(T) Later Metal HG vs Std HG

Old on the left, new on the right.

Metal part number - 55189864

Pic doesn't work for me?

They do for me.
So, are the thicknesses the same or diffefrent?

With a rule (haven't got vernier to hand), new one is 0.5mm as opposed to 2mm of the old style one.

thinner gasket = higher compression
Higher compression = more power
Metal gasket = better able to cope with more power & longer life

there must be a downside somewhere

I've been trying (and failing) to find it too

similar to head when skimmed to max it destroys the non interfierance charectaristic of the FIRE engine maybe?

and damn cant use on turbo need my low comp lol

Higher compression means higher probability for knocking, especially for ECUs without a knock sensor. Proceed with caution...

Yeah that did cross my mind. Have to use the more expensive fuels from now on methinks.

head skimmed to max is still safe.

i think the CR would be around 10.9:1 if this was used on a 'std' 1242.

ive not worked through the math, but Balidey did and i've nicked some of his info there.

also, have you overlayed both gaskets onto each and checked everything is 100% correct, ive heard the oilways dont match

edit: CR is actually a bit lower than 10.9

Yeah I've had them both over each other. Their a perfect match

You can run normal unleaded upto about 10.5 CR with out detonation probs. Over this then a good brand fuel is advisable, or an additive to raise octane is a good alternative.

I was looking for info on this HG a while ago, is that a FIAT part number??? It looks like just swapping the HG over with no head machining will give approx 10.3 ish CR, please note these are rough calcs i did a while ago without actually measuring the piston crown or head, but my head is currently in bits on my bench so i should be able to work it out more acuratly this weekend.

As a rough, and i mean rough, guesstimate, it looks like approx 1.5mm cabn come off the head (or block) without interference. Again, i can't check now as my cam and valves are all apart, but will measure and report back.

As for a disadvantage, you really need a vernier pulley as the head will be sat down further so the timing will be out. But if you have raised the compression to give more power then common sense tells you not to use the FIAT timing marks due to manufacturing tolerances so you should really use a vernier (or offset dowel etc) and a timing disc and DTI to set it up correctly or you could be losing more power than you could have gained with the raised CR.

Another disadvantage, i wouldn't advise using it if you have had any skim done at all or the CR could be way over what you want.

And finally, have you got a price?

Thanks for that info!

Price is £15.10, I think it's before VAT, that is a fiat part number.

Not bad price, seeing as a skim cost anything from £30.
I've just bought a new (standard) HG set so thats going on the 1108 and then i can look into getting one of these thinner ones for my 1242 when i get round to re-building it.

Thanks for letting us know.

Is the metal one the SuperFIRE (1368) "super" gasket?