SlosIIk

Hello all, I was wondering if someone could help me out and tell me what the measurement of the cylinder head combustion chamber on a stock f20c is across. What I mean by this is the diameter of the ring on the head side of the chamber. I know that the oem headgasket is 87.8 and the block is 87 but could someone please measure the head across the chamber. The reason I ask is that I have a fresh built engine with a word ticking noise. The block and pistons are at 87.5 and the gasket is the oem 87.8. The block and head has been surfaced. The ticking is leaving a lot of people clueless. So I called T1 and tony palo said it could possibly be the piston just barely kissing the edge of the chamber on the head but to rule that out if the chamber on the head is 87.5 or larger then that would give clearance for the slug. Thanks to anyone that could give this measurement

SlosIIk

Anybody?

downloader

how much did you machine the head and block? if your in the specs your ok. I would think that the valves would hit the piston before the piston would hit the head.

legros

Not sure but smaller then the bore because of the quench area

SlosIIk

just surfaced, I just dont get why cp pistons poke all the way around and not just in the middle. i even tried them in a stock block and they poked exactly the same

chris_barry

Pistons can touch the edge of the combustion chamber at 87.25mm bore.

Pistons come approx 1mm out of the block, gasket is thinner than this so pistons actually protrude into the void/combustion chamber in the head. They just catch the edge of the combustion chamber.

The piston is travelling very slowly at TDC so the touch will just rock the piston causing slap like noise.

You can machine at least 0.5mm off the head before it will hit on the flat of the squish area. ( allowing for approx 0.030 running clearance)

Pull the head and if it touching its only going to take a slight lick with a die grinder. Put an old gasket over the machined surface located by dowels to protect the head if you slip.

SlosIIk

lol I dont trust myself to do this, would a thicker headgasket fix this as inline pro will make one for about 125

chris_barry

Yes, but you will probably find its probably only touching in one place on one cylinder. Wont take much material removal to fix. If you are worried about slipping use something small like a dremel with a tiny sanding disk.

s2000Junky

I know the ap2 head has like 89.4mm if I remember correctly. It came up in conversation when I went with oversized 89mm CP pistons. The ap2/ap1 pistons are the same 87mm, so I’d be surprised if the heads differ enough for this to be an issue. If your having clearance issues with the head, it would probably be a valve, or inside the lip of the quench area. The lip does taper in slightly though, so if the head is milled down a lot, it would reduce some of the outer clearance, still don’t think it would be enough to hit the lip portion though.

SlosIIk

head has never been milled, just surfaced once and block twice but nowhere near out of specs. it was decked once when benson sleeves went in then valve dropped and one sleeve had to be redone so it was resurfaced again, but its makin a clicking like noise, we have tried everything, from new rocker assembly to 3 tensioners, injectors, cams and gears etc. finally i called tony palo and he said the noise is one he has heard several times and he would say his bet it piston to head contact. he also said on a slight bore it has happened. if it made contact with valve id have thought comprssion would drop due to valve being tweaked. but comprssion is 210-215-210-210 so idk