Which connecting rods to use

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HawaiiDuster

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I'm planning on building a 340 but nothing really crazy and was wondering want you guys thought would be a good choice for a connecting rod. Looking at around the 400 hp range. The choices I was looking at were the Scat 26123, Eagle 6123CB, or just getting one of the sets of stock 340 rods reconditioned at the machine shop. I got a 340 crank, a set of SRP pistons and need to get some rods so I can get things balanced.
 
eagle and scat are made at the same plant. Scat meet quality specs. eagle are all over the place. Scat 8 out of 10 are ok. eagle 4 out of 20 are ok. You only get what you pay for.

Ask a good machine shop that checks new rods instead of just throwing them in which are the best rod to use.

I went with. Carello on my 428. and Stock resized rods on a standard stroke.

Look for the rods with the smallest bump on top of the piston pin. These have the most meat/metal beams between the journal and the pin. These are your strongest rods fpor less money. Just get a bunch of 340 360 rods and use the shortest over all length. Have the big end re sized and get new bolts.
 
Stock rods would handle that and a decent n20 shot... :)

IMO, with budget in mind, I'd figure out the cost to refurb a stock set vs. buying a new set of Scat I beams. Go from there.

The Scat's are a bunch lighter than a factory rod.
 
crackedback said:
Stock rods would handle that and a decent n20 shot... :)

IMO, with budget in mind, I'd figure out the cost to refurb a stock set vs. buying a new set of Scat I beams. Go from there.

The Scat's are a bunch lighter than a factory rod.
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I did that. Just to resize and install new rod bolts cost almost 60 percent of a set of scat rods. Scats you loose the cost of pressing the pistons on, and you get the full monty.

Im going with scat rods.

EDIT: Just to protect the 340 block, and since going with SRP fordged pistons, at the very least I would go with the scats, and honestly would look hard at h beams. Even more so if its a fordged crank. Then the max HP limit would be the block.
 
Always over build your engine(s) for its intended use and you will never have a problem.
 
70aarcuda said:
Scat 4340 I beams would be my choice...
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This is what I have looked into. I started a similar thread and it was pointed out to me that by the time you get the stock rods re-sized and new ARP bolts, you are real close to just buying a set of new.
 
if it comes down to it budgets get tighter I have 15 to 20 rods I would give you for 25.00+ price of shipping I already bought scats and these are just taking up space I also have 360 pistons and 360+.030 used any body wants them for 75.00 + shipping just pm me
the rods would be fine for you I have had stock rods in my 340 for 30 years 380 hp
and never threw 1 yet not that I haven't seen guys throw there brand new aftermarkets in less than a season. I don't know the answer but I am finaly changing with technalagy
a lot of times older was better I hope I get the same luck with my scats
 
Thanks for the replies guys! I was leaning towards the Scats, but just wanted a little reassurance from the gang that I was going in the right direction.

PoisonDart74 said:
Why are you changing the rod? Balance it if anything, run that s*it.
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It's a new build so not really changing, just getting the pieces together. I want to try and get something together this summer, and here's the short/long of it.

I have a 72 340 Duster I was planning on selling with the original block. It's been machined and is about ready to be assembled. I also have a "fresh 10 years ago" 340 that I have never run. It has the old TRW pistons so I can't run my eddy's on it. So the plan was to pull the rotating assembly out of the "new/old" short block on the stand and put it into the numbers 72 block for the duster with a set of X heads that I have "new" and ready to go. The other block can then get the set of SRP pistons, Scat rods, and the eddie heads to go into the 68 Cuda thats just been sitting in the driveway.

I know it kind of sounds roundabout, but this way I can get engines in two cars. A close to stock one for the Duster and a slightly built one for the Cuda.
 
HawaiiDuster said:
Thanks for the replies guys! I was leaning towards the Scats, but just wanted a little reassurance from the gang that I was going in the right direction.



It's a new build so not really changing, just getting the pieces together. I want to try and get something together this summer, and here's the short/long of it.

I have a 72 340 Duster I was planning on selling with the original block. It's been machined and is about ready to be assembled. I also have a "fresh 10 years ago" 340 that I have never run. It has the old TRW pistons so I can't run my eddy's on it. So the plan was to pull the rotating assembly out of the "new/old" short block on the stand and put it into the numbers 72 block for the duster with a set of X heads that I have "new" and ready to go. The other block can then get the set of SRP pistons, Scat rods, and the eddie heads to go into the 68 Cuda thats just been sitting in the driveway.

I know it kind of sounds roundabout, but this way I can get engines in two cars. A close to stock one for the Duster and a slightly built one for the Cuda.
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Excellent plan.
 
Mo-Par said:
Scats are a great choice. Plus they have the bigger arp bolts than the eagles.
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I wouldn't say that, I eagles have the same 7/16 arp rod bolt, though my are the strongest arp makes in that size.
 
I like the stock ones. JMO.
 
How often have you seen stock rods go bad? Unless it is a severe build ...
Chevys throw rods because of poor rod ratios.
 
mbaird said:
How often have you seen stock rods go bad? Unless it is a severe build ...
Chevys throw rods because of poor rod ratios.
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twice..both were stock rods...both going thru the traps....not much left to engine....
 
Is that air I see under your front wheels? I would consider that a severe build...
Most guys building a 400hp or less motor should be fine with properly built stock rods.

I used Eagle I beams in my .638 roller w2 12.5:1 motor... but am using polished stock rods in this next motor...10:1 , ported J's , Lunati 403 , dougs header and LD340

I used these rods in an old 340 4sp dart ....launched at 5000 and ran high 12's.
They checked out fine at the machine shop for this build.

Now I've Jinxed myself... I will throw a rod in first 100 miles...lol
 
RustyRatRod said:
In all fairness, twice out of how many? And how long?
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remember the old saying...fool me once shame on you...fool me twice..shame of me...

and you learn from your mistakes...lol

ok...done being a fool......not telling anyone to go buy anything they dont want...just reflecting on personal experiences...

part of the problem..that i see....you get a used short block ....you have no idea..how many miles or abuse the rods have taken...

To me..the difference in price for the scat rods vs the rebuilding of stock rods is cheap insurance...

ok..i am mostly talking about racing....Yes...a stock every day drive...i certainly would use stock rods....just wanted to clarify that
 
Its kinda like cast cranks.... Herb McCandless told me he had seldom ever seen a stock 360 crank break....

Those were the days that you could actually talk to the guru's !
 
mbaird said:
Its kinda like cast cranks.... Herb McCandless told me he had seldom ever seen a stock 360 crank break....

Those were the days that you could actually talk to the guru's !
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actually even through a rod broke..the cranks survived...one needed to be cut to .030 ...but it survived...
 
Its a dollars and cents thing. Press off the old pistons, disassemble, clean, magnaflux, polish beams, cut cap and rod, install new ARP bolts, resize, weight match/balance. This all costs $ at the shop. Now you've got a set of weaker forgings with an unknown fatigue history. Heavier than any I-beam aftermarket rod, pain in the *** press fit small ends, and inconsistent lengths.
Now compare that to a set of after market rods. Its false economy IMO.
 
Cannot argue those points for sure. That said, I am not convinced that spending money on total chinkesium is anymore smart than using AMERICAN forged steel stock rods. I think for my money and power level, the stockers will work fine. Besides, I can install my own rod bolts. That saves a dollar or two. I can get rods reworked here for 150 bucks a set, so it's worth it. Yeah, maybe stock rods have been twirled around a lot, but I like um.
 
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