Bottom End Breaking Point

[6.5L]

Ok, I just had some questions about the limit of the stock bottom-end. Sorry guys, no carnage haha So I was thinking. Feel free to correct me, but I think the crankshaft in a GM 509 Block was rated to about 300rwhp? Am I correct? Now, I have the block and all rotating assembly from a International GEP 506 NA block from a military pullout. Did International use a stronger bottom end in the military trucks or is it rated for about the same as the GM bottom end? It had just got me thinking lately. I don't want to keep adding power until the weak points get fixed. I'd hate to have a 395cid paper weight.

 

[3500GMC]

Metal fatigue comes into play. Just how many 'cycles' does one last? Just ask those with 395ci paperweights. .. Mine made the transition at 212,107.

300whp for how long? That's the 10,000 dollar question.

A Peninsular forged crank would instill a bunch more confidence. I think ALL other diesels employ a forged crank.... but ours.

 

[6.2 turbo]

Head gaskets,connecting rods,and spun center 3 mains. This is what happened to me,quite often.

 

[6.5L]

I plan on going headstuds, around 25psi max. And I really do not use all the power often at all. Another 1/8 turn on the fuel maybe. Think it would hold it?

 

[schiker]

Unless its a GEP trussed bottom end its the same as a GM engine with better metalurgy. Not any stronger really from a design point (uses the last and best GM design) just better statistics on quality. IMO its basically better fatigue performance such that it actually meets the original GM design limits.

 

[Mike K3500]

The GEP blocks / heads are slightly beefier, better metals in both block, heads, crank

 

[6.5L]

I am not the brightest on metal and all that, but in a nutshell the GEP crank and block are rated for slightly more than a regular GM block?? That is what I am getting. Are the connecting rods also a slightly better quality??

 

[Twisted Steel Performance]

I am not the brightest on metal and all that, but in a nutshell the GEP crank and block are rated for slightly more than a regular GM block?? That is what I am getting. Are the connecting rods also a slightly better quality??

When I had my GEP balanced the rods were bad out from each other on both ends, and the crank also needed some weight removed , the motor parts are heavier than older GM stuff..

 

[WarWagon]

The TTY heads bolts tend to go first. However the stock bottom end fails just fine on stock power.

Extended WOT full load runs with the GM3 took a rebuilt crack free 6.2 to cracking on 2 mains in ~30K miles. 1/2 turn on the fuel screw and 14 PSI. The engine is still running today. I am curious as to when it will let go. However, I don't worry about it as a used engine is fairly cheap. PIA to swap in... So feel free to push the power level until you break it. After all it would make another article and bragging rights.

IMO the bigger turbo with less backpressure doesn't work the engine as hard.

 

[6.5L]

I feel as though with head studs and another 1/8 turn, I would be fine. I do not have another back up vehicle however and money is tight so I feel that it would be better to avoid breaking things. I still do have my 509 block from the first time, the heads are broke on the one side, but I guess worse case scenario I could swap everything over if not too bad.

 

[1999gmc]

I have to long blocks I need to pull apart and check. I know one is a 506 but I forget what the other one is. But if you end up needing a block, let me know. I have family in Montana so it would be an excuse to get up there to see them. I don't know if the engines are even good, but hopefully some day soon I'll be able to get them apart and check.

 

[6.5L]

well worst case scenario i imagine i would be able to salvage the heads and everything and swap them over to my other block. But if i do end up needing one, i will keep in touch. Thank you