How much damage can a blown head gasket do?

[Growlin8]

After thinking I needed a new camshaft it now turns out the head gasket has blown between cyl 6 and 8 resulting in no compression. Problem is I may have been driving it like that for a while!

Any idea if this could have damaged the head or block, or anything else? Head comes off tomorrow to take a look but can't wait until then before if anyone else has any experience of this!

[GreenV8S]

Worst case the engine could be severely damaged and beyond economic repair. Best case you just need to lift the head and replace the gasket. There's really no way to tell where yours will fit between these two extremes.

[chris52]

As has been said you could have done some damage but with it only going from one cylinder to another the chances are it will just need a replacement head gasket, the blocks and head are alloy so a blown head can eat away at the alloy so you may if your unlucky need to get the head skimmed in which case you will have to do both heads plus this will knock out the preload so shims will be needed at the base of each rocker pedestal. Its all guesswork at the moment so fingers crossed its just a gasket.

chris

[blitzracing]

If you do find minor damage, a bit of Red Hermetite may fill it in with the gasket. Worth a try before you start the expense and agro' of skimming.

[chrispitman]

Do you have to get the head skimmed if your changing the head gasket.

[Growlin8]

Went into workshop to see it last night. They reckon I was lucky - both block and head looked bad! Block cleaned up okay with no pitting but head is pitted and so off for maching (both heads) to be on the safe side. Also found pad on a rocker had gone and worn camshft lobe. So it is going to be an expensive job - only good news is it will go a hell of a lot better when it's fixed!!

[rev-erend]

I guess someone has got to say this - make sure it's the head gasket that has gone and not a liner that has slipped or has cracks behind the liner.

Has the garage doing the work got TVR V8 experience .. ?

The reason I mention this - is you could fix the gasket and still have the same problem ..

Edited by rev-erend on Wednesday 20th May 12:07

[Growlin8]

Thanks for the comment. The garage has been reccomended by several other TVR owners so I am confident they know what they are doing.
The gasket was completly burnt away between cyl 6 - 8 near the head bolt. How can you tell if it is a problem with the liners?

[chris52]

Growlin8 said:

Went into workshop to see it last night. They reckon I was lucky - both block and head looked bad! Block cleaned up okay with no pitting but head is pitted and so off for maching (both heads) to be on the safe side. Also found pad on a rocker had gone and worn camshft lobe. So it is going to be an expensive job - only good news is it will go a hell of a lot better when it's fixed!!

Make sure they do the pre-load, if the head is being machined your gonna need shims at the bottom of each rocker pedestal to compensate.

Chris

[spend]

Make sure the inlet manifold is 'adjusted' to match the heads sitting lower (splayed out) - I'm in the grind the ports to match camp on that subject

Adjustable push rods make a lot of sense if adjusting the rocker geometry - skimming heads effectively drops the valve stem height and shimming the pedestals means to an extent that the rocker is 'dipped' compared to original?

[rev-erend]

Growlin8 said:

Thanks for the comment. The garage has been reccomended by several other TVR owners so I am confident they know what they are doing.
The gasket was completly burnt away between cyl 6 - 8 near the head bolt. How can you tell if it is a problem with the liners?

The liner would sit lower that the surrounding block .. by about 1 ~ 2 mm .. it must be level.

As for leaks behind the liner - these are caused by the block being to thin or off centre and crack arrear in the alloy .. you cannot see these obviously because to the liner. What is seen though is water pushing up the gap between block and liner.. and escaping into the cylinder or across the head gasket face..

Only real fix is to fit top hat liners which is what Rover should have done in the first place..