LBZ: Stock Rebuild

[Doms]

So I’ve been looking at the GM part numbers.

Connecting Rod Bearings
19209593 - Green
97250338 - Yellow

Main Bearings
19256552 - Blue
97386927 - Black
97386937 - Brown

I have a mix of green and yellow for my rod bearings. Mains are black and what I thought was red, but I can find anything on that. Is this considered brown?

Edit: looking at the picture now it is obviously brown. Looks red to me in real life.

 

[ikeG]

I.E. -If you use a stock lbz crank with stock lbz pistons(stock rods obviously), you do not need to rebalance. That is exactly how it came off the showroom floor.
However, if you did rebalance using all stock parts, there will be room for improvement. Stock duramax engines are off several percent when new.

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I need to add that you will not need to rebalance if you use your truck's vin to order the stock crankshaft from GM. I ordered a 2008 crank using a vin from an identical (2008) truck I had on hand. Machine shop called and said it needs x amount of grams blah blah. So I retrieved the vin from the actual truck the engine is out of, and sure enough different part numbers. So an lmm has at least two different balance specs based on rod and piston weights. Machinist said, yea there are different weight rods for this engine.
Which opens up another issue, these lbz/lmm rods that people upgrade to, there apparently are sets better(at least heavier) than the next! This engine has the heavier set. The crank needs +70 grams in the back and +100 in front.
A mod could extract this and other relevant info from the thread and make a new one ??

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[Chevy1925]

There are 2 different LBZ rods that i know of.

little info from GM

 

[Doms]

So after a bit of a hiatus over the summer and then a long wait for a back ordered bearing I have gotten back into this.

I have assembled the bottom end and I measured protrusion this afternoon using a dial bore gauge on a magnetic base. My measurements concern me a tad and I’m looking for a bit of advice.

To get my measurements, I used my dial indicator to find TDC, confirmed zero on the block, and then set the indicator on the center line of the wrist pin as close to the outside edge of the piston as I could. This point should yield the highest reading as it is the furthest from the pivot point. I rocked the piston front to rear and recorded the highest measurement then moved to the other side of the piston and did the same. Here is what I got:

All numbers are front/rear/difference

1 - .005/.004/.001
2 - .004/.008/.004
3 - .007/.006/.001
4 - .006/.006/.000
5 - .009/.0075/.0015
6 - .003/.008/.005
7 - .003/.004/.001
8 - .003/.005/.002

The difference between front/rear on 6 seems to be a bit on the high side, and the difference between 5 (.009) and 7 (.003) of .006 seems high too. There will be a little bit of discrepancy here as my dial indicator is.001 so I’ve round my numbers but at most that would result is a total error of .001.

Is anything here overly alarming here or am I being paranoid? Rods are stock, crank is stock, pistons are mahle race cast, bearings are GM. All clearances and dimensions are within spec.

 

[Chevy1925]

i would be using something like this and an indicator that atleast goes to .0005.

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otherwise all you have written down could easily be from slight movement in the arm that holds your dial indicator unless you are again verifying the indicator is reading .000 after you find the numbers for protrusion. i would check each end 3 times to find averages then with your setup and make sure you are getting repeatable numbers.

if the block wasnt decked, this can play into your issue. if it was decked, i would suspect a rod issue or your measuring method is giving false info. where the rods checked for straightness at all?

 

[Doms]

No, the rods were not checked. That was the one thing that I didn’t do as I didn’t really have the means to do it. I guess ultimately I made the assumption that they “should” be fine and went with it. I could have had the machine shop do it, but I really didn’t think there would be any issue. It wasn’t a matter of cost, just a mistake on my part.

The block was not decked, but was bored .020. A torque plate was not used as there is nothing available at any of the local machine shops and I could not find anybody willing to rent one out online. I suppose either one of these can be a contributing factor as well. Bore diameter is within spec as is out of round. This was all measured to .0005. Clearances wer

When you rock the piston, how much force do you apply? If I was rocking it to the rear I would position by body at the rear of the block, hook my figures on the edge of the bowl and pull as hard as I could to get the piston to move as much as possible? Is this correct?

Also, is the point on the piston that I am measuring (as close to the cylinder wall as I can get my indicator, centred over the wrist pin) correct?

 

[Chevy1925]

No, the rods were not checked. That was the one thing that I didn’t do as I didn’t really have the means to do it. I guess ultimately I made the assumption that they “should” be fine and went with it. I could have had the machine shop do it, but I really didn’t think there would be any issue. It wasn’t a matter of cost, just a mistake on my part.

The block was not decked, but was bored .020. A torque plate was not used as there is nothing available at any of the local machine shops and I could not find anybody willing to rent one out online. I suppose either one of these can be a contributing factor as well. Bore diameter is within spec as is out of round. This was all measured to .0005. Clearances wer

When you rock the piston, how much force do you apply? If I was rocking it to the rear I would position by body at the rear of the block, hook my figures on the edge of the bowl and pull as hard as I could to get the piston to move as much as possible? Is this correct?

Also, is the point on the piston that I am measuring (as close to the cylinder wall as I can get my indicator, centred over the wrist pin) correct?

i doubt its rods so dont fret. im more inclined to say its your measuring method (both how you are doing and what you are using to measure)

socal diesel will rent them but you have to call. That said, many guys run without doing one. if you are not using studs, there is no point for it anyhow (dont remember if you said you are studding it)

thats waaaaaay too much force. all you have to do is push the piston to the side with your thumb or finger side to side and record the highest reading over the wrist pin, then move to the other side. If you are pushing so hard your fingers hurt or you are leaning your weight into it, you are pushing far too hard. at no point should the piston EVER see that much force while running.

you are correct on where to measure.

 

[bimmer95]

I wouldn't be concerned with those numbers but I will say it's hard to get a super accurate measurement with a dial indicator.Also the number 5 difference is .0015 according to my math

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[Doms]

I wouldn't be concerned with those numbers but I will say it's hard to get a super accurate measurement with a dial indicator.Also the number 5 difference is .0015 according to my math

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You mean real math haha? You are certainly correct. My bad. I’ve corrected it.

I will retake my measurements while applying less force. I have a .0005 indicator on hand and I should be able to make up a sled as shown without too much trouble if I can’t find something locally.

Is it normal to not see any protrusion before rocking the piston? I rolled a few through TDC for curiosity sake and they seem to be a couple thou from cresting the top of the block. I am more so just wondering. The variability in protrusion from GM is interesting to me. I would have thought that everything would be within a tolerance from new that it would not really be a consideration unless you were doing a rebuild where something changed. For instance, I had an “A” and a “B” gasket when I tore my engine apart. Are they aiming to maximize efficiency? Why didn’t they just call “C” the standard and offer one gasket?

Thanks for the advice guys. I really appreciate it. Sometimes I feel like an ass just popping in to ask questions. I’ve never been good at keeping a presence on forums. I guess it’s all good information to get out there and I hope it helps someone in the future.

I’ll update once I re-measure.

 

[Chevy1925]

I’m 90% sure mahle race cast pistons come .010 cut off the top compared to stock. Since you didn’t deck the block, that means protrusion dropped.

You will not have as tight of piston to head clearance as stock at this point. You can run an A gasket on both sides and still have plenty of clearance. You will be in the .030+ range which is pretty loose. This is why I’m not too concerned on your numbers.

The only thing it will affect is mpg over many many miles. Too many other variables to say that will be a noticeable difference once you get it back together.

It would be a good idea to get correct numbers just to know exactly where you are though.

 

[Doms]

So I re-took these measurements. I still ended up using the same setup. I cant hold my .0005 indicator on the mag base. I'm comfortable with these numbers. I found TDC, zeroed on the block, measured three times while rocking back and forth, re-confirmed zero and then repeated the process on the other side of the piston. I did still have to round my numbers up but everything was past the half way point on my increments. They're probably +.0003 at most.

Front/rear/difference
1 - .003/.003/.000
2 - .007/.004/.003
3 - .006/.006/.000
4 - .004/.006/.002
5 - .006/.006/.000
6 - .007/.004/.003
7 - .005/.002/.003
8 - .005/.002/.003

 

[Doms]

This is where I’m at right now. I have one head here ready to assemble and the other at the machine shop that I’ll pick up next week. I had a glow plug stuck in each head so I ended up buying a kit from time-sert kit to repair the threads that got damaged.

I bought a set of PPE factory length up pipes and a MBRP 3” down pipe to replace the stock pieces. They showed up the other day. I’m going to delete the EGR system. It was previously blocked off and full or crap.

 

[NevadaLLY]

View attachment 105210
This is where I’m at right now. I have one head here ready to assemble and the other at the machine shop that I’ll pick up next week. I had a glow plug stuck in each head so I ended up buying a kit from time-sert kit to repair the threads that got damaged.

I bought a set of PPE factory length up pipes and a MBRP 3” down pipe to replace the stock pieces. They showed up the other day. I’m going to delete the EGR system. It was previously blocked off and full or crap.

Which gasket are you putting in with those clearances?

 

[Chevy1925]

So I re-took these measurements. I still ended up using the same setup. I cant hold my .0005 indicator on the mag base. I'm comfortable with these numbers. I found TDC, zeroed on the block, measured three times while rocking back and forth, re-confirmed zero and then repeated the process on the other side of the piston. I did still have to round my numbers up but everything was past the half way point on my increments. They're probably +.0003 at most.

Front/rear/difference
1 - .003/.003/.000
2 - .007/.004/.003
3 - .006/.006/.000
4 - .004/.006/.002
5 - .006/.006/.000
6 - .007/.004/.003
7 - .005/.002/.003
8 - .005/.002/.003

maybe but look at how vastly different your numbers are from here and post #24. leaning on them like you were doing before has some affect but you shouldnt be getting higher numbers now on some as compared to before. thats why accuracy seems farther off to me. all i have to go off of is what you provide here though.

if you trust those numbers, throw an A gasket on both sides and roll on. otherwise, if you want stock tolerances, you will be disassembling the block and having it decked .005 but you need a better measurment method if you want to tighten things up.

are you using head studs or head bolts?

 

[Doms]

Sorry, the original measurements that I posted in post #24 are listed rear/front, not front rear as stated. That it where most of the discrepancy lies. The variance outside of that I blame on rounding due to the fact that I should be using something with better resolution.

Original measurements should read:

Front/Rear
1 - .004/.005
2 - .008/.004
3 - .006/.007
4 - .006/.006
5 - .0075/.009
6 - .008/.003
7 - .004/.003
8 - .005/.003

I will order "A" gaskets for each side.

Not that it will effect me here as things are quite loose, but if you have your head decked, do you add that amount to your protrusion to select a gasket?
If I had a protrusion of .010 for instance, and then I had .003 taken off my head, would I use .013 when selecting a gasket?

 

[Doms]

are you using head studs or head bolts?

Bolts. Figured studs were a little overkill for what I am doing. Couldn’t justify the cost.

 

[Chevy1925]

Sorry, the original measurements that I posted in post #24 are listed rear/front, not front rear as stated. That it where most of the discrepancy lies. The variance outside of that I blame on rounding due to the fact that I should be using something with better resolution.

Original measurements should read:

Front/Rear
1 - .004/.005
2 - .008/.004
3 - .006/.007
4 - .006/.006
5 - .0075/.009
6 - .008/.003
7 - .004/.003
8 - .005/.003

I will order "A" gaskets for each side.

Not that it will effect me here as things are quite loose, but if you have your head decked, do you add that amount to your protrusion to select a gasket?
If I had a protrusion of .010 for instance, and then I had .003 taken off my head, would I use .013 when selecting a gasket?

I was going to suggest looking at the bottom of the heads to understand you dont do that but realized you might be asking in reference to valve protrusion as they open/close.

No, you dont do that. generally, you are safe if you take .007 or less off a head to not need a thicker gasket or recess the valves into the head more. the gaskets give a range on what they will squish like an A is .0354-.0394. when using headstuds, its best to assume the lower end of that number. being you didnt deck the block, you can see that you have a little give with the gasket to the block as it will be tighter to the highs (lower protrusion numbers are a good reference to block variance) and looser on the lows (higher protrusion numbers). its not perfect science to say the low protrustion is where the block is higher but it gives a little picture of it.

so take your highest protrusion number for a bank of cylinders, subtract it from the gasket thickeness and that is your P to H clearance. Pass side will see .0284-.0324 clearance and driverside will see .0294-.0334 clearance, both at their tightest area. hence my "you will have a .030 piston to head clearance with an A gasket" i posted earlier. thats well more than enough as stock is .022-.025 clearance area. ive ran them as tight as .020, wouldnt go more than that.

Bolts. Figured studs were a little overkill for what I am doing. Couldn’t justify the cost.

ok, then you wont be looking at the lower side of the gasket thickeness range, you will fall closer to what i was posting above.

 

[Doms]

Makes sense. Yes I was referring to valve protrusion. That’s for the info.

 

[Bdsankey]

I’m 90% sure mahle race cast pistons come .010 cut off the top compared to stock. Since you didn’t deck the block, that means protrusion dropped.

You will not have as tight of piston to head clearance as stock at this point. You can run an A gasket on both sides and still have plenty of clearance. You will be in the .030+ range which is pretty loose. This is why I’m not too concerned on your numbers.

The only thing it will affect is mpg over many many miles. Too many other variables to say that will be a noticeable difference once you get it back together.

It would be a good idea to get correct numbers just to know exactly where you are though.

You are correct, the race cast has 0.010" taken off the top (measurement wise) compared to the OEM piston dimension.

 

[Doms]

Well just to check in, I ran this up to temp for the first time today.

First start was a couple of weeks ago.. just bare minimum to get it running and make sure that nothing was majorly wrong. Probably only ran it for 20 sec if that.

I wanted to prime the oil system before that first start so I made a new top plate for fluid extractor to allow me to pressurize the canister. I pumped 5 quarts of oil in through the oil pressure sensor port. It worked well. I was in no hurry so I just put 2-3psi on it and let it do its thing. Probably took about and hour or so.

Before I tried starting it I pulled the glow plugs and spun it for probably 30-40sec in shorter intervals. When I actually went to start it I cranked for about 10sec and it fired. Sounded really good.

After that initial run I checked it over for leaks and then started putting everything together. When I started filling with coolant I got about 4 gallons in and heard it start pissing out on to the garage floor. I had loosened one of the banjo fittings for the coolant on the turbo last year when I pulled it and didn’t realize I did it / missed it when I put it in. I pulled the turbo out and fixed that. I wasn’t too thrilled at the time but that’s pretty minor in the grand scheme of things. My other gaff was forgetting to install the dipstick for the engine oil. Discovered that one when I started filling it with oil for the first time. I was pretty happy about it when I realized how it’s routed.. haha.

I got everything back together today and ran it up to temperature while I bled the power steering system. No leaks, no surprises. I think I’ll change the oil now to clear out everything from assembly.

Next step is to put some miles on. I’m a little nervous, but not quite as nervous as that first start.. I was very thorough on assembly, but I’m also naturally pessimistic.. it will be a while before I really trust this thing.

Thanks for the help and advice.