slmorissette

Low Compression Results???

7 posts in this topic Last Reply

Recommended Posts

Hey guys,

I did a compression test on my 72 this afternoon. I think I have low readings for some reason. I've been reading on here that 150-200 is normal. My readings were: 1)125 2) 115 3)120 4)130.

I'm unsure if my gauge was not working properly or what. If these readings hold up whats would the diagnosis be?? I'm going to invest in a better quality tester tommow and redo.

I did a leak test using my compressor. It held up fine in all cylinders.

Suggestions anyone?

Thanks again guys,

Shawn

Share this post


Link to post
Share on other sites

Did you forget to open the throttle wide while cranking?

W. B.

Share this post


Link to post
Share on other sites

I had a friend hold the pedal to the floor. I'm going to block open the carb today after work. Hope it's just something I did wrong.

Share this post


Link to post
Share on other sites

While a bit low, those aren't 'endofworld(.swf)' numbers...

Warm engine? Stock cam?

t

Share this post


Link to post
Share on other sites

Cold engine. Stock cam. Recent head work, new valves and springs. Adjusted to 0.008'. I can live with the low reading, least they're semi-consistant.

I thinking the rings are just tired, I'm going to do a wet test tonight, just to confirm.

Any other suggestions?

Thanks

SHawn

Share this post


Link to post
Share on other sites
Guest Anonymous
I did a compression test on my 72 this afternoon. I think I have low readings for some reason. I've been reading on here that 150-200 is normal. My readings were: 1)125 2) 115 3)120 4)130.

I'm unsure if my gauge was not working properly or what. If these readings hold up whats would the diagnosis be?? I'm going to invest in a better quality tester tommow and redo.

I did a leak test using my compressor. It held up fine in all cylinders.

Suggestions anyone? Thanks again guys, Shawn

Your own post suggests your concerns are premature. Unless you know how well your gauge is calibrated, its readings are not comparable to another gauge. If you had readings of 200+ for each cylinder, would you automatically think your engine is Supercharged?

The proof is in the pudding. If your engine runs reasonably well under a load, fires evenly and gets acceptable gas mileage, you do not have much of a beef. If you are unable to sleep, try your gauge on another engine and see what's what or try another gauge. Besides, if you ran a leakdown test, and you found it "held up fine" (whatever that means) this negates the significance of your low readings. If you look at any generic shop manual regarding the use of a compression gauge, nominal pressure and consistency are the primary considerations.

Share this post


Link to post
Share on other sites

Warm engine will help. Possibly a lot.

Try the oil, but it's not a sure thing on an M10, because it sits at an angle...

t

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now