231 odd fire compression

Anyone done a compression check on your 231 odd fire? What was the approximate compression? I did a check on mine and all the cylinders were nearly the same at 120. This seems low for an engine that was freshly rebuilt with 30 or so hours. I am thinking the previous owner assembled the chain a tooth off?

 

No one on this site has ever done a compression check on a 231 odd fire?

 

Iirc correctly factory spec was 160 and ideally all should be within 10 lbs. I'd run it in longer and recheck. Depending on material your rings may not be fully seated. Since they are all close I wouldn't get antsy.

 

Where do you live?

 

30hours seems to low to get the rings to RELAX into their new home so they SHOULD show a low but even number, which you state is true. Please change the oil and filter NOW, to see if the worst has happened. Look for chips in the old oil . Tear the oil filter open to look for chips in the filter paper. If we pass THAT test, you did not kill the engine. I was trained to look for the WORST possible answer and look back toward a better happier place.

 

Answering from first to last; How many hours do you think it will take to get them completely seat? Do you think it possible the timing chain was installed incorrectly, or am I barking up the wrong tree? I live in Northern California (2500 FT). I will definitely change the oil this weekend before I do anything else and let you guys know.
Thank you very much for the help.

 

What kind of rings were used in the rebuild? Cast and moly rings seat fairly quickly. Chrome moly rings can sometimes take a couple hundred miles or more to seat.

 

Altitude does have a direct effect on compression readings...120 would be completely normal where I'm at, but that's at 6000 ft.
As mentioned above, most important thing is that they're even.

 

Back in the 60's the new car dealers recommended 500 miles for break in.

 

Unfortunately the receipt from the build doesn't specify the type of rings.
I have to put this project aside to move my daughters surprise graduation gift (03 Honda Accord) to the front of the project line. Ill tackle this issue by pulling the timing cover in a couple of months and let you know how it turned out.

 

What prompted a compression check on a new motor? What would make you think an engine builder would not be able to put two dots together on a timing set? Was break in oil used? What initially caused concern? Smoking? Any other vital signs odd?

 

I agree with Daryl. I don't see the issue. 120 across all six pistons sounds great to me. Is the motor not running well? Compression test numbers can vary. Rings setting in (as stated), engine hot vs cold, wet compression vs dry. The important thing is consistency across cylinders, which you have. Unless the motor is running poorly, I'd say you're good to go.

 

On my engine the PO said it was set up to be at a 9.5 to 1 ratio engine. The cylinders are 200 to 215. My point is unless our engines are built the same my numbers don't mean anything to you. I say your numbers are consistent, run it.

 

Thanks for all the input. I am pretty sure the engine was assembled by the previous owner and only the machining was done by the shop. What prompted the compression check is that I have been completely through the ignition/timing and carburation and the jeep coughs sputters and loses power (to the point of needing to pull over) once you have been in 4th gear for a minute or two. Worse on grades, and overheated a time or two as well. Also is slightly hard to turn over (sounds like low battery but isn’t).

 

Checked hot.
Did wet test immediately following dry test. Wet test raised the numbers to 130 to 121 range. I figured there is human error involved as I just used WD-40 shot in with an oil can.

 

Use a few drops of engine oil from a pump type oil can. WD-40 is too light for an accurate test, especially in a hot engine. It flashes off too easy. Probably why you got mixed results between cylinders.

 

Any chance you are running an HEI that is advancing too much? What you describe is exactly what might happen if approaching 45 to 50 degrees of timing.

 

Another thing to check for is vapor lock. If your fuel line gets too hot it can boil the fuel and cause the type of issue you are describing.

 

I was thinking the same thing.