I just don't think this is a wise place to cut corners and pinch pennies. Scat I-beams are $270 on ebay for a 4340 steel rod...and no I'm not a salesman for them, they are just a heck of a deal for a quality rod (I put a set in my current engine).

If you must go with the stock rod, at least get a good light weight piston to give the rods a better chance of living a long life…but those pistons aren’t cheap.

I also had a set in my 4 inch stroke 318 and they needed ZERO grinding the block to fit, during assembly I tried a stock rod to see and it would have needed a lot of grinding.

AFAIK, 340's and 360's use the same basic forging, but the 340's were bushed for a floating pin from the factory, 360's were pressed pin.

if it's going to be a pretty mild street motor, nothing revved to the moon, I wouldn't have a problem using stockers that have been redone. the only issues I can see would be these:


1) you'll most likely need to grind the block a lot more using them w/a 4" crank vs. say, the SCAT I beams (hotroddave didn't have to grind the block at all for the SCAT's).

2) balancing, the heavier rods might make it more expensive to internal balance, or you'll have to balance it externally to 360 specs, not a big deal if it's not being revved to the moon IMHO (Don, B3422W5 ran his old motor for what, 3 seasons running 10.70's externally balanced, and to 7K rpm without issue)

3) if they're currently pressed pin, finding a reasonable cost piston for pressed pin app to work with the closed chambered eddies. looks like the KB745 is your best bet. otherwise you need to bush the small end, adding to the cost.

4) the KB's need the small end narrowed to 1" (magnum rod width, also what most aftermarket rods are, since they're based off of a 6.125" SBC forging). that additional machining will add to the cost, or it will drive you to more expensive options (SRP, Diamond, etc)

I guess it all depends on how much time (block grinding) vs. ability to do yourself (do you have access to a mill?) vs. money you want to spend. cheapest and easiest might be to buy one piston and just fix your stock stroke motor.

How about using stock rods and polishing the beams. I have heard that that is a cheap way to get more strenght out of stock rods. How much stronger does this make the rods?

I only run alu or H beam rods this sounds like a MR P or Wise question to me, sorry never tried it before so cant answer

Good info , good point, thankx

Dirt,

My question would be, are you going to save money by buying the pistons and crank seperately, or would it be just as inexpensive to buy a ready to go kit with new rods??

FWIW, I have a 3.79 stroke 340 with stock rods, 6400 shift point, 10.70's in a 3000lb A Body. Well over 500 runs on this motor.