After talking with a number of reputable sources I'm a little confused.
I don't want to name any names because I don't want to offend anyone.
I've decided to use the C2 turbo head gaskets on 3.5 7:1 Mahle P&C's,
the motor is a 1988 3.2 and I'll be running boost in the .8 -1 bar range
Here's where the confusion comes in, I'm talking with two different guys
that both know what they're talking about, one says remove the .5MM
off the head, the other says it should come off the base of the cylinder.
If you have any experience with this please chime in, all advice will
be greatly appreciated.

 

Just curious, but, why did you decide to use the head gaskets? ....why don't you just hand lap the cylinders into the heads, have one sealing surface, and use some good head studs so heads don't lift.

 

You don't need the head gasket.

Get a set of good head studs.

 

You only use the head gasket with the C2T cylinders because it doesn't use a base gasket. Without a base gasket the deck height will be to low. The base is grooved and o'ringed. So the top side makes the clearance on the deck with the shim. If you shim the cylinder and head on a system that doesn't require it and you were going to be at 7:1 you are going to be much lower than that. To low is not the best scenario either. If you are doing this to simulate a flame ring then this is also the wrong choice. The only purpose of the shims was to set deck height, not prevent damage to the sealing surface under boost.

 

Thanks all for responding to a newbe’s question.

Stephen,
So let me make sure I understand you correctly, you’re saying that the C2T head gasket isn’t a gasket at all but rather a shim to make up for the lack of a base gasket on the C2T cylinders ?
Since I’ll be running a base gasket, either a .25mm or .5mm to set to correct deck height of 1mm, would I be better off running no head gasket since I plan on running relatively low boost of .8 ?

 

I ran the 0.5mm cylinder base shims and also the C2T head gaskets when I went from 95mm Carrera P&C's to 97mm 930 P&C's.

The reason why I did this was because the 0.25mm base shims tend to slide out under high boost applications (1.2+ bar of boost). I also went with C2T head gaskets & ARP fasteners because I was told the C2T head gaskets offer a better seal for up to 1.4bar off boost. Anything higher than this and flame-ringing is recommended. This was Protomotive's recommendation.

I don't expect to run more than 1.4bar EVER, so I decided to install the C2T head gaskets for extra measure.

However, I had to get the base of my cylinders machined down to retain the 7.0:1 C/R, otherwise, as Stephen said, I'd be running in the 6.x:1, which is too low.

Hope that helps?

Generally though, you don't need to run head gaskets. Just make sure the surfaces mate together nicely and use high quality fasteners and you'll be right.

 

The C2T heads are no better or less suited for boost than the 930 head. When properly machined and torqued you will not have any issues with either lifting under 1.3 bar nor base gaskets shifting. If you run 1.4 bar then several things should be done including the flame ring as mentioned. On a standard cylinder without a compression ring you will want to lap the cylinder into the head even though it has been machined. You will see why when you do this.

Turk, the only reason the shim is there is to adjust for deck height. That is all.

 

Stephen.
Thanks for the clarification.

 

Flame ringing is the ultimate sealing method though. At ultra high boost, your heads will crack in half before the flame rings separate

As Juan Ruiz over at Pelican. He's run close to 2.0bar on his drag Carrera with flame ringed 930 P&C's and hasn't had ANY sealing issues whatsoever