Advice on rebuild needed.....

[One_Ton_k5]

I am now fully committed to a 6.2 liter turbo diesel for my 1991 k5 with one tons.

I bought a 6.2 from a 85 Subby the other day and proceeded to tear it down today. I went as far as removing the heads and oil pan and of course the injector pump and related.

Now I looked it over as carefully as I could and it looks like it's in really good shape internally.

Since I also bought a 6.5 turbo setup off the e-bay, I am wondering if I should just go all the way and rebuild the entire engine. I'd really like to just start putting it back together and run the stock compression with about 10-12 lbs on the turbo and call it good but what do you guys think?

I also thought I'd get a water cooled, intercooler like this one:
http://www.siliconeintakes.com/prod...=1006&osCsid=13b78fc8f6a1c48b483ffe8e4f204f2c

Thoughts on that? do I need it? Can I run more boost with the cooler?

This sucks, I'm so into this already. Diesels are addicting!

One last thing, I'm in a cold climate state, so that is a big consideration for me. (Cold starting that is)

My truck has no electrical system of any kind right now as I'm doing it all new. I'll make a custom glow plug setup based on whatever I need but I mostly just wonder if I can get by without rebuilding the block.

Finally, what are some ways a guy in his garage can identify cracks in the block or heads and what mods are recommended on the heads for crack proofiness?

Thanks guys.

 

[MaxPF]

Check this thread: http://coloradok5.com/forums/showthread.php?t=221454&highlight=cracked+block

Words of wisdom: if you are going to rebuild the engine (i.e. put real money into it) have the block magnafluxed even if the inspection procedure in that thread shows no cracks. Make sure the person magging the block checks those webs carefully. If it is sound, put a girdle on it with studs - it needs all the help it can get

As cor cold climate use, Rene (tRustyK5) can probably give you some pointers there. I would say don't use reduced compression pistons, make sure you have good 60G glow plugs and a good controller (or a manual switch), a good starter, and good batteries with tight connections. As long as the engine is healthy it should start fine even below 0 degrees.

 

[tRustyK5]

I'll leave the rebuild advice for Max. As for cold climate starting, Max pretty much covered it, but I'd make sure you add or keep the block heater. Honestly the coldest I've ever started my K5 or pick-up at was about 8 degrees F. That's about the coldest I can ever recall here...

Block heater plugged in for about an hour before starting it...manual glow on the G60's for about 14 seconds, 3/4 throttle and let her rip. It sure sounds ugly for the first minute or so, but I've never had a no start in weather that cold.

Rene

 

[One_Ton_k5]

Well I spent some more time thinking about this today and I am rebuilding my whole k5 right down to the frame so I am not going to try and "get by" without a complete tear-down.

The motor and crank look really good though so I'm not too worried.

I live in Minnesota and it does get pretty cold here sometimes. Definitely much colder than 8 above. 20 below ambient isn't uncommon or unheard of in Jan-Feb.

I'll keep the stock compression and run with 10-12 psi + intercooler. That is a good balance I think. I'd be REALLY happy if I could get 200 horse and 400 torque from this motor and still keep some decent milage.

MaxPF, your build thread is sweet. I have a lot of money into my build already too because I NEEDED a Millermatic wire-feed and a Miller Plasma and a new oxy-acetylene set and......and......and.........

Will post anything useful as I go along.....

Thanks guys.

 

[diaric]

lol you guys should come visit the far north in jan and try to start one of these at 40 below

 

[One_Ton_k5]

Does it start at 40 below?

 

[diaric]

plugged in, light oil 0/40, and good glow plugs, yes it does. motor not in top shape, no it doesn't

 

[Wrench]

Does it start at 40 below?

That's where the 1500W convection heater comes in handy or if you do it lots, an Espar . . .

 

[diaric]

ya, recirc heaters help a lot. we use the wabasto's at work. but thats a bit of cash for pick up, for a few cold starts lol

 

[MaxPF]

Well I spent some more time thinking about this today and I am rebuilding my whole k5 right down to the frame so I am not going to try and "get by" without a complete tear-down.

The motor and crank look really good though so I'm not too worried.

Like I said, have the block magged just to be sure. As for the crank, you're between a rock and a hard place. IMO re-using a high mileage 6.2/6.5 crank is a bad idea - they seem to be susceptible to fatigue failure after a lot of miles, and there is no way to make an old crank "as good as new". New 6.2 (two-piece seal 3.80" stroke) cranks aren't available anywhere. The only options are to reuse the old crank and hope for the best, or get a new 6.5 crank and have it machined to fit the old two-piece seal block. I did the latter on mine, but since I haven't run it yet I can't comment on the success (or lack of). Keep in mind that the 6.5 crank has a 3.82" stroke, so the pistons will pop up .010" higher out of the holes.

I have already commented on the heads. Most other parts can be reused. The things that should be replaced are bearings (of course), oil pump and it's drive shaft, timing set (the IP gears should be reusable), and lifters. In theory the lifters are reusable, but in reality high mileage roller lifters are probably going to cause trouble eventually. These motors can run a long time between overhauls, so it is best not to put in components that may not have 300,000+ miles of life left in them. It would be a bummer to put a questionable part in a motor only to have it to pop after 50k-100k miles

 

[tRustyK5]

These guys are the cold start pro's...

Rene

 

[One_Ton_k5]

Like I said, have the block magged just to be sure. As for the crank, you're between a rock and a hard place. IMO re-using a high mileage 6.2/6.5 crank is a bad idea - they seem to be susceptible to fatigue failure after a lot of miles, and there is no way to make an old crank "as good as new". New 6.2 (two-piece seal 3.80" stroke) cranks aren't available anywhere. The only options are to reuse the old crank and hope for the best, or get a new 6.5 crank and have it machined to fit the old two-piece seal block. I did the latter on mine, but since I haven't run it yet I can't comment on the success (or lack of). Keep in mind that the 6.5 crank has a 3.82" stroke, so the pistons will pop up .010" higher out of the holes.

I have already commented on the heads. Most other parts can be reused. The things that should be replaced are bearings (of course), oil pump and it's drive shaft, timing set (the IP gears should be reusable), and lifters. In theory the lifters are reusable, but in reality high mileage roller lifters are probably going to cause trouble eventually. These motors can run a long time between overhauls, so it is best not to put in components that may not have 300,000+ miles of life left in them. It would be a bummer to put a questionable part in a motor only to have it to pop after 50k-100k miles

I thought most of the crank failures were due to the damper failing and the resulting harmonics and vibrations?

I joined the Diesel page and have been reading all the stuff over there in addition to here. I will have the block checked for cracks, should I do the heads too?

I read the head crack repair article about sleeving in the heads, do you feel that is a good way to go? The author seems to.

I've pretty much decided to spend a little more and get the Fluidampr and the timing gear set. The motor only has about 125k on it, should I go over-bore or do you think I can keep the standard bore? Are pistons re-usable?

Thanks to all of you.

I'm glad to know I'll be able to start my truck at -20 too. ;-)

 

[diaric]

a lot of time when the crank fails, the main webs break out. there is some speculation as to the cause then, webs or vibration. when you have the block checked for cracks they will usually measure it. if you can get away with a honeing, great, usually there is some taper to bore out.
head repair is going to depend how bad the cracks are, lots go many miles with cracks.

 

[MaxPF]

I thought most of the crank failures were due to the damper failing and the resulting harmonics and vibrations?

A failed damper can cause premature failure.. However, fatigue plays a role in long term failure. It is actually a tricky subject since there seems to be no documentation out there related to 6.2/6.5 crank lifespan. The cranks in these engines are made of nodular cast iron, which isn't as fatigue resistant as the induction hardened (and sometimes nitrided) steels used in most diesel cranks. GM compensated for this by undercutting and pressure rolling the rod and main fillets, which gives much more fatigue resistance than any type of heat treat. Still, fatigue seems to be a factor and sometimes high mileage cranks will break. This isn't just the case with 6.2/s and 6.5's, even though they get the most bad press. I have seen a Navistar/Ford 7.3 with a steel crank have the same failure.

There is no way of knowing how much fatigue a crank has. Still, if it only has 125k on it as you state below it probably has at least 200k of life left in it.

I joined the Diesel page and have been reading all the stuff over there in addition to here. I will have the block checked for cracks, should I do the heads too?

Yup.

I read the head crack repair article about sleeving in the heads, do you feel that is a good way to go? The author seems to.

I used to. With more research and thought on the subject I think it is a bad idea. The purpose of that drilled passage is to cool the area between the valves and direct water to the adjacent face of the prechamber. When you sleeve the passage you reduce it's ID, which reduces coolant flow through it. IMO it is better to get a new or good used head instead. I think after you figure out how much a complete head reconditioning costs you will find a set of brand new complete AMG heads isn't much more.

I've pretty much decided to spend a little more and get the Fluidampr and the timing gear set. The motor only has about 125k on it, should I go over-bore or do you think I can keep the standard bore? Are pistons re-usable?

It depends on how much bore taper you have. Once again, are you looking to get by with the whole deal, or do you want a truly rebuilt engine? I would overbore and get new slugs. There is no telling how much abuse the pistons have taken.

 

[MaxPF]

a lot of time when the crank fails, the main webs break out. there is some speculation as to the cause then, webs or vibration. when you have the block checked for cracks they will usually measure it. if you can get away with a honeing, great, usually there is some taper to bore out.
head repair is going to depend how bad the cracks are, lots go many miles with cracks.

Normally if a crank breaks the main webs are unharmed. When you find a broken crank AND broken main webs, it is the webs that failed first. The crank then breaks from lack of support.

 

[One_Ton_k5]

It depends on how much bore taper you have. Once again, are you looking to get by with the whole deal, or do you want a truly rebuilt engine? I would overbore and get new slugs. There is no telling how much abuse the pistons have taken.

Well, I'm not trying to get by anymore. I just thought that it would be better to keep more metal in the block if possible. In a gas motor I wouldn't have even asked because they usually have a lot more wear by the time they have 125k on them. I haven't checked taper but I did look for a ridge in the bore and I measured it with my micrometer and it looks really good.

I am not opposed to new pistons and such, I was just looking ahead and wondering if I should bore it or not.

Thanks.

 

[MaxPF]

At 125k, you will have some taper. It may only be a couple thou, but you really want a nice round bore for your new pistons. As a rule these blocks have plenty of metal in the cylinder walls - so much so in fact that you don't normally hear of cavitation issues like you do with the Ford/Navistar 7.3 IDI's. Some of the early 6.5's were susceptible to cracking #8 before GM fixed the weak spot in the castings, but 6.2's have never had this issue.

Speaking of cavitation, even though these motors have never been abnormally prone to damage from cavitation it can still happen to any diesel (and even industrial gassers that run under sustained high load). Make sure you use the proper coolant with the proper additives to prevent the problem.

 

[One_Ton_k5]

What specifically is the cavitation problem?

 

[kennyw]

Last time I was in MN with a 6.2L it was -25*F at night... and I had a single battery with 2 ga cables. With a new block heater installed and plugged in for an hour I had no problems starting the truck.

 

[MaxPF]

What specifically is the cavitation problem?

When a cylinder fires the internal pressure causes it to expand slightly and then reduce back to it's original diameter. When this happens bubbles instantly form on the exterior (coolant-side) of the cylinder and then implode immediately. The high implosion pressure in the tiny area of the bubble actually erodes metal from the exterior of the cylinder walls. The bubbles tend to form time and again in the same place, and after a lot of miles (usually 150k-ish for Ford 7.3 IDI's) it can erode a hole through the cylinder, allowing coolant into the cylinder and/or crankcase.

The prevention for this are called Supplemental Coolant Additives. They contain nitrites and other chemicals that form a thin protective layer on the metal. The layer is sacrificial, so the cavitation bubbles erode this coating rather than the underlying metal. In between firings the additives recoat the metal, keeping it protected. Since it is sacrificial the chemicals in the coolant are eventually depleted and need to be replaced. In addition, the coolant itself needs to be changed on schedule (but that is the case with any engine). There are test strips that measure the amount of SCA in the coolant. SCA's can be bought to add to coolant, but there are also coolants sold that already have the SCA in it. If you use something like Cummins DCA-4 you have to make sure it is used with a low silicate antifreeze. It actually has gotten complicated with the new antifreeze formulations (regular green, Dexcool, etc.) because some additive formulations may not be compatible with different types of antifreeze. The best place for good info on these things are sites such as Cummins/Fleetguard. There you can find the info for what SCA's are compatible with what antifreezes.

Like I mentioned, GM 6.2/6.5 diesels haven't had much issues with cavitation due to relatively thick cylinders and modest firing pressures. They could eventually erode through (it is cumulative - the more miles, the further the erosion will have progressed), but it will take longer than a 7.3 Ford. Still, since the block already has 125k on it, it is that much closer to a cavitation failure if it has never had SCA in it (it probably hasn't). Run the SCA in it after you rebuild it and you will prevent any further erosion.