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Planning a rebuild, need advice

896 views 8 replies 3 participants last post by  Southtowns27 
#1 ·
Hey guys, I'm beginning to plan to rebuild my Cummins next spring. The truck in question is the one in my sig, with all the mods listed. It has 242K miles on it, which seemingly isn't a whole lot for one of these things, but this thing worked hard all day everyday before I owned it. I'm getting a LOT of blowby now and it sounds like I have a weak cylinder at idle. It still runs fine under load and pulls hard, but I'd rather just go through it before I have big issues.
The truck is a daily driver, but I have no commute. I use it for moderate towing and hauling, but not everyday. The way it's set up right now works pretty well for what I do with it.
My buddy owns an engine machine shop and he's done quite of few of these engines, mostly for pulling tractors, so I have that end covered. I'll likely have him do the machine work and I'll do the assembly.
I plan to firering the head and install head studs. I also plan to upgrade the valve springs.
Would main bearing studs be overkill for my setup?
Would an aftermarket cam gain me much for what I'm doing?
How far can one of these engines be bored? I see .020 and .040 pistons for sale, but I've heard it's common to bore the engine then sleeve it back to standard.
I've heard some talk that marine pistons are an upgrade...yes, no, maybe?

I'm sure several of you have been down this road before, so please let me know if there's anything else I need to be looking for or I should fix/upgrade along the way.
 
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#2 ·
Really? No one?
 
#3 ·
Thera many options. I plan to do this soon as well I've got 460k. I feel it's all in ur end hp goal bc a lot of stuff can be done with the motor out. But I'm planning on following what a buddy did.... He's got 14mm main studs, head bolts, cam (I'm not gunna do), hd pushrods, 110# valve springs, titanium keepers and retainers, .010 over head gasket to reduce compression. His pump is a whole other monster!

He has not but I'm going to port and polish head, as well as what's above
 
#4 ·
Yeah, I'm not going for all out power..yes it would be fun to do, but it's just not practical for my application. I'm not ruling out a mild set of compounds down the road, but that would be just to keep EGT in check while towing.
 
#5 ·
I'm planning to do the Ht3b and use my hx35. With what I mentioned above and the compounds I feel that will be a safe reliable set up to hold 500s hp DD.
 
#6 ·
I wouldn't worry bout fire ring, it's not the best for a dd, but oring would be more suitable if u want extra protection. I'm not planning on it bc I don't plan to push that much. And when u tare it down look at the cylinder bores for factory cross hatches, u might not have to re bore or sleeve
 
#7 ·
With the amount of blowby I have, I can't imagine not boring it...
 
#9 ·
That will happen when the engine gets torn down.

So, does anyone have any input on my original questions?
 
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