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Gtir Motorsport club » Tech room » Help and Advice » Head Gaskets

Head Gaskets

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1 Head Gaskets on 5th January 2016, 9:52 am

hagger


I know this subject has been covered before but can anyone tell me if it would be possible to use an 87mm head gasket on an 87mm bore.I dont think cosworth do 87.5mm or 88mm head gaskets and im not happy to use cometic as so many people have said they are not a great fit. Any thoughts on this would be greatly appreciated.

2 Re: Head Gaskets on 5th January 2016, 11:35 am

Mr B

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gtir technician
gtir technician
Is another minefield of opinions & manufacturers stating block bore or gasket bore size so you need check that with suppliers if not stated.
Apexi (my favourite gasket) always go by block bore size so you order a gasket based on your 87mm block bore & you will receive a gasket with bore around 88mm uncompressed .
Ideally gasket bore wants be 1mm bigger than the block bore .
Cosworth gaskets are very good & a bargain price in uk but size range is shite . Tomei gaskets are worth reviewing too .

3 Re: Head Gaskets on 5th January 2016, 2:23 pm

hagger


Cheers Mr B,as you say its a bit of a minefield.

4 Re: Head Gaskets on 5th January 2016, 3:18 pm

hagger


Just out of interest has anybody used an 87mm gasket on 87mm bore? will this lead to hot spots on the edge of the gasket?

5 Re: Head Gaskets on 5th January 2016, 8:46 pm

Cosmic73

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Sounds high risk to me.
Due to manufacturing difference between parts the gasket wont sit perfectly concentric with the bores so the piston could potentially contact the gasket if they were size for size, especially if you take into account a bit of shrinkage as its compressed.

6 Re: Head Gaskets on 5th January 2016, 11:42 pm

hagger


fair point cosmic.It does make me wonder why Cosworth dont make more gasket sizes as im sure they could sell them.

7 Re: Head Gaskets on 6th January 2016, 8:58 am

Mr B

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gtir technician
gtir technician
Like cosmic says you should not use a matching bore size gasket (use the oem gasket measures to give you idea of required difference), closest you would probably go is 0.5mm, example being I use 87mm bore HG with 86.5mm bore block, Tomei also used/supplied gaskets around 0.5 to 1mm bigger bore.
Gasket protruding could catch piston & also is a heat spot det risk, too recessed gasket is also an issue for heat spot det .
I don't use cosworth much as they not easily sourced or as cheap here compared to UK, apaxi & tomei cover good size options & are about £30-£40 more than UK priced cosworth for me in asia but probably far more in UK/EU . might be worth contacting cosworth for full size options or seeing if will increase size range.

8 Re: Head Gaskets on 6th January 2016, 12:53 pm

Cosmic73

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I've just bough new 86.5mm piston from Erics and they recommended a 87.5mm cometic HG

9 Re: Head Gaskets on 6th January 2016, 2:03 pm

Mr B

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gtir technician
gtir technician
I wouldn't, if you finish block & head to good standard I would use a metal layer gasket at 87mm from any of 3 brands mentioned above.

10 Re: Head Gaskets on 6th January 2016, 2:07 pm

Cosmic73

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what's wrong with Cometic? Have R suffered failures when used?
i'm getting a bit worried now

11 Re: Head Gaskets on 6th January 2016, 2:24 pm

Mr B

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gtir technician
gtir technician
Quite a few had issues with cometic, they have quite poor sealing around bores compared to others, mixed with arp head studs they are a complete nightmare.
Fitted well using original head bolts & sensible boost they should be ok. I use Apexi with 87mm bore for 86 to 86.5mm bored blocks & 88mm gasket bore for 87 to 87.5mm bored blocks.

12 Re: Head Gaskets on 6th January 2016, 2:34 pm

Cosmic73

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i've skimmed the head and will reuse the std head bolts, not planning on going over 300bhp,
Neutral

13 Re: Head Gaskets on 6th January 2016, 5:43 pm

hagger


Hey there cosmic sounds like your building something similar to me.Im not building a big power car as i dont need more than 300bhp.I have also ordered lots of bits from erics ( new 87mm je pistons e.c.t) Mazworx do a Tomei HG and they can drill the dowel holes for the gtir.

14 Re: Head Gaskets on 6th January 2016, 8:06 pm

Cosmic73

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Sounds like we are doing a similar project. How you getting on?
Im going to go with the cometic HG, if it goes ill only have myself to blame. Im pretty much brassic now anyway Sad

15 Re: Head Gaskets on 6th January 2016, 9:48 pm

hagger


im just waiting for a few more bits to turn up next week then i can put it all back together.When its all done i will put up some pics for all to laugh at ;-)

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