When is too much boost too much?

[turbovanman]

Guess I'll try this here, waste of time on the other site, maybe its just me,

I think it would be a good thread discussion, as in all the info in one thread, IE when is too much boost too much?
In my case, stock 6.2 with stock compression, 6.5 head gaskets, studs, good exhaust setup, 20 psi of boost, 25 psi drive pressure, so at what point will it go boom?

For a stock 6.5 with a decent turbo, IE HX40, what is too much? How much does adding studs raise the boost threshhold etc?

The info is all over the place, on different forums, so if we could condense it and people post up their own setups.

Of course, gauges and proper fueling are a given.

I do realize of course we have different turbo's but for the majority of us, it seems the HX35/40/40ii and the ATT are the turbo's of choice and NO, I am not talking about the using and maxing out the stock turbo.

 

[THEFERMANATOR]

This could be a really loaded question with so many variables in it. Some engines will go all day long at 20+ while others let go at the stock 7-8. I know some have run 15-18 on GM-8's with turbo masters and never had a lick of trouble while my 6.5 let go at 12 pounds and blew both head gaskets. The 6.2/6.5 engines don't seem to have any consistency as to what each can take. It's not like the DURAMAX where if you go beyond 500HP to the wheels you better invest in head studs, and at 550 or so the LB7/LLY rods begin to shorten up. The 6.2/6.5 engines all seem to fail at considerably different power levels.

 

[WarWagon]

:iagree: Well said.

Keep in mind this is a high compression light duty diesel that was designed as NA. The first 6.5's only went to 6 PSI boost.

IMO back pressure is hard on these engines. Other turbo's with less back pressure reduce the stress on the exhaust stroke. Less back pressure also reduces the heat trapped in the engine. Plenty of cracked NA engines around so the design wasn't that strong to begin with. 100K was the design goal for warranty purposes. This engine was designed when 50K was the EPA measure for emissions life. (Late 1970's/early 80's era)

TTY head bolts is what gave GM and American diesels a bad rep with the 5.7. Going with studs helps. TTY bolts are a whammy waiting to happen when you want to push the limits. The rest of the block weaknesses are known but, quite frankly, who cares? Low mile take out 6.2's are $1200 a pop vs. high cost of most other diesel engines that can go boom. FWIW I push a known main cracked block to 18 PSI ATT and have done so for 20K miles. It has at least 60K of other hard abusive towing miles and was rebuilt before I got it surplus.

Unless you have the latest design block it is just a matter of time/miles before they fail. Could be a lot or a few.

 

[6.5L]

I think back pressure honestly has more to do with blowing headgaskets that boost pressure does on these engines. I have ran 22psi on an ATT, HX35, and even my GM3 and never blew a headgasket. It all depends on how hard the motor is abused too and how old the head gaskets are. Those which are continually exposed to 18+psi like mine I know will tend to give out a lot faster. Headstuds are NEVER a bad idea though. I think even on stock motors that have NOTHING done to them that they are one of the best investments you could do. My parents 6.5L has not a thing done to it and blew a headgasket at stock levels. I actually peaked my HX35 at 25psi the other day on TTY's so I completely agree too that it could blow at any level. Just depends. That is why I say it is never a bad idea. I am going to get studded and a moose pump this coming summer or maybe winter, depending on time

 

[dmaxx3500]

50-60 lbs?

 

[6.2 turbo]

Had it my 6.2 up to 38 psi with fresh head gaskets,and got a few bubbles in the overflow. Apparently the heads start lifting somewhere between 30 and 38 psi. I'm running 25-30 psi every day now,and it seems to be ok. This is with approximately 18-1 compression.

 

[WarWagon]

Had it my 6.2 up to 38 psi with fresh head gaskets,and got a few bubbles in the overflow. Apparently the heads start lifting somewhere between 30 and 38 psi. I'm running 25-30 psi every day now,and it seems to be ok. This is with approximately 18-1 compression.

With or without head studs?

Next question is what boost level do you need an intercooler? :hihi:

 

[6.2 turbo]

Head studs and the 4 outer cyls oringed. I also torqued the end cyls tighter.

 

[turbonator]

Guess I'll try this here, waste of time on the other site, maybe its just me,

I think it would be a good thread discussion, as in all the info in one thread, IE when is too much boost too much?
In my case, stock 6.2 with stock compression, 6.5 head gaskets, studs, good exhaust setup, 20 psi of boost, 25 psi drive pressure, so at what point will it go boom?

For a stock 6.5 with a decent turbo, IE HX40, what is too much? How much does adding studs raise the boost threshhold etc?

The info is all over the place, on different forums, so if we could condense it and people post up their own setups.

Of course, gauges and proper fueling are a given.

I do realize of course we have different turbo's but for the majority of us, it seems the HX35/40/40ii and the ATT are the turbo's of choice and NO, I am not talking about the using and maxing out the stock turbo.

opcorn:opcorn:

 

[great white]

GEP has stated the Optimizer blocks are good for a sustained 25 PSI.

Not sure if that relates to a stock 6.2 very well. The optimizers are a point lower in compression (20.2:1) and other than the change in chromium quantity in the head castings and molybdenum in the block, I do believe the basic architecture (IE: head bolt arrangement, TTY bolts, gaskets, etc) are very similar if not the same...

 

[turbovanman]

:iagree: Well said.

Keep in mind this is a high compression light duty diesel that was designed as NA. The first 6.5's only went to 6 PSI boost.

IMO back pressure is hard on these engines. Other turbo's with less back pressure reduce the stress on the exhaust stroke. Less back pressure also reduces the heat trapped in the engine. Plenty of cracked NA engines around so the design wasn't that strong to begin with. 100K was the design goal for warranty purposes. This engine was designed when 50K was the EPA measure for emissions life. (Late 1970's/early 80's era)

TTY head bolts is what gave GM and American diesels a bad rep with the 5.7. Going with studs helps. TTY bolts are a whammy waiting to happen when you want to push the limits. The rest of the block weaknesses are known but, quite frankly, who cares? Low mile take out 6.2's are $1200 a pop vs. high cost of most other diesel engines that can go boom. FWIW I push a known main cracked block to 18 PSI ATT and have done so for 20K miles. It has at least 60K of other hard abusive towing miles and was rebuilt before I got it surplus.

Unless you have the latest design block it is just a matter of time/miles before they fail. Could be a lot or a few.

I can't kill mine too, even with a cracked block, lol.

My customer has a 98, wanted a Dmax conversion so bad until his friends 05 needed injectors for $8k, he suddenly likes his 6.5 again, :rof: and now I get to put a new turbo on it, :agreed:

 

[THEFERMANATOR]

I can't kill mine too, even with a cracked block, lol.

My customer has a 98, wanted a Dmax conversion so bad until his friends 05 needed injectors for $8k, he suddenly likes his 6.5 again, :rof: and now I get to put a new turbo on it, :agreed:

I'm calling BS on injectors costing $8K for an 05. They must have padded it and wrote up a lot of other stuff. You can buy all new injectors for one for about $550 a piece, and book time is 7 hours to replace all 8.