Oil Blowing/compression questions

[SGT]

Alright, Aside from all of the other issues that my 78 CJ7 AMC 258 i6 / 4.2l has, the oil blowing out of the dipstick is the main issue that needs addressed. So with the little bit of research that I have done there is only a few things that can be the issue.

The first thing I did was get a new pcv valve and vented the valve cover with a mini filter.... and nothing changed.

So, I decided to do a compression test (not a leak down) and came up with these results:

Cylinder 1 - 85 psi
Cylinder 2 - 85 psi
Cylinder 3 - 95 psi
Cylinder 4 - 95 psi
Cylinder 5 - 95 psi
Cylinder 6 - 100 psi

Then I put a cap full of oil in each cylinder and retested and the results were:

Cylinder 1 - 100 psi
Cylinder 2 - 110 psi
Cylinder 3 - 115 psi
Cylinder 4 - 115 psi
Cylinder 5 - 115 psi
Cylinder 6 - 115 psi

So asking people that have had experience with this does this compression seem good? I believe the compression should be at AMC 150 psi...correct?


Thanks

 

[Torxhead]

I really don't think your compression is all that bad. Although you do have a tired engine, it is not really ready for an overhaul, unless you want to play with that kind of operation. I don't think much of those mini filters, The inlet hole is quite small and the filter is a bit restrictive. There are less restrictive versions available, but they aren't as pretty, but will allow for better breathing.

 

[mtnwhlr]

Yes you have a tired motor with those # but blowing oil out the dip stick is a PVC problem.

 

[Saddle Tramp]

My bet is that the oil out of the dip stick is at least in part caused by blow by. A new PVC/What Ever may help but to me the compression readings you give show the engine on its last legs at best. You can run them that way but the oil mess is most likely here to stay until rebuilt.

 

[SGT]

Thanks for the input guys!

I pulled the mini filter off and started it today and there was a decent amount of white smoke coming out of the valve cover hole.

I am probably going to rebuild it.

 

[mtnwhlr]

I have found that if you have a good engine builder in your area it is cheaper to just buy a long block and give them your core and it will come with a warranty. Unless you want to build it yourself.

 

[Tinman22]

I just tore down the engine that came in the new 7
with about the same numbers

It was blowing oil out of the dipstick it would also blow the breather out of the valve cover--neat!

Ring end gap was a nifty .049 and all 6 skirts had fractured and the upper rod bearing was blown through to the base metal from po's attempt at ignition timing (I guess 63 degrees is a bit much)

Best part was it ran fine and was getting good mileage!

 

[mstar]

Are you kidding .That think is toast. BTW proper procedure for compression test includes:
test battery ,must be fully charged
Clean battery terminals, both ends
test starter motor amp draw should be within specs
block throttle wide open, air has to get into cylinders
disconnect ignition or coil wire
with tester in hole crank 4 compression revolutions not 3 or 5 just 4
did i forget any thing. It's been awhile but that is SOP

mike

 

[truck101]

Warm engine


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