How much rpm is every body spining there stock rod motors to? My engine builder strongly recomened not going over 6000 rpm. another engine builder agreed. they both reference the piston end of the rod being too small to survive above 6000rpm. ive hear lots of people talking about 7000 rpm or 6500 rpm all day long. not shure if they have stock rods or not. so let me know what you spin your stock rodded motor to and if anybody had had rod failure what did you spin it to?
I ran my first motor to 6200-6500 all the time and no issues. A sucked valve finished that engine off. My next motor I bought refurbished rods with the over-sized rod bolts and the guy that bought that short-block said he still spins it to 6500 on a regular basis. Just my .02
Stock 302... I'd say 6000 is safe, 6500 is gray area, and 7000 is a no-no for more than a second. That said, the weak link is the stock rod bolts. You can go with an aftermarket bolt, like ARP, and add 500 easily I'd imagine. Then if you polish the beams and balance the rods and entire rotating assembly, you should add another 500 rpm. However, you have to worry about horsepower level too. A 302 with 300 hp will tax the rods far less than a 302 making 400 hp.
oem rods where used in the 289 hi-po and shelbys... the weak spot are the rod bolts as mentioned above...
I assume we're talking about a 302? The block will break before the rods ever give you a problem. The rod BOLTS though....they aren't the greatest. Because of the design of the rods, you can't drill them out & put in 3/8" bolts. There's not enough meat to do it safely. So you're stuck with 5/16" bolts...ARP does make a much better bolt than the factory ones. Because of the short 3" stroke, piston speed is relatively low, which reduces the stress on the rods somewhat. I personally have beat the living the heck out of stock 302 rods with not a single failure. I know people (lots of them) who have used stock bolts with success as well. Only one failure and it was a 289, the bolt broke not the rod. Even my old turbo 302 never had a rod fail (or bolt). 302 rods are stronger than people give them credit for! 351w stock rods are a different story.
Bullzeye! The 302 can really take some abuse just because of the short stroke. 289s even more so, if you replace the stock rod bolts!
thanks for the info. i am using 289 hi po rods. they have 3/8 bolts. i think ill do some runs at the track while increasing the shift point up a 100 rpm or so each run. thanks agian
THAT is a great idea. Keep increasing it 100 until you toss a rod or split your block, and THEN you will have your answer:bananaman I ran my stock block consistently at 5500, it seemed to fall on it's face if I went over that. I shifted a couple times at 6000 but actually lost time on my slip. That was due to my intake/head/exhaust setup. But the block took the abuse no problem. (that was stock cam, P heads, hooker 6901, Edel 600 cfm, on Torker289, with the cam as my most likely limiting factor, since the rest of the setup was rated for 6500). I was uncomfortable shifting at 6000, and I don't think I ever went over that. With my current 5.0 roller block, I shift at 6500 without fear. It feels like it pulls all the way through, but my new cam is made to go that high. This is a reman O'Reilly short block converted to roller cam, with all my other goodies slapped onto it.
tried to find the chapter on 289 hi-po rods... from what I could remember they where specially selected,3/8th rod bolts, Brinelled hardend... BTW I might edit if info is not factual...
The stock C8OE 302 rods are good to 7500 with ARP bolts. Otherwise the stock rod bolts are the weak link. The 90's 302 rods are weaker, I've seen two broken in stock grocery getter applications.
Had a set of early rods with the beams polished, shotpeened and ARP "pro series" wave-loc bolts. I spun the motor to 8200 over 4 years and never had a bottom end problem. They were even swinging those heavy TRW pop up slugs around and those things weighed a ton. I think you would have a crank failure before a rod failure if the rods were machined correctly, had the right hardware installed and were assembled properly. In my case the front edge of the first main bearing was worn due to high rpm distortion of the crankshaft. That said, if you are not willing to go through that expense (you're getting into the cheap eagle/scat I-beam price range at this point), I know you can get by with 6500 and probably even 7000 with stockers.
My cousin turns his 289 to about 6700, strip and weekend car. Probably doesn't have 10k on the shortblock, so I can't say for longevity, but its been around 4 years, its still hanging on. Dunno if there is any difference in the 68 rods and 70's though. I know they're still puny, and he has upgraded rod bolts. Don't know if they are ARP, but I think so.
I,ve heard stories of 289's that hit 9k on the tachs. But thats a 289 as has been mentioned in this thread a 289 rod is longer than a 302 (289 shorter throw on the crank) as far as i know the rods cannot be swapped. And if someone on here has done this i would like to know piston pin location
