Technical School me on SJ SBC Connecting Rods

I'm in the process of collecting components to build a healthy (but dependable) 283. I have .030-over forged pistons, a steel .010 under crank, a Mallory dual point distributor, and a Weiand 2x4 intake with Carter/Edelbrock carbs. I'm planning to use a 327/350-ish cam, probably a true L79-spec unit. The assembly will feed HP through a Muncie M-21.

My block has been cleaned, bored (for forged pistons), and surfaced. The main caps were machined to allow for a fresh line bore. It's now wrapped in plastic awaiting assembly.

My question in this thread is...What advantages/disadvantages (if any) do aluminum connecting rods offer over OG GM steel rods?

Any other info or pointers would be greatly appreciated.

 

They fail on the street more often where as steel kinda like it there.

 

Aluminum rods look much more beautiful that stock steel rods. But you can't see them once the engine is together, and you really can't see the work hardening, and you can't easily predict when they'll come apart. So you might just want to stick with steel rods.

How many RPM do you plan to spin this engine? If it's over 6500, you might want some aftermarket steel rods. Otherwise, a set of magnafluxed and resized OEM rods with new ARP bolts should be just fine. That's what I put in my 327.

 

Thanks @squirrel

Not planning on anything that radical. Definitely not a race engine, more of a "spirited" street engine. If it has 300 hp, I'll be ecstatic!!! OEM it is.

Any other recommendations?

 

Are you getting the engine balanced? This might not be necessary if the crank and rods are the original set out of one engine.

 

@squirrel Haven't thought of that. I might need to since I'm pulling good parts together from different engines.

I have 3 sets of rods. Should I use one complete set, or should I weigh/measure and match the best 8 out of all?

 

Get it all balanced including flywheel or flex plate. Clutch too if stick!

 

I just had a 283 done for my 1917 roadster pickup. The shop that did the engine suggested a kit with crank, rods and pistons for a 30 over 283. I would think you would want to match all the rods including weight as you said, a street engine. Neither of us is going to beat the crap out of a small engine on the street other than just showing off. Here is how mine turned out

 

Getting rods reconditioned will cost you more than purchasing some inexpensive aftermarket rods with ARP bolts already installed. The aftermarket rods will most likely be much stronger and similar in weight.
You are using completely different pistons of unknown weight compared to the OEMs. You might want to get a scale and weigh all those components just for comparison. You can lighten the pistons to match, and you can lighten the rods to match their weights as well. Its a learning experience.Get a cheap digital scale. Rods are also weighed end to end as well as overall weight. Then take them to the machine shop and pay them to balance the crank to them.
Something to consider is that the 283 will need mid range torque to make it a good driver. Look at the hp produced in the mid-range instead of just the top rpm hp. Larger displacement engines can get away with a peakier cam, but the wrong cam/too much cam in a 283 will be disappointing.

Here is some older information which may help you .









You can recondition the old rods, but if you go thru the whole process of replacing the bolts and resizing the rods and magnafluxing them.....check the cost first. Bare minimum is new ARP bolts.


Something else to consider. Buying the cheapest rods may be more expensive. Look at the weight of the rod. A lighter rod will be easier to bring into balance. If the rod is heavy, it may require the addition of Mallory metal in the crank to bring it into balance. Thats expensive. Weigh your stock rods and get some lighter than that if you can. Ask your machinist how much it costs to install mallory metal before deciding what to do.

 

As Squirrel stated, aluminum rods have a fatigue life. Most pros running them keep track of run time and trash them on a set schedule, or so Ive been told. Not many people I know have the money or time for that.
For reasons I cant remember the stock rods marked with a B, O, or X on the cap were supposed to be better than the unmarked ones. For the cost of magnafluxing, new ARP bolts and resizing, youre pretty close to the cost of a new rod that has no run time on it. Good Luck.

 

FWIW there are different small journal con rods, for 1962 Chevrolet beefed up the area at the rod bolts so you might consider that when selecting your rods. Also, rods are not just weight matched, the small end and big ends are weighed to ensure the reciprocating weight is the same.
‘55-‘61 rods-

‘62-‘67 rods-

 

Thanks for posting that article. I understood that aluminum connecting rods were only good for so many cycles, then had to be replaced. I could be, and often am wrong(according to the other person in my house).
For street use I would at least use quality rod bolts, sized and weight matched rods.

 

SCAT and others sell very good replacement rods that are way better than stock but are not up in the high dollar H or I beam racing or light weight style. They come perfectly match weighted and are an excellent way to feel safe with a street performance engine. I would check the Competition Products website or their catalog if you have one. I use it reference all the time.

 

I’m asking this question because I really have no idea- is there a reasonably priced, aftermarket small journal (as in 265-327) connecting rod on the market?

 

Eagle makes a nice I beam small journal rod. About $ 350? For a set

 

But it doesn't scare me to use a reconditioned facrory rod with good bolts on a street engine.

 

I like to use as many old parts in an engine as I can, so maybe I look at it differently than most folks.

We're on the HAMB, aren't we, not the 1-800 rodding forum?

 

I had Jimmy in Lanexa at Jimmy's Engine Service redo all my short block stuff in my 283, Then I assembled it. He redid the rods, it was about 300 bucks, but I'd rather give Jimmy 300 bucks than buying a set of scat rods that were probably made in China by a 12-year-old and machined in Long Beach by a guy barley being paid enough to live in the Peoples Republic of California. I used an old part and supported a local small business.

That being said, take your rods, pistons, flywheel, damper, and clutch all to Jimmy ( I think he did the work, I I think the block you have is one of my spares we swapped around a while ago) and have jimmy balance everything, along with installing ARP rod bolts and resizing the big end. He did a fantastic job on mine. if you haven't already, bring the block to him to so he can final hone the block to fit to the pistons perfectly. Also, if you are going to run the 327 350 cam, make sure you have enough compression to run it. Stock type rebuilder pistons will put the piston down in the hole because the manufacture assumes a deck cut for cleanup. If your block hasn't been decked that increases cylinder volume, and lowers compression, also, head gaskets are an issue. With the smaller bore, off the shelf Fel Pro head gaskets are typically between .035 and .045 thickness when compressed. Add the valve relief in the pistons, plus how fa down in the hole the piston is, plus the head gasket thickness, plus the CC of the cylinder heads.... and It doesn't take long to put together a brand new 7.5 to 1 compression 283. I had to cut .020 of the deck surface on mine, to use my speed-pro pistons, and that still left the piston .025 down in the hole but combined with some SCE steel shim head gaskets at .015 that put my compression height at .040 (optimal for a small chevy) plus my cylinder heads with 53 CC chambers, gave me about 10.0 to 1 static compression. Anyway, call or text me if i can help Brett! and PS i really wish i had not traded that 2x4 intake to you! now I cant find another one! Trade ya for an early Vette one!

 

@Nailhead Jason Your memory on the 283 block is correct! Jimmy did all the work including finish boring the cylinders to fit my forged pistons. I'll have to measure the deck height...not sure if he cleaned them or cut the .020 or so for proper compression height.

I have a pair of early PowerPak heads that will get machined and cleaned.

I'm sure I'll be leaning on John, Jimmy and probably you as well to get this one bolted together.

 

Let me know! Theres lots of little stuff that make big improvements that cost almost nothing. If you want to use the steel shim head gaskets and cant find them for the smaller 283 bore, let me know, i have some spare SCE ones and stack of NOS Gm and Fel-Pro steel shim gaskets from the 60's that have the smaller bore. I hate using the 4 inch bore gaskets on a 283.

 

@squirrel I'm with you on resourcing old stuff. That's why I have 3 sets of SJ rods, along with 2 complete engines, 3 extra blocks (2-283, 1-327), and enough extra stuff to get a good start on two more engines.

 

I always replace the rods. I like SCAT rods. They are as cheap as the reconditioned rods and I know they have zero hours on them. With a stock rod, you don't know the life they led before you found them. They could have 879,000 miles on them. It's cheap insurance.

I used stock rods when I was in high school and they were fine, but dude.....that was 40 years ago, so the rods predate me. Dang, I'm old, not as old as Lumpy though.

No aluminum for the street.

 

From experience, as far as strength goes, for a street 283", anything beyond reconned stock rods is wild overkill. We recon stock rod big ends with ARP bolts for cheap. Making them all the same center-to-center length doubles the cost. The best thing about aftermarket rods is they're good to go out of the box. Center-to-center length is dead nuts on all of them, weight is within a gram on each end.

Today's pistons are also all within two grams out of the box. A balance job today takes half as long as when we were trying to make crap OEM pistons and rods all weigh the same.

One caveat; someone reading previous recommendations here just brought us a set of Scat rods and a set of hypereutectic pistons, pin bores not cut for circlips. Now, he's got to get another set of pistons.

jack vines

 

That’s unfortunate. I’ve ordered many sets of pistons from different manufacturers and all were what I specifically wanted and I always read every line on the order blank.

 

Most pros also bin them if they ever hit the rev limiter [especially at the top end of the quarter]

Why would he do that? All he needs is Teflon Buttons

 

Those only work on barrel skirt pistons where the pin bore is flush with the cylinder wall. Most aren't today.

 

I have never even considered aftermarket rods on any engine I have built. And, I have only messed up rods because of some stupid mistake or a faulty part that wasn’t a rod. Anyway, I guess I am in the “make junk work” boat and that usually works good for me. I have had multiple 8000 rpm small blocks with GM parts in the bottom end. Pretty sure I’ll keep doing that since if it does blow up, it is less money wasted.

 

Used to be "Pink" rods, sure if over the counter or not.