Mechanos

By stock 24V, I'm talking about the stock, head gasket, head bolts, internal pieces-parts, etc. I've got an '01.5 with the 47RE. I have an Edge EZ, BHAF, and 4" straight pipe and I have the wastegate disabled on the turbo so when I'm fully gettin' it, I'm building about 33psi of boost. My tranny is starting to go (I think it's the TC acutally) and when it does I'm going to upgrade to one of the aftermarket trannies that are capable of holding up to even more power than I'm making now. When I get the new tranny, I know I'm going to want more power and will probably drop in a new set of sticks.

As the engine stands now, when I'm pulling my other truck on the gooseneck, I have enough boost to keep the EGT's out of the danger zone.... even when I was flogging it up Vail pass on I-70 (both directions for those who know the pass). Now I'm pretty sure that when I add more fuel, I'm going to need to cram some more air through the engine to keep the EGT's in check. Since my turbo is already running on the ragged edge of it's efficiency, I realize that a new turbo will also be in order. That brings me to my question. How much boost can the stock upper end hold before I need to look into new/upgraded head gasket (or fire ringing), HD head studs, etc. to keep from launching the head through hood? I have no real basis for how much boost I'll need, but I'm thinking somewhere around 45psi ought to do it. Any suggestions on what size turbo/exhaust housing to get? (Oh yeah, I'm thinking about adding 115hp injectors).

CTD NUT

Assuming cylinder pressure won't be excessive, the stock HG and head bolts will be good for 45 psi......with studs, the stocker can has gone to 50+psi, but you must realize you will be pushing your luck at that point. It is a safe bet that if you plan on twins for more air, you will be wasting your time with the stock HG. O ring/fire rings will be the only way to go for a durable set up past 50 psi.

Beast2B

I have read anywhere between 40-50 psi for safe operation. I personally won't go over 40, but gaskets have blown below that... Re-torquing the head bolts can help, 12mm studs help more, etc.
as far as turbo, an hx35-12 from a manual trans truck will be a cheap/small step in the right direction, but any of the s300 based turbos will get you where you want to be.

cumminsdriver635

45psi is about as high as I would want to go with one. Some have put 55psi or more through their's but i think they are on borrowed time. With a bigger turbo you wont need more boost really. A bigger turbo will flow more VOLUME, so you dont really need more boost; just the cooler air that the bigger turbo provides. Its hard to explain, but an HTB2 at 40 PSI will do much better than an HX35 at 40psi. Its hard to explain, but that is how it works.

Eric

storx

its a complicated graph between drive preassure, boost, and fuel.......

Beast2B

not to mention the less-than-tight tolerances on factory parts! one engine may handle 60, another may fail at 40... about the same as asking how much power the stock clutch will handle, or a stock auto trans.

BigBlue

I'm holding 40psi and have been for the last 3 months or so. I was hitting 50 there for a while.

Upallnight46

I'm maxing out at 28 PSI with the same setup, stock everything and disabled waste gate. How can I get 33 PSI like him?

VADSLRAM

I can't say for boost but I have experience in the Auto tranny department. They self destruct behind a bone stock muzzled Cummins. You put more air and more fuel into the beast and your tranny will become a spectacular oil stain on the ground.
Personally if the engine is running I would do the tranny first then boost and fuel... You're less likely to end up on the side of the road cursing that way.

KATOOM

If you have no plans on upgrading the turbo then this is all mute..... Because the HY35 maps out at about 30 psi and starts building more heat than its doing good, and becomes unsafe. So in point, you'd probably blow up the HY before anything else if you try to push it that far.

And storx is right on the money. Drive pressure is what causes the problems you're concerned with, not necessarily boost.

Upallnight46

I have a 45gt turbo that I am going to put on when i get the adapter plate, is that to big? My tranny has been rebuilt and beefed up a bit. I have a bully dog gt but no other upgrades

KATOOM

Not familiar with that turbo.

Upallnight46

It's a cheap one. I'm a redneck on a budget, a tight budget! Lol.

gorms

If that is a Garret GT45, I think they run up to ~80mm compressor, would be too large as a single turbo, pretty good as the atmosphere turbo in compounds. Would need to know what the specs are to be sure. Careful of cheap turbos.