GM #3864881 Connecting Rods

[Joe L.]

Looks like some EBay buyer thinks these rods are pretty special. As a matter of fact, these are the best rods that GM ever supplied for small journal small blocks. However, for about this money one can buy a set of FAR better aftermarket rods "and only the engine builder will know for sure".

NOS RODS 63 64 65 66 1967 CORVETTE CHEVELLE NOVA CAMARO
VINTAGE SET OF 8 SB V8 CONNECTING RODS ALL IN GM BOXES




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Item condition:New
Ended:Apr 28, 201020:30:00 PDT
Bid history:19 bids

Winning bid:US $536.56



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[Timothy B.]

Re: GM #3864881 Connecting Rods

Joe,

That's a nice set of connecting rods but $$. What's your second choice for small journal engines. I am wondering how close in weight the aftermarket rods come to the 881 parts.

When I rebuilt my 63 engine the rods had been modified for full floating pins so I ordered a set of reconditioned rods. These are what came for the engine best I can tell because of the extra metal around the big end by the bolt boss.

Pics are at the end of this post in the link.


https://www.forums.ncrs.org/showthread.php?t=73933

[Lynn H.]

Re: GM #3864881 Connecting Rods

Joe,
I am GLAD to see this post from you. I was in the bidding early on and dropped out due to what I presumed to be the case. I feel a lot better now, having you confirm my suspicions.
Lynn

[Duke W.]

Re: GM #3864881 Connecting Rods

Over 500 bucks is nuts. That's a about what a new set of Crower Sportmans- a far, far superior rod - would cost.

And a new set of Eagle SIR5700SP, which are probably as good as the Sportmans are about $250.

Given the price of current aftermarket rods, which have superior design, materials, and processing, it doesn't make economic sense to run NOS rods or rework used rods to qualify them for additional duty.

The above rods are about 590 grams, which is nominally 20 grams heavier than the OE 881s. They are available in both fixed and floating pin, and I recommend fixed pins for engine restorations that are assembled for long life. Floating pins require very careful attention to rod bushing clearance, and are primarily a convenience for racing engines that are frequently disassembled for inspection and refresh.

Duke

[Jack H.]

Re: GM #3864881 Connecting Rods

Joe,

That's a nice set of connecting rods but $$. What's your second choice for small journal engines. I am wondering how close in weight the aftermarket rods come to the 881 parts.

When I rebuilt my 63 engine the rods had been modified for full floating pins so I ordered a set of reconditioned rods. These are what came for the engine best I can tell because of the extra metal around the big end by the bolt boss.

Pics are at the end of this post in the link.


https://www.forums.ncrs.org/showthread.php?t=73933

I know you asked for Joe's opinion, but hopefully you won't mind another...

My first choice would be a good reconditioned set of GM small journal rods that had ARP rod bolts installed as part of the reconditioning. As long as you get the rods with the extra material on the big end as you mention, you are fine. These can be had for a fraction of what those NOS rods sold for, and with the ARP bolts they are far superior to boot. The rod bolts are the weak link to the small journal engines, and I've found this out personally, as have others unfortunately.

I wouldn't bother with aftermarket rods unless you were turning high revs on a consistent basis. On the other hand, the 2nd weakest link on these engines is arguably the rods themselves so it's not bad insurance either. As Joe mentions, only the engine builder will ever know.

Just my 2 cents.

[Duke W.]

Re: GM #3864881 Connecting Rods

The only configuration I'd recommend used ...881 rods for is a 250 or 300 HP engine that only provides a useable rev range to 4500-5000 without head work. With some head work and retarding the OE cam or using a McCagh Special cam the useable rev range is increased to about 6000.

Likewise, a L-79 with head work will provide useable power to 6500+ and a mechanical lifter cam will go to 7000+.

If you have a pre-'66 engine that has the earlier rods without the little hump of additional material adjacent to the bolt seat, they are paperweights, period!

Does "reconditioning" include a Magnaflux inspection? Without proof I assume NO, so a "reconditioned" set of rods could have a crack or other flaw that could eventually result in a failure.

Metal has a "memory" and microscopic surface features are critical. The only way to erase this "memory" and bring the fatigue life of a set of used rods back to something near what it was when they were new is to shotpeen the surfaces.

Add up the cost of Magnaflux, resizing, shotpeening, and new bolts and you exceed the cost of the vastly superior aftermarket rods.

The 327 forged cranks are pretty bulletproof, and for a small additional cost you can get a set of bulletproof rods that could run the 24 hours of LeMans at least twice before you need to worry about them.

Given the value of having an original numbers matching 870 block it doesn't make any sense not to spend a few dollars more to buy new aftermarket rods over the cost of a set of "reconditioned" rods that may be a failure waiting to happen - even on a stock rebuild 250 or 300 HP engine.

Duke

[Jack H.]

Re: GM #3864881 Connecting Rods

Duke, thanks for the heads-up on the Eagle rods. I agree that's a very cost effective way to go that is MUCH better and maybe even cheaper than the re-doing factory rods. The eagles have 3/8" ARP bolts instead of the factory 11/32" size too, which I really like too.

I've not seen the Crower Sportsman's for a while now, and last time I saw them, they were fairly pricey....but these Eagles look like the golden ticket.

Thanks again,
-Jack

[Duke W.]

Re: GM #3864881 Connecting Rods

As far as I know the small journal Crower Sportsmans are now a special order item, and Crower does not maintain an inventory, so they can take a couple of months to obtain.

I believe the case with both the Sportsmans and Eagle SIR5700SP is that the small journal versions are machined from the same raw forgings as the large journal versions, so the small journal versions are probably a bit stronger due to more material on the big end.

I believe some of the big mail order houses have the SIR5700SP in stock, or if not, they can probably get them from Eagle within a week.

Since the last small bearing 327 was built over 40 years ago, it's no longer a popular configuration, so when planning a restoration, it's a good idea to select pistons and rods as early as possible and order as soon as possible. In the case of rods this could be years, but in the case of pistons you should probably wait until you have bore measurements, which will dictate the suitable oversize.

Beyond pistons and rods most other internal 327 rebuild parts are generic to 350s and supply is not an issue.

Duke

[Richard G.]

Re: GM #3864881 Connecting Rods

I know that GM used full floating wrist pins in the 69 302. What others did they use them on? No bushing right on the rod. Interesting this works as well as it does.
Rick

[Joe L.]

Re: GM #3864881 Connecting Rods

I know that GM used full floating wrist pins in the 69 302. What others did they use them on? No bushing right on the rod. Interesting this works as well as it does.
Rick

Rick------


Full floating piston pins were also used on 1969 L-88 and ZL-1. Other than the 1969 Z-28, they were not used on any other Chevrolet V-8 engines going back to 1955.

After 1969 no Chevrolet engine used floating pins until the 1990-95 LT5 (ZR1). They came into use again for some later LS-series small block engines.