Rings and bearings while I have the engine out?

[malpana]

Main 3, cap:
main cap 3.jpg


Main 4, cap:
main cap 4.jpg


Main 5, cap:
main cap 5.jpg


I haven't looked into the number yet, but the first thing that caught my eye was the difference between the main cap bearings for 1, 2, and 4: 1 has 973S on it, but 2 and 4 have 974S on them, even though the part number for all 3 is the same, and the block side bearings for all 3 mains are exactly the same.

[Robyn]

Good deal
RODS ARE STANDARD.
Use plastigauge to check clearances

NOT PERFECT....But it will get you close enough to know wassssup.....
Too tight....BAD JU JU
Too loose just as bad

[More Power]

Main 3, cap:
main cap 3.jpg


Main 4, cap:
main cap 4.jpg


Main 5, cap:
main cap 5.jpg


I haven't looked into the number yet, but the first thing that caught my eye was the difference between the main cap bearings for 1, 2, and 4: 1 has 973S on it, but 2 and 4 have 974S on them, even though the part number for all 3 is the same, and the block side bearings for all 3 mains are exactly the same.

GM indicates in their service manuals that different bearing halves can appear on the same journal. This is sometimes done to split the difference in bearing clearance to help get a more perfect fit. For this last engine I/we rebuilt, I used a standard set of rod/main bearings even though the engine originally had a couple of unmatched bearing sets from the factory. I didn't worry about it during the rebuild because all clearances were checked and all were in the mid range for acceptable clearance using Plastigage. To boost confidence, I inside/outside mic'ed the bearings/journals, and found the Plastigage to be just as accurate (and much faster) as I could measure with good mics.

Time will tell, I suppose, but the engine has about 5K on it now. Oil pressure is typical and it is amazing how smooth the engine is when idling. I plan to shoot some video of the idling engine in the weeks ahead with a clear plastic cup half filled with water sitting atop of the intake manifold.

[malpana]

Thanks, More Power. Good to know plastigage can be trusted. I'll use it.

Any ideas about this: "the difference between the main cap bearings for 1, 2, and 4: 1 has 973S on it, but 2 and 4 have 974S on them, even though the part number for all 3 is the same, and the block side bearings for all 3 mains are exactly the same." That's got my wondering.

[Robyn]

One of the biggest influences on the idle "Smoothness" is the pop pressure on the injectors.

AS IN having them all very very close to the same pressure....
A set of squirts that are scattered all over the map with some low and some high can make for a rougher running engine.....
This difference also places more torsional stresses on the crank as well....
I had the shop that rebuilt my squirts on the last 6.5 I built tweak things down to as close as they could get to perfectly the same.

Maybe this is being too anal....But that engine was a smooth runner.....

[malpana]

I'll see about getting the injectors checked.

No crack in the block, so I ordered a set of Clearwater heads. I might go with Flepro for the gaskets and bolts, but does anyone have any strong opinions? What about Mahle gaskets? The block has most likely not been resurfaced. In the absence of absolute certainty, is it better to err toward standard thickness or +0.10"?

[Robyn]

FELPRO is the best gaskets and bolts....

Check the deck height when you get a piston/rod back in.
With the piston at TDC it should be .004" to .006" above the deck. (Out of the hole)
I have seen the pistons flush with the deck......
If the piston protrudes more than the .006" out of the hole then it is a good bet that the deck has been cut
If the deck height is standard you do not need to use the thicker gasket.

Any good rebuilder will stamp near the front of the deck or along the top upper portion a number .XXXX if the deck was cut.

NOTE
The bolt kits come with the torquing specs on a little sheet.

Torque to yield bolts (TTY) Use once and then toss......Not like the old stuff we saw in SBC from decades ago...

The torque sequence will give a number...XX ft lb through the pattern....Then a second number XX ft lb through the pattern and then 1/4 turn or 1/2 turn. ?????

THIS IS CRITICAL....Follow the spec sheet.....TTY bolts must be put in the "Stretch zone" so they provide the proper clamping force throughout the operating temperature range....

Make sure the bolt holes are clean and free of all oil and crud..(Brakleen.works great)
The bolts have a dry silicone sealer on them....DO NOT oil the threads or the bolt....Install as they come from the box.....
The threads are metric.....I like to carefully run a tap though all the holes to clear all the crap.
Then flush with brakleen....allow to dry...



Metric taps are available

[malpana]

Thanks, Robyn all very helpful info. I'm itching to go with main and head studs, but maybe I'm just going overboard.

I'm also considering replacing the nylon rocker arm retainers with another setup. I know there have been discussions of this here and elsewhere, but they seemed to be mostly at the point of trying something new out. Does anyone know what's been tried, tested, and proven to work over the long haul? I'm a bit uneasy about just getting new nylon ones, and Harland-Sharps would be a hit to the wallet.

[arveetek]

I rebuilt my engine about 50K miles ago, and at the time, I was debating about whether to use head studs or not. I decided to go with the stand TTY bolts, since that was proven technology.

However, after studying and learning more since then, I would go with head studs next time around. Mostly this is due to the fact that I am using a Holset HX35 turbo that can push 15 psi pretty easily. I'd feel more comfortable letting the boost go where it wants if I had a studded engine. As it is, I tend to be cautious and keep my foot out of it when towing to prevent high boost situations.

I don't know of any other options for the nylon buttons (other than the Harland Sharp rockers, which aren't necessary for a stock build). I put new nylon buttons in my engine and am satisfied with those.

Casey

[malpana]

Hi, all. I hit a snag getting the pistons and rods back together. One of the wrist pin bushings was cracked. I can't find a GM part number for it and am having trouble finding an out-of-the-box replacement. Enginetech sells sets, but they need to be honed to fit, and I'd like to find them sold individually, if possible. I'm assuming I can't just get a new GM rod without having it balanced with the others. Any ideas? Thanks.

[Robyn]

Hey

Tomorrow I will snoop in the shop
I think I have some piston/rod assemblies for the 6.5
If I do I am happy to send you one.
I need to make sure they are 6.5
These are not balanced in sets.
The rods are balanced to a standard spec and will be fine to go right in.

I will look in the morning and then get back to you...

If I do have you can PM ME an address and I will get it on the stage heading your way.

Which cylinder ????

Later

[malpana]

Wow! That would be fantastic, thanks. #6

[Robyn]

No worries

If the ones I am thinking of are still where I think they are....
I will let you know...

[Robyn]

I got in the shop a bit ago.....Bad news...The parts were where I thought.....Sadly they are from a 454 and not a diesel....
Sorry ....

[Robyn]

Check this out

https://www.ebay.com/itm/38815687418...Bk9SR7aqxb7TZQ

[malpana]

Just bought one. Thanks for looking in your shop and online. Much, much appreciated!

[Robyn]

Glad you got one coming.
Good luck on the project