Outer Limits 4x4 Board

1986 RR V8i, 3.9 short motor, 3.5 heads, done about 150,000ks since rebuild.

It runs like crap, missing on one or two cylinders. Known good dissy, leads etc.
Runs hot, upto red, and forces coolant out overflow.
Lots of blowby from rocker cover hose.
No coolant in oil or oil in coolant.
Possibly a little white smoke from exhaust some times.
Compression about 150 on 6 cylinders, 70 odd on one with the the adjoining one bugger all.

My diagnosis is blown head gasket, but would this account for the blowby?

Well the low comp means you have to pull the head anyways, but it could be a headgasket or a slipped liner. Only one way to find out...

Sounds like the poor thing has been barbecued.

Definitely going to have some sort of headgasket dramas but the blowby suggests ring failure as well.

You're gonna have to pull it to bits, unfortunately.

Squirt some oil in the low cylinders.
Then retest the compression.
If it has increases, then more than likely rings.

Not sure if the 86 has a radiator fill plug, but if it has remove it.
With the engine running, a blown head gasket MAY blow bubbles that you can see.

Another option could be a burnt valve.
I just replaced one because the compression was 15psi.

As stated, whatever is wrong, the head has to come off.

Glad to report she's all fixed now.

Pulled both heads, found bits of head gasket inside valley area. Both heads had gasket missing, but only one side had bad comprerssion readings.

Machined 20thou of both heads, recut valves and used composite gaskets.

Goes the way it should have when I bought it 3 weeks ago.

Now to fix the myriad of other little problems.

Anyone have a spare fuel tank for a 1987 RR lying about?