Compression readings

[Cahoon520]

I was wondering what a good or good enough compression reading for my j13

mine was:

1 100psi

2 98 psi

3 100 psi

4 100 psi

I am planing on a re ring job anyway as soon as I n find all the parts needed I just anted to know how bad it is.

Thanks

[datzenmike]

It's quite low, but should run just fine as long as the oil rings are doing their job and there is no blue cloud behind you. The most important thing is that they are all close to the same reading. This will allow to to run smoothly.

 

Expect to re-ring it in the near future. A rebuilt compression should be in the 180s and should give a small power increase and better starting.

[Cahoon520]

Thanks

I guess I will order the rebuild gasket kit today and try to hunt down some rings and bearings should I be able to get the rings and bearings from my local machine shop? The are just standard sizes right?

[datzenmike]

Auto parts store would be best. The cylinders should be measured for wear. If they are above the wear limit then the stock replacement rings won't do their job or, not for as long, before you are back where you are now. Chances are you may only need to hone the cylinders to roughen them up and allow new stock rings to wear themselves into a nice snug fit.

 

If they are worn over the limit the cylinders will have to be over bored to match oversize pistons and matching rings. Best to select the pistons you need and take them to whoever is doing the boring so that you get the best fit.

[ggzilla]

I am planing on a re ring job anyway

Why? The cylinders are within 10% of each other, it doesn't indicate a need to rebuild.

 

If your gauge is calibrated, than it is a low reading. But otherwise pay zero attention to the actual reading, only look at the difference between cylinders.

 

The reasons to re-ring an engine include:

- Burning oil smoke (blue smoke) out tailpippe when you let off the pedal

- Burning oil smoke (blue smoke) when you floor it

 

This is not a reason to re-ring:

- Burning oil smoke (blue smoke) when you first start the engine. For that, replace the valve seals with umbrella type seals. You may need new valve guides.

[Cahoon520]

Ya it smokes quite a bit thats why i tested it. I was hoping it was just valve seals. It starts good just turn the key and it starts right away. Oh well so much for the easy way out. Now it should be good for another 41 years. Thanks for your help you guys are the best.:)