john-dickjr
Well-known member
whats the highest rpm a stock 240 rod with good bolts will take.
highest rpm on stock rods
- Thread starter john-dickjr
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nitrousnick
Well-known member
I think piston weight matters too
john-dickjr
Well-known member
arias pistons, 12-1 compression,using a 240 rod, 300 crank , will be in a gutted 97 mustang..around 2800 pounds
Its hard to say what the breaking point is for components such as this for these engines. Because these engines and there components were never engineered for any kind of use, other than better gas mileage than a V8, and cheaper base models for people that either couldn't afford or want the more expensive V8 optioned vehicles. The 240 rod being used on the 300 crank is going to subject it to stresses and loads, it wasn't going to see on a 240 crank. The .800 stroke difference is adding a huge amount of angular load to it, it just wasn't designed or engineered to endure. Then adding that much compression on top of that is really going way beyond any kind of safety factor that was designed in to it. Adding ARP style rod bolts and polishing and shotpeening the rods might extend their life to some degree. Im sure that you could get some use out of them to justify the expense, we just dont have a crystal ball to let us know when we have gone beyond the grey area into the "red zone". I would hate to even speculate on a safe RPM. Maybe others who have used these rods in similar setups could share their experiences with us....
goinbroke2
Well-known member
Of course i'll never find it if I look for it, but I had a calculator that determined approx fatigue and failure rates. It's based on a XX oz rod at Y rpm produces Z force or weight. The type of material is forged cast iron which equals line 3 for example.
Basically, you put in alum or cast/forged and weight of pistons/rods/crank and it would determine max rpm.
Cast piston with a 3" stroke would be 2000 FPS or 6700rpm for example, 4" stroke all being equal would be 5800rpm.
There is a limit, when I ran 300 rods in a 514BBF (old skool) I maxed out at 5800rpm and it lasted forever. I know of a 498 or something like that with 300 rods and he went to 6500 then replaced rods every 25-30 passes. (I think by 35 they were pinching the bearings and leaving black on the crank)
With a 3.98 stroke I'd stay around 6000 and live forever. (seem to think the older 240 rods were better than the newer 240 or 300 rods)
Basically, you put in alum or cast/forged and weight of pistons/rods/crank and it would determine max rpm.
Cast piston with a 3" stroke would be 2000 FPS or 6700rpm for example, 4" stroke all being equal would be 5800rpm.
There is a limit, when I ran 300 rods in a 514BBF (old skool) I maxed out at 5800rpm and it lasted forever. I know of a 498 or something like that with 300 rods and he went to 6500 then replaced rods every 25-30 passes. (I think by 35 they were pinching the bearings and leaving black on the crank)
With a 3.98 stroke I'd stay around 6000 and live forever. (seem to think the older 240 rods were better than the newer 240 or 300 rods)
john-dickjr":1pgw1vlf said:
hi, i would say 6000rpm but some might take more and some less..
i prep my rods by beam polishing first from big end to small end on a belt sander, then i shot peen them with the old std bolts in them, then fit the ARP bolts and then balance.. then they are good for 6500+rpm..
but all things equal, these parts are getting old and so am i...cheers
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