Speaking of rods...

[Doug Wilson]

Sailor son's 340 is being built with reconditioned stock 340 rods, with no trick stuff done to them, like shot peening. Where is their failure point?

Ed. Alum Heads 10.5:1, forged SRP pistons, Air Gap, 750 cfm carb, ARP rod bolts, headers. All the machining tricks.

[Doug Wilson]

No thoughts on this, anyone?

[1972roadrunner]

my GUESS would be near the center, or closer to the crank....i couldn't tell ya.

w/only 10.5:1 compression there shouldn't be any problems...

actually, i have stock rods on my 340 w/12.5:1 compression...i have never had any problems. they should be ok...

my $0.02

[JCFcuda]

I would think they will last a long time if they dont get spun tooo high. Did he take a look at those Eagles SIR I beams For about $250? Jim

[phoenix]

Doug, if using the "stock" bushed small end 340 piece make sure they "pin-fit the pin to bushing clrc. at no more than .001", around .0008" is better, if not re-bush 'em. The weakest point I found racing the old 340 rod was at the "broaching" point right beside the head of the rod bolt. The factory cut "groove" or "relief" for the head of the bolt before the beam section continues upward towards the small end. Inspect 'em and try for the ones with the smoothest "broach".
While we're on the subject, I hate to tell you this, but, we had a lot better success using the later "flag" designation 360 rods. Rockwell testing indicated they were in fact a harder steel, usually visually they also had thicker beam section widths, and better broaching at the bolt head corners to boot! Not to mention another visually pleasing characteristic of a smoother, less porous forging surface to the "flags" in general. Look for the "flag" ( a "P" on a small rectangle) for lack of a better description, about half way up the rod above the forging number.
True, they're not full-floated, we always ran 'em pressed anyway up to 7500 rpm and never had a problem, do however make sure the pins are fit in the pistons at .001".
Just my 2 cents worth, hope it helps....

[phoenix]

Doug, just to clarify the above. That's where the 340 rod will break if ever, is at the corner by the rod bolt head into the big end. Usually a crack will propagate from a sharp end in the broaching at that point. Good luck!

[Doug Wilson]

Thank you very much. I talked to the machinist, and they are now shot peened and polished.

His "max useable/red line" RPM for the engine is 6500. This is due to the cam specs, which are pretty mild.