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My 6.2 build!

afroman006

afroman006

1/2 ton status
Joined
Aug 21, 2002
Posts
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Location
College Station & Kingsville, Texas
Well I have been scarce around here for a few months cause school has been beating me down but its time for some motor building action. The 6.2 I had in my trail truck died rather disappointingly in the mud pits during the summer. The motor never ran very well, I got it for free and never too the heads or anything off. Well it turned out to have three cracked pistons, and I think the injection pump and/or injectors finally wore out or broke too which caused its final death. So I got a whole new (to me) motor to rebuild and thats where I'm at now.

The rebuilder is sourced from a CUCV so its probably an 84. It was prety rusty on the outside but once I got it torn apart the inside was great looking except one cylinder had some water and rust in it from sitting outside. We got the block all cleaned up and I ordered a ring, bearing and gasket kit with standard bore rings. My friend that is helping me build the motor was checking the ring gap and said that it was too big, indicating worn cylinder walls and that I would probably need to get the block bored out. I was hoping to avoid this because of the added expense but the block is at the machine shop getting checked out right now.

Now I am expecting the machine shop to confirm my friend's opinion that it needs to be bored out, which means I am going to have to get new pistons, which means I am going to have to re-balance the rotating assembly. My friend told me that once we get the pistons we can put them on the rods, and then ballance the rotating assembly ourselves. I am not familiar with this kinda stuff at all but he seems to know what hes doing. He said that the crank is already balanced by itself so all we need to do is put the pistons on the rods, weigh them, find the lightest one, and then grind off the skirt of the rods until the heavier ones match the lightest one. Is this all as easy as it sounds and a credible and reliable way of doing it? I would love to save the $175 the shop charges but not at the risk of destroying my motor with killer vibrations.

I am just sticking an old set of heads on there for now and re-using the factory head bolts. I know this is a typical no-no but I seriously cannot afford to get new bolts or rebuild the heads right now so the plan is once I pay off the bottom end rebuild I will rebuild a set of heads and install them with new bolts.

I am having the injection pump and injectors rebuilt by accurate diesel, since everyone seems to like them so well. I was wondering though, has anyone given any thought to raising the governor limit on a 6.2? From what I have heard the governor is in the injection pump and I have read a few articles about 6.2's mod'd to run 5-5500 rpm. I know the factory redline is 3600, would it be safe to have it bumped up to 4000 with a bone stock bottom end? I just want a little more horsepower for playin in the mud and making lots of noise. Thanks for the help, here's some pics.

What killed it
100_1287.jpg

Cracked piston 1
motor010.jpg

Cracked piston 2
motor008.jpg

Cracked piston 3
motor005.jpg

And the new block all cleaned up and ready to go.
motor001.jpg
 
From what I can see the pump or the injectors went way lean to cause the pistons to crack like that. If the motor had over 250,000 that is what also happens to them. My dad's 1990 6.2 had 289,000 miles on it when it started to develop piston knock (double knock sound when running) and pulled the heads to find a small crack in one of the pistons. I ADVISE you DO NOT REUSE the bolts the bolts are torque to yield bolts mean they can be only torqued once after that the head bolt will keep stretching till the bolt breaks. You better just slow down on your build time before you destory your fresh motor with a stupid move like that and that is coming from alot of experience with diesels. It looks like you had fun before it gave up.

bigred81
 
bigred81 said:
From what I can see the pump or the injectors went way lean to cause the pistons to crack like that. If the motor had over 250,000 that is what also happens to them. My dad's 1990 6.2 had 289,000 miles on it when it started to develop piston knock (double knock sound when running) and pulled the heads to find a small crack in one of the pistons. I ADVISE you DO NOT REUSE the bolts the bolts are torque to yield bolts mean they can be only torqued once after that the head bolt will keep stretching till the bolt breaks. You better just slow down on your build time before you destory your fresh motor with a stupid move like that and that is coming from alot of experience with diesels. It looks like you had fun before it gave up.

bigred81
Click to expand...

I second that.
As for balancing, the way your buddy is describing it, you are balancing individual parts which is one way, you will end up with balanced parts, but the better way is to balance the complete rotating assembly dynamically instead of statically piece by piece, but I don;t know who here does this and how much they would charge.
What you are doing would be better than stock anyway and that for free is a good thing. :D
 
The 6.2L crank is not internally balanced. I would not have a problem balancing the piston and rods the way your friend described, but then have the rotating assembly (including the flywheel or flexplate) balanced at a shop.
 
Having the balancing done at a shop is what I am trying to avoid. As far as the head bolts go, whats the worst that can happen? I am using a set of cheapo head gaskets till the head swap and when I put the rebuilt ones on I will put some fel-pro's on there. I figure if a bolt backs out or something causing a head gasket failure, meh, no biggie.
 
The bolts could break or never reach the correct torque value letting water get into your rebuilt engine and cause it lose a piston. I had one in the shop where they did something like that and the head gasket let lose between two cylinders not going into the water jacket but it torched the block ruining the block and the head. You can try it but it is a lot of wasted time and energy to do the job twice when all you had to was wait for the parts. Have fun

bigred81
 
bigred81 said:
The bolts could break or never reach the correct torque value letting water get into your rebuilt engine and cause it lose a piston. I had one in the shop where they did something like that and the head gasket let lose between two cylinders not going into the water jacket but it torched the block ruining the block and the head. You can try it but it is a lot of wasted time and energy to do the job twice when all you had to was wait for the parts. Have fun

bigred81
Click to expand...

Agreed

If you want to save money, do the head work yourself.
What is it you want to do? port match and polish?
The bolts are not that expensive so do the head work and buy the bolts, just wait a few weeks or months till you can afford those and do it once for good.
 
it's all been said before, but because i think it's so important, i'm gonna repeat... :)

my new head bolts were 60 bux - not too bad all things considered. the only ones i could find were torque-to-yield, so if that's what was originally in your engine, then those are absolutely not usable - they'd already be stretched and to torque them down again would put stresses on the bolt which the bolt wasn't designed for.

again, i wouldn't recommend trying to balance it yourself. the engine is extrenally balanced, so just balancing the internal pieces will do next to no good for you. besides, if you do it wrong, you are liable for the parts. if you do decide to start machining off pieces of your new parts, be unbelievably careful, otherwise you'll be spending a ton more than you'd have intended.


what i believe is more important than a balance job on these engines is making sure that the (crap - i'm having a brain fart on the names) holes in either end of your rods are perfectly round and that your wrist pins and crank are round too. don't machine that crank - if it's out of round you need a new one. don't just check if the holes are with in spec of movement, as that's not a very good check b/c if they're out of round, they may be within spec of the movement of the parts, but out of roundness causes undue wear. i hope that made sense. :)
 
Are the aftermarket bolts out there reusable? Waiting on the motor build to rebuild the heads is absolutely out of the question because I am aiming to make a trip in mid december and will not miss it, period. So I will be changing the heads out soon one way or the other, they will probably only get the one trip on them before I changeum out. Fel-pro makes some that are cheaper than the ARP stud kit right?
 
Does anyone know where to get the aftermarket bolts? The ebay seller I'm getting my pistons from has new OEM bolts for $48 but the jew in me really wants to get a set of reusable bolts.

What all is entailed in rebuilding the heads? As in, how much does it cost. Do I have to get new valves and springs in addition to all the seals and some machine work?
 
anybody know bout the governor question he mentioned bout changing the rpm limit?
 
muddybuddy said:
anybody know bout the governor question he mentioned bout changing the rpm limit?
Click to expand...

I know it can be done, there wa sone in fourwheeler a few years back who did it, it was up to 4500RPM IIRC, but why?
I think 3600RPM is plenty, try working with 1800 max, that what my Perkins has at the moment, and I am living with it.
I talked to a few mecanics and they said it can safely be tweaked to 2800 3000 and I didn't do it.
3600 is plenty if you have a 4 speed with proper gearing.
 
I just want a little more wheel speed for muddin' :D

Today I discovered my radiator was stolen, which brings this motor build to a screaching halt. I was in a rush to get everything done for my club's annual trip to Clayton, Oklahoma in mid december and was on my way to maxin out the plastic to get there. There's no way in hell I can afford a new radiator now so I wont be wheelin on the trip. I'll probably still tow someone though.

In the grand scheme of things this might be for the best, I can take my time on the motor build and do it right all at once, but before that I can pay off the credit cards...
 
afroman006 said:
I just want a little more wheel speed for muddin' :D

Today I discovered my radiator was stolen, which brings this motor build to a screaching halt. I was in a rush to get everything done for my club's annual trip to Clayton, Oklahoma in mid december and was on my way to maxin out the plastic to get there. There's no way in hell I can afford a new radiator now so I wont be wheelin on the trip. I'll probably still tow someone though.

In the grand scheme of things this might be for the best, I can take my time on the motor build and do it right all at once, but before that I can pay off the credit cards...
Click to expand...

Man that sucks.
Well let me check, I think I have one here, or would you rather buy one new?
 
I was in San Antonio this past weekend and there were 2 6.2 trucks at pick N pull that still had the radiators and they were in good shape. You might want to make a trip during the thanksgiving weekend to pick n pull because the trucks still had very thing intact.

bigred81
 
i suppose i can see why that might be an offensive comment, but, the stereo type from which this comment comes is simply a stereo type which says that the jewish community is often frugal and good with their money - 2 very good qualities. for what it's worth.
 
running lean won't do that to a diesel engine. cracks are from running hot, and diesels actually run cooler under lean conditions. But it still sucks that happened. more than likely the injectors were wore out, letting fuel drip, or timing advance too much(sloppy timing chain), etc.
I would'nt mess with the governor either. its gonna break the crank if you twist it too fast for too long, without spending big money on balancing the whole assembly for that speed. find yourself a 6.5 turbo setup to bolt on it.
 
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