Tahoe Motor Is Blown Up

[Mike K3500]

I wish I had the money to purchase and donate an Optimizer and mechanical 4 plunger to ya for testing purposes... LOL It would be great to see how far the envelope could be pushed.

 

[oldblacksmoker]

I've got a similar broken rod problem with one of my engines. I think it happened because I didn't fix the thumping in the intake (Lifter issue, I suppose). The explosion looks just like yours. I'm just trying to figure out how to build so it won't recur.

 

[6.2 turbo]

O rings only help the head gasket,since it can't blow the next weak link shows up. I researched bbc rods and 396 pistons,about the closest match I can find. This would need the crank ground to fit the bbc rods. I might call Penninsular about the p400 rods.

 

[oldblacksmoker]

I think I have a set of 454 rods.

 

[buddy]

Wow, that really sucks, need to figure this one out, seems odd since most guys break the crank or block first.

How much boost were you running on this build? If it was 40psi and less I would think you should have been alright with 18:1 CR. How did you get down to 18:1? Shaved pistons?

What kind of EGTs and engine temps were you getting?

Any guess on what kind of injection advance you are getting with the modded IP? Or about where you had the base timing set?

 

[turbonator]

I wish I had the money to purchase and donate an Optimizer and mechanical 4 plunger to ya for testing purposes... LOL It would be great to see how far the envelope could be pushed.

he already has an optimizer that he bought from the mil. auctions.... it had bent pushrods and i think broken valves? the rods are all the same between optimizer and earlier motors, all forged... like was mentioned, the p-400 ones might be different, i do not know.....

to bad it blew again, when it blew last time we were looking at aftermarket rods for 454... lots of machining for them to fit though.... but they can be had used for good prices.... the ones we looked at were 200.00 for 8

 

[6.2 turbo]

I had base timing at 12 degrees ,I don't know what the total is. It's set about were it makes the most power in midrange,a little more would give it more top end.

 

[littleboy]

Too much drive pressure from crappy exhaust manifolds?

 

[oldblacksmoker]

he already has an optimizer that he bought from the mil. auctions.... it had bent pushrods and i think broken valves? the rods are all the same between optimizer and earlier motors, all forged... like was mentioned, the p-400 ones might be different, i do not know.....

to bad it blew again, when it blew last time we were looking at aftermarket rods for 454... lots of machining for them to fit though.... but they can be had used for good prices.... the ones we looked at were 200.00 for 8

I think I've got a set of big block rods. One of them I think needs machined from a spun bearing. I'd be glad to donate them if someone would be willing to machine them for 6.2 . This is a good opportunity to put together a better combination.

 

[6.2 turbo]

They would have to be aftermarket H beam,stock big block would probably be weaker than stock 6.5. I called Peninsular,the P400 rods are not yet available,and they only fit the P400 pistons.

 

[sshewins]

Just thinking out loud here, but my cummins friend recently tore apart his VW with the n/a diesel. He was suprised how huge the con-rods were and similar in size to a bbc. Could it be possible that rods from a jetta might be close to your needs? Long shot I know, but...

 

[buddy]

Would you like a set of DMax rods and pistons to play with?

To bend the rods I have to believe you were getting considerable combustion before TDC and also transferring a lot of heat to them. You mentioned the injector spray pattern was more like a straight beam up over 3000psi pop, could it have shot right out of the precup into the cylinder?

Do you happen to know what your drive pressures were and EGTs?

 

[turbonator]

Would you like a set of DMax rods and pistons to play with?

To bend the rods I have to believe you were getting considerable combustion before TDC and also transferring a lot of heat to them. You mentioned the injector spray pattern was more like a straight beam up over 3000psi pop, could it have shot right out of the precup into the cylinder?

Do you happen to know what your drive pressures were and EGTs?

maybe we would give them a try... i know jim was measuring and came up with some numbers, and what needed to be done to them, after supper we will talk about it just to see if it is worth it/ feasible.....

 

[littleboy]

Not sure how the duramax pistons would work with them having a bowl instead of being flat top.... The bowls design is for fuel to be sprayed directly into the bowl. But,the rods come really darn close to working!!

 

[buddy]

The rods are close, which was the main reason I picked them up a while back. The pistons I figured would need some of the top shaved off to work. The bowl would simply lower the compression ratio, be a secondary combustion chamber and also protect the rings from combustion. But if someone could even just use the rods that would be interesting.

 

[oldblacksmoker]

And one step closer to figuring out how to make a direct injection conversion. Probably one of the most radical changes to a 6.5 yet. Please try it!

 

[6.2 turbo]

I would like too try bbc rods,and offset grind the crank for more stroke. Just not sure if I want to do that now. The last time it blew there was a lot of carbon on top the pistons,and head. It looked almost like it smashed ? The fact that the block has concrete in it ,and never gets hot is also a suspect. I had two other motors,one 6.5 stock compression with 38-40 psi boost,it never threw rods,my 6.2 very low compression and 60 psi boost never threw rods. The only radical difference is the concrete. The 6.2 has smaller bores,which might save the rods ? The last time there was no signs of the pistons seizing to the cyl.

 

[buddy]

I forgot about the concrete. maybe the bottom of the block is getting hot, and maybe the oil is getting hot. Perhaps check to see if the oil cooler is plugged and not functioning.

 

[6.2 turbo]

I have it set up with no bypass,not even in the filters. It has remote filters,and I removed,and added some plugs in the block. Oil psi is 80 cold,and hot 40-70. The only oiling problem it ever had was priming after an oil change,I guess because of no bypasses anywhere. I don't know how much power this engine was making,but It ran pretty good. Just not sure if the power and boost was high enough to be the main problem.

 

[6.2 turbo]

Well I took it all apart,I'm leaning towards machining a huge dish in the piston. I drilled a hole in an old piston,they are .650 thick in the center,which is the thinnest part.