Tahoe motor rebuild

[tanman_2006]

yeah timing melt pistons. it happens to common rail cummins guys all the time because only off the shelf tuning is availble really beseides uber expensive standalone stuff. this leads to stacking which advances the timing dramitically and melted pistons start occuring rapidly

THEY HAVE A WEAKNESS! artay:

 

[6.2 turbo]

I have 21 crankshaft degrees of timing on my Cummins,stock was 12,all though I had to oring the head. It gives it better top end especially with a partially locked governor.

 

[Woody35]

not syaing advancing is bad on a cummins just saying some of the common rail guys advance too much because not enough info is known on the boxes and programmers they use so sometimes they cross that line and melt a piston. happens a lot less on 12 valves because you have to physically turn the pump to advance it.

 

[6.2 turbo]

Bought a DB4 pump on ebay for $40 I'm hoping to use this on the 6.5 . Also I am debating on getting the crankshaft balanced,and maybe the pistons and rods.

 

[buddy]

On the 6.5 I run nearly 45 degrees of crankshaft advance at fairly high RPM and high fuel rates. That is measured as 22.5 degrees camshaft timing. The pop pressure will effect actual injection event and precombustion chamber delays actual full ignition. I never hit that value in normal acceleration or driving, but commonly am over 40 degress crank timing in acceleration.

You dont hear about melted, and not really a whole lot of broke 6.5 pistons either. More likely crankshaft or head gasket are going to go before the piston.

 

[6.2 turbo]

My old 6.5 had a broken piston,and my one parts motor .

 

[buddy]

There are bound to be some, but most likely because a valve went through it. Are they just broke pistons or from some other failure?

These things idle at 18 degrees crank timing all the time, some higher, much higher when cold. Some programs run them lower. The precombustion chamber probably delays things 5-10 degrees though compared to direct injection.

 

[6.2 turbo]

On the parts motor there is just a small crack,this engine is not well,there is a bent rod on a different cyl, and lots of junk in the pan,on my own 92 6.5 the piston broke so bad that there was a sizable hole,and a chunk missing at the wrist pin,the cyl was also scarred,this engine didn't see near the exhaust temp that my 6.2 has,it was rebuilt before I bought it and had aftermarket std size pistons,but it always had a lot of blowby, could have been scarred before,maybe they fit to tight ? Also I beat the crap out of this motor,so it could be simply from that. On the Diesel Page I read an article about 18 -1 compression, they said Peninsular tested a motor with stock compression and it only lasted 3 hours, and cracked a piston, and the 18-1 lasted indefinetly. I think they are omitting some information on that one ?

 

[buddy]

The info they probably omitted is at what power level they were running the engine. Is that 3 hours of WOT in a boat environment. And how did they achieve 18-1, could have used a ceramic coated top and skirt piston for that vs an OEM piston.

 

[6.2 turbo]

I imagine they were at full load on a dyno,but I agree 100 percent with you,the 18-1 pistons where probably simply better by design,not nesecarily just compression ratio.

 

[6.2 turbo]

Honed 2 of the cyls yesterday,looks fine,no low spots except at the top,checked piston clearance,a little less than .005 at the skirt,and .011 at the ring lands. The cheapest rings I have found are Perfect Circle at Summit around $200,still seems like a lot to me. I'm thinking of piecing together a used set,but thats probably not the best idea I ever had. Total Seal has a listing for a gapless 2nd ring set for the 6.2 but not the 6.5,I might have to give them a call,sounds like they can make them any way you want,but I'm sure its expensive. I can see bad rings causing a problem with high compression and 30 plus lb of boost,a gapless second or top would probably make a noticeable difference in power and oil contamination.

 

[ak diesel driver]

If and when I rebuild mine the gapless rings are something I want to look into.

 

[buddy]

The rings are expensive because of what they are made out of of. Has to be strong stuff to withstand the CR and boost. I would go with the gapless too, sounds too logical if its an option.

 

[6.2 turbo]

I called Total Seal they would make me a set with a gapless second ring but it will cost over $600 part #S-4474 if anyone is feeling rich there you go,up to 20 percent less leak down,probably make all kinds of power,but that's to much money for me,especially since this motor is not bored and is still standard I don't think its worth it.

 

[buddy]

If anybody needed better seals its the guy running 3 times more boost than anyone!

Well at least now $200 looks like a deal. I wonder if Diesel Depot can sell them for less. They have gapless rings as an option on their page.

 

[6.2 turbo]

Could be. I called Summit they were a little cheaper,but still over $600,Total Seal said if I had an account I could get them cheaper,but wouldn't say how much. Guess I need to befriend somebody that has an account with Total Seal and get them at cost. Maybe start with the Machine shop,doubt if he would sell them at cost but he might give me a little break on them.

 

[6.2 turbo]

Started working on the oil pan tonight,have a 4 inch extension tack welded on,looks like I will need a custom pickup tube.

 

[6.2 turbo]

It's water proof.Picture 2010.jpg

 

[tanman_2006]

Will that pan still fit in the tahoe w/o risking getting drug off? Is the only reason for doing this the extra oil or is there a deeper reason?

Looks good!

 

[6.2 turbo]

I hope it won't hang to low,I thought it would be nice to hold more oil ,and hopefully stay cooler longer. I also wondered if the motor will fit in with the front axle in the way,it might be a pain.