Crower Sportsman Conn. Rod Group Purchase

[Duke W.]

As many of you have probably heard me and others say, the early SB connecting rods are WEAK and many high revving engines have been lost over the years to broken connecting rods.

A better design rod went into production in either '66 or '67 and can be indentified by a little hump of material adjacent to the bolt seat, which is where the earlier rods were prone to break. These rods, if qualified by Magnaflux inspection, are okay to reuse on base engines and L-79.

Mechanical lifter engines should definitely receive a rod upgrade.

There are several stronger aftermarket rods available, but most of them are considerably heavier than OE, which is going to require significant "heavy metal" addition to the crankshaft to achieve proper balance.

I have always recommended Crower Sportsman rods because of both their proven reliability and relatively low weight - not much more than the OE rods, so crankshaft balancing will be less complicated.

Unfortunately, the volume of small bearing Sportsmans is now so low that Crower has decided to no longer manufacture them for stock - special order only.

Scott Marzahl is putting together a group purchase program over on the Corvette Forum, which will lower the cost relative to special ordering a single set.

If you anticipate EVER rebuilding a pre-'68 327, especially if you go with a mechnanical lifter cam, I highly recommend that you get involved with this program. If you decide at some point you don't need them I don't think you'll have any problem getting at least your purchase price back.

The 283 rods are even more spindly looking and weak that the 327 rods, but with a shorter stroke and slightly lighter piston the rods are somewhat lower stressed. A good set of the late 327 rods would be fine for most 283s, but you should consider the Sportsmans if you have a mechanical lifter 283.

I recall that Mike Ernst lost a rod on the '57 FI engine about a year ago.

Here's the link to the group purchase thread on the Corvette Forum:

http://forums.corvetteforum.com/show...863&forum_id=4

Or you can contact Scott by email:

scott.m.marzahl@boeing.com

Duke

[Clem Z.]

Re: Crower Sportsman Conn. Rod Group Purchase

how about chevys PM rods and use "king bearings" insert with a thicker insert wall? chevy PM rods are only $250 a set and are good for 500 HP at 6000 RPMs

[Duke W.]

Re: Crower Sportsman Conn. Rod Group Purchase

What about weight? I think you've posted the how to contact the source, but it's not well known how to obtain it.

Duke

[Scott Marzahl]

Re: Crower Sportsman Conn. Rod Group Purchase

Hi Clem,
I thought about that setup and then I priced the bearings, they run around $90 a set so for another $100, you can get the Crowers.

[Clem Z.]

Re: Crower Sportsman Conn. Rod Group Purchase

it is just a case of you do not have to buy them now when you may not need them for a while.

[Duke W.]

Re: Crower Sportsman Conn. Rod Group Purchase

Are these special thick shell bearings, or is it a sleeve that you install and then use an off-the-shelf 2" bearing?

Duke

[Scott Marzahl]

Re: Crower Sportsman Conn. Rod Group Purchase

It appears that it is just an overly thick bearing Duke.

[Mark #28455]

why not just use a stock 350 rod with the bearings

If you're rebuilding a stock type engine, why not just use the factory 350 rods (practically free at any engine builder), rebuild them with good rod bolts, and use the King bearings. The rods will run you about $150 a set rebuilt or less.

I doubt that you'll hurt the 350 rods unless you're really revving it.
Mark

[Clem Z.]

Re: why not to use used rods

used rods are crap shoot because you never know how many cycles are on them. i once built a BBC race engine with used rods supplied by the customer. maged,reconditioned,new bolts and one still broke the first night of racing. never built any more engines with used rods unless i build the engine new so i knew the rods history

[Terry B.]

Re: Crower Sportsman Conn. Rod Group Purchase

Duke,

I sent a couple emails to Scott but he has not replied.
I want a set. Can you let him know?
tboling@samuelstrapping.com

Terry

[Louis T.]

Re: Crower Sportsman Conn. Rod Group Purchase

This is all very enlightening and at the same time quite troubling.

For identification purposes, can someone post a picture of an original SB connecting rod, and well as the redesigned rod with the little hump of material adjacent to the bolt seat?

At what RPM limit are either set safe to use in a driver - or are they not safe under any circumstances? I own a '65 L76 whose motor was redone less than 15 months and 1,000 miles ago, and I want to assess the degree of risk, and under what conditions, I am taking to drive the car as is.

Are the Crower Sportsman rods the only suitable alternative? Will the slightly higher weight inhibit revving?

Thanks to all in advance,

Louis

[Duke W.]

Re: Crower Sportsman Conn. Rod Group Purchase

I have a photo, but don't know how to post it. If you e-mail me I will send it to you. If anyone knows how to post photos, please e-mail, and I will send it to you to post.

Connecting rods are subject to fatigue failure, and failure usually starts with a surface flaw that develops into a crack and then propagates until the rod breaks. One of my '63 L-76 rods had a very bad crack right at a bolt seat.

It's a matter of durability. The engine isn't going to blow up the next time you rev to 6500. It's a matter of how many times you can do this.

Other alternatives like large bearing rods with the sleeve bearing have been discussed in this thread, and there are other small journal alternatives like Scat and Eagle, but those rods are over 600 grams, versus about 570 for the Sportsmans, which are just a little heavier than OE.

The slightly higher weight of better rods doesn't add that much to rotating inertia, but does require crankshaft balancing probably with the necessity to add heavy metal. The lighter the rods, the less heavy metal.

When I rebuilt my engine years ago about the only good aftermarket rod was Carillo and they were very expensive, so I replaced the one rod, went through the grinding/lightening process, and had them shotpeened. Nowadays it's probably more cost effective to buy a set of fully prepped and reliable weight matched rods, even if you do the grinding/lightening yourself.

I hope you at least had your rods Magnaflux inspected to ensure they were crack free. I've discussed the weak early rods a number of times here and on the Corvette Forum.

Duke

[Tracy C.]

Picture of Duke's Rod...no not THAT rod

Still have this in the "gotta save this" file...

tc

[Frank C.]

Re: Crower Sportsman Conn. Rod Group Purchase

Duke you're absolutely right about rods. Magnifluxing didn't tell you how tired they were. The only thing that told you that was almost 10k rpm. I just cringed everytime I had to trash a set of $600 Carillos because it was time. Regards Frank

[Duke W.]

Re: Picture of Duke's Rod...no not THAT rod

The rod on the left is from a 283. Note how spindly looking it is compared to the 327 rods. The late 327 rod has the little hump of material adjacent to the bolt seat, which is where the early rods typically develop a crack that can leak to fracture. I believe the late rods should be in '66 engines, '67 for sure.

The late rods IMO are okay to reuse on 300 and 350 HP 327s if they pass Magnaflux inspection, and the early rods are probably okay to reuse for 300 HP engines if they pass Maganflux, but better rods should be used for SHP engines, particularly with Mechanical lifters.

Higher quality rods are cheap insurance for any small bearing SB rebuild. Forget about hot rod parts. Use all OE or OE equivalent replacement parts except the rods.

AFAIK 350 and BB rods are okay to reuse if they pass Magnaflux inspection.

Duke