Composite Gaskets

[stu e]

Hi All

I've been reading old posts about fitting composite head gaskets.
I understand if the heads are not skimmed by 26 thou you lose compression, can anyone tell me how that will effect the performance? My engine has composite gaskets fitted but did not have that much taken off the face, i was just wondering if they were skimmed if i'd notice any difference, or would it be a waste of time?


Regards Stu

[kev]

If you fit composite gaskets to a 36cc volume head then you'll lose about 0.5:1 on your cr. If your cr is already low then it'd probably be worthwhile getting it back, if higher say 9.5:1 or more then probably not, my opinion.
Your call

Kev

[Sidecarbod]

Originally Posted by stu e

Hi All

I've been reading old posts about fitting composite head gaskets.
I understand if the heads are not skimmed by 26 thou you lose compression, can anyone tell me how that will effect the performance? My engine has composite gaskets fitted but did not have that much taken off the face, i was just wondering if they were skimmed if i'd notice any difference, or would it be a waste of time?


Regards Stu

Bit of a "half educated" guess but you'll probably have lost round 10 BHP, maybe a bit more. whether you'd notice that is anyone's guess but tuning is all about small gains here or there adding up to something that is noticable.
If the heads are coming off for another reason that it might be worth having done otherwise its a fair amount of work for not that much BHP.

This is all JMHO, someone like V8 developments could give you a better idea. (They did a good job on mine).

To do the work properly you need to remove the heads, then do the following on least one piston:-
Put the piston on TDC using a clock gauge, not by guessing! You need to seal the piston to the bore with a smear of grease then bolt a piece of perspex to the head also sealed with grease then use a burette to measure the volume above the piston using white spirit poured in via a small hole in the perspex.
If your not a million miles from Bagshot you can borrow the stuff that you need or I could give yo a hand.


Regards,

P.S. 9.75-10:1 is around what you want, anymore and your going to be have to careful with mixture strength and ignition, not to mention the octane rating of the fuel itself!

Pete

[stu e]

Thanks for the offer of assistance Pete.

I live in Devon so it would be a bit awkward. The heads weren't overhauled when the engine was put together so I may have a go when the weather gets too bad to play. 10 HP sounds like quite a gain for relatively little outlay, the only thing that puts me off is getting the airlocks out when it all goes back together.

Thanks Stu

[Sidecarbod]

Originally Posted by stu e

Thanks for the offer of assistance Pete.

I live in Devon so it would be a bit awkward. The heads weren't overhauled when the engine was put together so I may have a go when the weather gets too bad to play. 10 HP sounds like quite a gain for relatively little outlay, the only thing that puts me off is getting the airlocks out when it all goes back together.

Thanks Stu

Er...Devon, a bit far!

The 10 BHP was a guess, it might be more! V8 Developments are very good, its worth having a chat with them.
You should be OK when refilling the motor with coolant if you fill it slowly and then run the motor up with the rad cap off for a short period. This allows the air to escape and for you to tip in extra coolant whilst the motor is running.

The only rather big fly in the ointment is that you will need to check the preload clearance and probably shim up the drain pipe! er I mean rocker shafts!! (my wife made me type that!) Realsteel to shim kits.

Regards,

Pete