How much boost can you give a 12 Valve before you run into head gasket issues?

 

I have been told that if you keep it under 50lbs you'll be OK. I've been running mine at 48lbs with no problems

CRIS

 

Cylinder pressure is the key factor in head gasket failures........boost is only one factor.......timing plays a key roll in cylinder pressure........advancing the timing allows the cylinders to start filling sooner in the stroke so you can often get a larger air charge into the cylinders in the same amount of time - this also raises cylinder pressures without raising actual boost........how the truck is used and the rest of the mods that have been done also play a role..........this is why we see variations in boost levels and gasket failures......some guys can't keep a gasket in at 50 psi where as others somehow manage 60 psi.......A general rule of thumb would be 50-55 psi as the limit.

 

When timing is advanced in our diesels, the point at which fuel is injected is advanced earlier into the stroke, thus creating higher cyl. pressures.

Earlier opening valve duration is only changed with a different cam profile.

Or am i missing something??

 

So 40psi and stock timing is good forever

 

Well if you are on a HX35 you are overspeeding it and running it out of it's efficiency map when you are pushing 40psi of boost, 35psi is about the max for efficiency and 38psi for compressor speed.

 

I though so, but when I bought the 14CM non gated housing I was told about 34 psi was the max it would achieve, but I can get to 39-40ish.

 

You might be able to get that high for boost but it isn't as efficient from what I hear. My PDR 35 hits 42 pounds without a problem. But I do notice a slight power loss when it is that high. Not so much as loss but just don't feel it as much as it does when it is around the 35 - 39 pounds of boost. I am hoping that my 3000 gsk might help out a little for power at that boost level. Though I really don't need it that much, most of the time I am trying to let it shift when I am watching the boost and tach go rocketing to the right

Then look quick in the left rear mirror watching the smoke off the tire...

 

The 14cm will lower your EGTs but it will not change the compressor traits. If somebody told you your max was 34 either they underestimated the amount of fuel you were pushing or you misunderstood what they said, that it should only push 34psi.

 

Yes and no.......true, only a cam can alter valve timing however, the cylinder pressure increase is coming from the larger air charge that the extra fuel injected sooner in the stroke creates in the form of more boost, sooner in the stroke.......this is why advancing the pump timing doesn't directly increase peak boost but does increase cylinder pressures.

 

Oh I gotcha, i see were your coming from