All I have seen is the old data from Cosworth but it seems to show that even out to .475" lift it doesnt drop off on a stock head. Whether that data is relatable to everyone else's flowbenches I am not sure. I would assume the curve is accurate though.

.475"=12.06mm

tephra, I have two friends with IX's that have put in cams and have seen minimal, if not zero gains (dynos were some time apart). I know others have sworn by them but they installed FP4R's and Kelford 272's, same results. Neither of them did springs, and both were on stock FMIC.

I have seen you poking around looking at the BBK as well....on your IX, I'd go that route first.

yup ordered it yesterday

i will get that installed and running b4 any more mods hehe

Hope you got head studs

no.

i have been umming and arring about those.

on the one hand, I have a factory sealed motor, supposedly this counts for something, also as far as I understand, its not boost that lifts the head its detonation, so as long as I am not pinging like a ***** then I should be ok - correct???

on the OTHER hand, doing headstuds its recommended by most ppl, but breaks my sealed motor...

thoughts?

I dunno about that, ask Bryan (razorlab) what happend when he stretched his studs. Granted that was a few years ago but to this day he doesn't really like running more than 25psi on the stock bolts (course that my just be cause the 91oct we have here). I did them with my cams and glad cause my BBK is easily doing 25psi on 91oct and 30psi on e85.

Or you have people like me that dont believe in headstuds on stock appearing turbos. I have run my car at 28-30psi for 36k on the stock ones and so far no issues. Racegas, Pumpgas, and E85 have all been used so every timing combination and a few cam combos and they havent stretched or lifted. If you were going to a LARGE frame turbo then I would consider them, but the cylinder pressure on a car thats not knocking on decent fuel doesnt seem to cause failures.

That being said I could have a golden goose.

which of these 3 are the main reason why you upgrade headstuds?

1) detonation - creates MUCH higher cylinder pressures than the equivalent non-detonation???
2) boost - 20 psi vs 25 psi vs 30psi - personally I think the cylinder pressures are much higher than boost anyways
3) power - obviously a combination of boost and fuel, more power = bigger explosion = higher cylinder pressure.

anyone want to run off some cylinder pressures for #1 and #3?

assuming my head DOES lift, what will happen?

Detonation is by far the greatest cylinder pressure spike, up to 10 times normal combustion.

The significance of higher boost is not the actual pressure but the resulting pressure spike from the greater charge, however, this is spread over a wider crank angle as you increase the boost, so a doubling of torque only gives a modest increase in peak cylinder pressure on a turbo motor, even though the mean effective pressure is in proportion to torque.

If your head lifts you'll get combustion pressure forcing out the coolant and going out the overflow. If not noticed you could overheat, warp the cylinder head, damage the headgasket etc.

yeah so as long i dont get bad knock then I should be ok hehehe

I think putting in the head studs is cheap insurance for that odd chance you do ping or have a boost spike. You can install them one at a time and never break the seal on the head. If you can install a turbo you can do the studs.

Which cam did you decide on?

I personally am going the route of no headstuds. I also do not see a reason risking the factory seal when i have read so many varying opinions. Personally if i ever pulled my head i would upgrade to the L19 studs since i have even heard the regular ARPs are no better then the stock bolts. Who knows...

Tephra, just keep an eye on your coolant, if you start to see any oil in it or coolant in the oil you know you are stretching the bolts.

Oil and coolant mixing is a late/terminal sign on many engines, not sure about the 4G63 but I would expect pressurization of the coolant system and overflow/overheating before making mayonnaise.

oh i thought it was the early sign. The last time i have saw severe pressurization of the coolant system it was a locals 35r setup that lead to the upper radiator hose blowing off and breaking the cam angle sensor. This was with ARP headstuds too.

Maybe I misapply EJ20 experience, but on those the combustion chamber pressure would find the coolant passage first and relieve that way with no oil/coolant mixing, one of my friends used to put the radiator blow off pipe to the windshield so he would see a spray when he overdid the NOS and was lifting the head The water jacket was much nearer to bore than the oilways IIRC. Not got a pic or diagram of the 4G63 headgasket/cylinder head in front of me to compare.