about 3 weeks. Exactly 90 on all 4 cylinders. Are these acceptable numbers?

 

[pnwboat]

90 pounds is lower than you'd want to see, however, considering the conditions, 45 degrees, it might affect your readings. Also if your starter is not spinning the motor at normal cranking speed, it will affect the readings. The good thing is that there is not a significant difference between the cylinders. I don't think that you should worry too much about the actual readings until you get your starter issue resolved.

 

[jerryjerry05]

The temp shouldn't make any difference.
The 90# is low but that could be the way the
test was performed or the gauge used??
But 90 on all 4 is good.
With a different gauge you'll probably see
better results.
Harbor Freight or any tools made in China
will probably give bad results.

I was selling a 2002 225EFI Mercury.
The buyer said he wanted a new compression
test. The numbers I had gotten were all about 150#
He opens his new Harbor Freight compression
tester, hooks it up and the first reading was 85#
and the second was 90#
I told him stop and well use a good tester that
I owned.
Got my Mac tester out and the reading went to
150 on all 6 cyl.
He said he's returning his new gauge as soon as
he gets home.

 

[WinnerCougar74]

Great story, yup mines a Harbor Freight, Prolly some what good even with this gauge that they are so similar. Thanks!

 

[jerryjerry05]

The HF gives results just not the right results.
The good is all cyl. are the same and that shows
they're probably ok.

 

[WinnerCougar74]

Just tested with a new compression gauge (Blue Driver $40 on Amazon) now I get 140-140-142-140. Harbor Freight gauge is junk.

 

[jerryjerry05]

It's amazing what Quality can do for you!!

 

[The Force power]

It's amazing what Quality can do for you!!

Jerry, you have been saying this for years and we all have to find out personally

 

[jerryjerry05]

I bought mine from the MAC tool guy,1986/7 185$
It still works better than most!!
There are some things from HF that work good, I
bought a battery load tester 25$ and it works good.