Thread: Gasket recommendations for V8 heads, intake, exhaust

Originally Posted by ozscott

Thanks mate. The 4.6 I thought was 94mm same as the 4.0....only stroke difference. They have a 94mm bore gasket... mine is a stock motor so original bore.

HEAD GASKET

Cheers

G`day ,

yes , 94mm hole but 96 mm fire ring will sit on the liner and when it is compressed there is a little more cover .

The elring that is put forward as the factory gasket has a 96mm hole .

I have a used 96mn elring type from a 94mm bore and the liner movement on one cylinder shows that it sure does sit on the liner .

The liners are not very thick .

If these cometic type have little squish when tensioned they will still at 96mm sit on the liner at 97mm i`m not sure .

I didn`t look at your link before posting but if the 94mm bore gasket has a 94 mm hole it may be ok but the chamfer on the top of the liner makes the very top of the hole bigger than 94mm , it would only mean that more area of the fire ring would be affected by the bang and if it would matter i don`t know .

If in doubt ask the people selling the different size hole for clarification .

Cheers

Thanks mate. So you are looking for the gasket to cover the point between the liner and the alloy block to assist in clamping the liner to keep combustion gases from getting between liner and block and keeping any minor coolant leaks from any block fissures at bay?

Cheers

I suppose I will ring Cometic and see if their 96mm bore gasket is the measurement of the gasket hole or the nominal bore measurement (ie they assume a re-bored block and liner to suit...?)

Cheers

Originally Posted by ozscott

Thanks mate. So you are looking for the gasket to cover the point between the liner and the alloy block to assist in clamping the liner to keep combustion gases from getting between liner and block and keeping any minor coolant leaks from any block fissures at bay?

Cheers

G`day , there is nothing to be done about a liner moving downward towards the crank , if there is an air space at the bottom of the liner , the liner can move that way . ( This happens in factory fitting and some will have air spaces and some will be home on the ridge the liner should sit on . )

The only thing that can be done is to make sure the liner can`t move upward towards the head by having the fire ring on the liner .

The sealing from the coolant on the ends seems to be a time thing and something that will happen . If your able to get 10 or 12 years i think your doing ok , i seem to get around 6 years ( that was at almost 11 to 1 ,now it`s 8.23 to 1 or whatever std is ) but i don`t have the heads machined anymore i tidy them myself with paper and the last ones i did i used hylomar and the next ones i do i`ll try the copper stuff , well the next ones i do when i get the mindset will be tin ones and they go on with nothing .

Originally Posted by ozscott

I suppose I will ring Cometic and see if their 96mm bore gasket is the measurement of the gasket hole or the nominal bore measurement (ie they assume a re-bored block and liner to suit...?)

Cheers

I think that`s a good idea , i`d suggest you tell them what your doing and ask what the inside diameter of each hole as in 94mm , 96mm and 97mm bore size gasket and also which one they recommend for a std 4.6ltr and why .

It should be no drama , they should have the information on hand .

Many thanks mate. I am thoroughly enjoying getting down and dirty again. Last time I built up a motor it was 30 plus years ago and it was a cast iron 6 cylinder. Cheers

Originally Posted by ozscott

Just means even less wall thickness....Cheers

Less liner thickness,,
I would like to assume those expensive new tophats I bought could run without being so thick---

Heres a pic of a tophat installed,,
there is a bit of leeway for the fire ring, though it should be kept as small as possible,
I know I've posted a drawing, of where the fire ring is supposed to sit on a tophat, in here before. But the original on my pc has gone like the rest of my data...