Second design SB Rods or Not????

[Jim V.]

Is the rod (pictured below) a 67+ second design or pre 67 first design? With all the talk about early rods being the weak link I would like to be sure.

From previous posts, I thought the slight bumps at the 10 and 2 o'clock positions on the rod face were telltales of the beefier second design. The problem here is these rods came out of a original late 65 motor..... hmmmmmmm.

Thanks
JimV

[Duke W.]

Re: Second design SB Rods or Not????

It appears to be second design. It's never been clear to me when they went into production. I thought is was the beginning of the '66 model year, but maybe some late '65s had them. Chevrolet realized that the first design was weak and such a change is easily implemented as a "running change" whenever the new design parts are available.

The first design was definitely weak at the bolt seat - that's where they typically break, and those little humps of material adjacent to the bolt seat signficantly improved this area's strength, which improved fatigue resistance and makes a for a much more durable rod.

These second design 327 rods are okay for a 300 HP and are probably okay for L-79, but somewhat "iffy". It was the high revving mechanical lifter engines that needed them, but by the time they were available, these engines were out of production or nearly so.

In any case, I would have them Magnaflux inspected, and if there are no cracks, I think they're fine to reuse for a 300 HP engine rebuild.

Duke

[Jim V.]

Cost/benefit...vs Skat

This is a very late 65....June 30 motor.

The obvious issue will be determining the cost/benefit given the magnafluxing and reconditioning costs of using these versus a new Skat rod.

The mag and recon for the old rods will probably run close to $200 which is a few dollars less than the new Skat rod.... These old original blocks easily justify a bullit-proof rotating assembly.

Thanks as usual Duke!

[Scott Marzahl]

Re: Cost/benefit...vs SCAT

If you shop around, SCAT rods can be found for $200-$225 and being 4340 material much stronger than these old stock rods and they will not have been fatigued like these old ones. However, they do weigh a bit more, anywhere from 620-640 grams/rod vs 575ish for the stock ones, but since you are having the engine balanced anyway it really doesn't matter.

[Duke W.]

Re: Cost/benefit...vs SCAT

I wouldn't say it doesn't make any difference. Heavier rods will probably require "heavy metal" to be added to the crankshaft, which will likely increase balancing cost. The Crower Sportsmans are closer in weight to the OE rods, I think the spec is 585 grams.

So one should discuss the cost of balancing for "light" versus "heavy" rods. The Crower Sportsmans may end up not being that much more expensive if balancing is cheaper than with a heavier rod.

Duke

[Scott Marzahl]

Re: Cost/benefit...vs SCAT

Agreed Duke, perhaps my choice of words wasn't the best. I simply meant since he was going to have his assembly balanced, he could use either rod but heavier parts equate to more time on the balancing end which in turn equates to more money. The Crower published spec is 585, however all of the 16 sets that came in were 600 +/- 3 grams per box so a little heavier than I expected.

[Jim D.]

Re: Cost/benefit...vs SCAT

I'd go with the Scat rods. In fact, I just ordered at set. I know of several drag racers that use them. 500+ HP at 7000 RPM and no problems with balancing or failures. $200 vs. $500+ for the Crower rods. You are going to have to have your engine balanced either way you go.

[John G.]

Re: Cost/benefit...vs SCAT

The rotating assembly in my 327 was balanced along with new SCAT rods. The SCAT units are significantly heavier than stock weight rods, I came to find out.

I remember when I went to pick up the engine assembly parts the balancer told me he was "able to get it" and "you got your money's worth". Those comments seemed to suggest that there was at least some bit of difficulty in the balancing operation with these rods and that the balancing took more time to do.

A MIG welder was used to add weight back onto the crankshaft via the factory drilled holes.

John

[J M.]

Re: Cost/benefit...vs SCAT

I, too, used the SCAT rods to rebuild my 327/350. I would have used the Crowers had there not been a 5 month wait at the time. Since I did most of my balancing work myself, it really didn't cost me more to add the weight and balance. Rod side clearance is a little much at .019", but I am told that will not be a problem. They are definately quality rods and I see no problems with them. But, if I had to do it over again and the Crowers were available, I would spend the extra money and get them. Just my opinion.

[Duke W.]

Re: Cost/benefit...vs SCAT

Scot -

Are those rods the "Stroker" Sportsmans with cap screws or the standard "through bolt" Sportsmans?

My Crower catalog lists the 5.7" Stroker Sportsmans at 590g and the standard 5.7" through bolt type at 600g.

It's never been clear to me which type you ordered.

What Crower part number did you order?

Duke

[Clem Z.]

why not GM PM rods #12495071 and king spacer

rod bearings,use 2.100" rods on a 2.000" crank pin. rods $250 for 8 and king bearings $80 total $330 and no balance problems and the rods are good for 500HP.

[Terry B.]

Re: Cost/benefit...vs SCAT

Crower Sportsman Rods with cap screws Part # SP93200B-8.
Latest catalog indicates Sportsmans Rods come with thru bolts or cap screws and also as Stroker Sportsman with cap screws. The paperwork indicates 601 grams. I ordered a set with Scott.

[John G.]

Re: Cost/benefit...vs SCAT

The SCAT rods in my engine also came in at .018 - .019 thou side clearance. I asked around about that as I had thought .015 thou was the normal rod side clearance spec. .. Consensus of opinion was that the .019 thou rod side clearance won't be an issue.

[John G.]

Re: Cost/benefit...vs SCAT

Added . .
I did grind and and smooth down the parting line on either side of the rod beams to knock off a few extra grams of weight. I noticed when I got my rods back from the engine balancer some of the big end balance pads on some rods had been ground on significantly to bring those particular units into balance.

[Clem Z.]

the king spacer bearing # CR867HP

and they are available thru holleys lunati brand