Constant head gasket sealing problems

[jikovron]

Hello I've spent a few months cleaning an early 3.5 and basically doing minor fettle jobs to refresh it, one thing that is causing a minor headache though is that the heads wont seal to the block at all!! I've pressure tested the heads individually and also the block to 80psi and could see any drop over night, however if I fit the heads to the block it leaks air all the way along the joint as if its somehow tracking along the gasket from the outer jacket transfer windows in the deck
I've tried both types of head gasket and they both do the same thing albeit the composite type allowed the jacket to pressurised the oil gallery even!
Has anyone come across this sort of thing ?
Many thanks

[DEVONMAN]

Unless you are torqueing the head bolts up then the fire rings will not fully compress and will prevent the rest of the gasket sealing fully.

[jikovron]

That's with the heads torque to 70lb/ft and going round after to ensure they are all equally tight, it's a proper head scratcher as the air is absolutely blowing out the joint in the valley audibly yet cracks are ruled out and the faces seem flat as far as the straight side of an extra long vernier caliper goes.

[ChrisJC]

How many head bolts are you using? 10 or 14?

Chris.

[jikovron]

Just had another look and it almost seems to be leaking literally all the way around the edges of the gasket even bubbling out of the little v joints that the end seals for the valley gasket seat into !!

[jikovron]

10 torque to 70, and the outer ones were torque to 70, then backed off and redone to 20

[jenand40]

If the heads have been skimmed then the two locating dowels in the block for each head, could stop the heads from fully seating, just a thought.

[jikovron]

That's a valid point certainly ! In this case the heads are untouched aside from being vapour cleaned and ported etc I reckon I've narrowed it down to cheap gaskets showing up weaknesses prematurely, the composite headgaskets were comparatively cheap at 16 quid as were the tin gaskets at 2.40 each, I'll try on different heads and see how they fair before spending out on pricier options

[stevieturbo]

Have you checked that the heads and deck are flat ?

Obviously you've had problems before, or you wouldnt be going to these lengths testing ? So what's the background ?

And no real need for the outer row of bolts.

[jikovron]

All this test gear has come about due to this engine upon first fire leaking coolant onto the exhaust manifold and also emulsifying the oil straight away, I pressure tested the block and heads as separate entities to rule out internal cracking etc and then added the heads to the block multiple times with differing head gaskets, the composite gasket allowed air to pass into the oil gallery and leaked from the front and rear face of the gasket joint, and the tin gasket allowed air to pass across the entire gasket , my feeling with this is that as the composite gasket was compressed uniformly and that the block deck and heads are straight (according to the ground edge of a long vernier caliper) that there are instances of gaskets with inherent faults and also the tin gasket requires the water jacket openings in the deck to be basically freely of any corrosion damage of any sort as the indentation passes really close to the edge of the opening and also I noted the raised indentations dont completely flatten so any leakage path will track around the gasket face unhindered.

Prior to this engine I've had numerous 3.5 engines all without fault and 6 94mm bore engines ironically all with liner problems solely .

[ChrisJC]

In my experience, the composite gaskets compress on the fire rings OK, but the other sealing points (water jacket + oilways) leave something to be desired. I've seen oil appear on the outer join between head & block, where it's migrated from the valley area and just run out.

As a result, now I use a small smear of instant gasket around the oilways and water jacket, and also along the edge adjacent to the valley. I do this both sides of the gasket.

Chris.

[jikovron]

I note some random brands of composite gaskets have a PU seal ring applied to the oil drilling and water passages which is possibly what your emulating with the silicone sealant , I see felpro gaskets on ebay but that's a 90quid gamble on this engine certainly

[stevieturbo]

And it is just one head, or both sides ?

Are the bolts actually clamping down correctly and not bottoming out ?

It makes no sense at all for things to leak that badly, with any type of gasket, especially a composite.

IMO everything would be pointing down to it not being clamped ? ( well assuming both are actually flat of course )

[jikovron]

I'll check the head bolt insertion depth and report back, it's both heads that are doing it and one deck has not had any repairs, I'll pressure test a spare clean engine block and see if that is doing the same thing.

[stevieturbo]

Although obviously the cooling system itself....would never ever see 80psi...and if it did, things would already be in a bad way.

Realistically, Even at 20psi in the cooling system, something has went wrong.

Simple test for thread length etc...just chuck another washer or two under the bolt heads. But it's easy to screw them into the block to see where they bottom out, and what that depth is compared to head/gasket.