b727pic

iTrader: (1)

I need some real world info here guys....please no speculation or "I once heard of a guy...."

I am currently in the process of tuning my Procharged 408, currently I have reached 13 PSI through the airfilter and Max P1SC-1 impeller speed. My plans are to install my F1-C after I have totally dialed in the OLSD tune on the P1.

My engine is an Iron block 6.0L with ARP studs squeezing cometic .035 gaskets under some Dart 225's.....SCR is right at 9.5:1

so here is the million dollar question.....at what boost level have folks started having head lifting / head gasket issues? I have seen some pretty wild boost #'s floating around and just wondering just how far into 3bar territory can I expect my heads to stay attached to the block???

02SSLE

iTrader: (26)

I was told by ETP today that a member on here similar setup runs 30psi of boost on same short block just ETP heads. The customer told ETP he didn't experience head lifting till about 26psi. The head bolt's start to stretch.

HUNTER02SS

iTrader: (24)

The head's lifting at a certain boost pressure isn't going to be the same for everybody. It depend's on the tune also. I started lifting then head's at 15psi, but my exhaust was very restrictive trying to push all the exhaust through a single magnaflow catback.I now have cutout's and o-ringed the head's and pushing 18psi and everything is good.I also run race fuel to help with the detonation to.

HUNTER02SS

iTrader: (24)

My other question is since you are tuning with the P-1 on there now and switching to the F1-c won't you have to re-do all of your tuning again. A bigger blower equal's more air. Not flaming,just wondering!

b727pic

iTrader: (1)

I am sure there will be some retuning to do. due to the fact I live in california I wanted to build a good box tune for the P1 as it it is CARB certified. My plans were to gradually max out the P1 "can" the tune for future P1 reinstall smog recert day, then start in on the F1-C. I figured Knowing I was safe up to 15 PSI then gradually spooling up was a fairly safe way to approach the "tuning issue"

b727pic

iTrader: (1)

This is exactly what I was talking about, some folks are getting deep into the 20's while others have trouble much past 15 PSI.

My way of thinking is the cylinder is simply a container being held together with bolts. I would not think that flow would enter too much into the "containers" ultimate strength....meaning pressure is pressure right? why would one motor be ok with 15 and another good up until 26...assuming identical block, studs, head combo's???

b727pic

iTrader: (1)

I can see where detonation is a bad thing, my AFR at max boost and 6500 RPM is low 11's, fuel pressure is 76-77 PSI with 0 KR and up to now only 11 degree's of timing.

I also have a restrictive exhaust setup with JBA shorties, Highflow cats, and a corsa touring 3" catback. While I am sure this is why I have 13#'s of boost on a 408 with a little P1, I am still thinking pressure is pressure regardless of how it gets there???

Texas_WS6

iTrader: (9)

The pressure you read on the gauge is not what lifts the heads. What you are reading is the resistence into the cylinder. What I mean is some people have very good flowing heads, intake and cam valve timing which might make x HP at 15 psi were others with poor flowing combos will have to have more psi to achieve the same power. The internal cyl pressures are what lifts the heads, and what dictates that is the power developed. Assuming great fuel and no detonation, the real question should be at what power (which equals internal cyl pressure or Brake mean efective pressure, BMEP) does your head stud/gasket combo, tend to lift.

Thats my two cents, and I feel your question is a good one that I would like to see answered. Problem is there are so many different combos out there, it is realy hard to answer that one as left. Maybe some with a similar combo as yours can give you a resonable answer. Can you give more detail on your combo?

b727pic

iTrader: (1)

I will have to look up some more details....on the road at the moment.

Off the top of my head

408 CI
9.5 SCR
DCR I will have to look up, but as I recall it was less than 8
Dart 225's flowing 315 @ .600 Intake
Cam: 224/232 600/600 114
LS6 intake
JBA shorties with catted midpipes, Corsa 3" catback
Devils own Alky: not currently in this equation, hooked up but not in use.
13 psi via a procharger P1SC-1 @ 6500Engine RPM

Fuel is a totally custom modified OEM tank, with external surge tank. Internal Walbro, with a staged Magnafuel 4303. Boost reference regulator. -8 fuel feeds and OEM -6 return. Base pressure set at 60 PSI, Logged fuel pressure at boost is 76-77 PSI.

Let me know what other info you need be glad to supply, would really like to get everones thoughts on this.