how much boost before she'll blow???

[mudduck]

so i did a ton of research before i made a side mount turbo for my 91 7.3, im using an external wastegate that was set at 11lbs and never had any problems. but i keep ripping the skirt inside the wastegate every few months, going into winter i have a huge list of things i need to get ready on my truck and i know a new wastegate (again) should be at the top of the list but im slackin.

im really just curious to see how many of you guys have blown these things up by boostin too much and how much boost were you pushin . just regular intown driving im hittin 15lbs which made me very nervous at first but the past month that my wastegate has been broke im starting to wonder where to draw the line. ive raced a few trucks around town and im hitting anywhere from 20-26lbs of boost when im on it and no problems so far. i know im skating on thin ice here. the only things done on my engine are this
-pump cranked all the way
-side mount turbo
-road draft tube

am i just lucky or have others got away with this on a consistant basis?

 

[The Warden]

I've never actually lost a head gasket (I replaced my head gaskets in 2004, but that was mainly PM and I was digging almost that deep to replace the lifters; figured I might as well go all the way), but IIRC the rule of thumb is you don't want to go much over 12 PSI with the stock head bolts. I'm not sure what the "true" limit is with head studs, but I wouldn't want to go above 15.

IIRC some have pushed it past 20 without any major modifications (i.e. lowering the compression ratio), but last I knew, the jury's still out on how long the head gaskets etc will survive under those conditions...personally, I wouldn't want to push it on an engine that I don't want to leave me stranded on the side of the road when I least expect it.

Just my $.02

 

[93f250idi]

dyoung got away with mids 20s boost numbers for a while. he never had any problems untill he hit 28 psi. i would say keep it around 15 and youll be fine. if your feeling brave keep hitting 20s and report back to us and let us know how long it lasts.

 

[Ididriver]

What turbo are you using to push 26psi? Did you use the old style rajay kit or was it a custom sidemount design? I'm very interested in this setup.
But to answer your question. On the 7.3 the stock headbolts are good to 15psi. So personally 15-17 psi is all I would take it on the stock head bolts.

 

[icanfixall]

I really think the bust pressure depends on the rebuild or the original engine made at the factory. Not all engines come out the same. Machine work and how something fits togehter are the real tells. With my build thats publiched below I could maybe hit 30 lbs but would I.. Nope.. Its not worth it to me even just saying that seems wrong. My original engine with well over 275 or 375 thousand miles on it still pulled great with the original passenger side head gasket.... When I cavitated the block around 180 thousand miles the shop that did the repairs wouldn't change the head gasket even though it was so easy to do with the engine out of the truck. I'm sure they were thinking I'd be back later with a blown gasket and the labor was more appealing to them.. Well that never happened. They threw the dice and came up loosers. I personally rarely rev past 2500 rpm. I have seen the rev limit twice.. Some can run bounching of the limits all day long... And these engines can take that kind of work too. So I don't think there is a answer that will qualfy as the absolute bust pressure. A good machined block and heads with a quality head gasket plus properly installed studs is the key to keeping it running. A 2 or 3 thousands mistake near any rire ring sealing surface and you have a blow torch cutting the block and heads. Then there is nothing left but a boat anchor for the heavy parts. Sorry I couldn't give you an answer better than this as to the bust pressure....

 

[typ4]

I think bust pressure is directly related to how hard you squeeze the ummm , yeah those.

 

[mudduck]

its a sidemount that i made at my shop, garret turbo. i do a lot of wheeling with this truck and the tach see's 3k often but i also rely on it to get me where im going everyday all year round. think im just gonna slap a new wastegate on and set her for 15

 

[Thatguy]

I don't know if this helps or is even relevent but I used a GM-4 on my tired 6.2L and when the wastegate froze shut (actually I wired it shut) I regularly boosted it to a peak of 22 psi ........ 26 psi should have been easy with a 6.9 or a 7.3..... The goal should not be the amount of boost but the amount of air you flow. A bigger non wastegated turbo that flows twice the air at a lower pressure (like a big rig turbo). There is a turbo (the A Team Turbo) that is used on GM builds (I used one on my copy of a P400 optimizer) and often wondered if it would feed a 6.9/7.3......