New head - Which head gasket to use???

[Rob]

Hi Guys,

Dropping a new head on my 7m-gte today and cannot decide what head gasket to go for... head was skimmed and rebuilt about 13 months ago and I am told it had no problems on the previous engine (ozzizere's old head). The reason for replacing it is my exhaust studs have gone in the back of my head and it saved time and a lot of messing about just swapping the head over.

I have a metal head gasket that came with the head (used) but I also have a head gasket that came with the full gasket kit when I rebuilt the bottom end of the engine. Looks composite but I could be wrong... (this has been torqued down once, and removed again now... about 2 miles covered until i discovered how bad the exhaust was blowing)

I do not know the condition of the block face, however it didn't appear to have and head gasket issues when it was rebuilt (big ends went)

I am hoping to run around 300hp on the standard CT-26 turbocharger so I was wondering if it is worth taking the risk with the metal head gasket...

Will 12- 14 psi (whatever boost is needed for around 300hp) blow a normal HG very quickly or will I be safe just using a standard one???

Thanks
Rob

[mark3]

1st
throw the old used gaskets in the bin, composite AND metal.

2nd
if the head and block surfaces havent been preped to the metal gaskets manufactures requirements dont bother fitting one of them either, use a Toyota gasket and run boost to about 12psi and it may last...

[Darket]

Right .. befor you do anything you need to check the condition of the blocks surface .....

At the factory the blocks are machined perfectly straight and to a near perfect surface .. its what happens in the years after that will cause you issues such as corrosion on the sealing areas and major overheating that can distort the block... just because your fitting a Mhg does not mean you need to rush to a machine shop and have x amount of material ground off the block for no apparent reason .. anyone that suggests this is talking rubbish.

[Rob]

Originally Posted by Darket

Right .. befor you do anything you need to check the condition of the blocks surface .....

At the factory the blocks are machined perfectly straight and to a near perfect surface .. its what happens in the years after that will cause you issues such as corrosion on the sealing areas and major overheating that can distort the block... just because your fitting a Mhg does not mean you need to rush to a machine shop and have x amount of material ground off the block for no apparent reason .. anyone that suggests this is talking rubbish.

OK that is good news... would using a straight edge and feeler gauges be enough or is there a better way to do this?

Sounds like I cannot re-use either head gasket then?

Cheers.

[Rob]

Just heard back from Andrew Page and they have quoted £32 for a new steel HG. I think that's very reasonable so would be happy to spend that little bit more to make sure it doesn't blow 100 miles down the road

Do you think that would be alright? From what I have read I assume this is what Toyota now fit to the 7M?

Do you think just a normal steel head gasket would be forgiving enough on a non-machined block (that had no head gasket problems with the previous gasket) and also be strong enough for the boost I would like to run?

[Darket]

Originally Posted by Rob

OK that is good news... would using a straight edge and feeler gauges be enough or is there a better way to do this?

Sounds like I cannot re-use either head gasket then?

Cheers.

That will do fine.. i wouldent suggest using the old mhg again .. some people have without problems but its still a gamble.

Also £32 for a metal gasket sounds far too cheap ... this would be the price for a nasty standard composite type ... you'll be paying in the region of £100 minimum for even the cheapest MHG.

You will also need a ARP stud kit.

As for an "non-machined block" the only time this will be an issue is if its distorted or badly pitted .. if not you gain nothing.... the only thing is to make sure that the rear of the timing casing is level with the blocks surface... if it isnt carefully sand it down untill it is .. you seem to know what your on about so youll know what i mean when you look at it.

[Rob]

ok thanks mate, I have an ARP head bolt set already so that's ok

so... dont re-use either of the gaskets, measure the block, then decide which to go for?

Do you recommend using any kind of sealant with the head gasket? I've heard of people soaking it in oil, applying hermatite etc... to get a better seal but i've never done it myself.

[Darket]

there is a copper based silicone spray that some people swear by when fitting MHG's .. i have used it will no ill effects.. as for anything else i wouldnt be so confident