Lz9 rotating assembly weights

[eHoward]

That sounds like a nightmare. Thanks for the heads up. I wondered why people were pulling "good" rods.

If you go used, you probably could find a set of Ti rods, on a budget. This one is $1,250:

https://www.ebay.com/itm/266472618709?m ... media=COPY

I would be very cautious about used LS7 rods. They have an anti-friction coating on them from the factory that wears off naturally over time and usage, and once gone they start shedding titanium flakes which quickly destroy the engine. Ask me how I know, and what happened to my previous C6 Z06 time attack car...

There used to be some places that were re-coating rods, but I don't know if that's still an option.

[The Dark Side of Will]

If you go used, you probably could find a set of Ti rods, on a budget. This one is $1,250:

https://www.ebay.com/itm/266472618709?m ... media=COPY

I would be very cautious about used LS7 rods. They have an anti-friction coating on them from the factory that wears off naturally over time and usage, and once gone they start shedding titanium flakes which quickly destroy the engine. Ask me how I know, and what happened to my previous C6 Z06 time attack car...

There used to be some places that were re-coating rods, but I don't know if that's still an option.

Ditto on the protective coating. Because of the way "naked"(*) titanium galls, it must be coated with something anywhere it sees relative motion. Playing with Ti rods when you're not an OEM is difficult and expen$ive. Modifying Ti rods is downright foolhardy

So the ls9 small end can be bushed I would assume, and maybe the big end bored out or a larger bearing installed? I am also unsure of the width on the ls9 rod

For the reasons cited above related to Ti and others related to the basic strength of the part, boring the big end would be a terrible idea. Cut the crank instead.

(*)Titanium in air is never "bare", since it immediately forms a tenacious oxide layer. The oxide layer is protective from corrosion, and there's nothing more corrosion resistant than titanium, but the oxide layer is not suitable for a mechanical interface.

[Shaun41178(2)]

So the big end would need to be narrowed like a typical SBC rod when converting to our engines as the LS engines have a similar rod width to the old sbc rod

It seems that the coating comes off the rods at the big end, since that's where the rods in a stock V8 application share a rod journal, so they can rub on each other. This isn't an issue with the v6 crank. I haven't looked to see if recoating is still possible but I know it was offered at one time. I am sure it is still around however because aftermarket companies are still making Ti rods, so those would have to be coated when new.

Cutting the crank would change the necessary compression height needed for the piston. So perhaps off the shelf pistons wouldn't work any longer making custom ones necessary which would then add a cost that would prob make a build not worth it financially. Also I would worry about the crank strength being compromised.

[The Dark Side of Will]

So the big end would need to be narrowed like a typical SBC rod when converting to our engines as the LS engines have a similar rod width to the old sbc rod

It seems that the coating comes off the rods at the big end, since that's where the rods in a stock V8 application share a rod journal, so they can rub on each other. This isn't an issue with the v6 crank. I haven't looked to see if recoating is still possible but I know it was offered at one time. I am sure it is still around however because aftermarket companies are still making Ti rods, so those would have to be coated when new.

Titanium rods are slowly becoming more common; the technology is definitely proliferating. I haven't looked into having titanium recoated.
What's the rod end clearance in the V6? The cheeks of the crank throw do rub on the sides of the rods, although the oil that's squeezed out of the bearing lubricates the sides of the rods.

Cutting the crank would change the necessary compression height needed for the piston. So perhaps off the shelf pistons wouldn't work any longer making custom ones necessary which would then add a cost that would prob make a build not worth it financially. Also I would worry about the crank strength being compromised.

Cutting (grinding) the crank would not change the piston compression height. Offset grinding the crank like Upson did would change the required piston compression height.

I guess Ti rods for a 4.3 V6 would be too expensive as there are no factory take-outs to snag used. Don't the LZ4/9 use the same size rod journals as the old 4.3's? (Do the LT based 4.3's use the same journal size, for that matter?)

[Shaun41178(2)]

Cutting (grinding) the crank would not change the piston compression height. Offset grinding the crank like Upson did would change the required piston compression height.

I guess Ti rods for a 4.3 V6 would be too expensive as there are no factory take-outs to snag used. Don't the LZ4/9 use the same size rod journals as the old 4.3's? (Do the LT based 4.3's use the same journal size, for that matter?)

Don't know about the old 4.3s. They were essentially a SBC with 2 cylinders cut off. The newer lt 4.3 I have no familiarity at this time but suppose I could research but there are no Ti rods from gm for that engine.

Your right about the crank. Only if I was offset grinding.

So the lz rod big end is 2.374 diameter according to Pauter. Gm lists the ls7 rod as a 2.225.

The lz9 crank has the journal for the rod listed at 2.248-2.249

The ls7 rod journal is listed as 2.100

[The Dark Side of Will]

The SBC started off with 2.000" rod journals, then went to 2.100" rod journals.
The 4.3 at some point (IIRC) had 2.250" journals to help with crankshaft stiffness because it had split crank throws. IIRC, the 4.3 started off odd-fire, then later GM split the journals to make it even-fire. Keeping crankshaft stiffness high enough with split journals required upsizing the journal diameter.

The earliest V6/60's had something smaller than 2", then upsized to 2.000" for most of the production run. Obvi that's why they can use small journal SBC rods.
As you noted, the LZ4/9 have ~2.250" journals. This *should* allow them to use 4.3 V6 rods narrowed the same way SBC rods are narrowed. I *think* someone on Pfiffle at least mentioned this possibility, if not outright doing the build. I want to say it was a 3.4 TDC with LZ9 crank (Does the LX9 have 2.000 or 2.250 journals?), but it's a vague memory.

Also note what piston pin diameter you're designing around... 1.100 is an extremely short compression height, and you may (probably will) run the oil rings into the pin bores. Pin diameter affects the degree to which this happens.

Unrelated:
The Northstar has 54mm rod journals, but slightly thinner bearings than SBCs run. The Northstar rod BE bore is 2.226 vs SBC 2.225. So with narrowing, re-keying and maybe a slight hone, a Northstar can also use SBC rods.