Small Block Connecting Rods

[Joe L.]

As some of you may know, GM has replaced all large journal, small block SERVICE connecting rods with a forged powder metal rod of 10108688. This rod is now the only SERVICE connecting rod available for 1968-96 Corvette small blocks and replaces all earlier rods, including the "pink" rods used for 1969-81 L-46, LT-1, and L-82 . This rod was also used in PRODUCTION from about 1993 to 1996 for LT1 and LT4 engines. It's also used in most current GMPP crate engine assemblies, including the ZZ-4, "Ram Jet" FI, and "Fast Burn" 385 hp. Powder metal rods of a different configuration and part number are also used in all Gen III and Gen IV small blocks (except 2006 Z-06, of course).

For a long time, I've had serious misgivings regarding the powder metal rods. I tend to be "conservative" in my thinking and don't like the idea of "powder metal ANYTHING". Well, after doing a bit of research and checking things out thoroughly, I've come around 180 degrees. I'm convinced that the powder metal rods are THE HOT SETUP. If you're building any STREET small block, these are definitely the way to go. FORGET the old "pink" rods that sell for Big $$$ in USED condition. The powder metal rods are at least 25% better than the "pink" rods in every important parameter of strength and durability. Not only that, they are comparatively inexpensive. You can purchase a set of these things under GM #12495071 and that SET carries a current GM list price of $300.44 and shouldn't be too hard to get for $250, or less.

If you're rebuilding any 1968-96 Corvette small block, it's going to cost you at least 100 bucks to have your old rods reconditioned. So, for about $150 more you can have a BRAND NEW set of rods that are superior to ANYTHING originally used in your engine and capable of supporting 500+ horsepower EASILY. This is a true "no brainer" decision. At least, it would be for me. Now, let's see how many morons pay big dolars for a USED set of "pink" rod on eBay or, better yet, what they'll pay for a set of NOS "pink" rods.

The small journal connecting rods (i.e. pre-68) are not available from GM in any form. However, forged powder metal small journal rods are available in the aftermarket. Also available in the aftermarket are higher stength, cap bolt style forged powder metal rods which are superior to GM "Bowtie" rods.

[Joe R.]

Re: Small Block Connecting Rods

Joe,

I agree with you BUT some problems have come to surface with the powder rods that chevy is using in the crate motors. It seems that the end clearance on the big end has not been a big quality control thing with chevy as some crate motors have experienced seizing and rod breakage. As always when buying rods the tolerances should be checked and ground to specs.

Also, there are many manufacturers of rods and cranks that exceed the old pink rod specifications by a mile. What it comes down to is the "pink rod" era has been over for 20 years. When you want a good set of rods, go to Chevy but when you want a great set of rods think 4340 and H beam. Several manufacturers can fill the bill but they will empty your wallet at the same time.

Regards,

JR

[Clem Z.]

Re: Small Block Connecting Rods

the SBC PM rods were tested by GM in a 550 HP engine at 6000RPM for 45 hours without failure

[Clem Z.]

Re: Small Block Connecting Rods

if the "big end" ID is under spec, 2.2247/2.2252, you can hone it to spec but since the rods are "cracked" after big honing they can not be resized smaller as you can not grind the 2 mating surfaces. mass rebuilders use a oversize outside diameter rod bearing insert so all they do is hone the big end to a larger size when they recondition the PM rods

[Duke W.]

Re: Small Block Connecting Rods

Joe - do you know what vendor offers small bearing OE replacement SB rods (not "high performance/racing", but just plain vanilla pieces that are suitable for medium performance street engine rebuilds) either powdered metal or conventional forged steel?

Like you I've always been a little suspicious of "powdered metal" rods. IIRC they were first used on the Porsche 928 V-8 when they came out circa 1977, and have seen increasing use ever since.

Despite my reservations, powdered metal connecting rods appear to have established an excellent reputation - at least in OE applications.

Duke

[GL Anderson]

Re: Small Block Connecting Rods

Duke: Scat offers small journal small block forged rods that would work in just about any application. They are fairly inexpesive at about $250 street price for a set of 8. GL

[Scott Marzahl]

Re: Small Block Connecting Rods

Yes, Scat has several levels of small Journal rods available for a very affordable price, the standard 4340 replacement, their premium 4340 with cap bolts and polished beams and then their H Beams. Duke, you should swing by, they are in Redondo Beach. They also make a nice replacement and custom crank.

[Duke W.]

Re: Small Block Connecting Rods

Yes, I have looked at their onlind catalog and talked to them at SEMA, but have not visited their facility, which is only a couple of miles from me. I should stop by sometime.

One concern that I have about aftermarket high performance rods is that most are significantly heavier than the OE rods, which may increase the cost of balancing if heavy metal has to be added to the crank.

My choice for mechanical lifter SBs is the Crower Sportsman. There are cheaper rods out there, but the Sportsmans are barely heavier than OE and Crower has an impeccable reputation. One thing I will not skimp on is rods, tires, and shock absorbers. Only the best will do, and price is not an important criterion.

My question to Joe was on available OE spec replacement rods - something that could be used for a medium performance engine that is at least as good as the late small bearing OE rods.

Of course, as I have said many times before, the early small bearing rods are weak, and I don't recommend reusing them for ANY rebuild.

Duke

[Scott Marzahl]

Re: Small Block Connecting Rods

Yes they do have a good reputation for rods, cranks, rockers but I went to install one of their cams once, it had bounce all over the base circle. They took it back and the new one was a little better but not a lot. I would prefer to use a Jack Engle cam anyday, Traco always did.

[Joe R.]

Re: Small Block Connecting Rods

Duke,

Sorry, but I don't know of any rods that are as economical as the powder rod by GM but Eagle has a 4340 H beam in the range of $439.00 to $499.00 for a set of 8 depending on stroke.

The problem with the powder GM rods is that if you drop one, chip or otherwise hurt the rod it's trash. Because of the construction it cannot be used after any trauma.

The problem we had with a GM crate engine was the 7/8 side clearance was not enough. The 7/8 rods welded together and broke the 7/8 rods, punched thru the cylinder wall and generally destroyed the engine. This engine was sitting in a 65 Corvette with exactly "0" miles. Cranked it for the second time and after warming up, turned it up to about 2500rpm and "bam".

Chevrolet admitted problems with the engines and replaced it with a LS-1 free of charge.

You won't find me spending my hard earned money on what I think is a great engine and cutting corners with those cheap rods. A couple of hundred dollars more from any company can insure having a set of strong and dependable rods.

Regards,

JR

[Joe L.]

Re: Small Block Connecting Rods

JR------

Your last sentence summarizes the situation. There are LOTS of very high quality rods on the market but the price is very high and, certainly, no one is going to get a set of them for $300. Street engines, even SHP or modified street engines, do not need these high dollar rods. When someone is trying to make a decision between having their old rods reconditioned or buying a new set of rods, they're not going to likely consider an $800+ set of rods in their "deliberations". And, quite frankly, they shouldn't consider such a set of rods. It's really foolish to spend that kind of money on a street engine's rods.

The PM rods offer the best of both worlds; strength and durability superior to the old "pink" rods and very modest cost. The "pink" rods were really more than adequate for any street small block engine, but they were expensive. So, the PM rods give you 25-50% BETTER strength and durability than the "pink" rods and cost 1/3 as much. You don't get a deal like that very often.

The GM rods I believe use powder metal forgings manufactured by GKN Sinter Metals in the USA. However, the rods are machined and finished at GM's Toluca, Mexico engine plant where ALL Gen I small block engine and component manufacturing has been "consolidated". At least some of the aftermarket PM connecting rods are 100% manufactured in the USA from GKN forgings.

Also, while there are stronger and better non-PM rods available in the aftermarket, that's as compared to the above-referenced OEM rods. There are better quality PM rods available in the aftermarket which rival the strength and durability of the best aftermarket non-PM rods and they cost less than those rods. When you compare "apples-to-apples", the PM rods come out in front with respect to both strength/durability and cost.

[Joe L.]

Re: Small Block Connecting Rods

Duke-----

Howard's Cams offers small journal small block rods in forged powder metal that are equivalent to or better than the large journal GM powder metal rods that I mentioned. I don't know what they cost, but I believe that they are quite reasonable.

The Howard rods also use "fractured cap" technology. Instead of a saw cut rod-to-cap interface, the caps are "precision cracked" from the whole round forging.

[Joe L.]

Re: Small Block Connecting Rods

JR-----

Oh, I'm a big believer in that! Using the best quality rods has no "downside", except price. I do things like that all the time. "Overkill" is my "middle name". Just because I do it doesn't mean that it's SMART, though. In fact, in many cases, it's quite foolish.

For most folks who are rebuilding a stock or even somewhat modified Corvette engine, though, the powder metal GM rods offer a GREAT alternative to having their original rods rebuilt (which is what most folks do). For a few hundred dollars more, they get a brand new set of rods that are superior to the originals, no matter what originals were used in their engine. And, they get a rod which is PRODUCTION-validated by GM. These rods may be relatively inexpensive but they're not "cheap". Like I mentioned, a guy who would be satisfied with rebuilt original rods is not going to suddenly decide that he has to have a set of $1,000+ rods. However, he might decide that it's worth it to spend an extra $200 and get a set of brand new rods that are superior to whatever came out of his engine (and, was going to go back in).

GM Bowtie rods are one of the best rods out there. The profiled Bow Tie rod, GM #14011082, carries a current GM list price of $167.30 EACH or $1,338 for a set. You can buy a set of these for about $1,000, though. They'll work great in most small blocks, too. The BEST aftermarket rods cost well over $1,000 a set. They'll work great in most small blocks, too.

[Joe R.]

Re: Small Block Connecting Rods

Joe,

I agree that we spend way too much on these Corvettes that we are afraid to drive. I just happen to have a set of those bow tie rods, GM forged crank and the 12.5:1 heavy duty pistons. Have had the rods bushed and the entire assembly balanced. This assembly has been on the shelf since sometime in the 1980's. Just waiting for a opportunity to try it out! Just not a motor to use for getting a gallon of milk.

Regards,

JR