Josh B

This head was o-ringed when I got it and I've been running it on the car for probably the last 10k with a widefire head gasket.

I inspected the deck of the block before I put the head on and couldn't find anything - also put the head on without the gasket (not tightened down) to see if would rock around at all and it did not.

Block has never hit the ground and never had anything drop on it.

I checked the pins and holes and made sure the gasket was aligned on them too.

Thanks for all the questions and ideas. This seems to be a stumper for sure. I guess reguardless of the problem I need to pull the exhaust, transmission, slid back the torque tube and get this short block out of the car. Sure don't feel up to that..... I would be in a lot better mood if I knew where my failure came from.

Josh B

I suppose I should be thankful to have a spare short block but sucks that it is an 86, that it is stripped down and that while it is easier to do I should swap out the rod bearings and reseal the balance shaft covers.

alxdgr8

I wouldn't jump and say it's a failure just yet...still sounds like an install problem with the head not seated properly. Seems like the only way to explain "failure" in all cylinders.

I'd pull the head and double check the install and see if something is catching on something.

Van

One thing you might be able to do is put some paint or layout dye on the head, then bolt it down without the head gasket. That might help you locate if there's an air gap between the two.

I was also thinking, if you had damaged or stripping head studs, could that cause part of the head to not clamp down?

Going back to the paint, I'm thinking about like kid's water-based paint (maybe use watercolors? the point is to not have it dry...) - then put it on the block deck, on both sides on the head gasket and on the head. Bolt it all up, do your leakdown tests again, then take it all apart. You should be able to clearly see where the air is escaping because of the trails in the paint.

But, wait a minute, you said the air was coming out of the air/oil separate.... The cylinders are surrounded by the water jacket - that would pressurize your cooling system - not the oil sump. Now I think your problem is with pistons / rings. Tell us about those... Original pistons? What tolerance group? What rings? how were they installed and oriented on the pistons?

Josh B

Original rings and pistons - nothing was touched on the short block. What is so strange is that there is no scoring in the cylinder walls and how consistent the compression numbers are on 1, 2, and 4.

blown 944

with those numbers it sounds like cam timing is off slightly. The cylinders look good to me.

If you are dead confident that the cam is timed properly, the no start problem could be stuck injectors or the cycle is off on the injector firing (can't come up with a better way of saying it). I have seen that if the harness gets shorted that trying to use a test light on one of the injector leads while cranking will momentarily ground the circuit and get it back in sync.

Also if you are confident the cam is timed right, I wouldn't worry about those numbers until you get it warmed up.

lee101315

Maybe you should try advancing or retarding the cam one tooth to see if your compression improves, but turn the engine by hand first before you fire it up

ilikemy944

This is a replacement cam.

Is there any way the cam could be timed (degreed?) improperly?

I know they are keyed - but it is a web cam - what if...?

Josh - what if you dropped your old cam back in and tried again?

Tom M'Guinn

If all the cylinders had 80% leak down without the cam tower on (when all the valves are shut tight), then it can't be the cam timing. Otherwise, I'd look to make sure the woodruf keys had not sheared.

Have you checked the deck and head with a precision straight edge? O-rings all seated as intended? Seems like it has to be the seal at the head in order for all cylinders to lose their compression.

INURGRL951

I think the problem is in the head what all exactly they do ot it again?

951Saga

Someone please explain how crank case pressurization can be caused by a poorly sealed, cracked head or valve timing issue. Is it possible for air to make its way to the block under any of these conditions?

ilikemy944

Oil passage to the head?

brad-cam

And I would think a poor sealing head, for whatever reason, would show up some pretty nasty coolant leaks around the head gasket, no ? Josh, this is certainly a stumper...

Tom M'Guinn

Agreed, as I understand it:

1. the head was tested on another block and had good leak down numbers.
2. when this head is installed on the car's block, all four cylinders have 80% leak down and bad compression
3. Even with the cam tower removed and valves sealed tight, the leak down on all four cylinders is 80%
4. The leak down air is getting to the crankcase only

Just doesn't add up unless the rings are bad/broken in every cylinder, or there is a great big crack affecting every bore, or ???

Josh B

I am stumped as well. I mean for air to be getting to the crank case it has to be going by the rings. There is no way the head could be cocked in such a way that it would go past the water jacked and into the oil passages at the head. When I initially drained the fluids in the car there was no easily noticed contamination of the oil or water.

It is as if all the rings were drawn tight into the pistons heads so that air could get by. If it was just on one cylinder that would be easier to justify but for it to be all four and with so much consistency too.

If timing were off that wouldn't cause air to be getting into the crank case. I checked the cam tower when it was off and went through all four positions of TDC for each cylinder. The lifters were fully retracted at each point.