? Passes on Aluminum rods you have!

Many variables but how many have you got on your aluminum rods ?
Thanks Mike

I was going to be a wise guy and say 10,000 on my lawn mower but only 1 on the top fuel motor, but i think you already get that concept. Had i kept the 4 inch stroke 440 deal with BME rods, i would have never worried about how many runs since the motor never saw more than 6200 rpm max. I would bet it could live for 1.000s of runs since the pistons were very light, 600 hp and low rpm. On the other hand i was told 300 by grp for a 4.41 stroke deal going 7500 rpm max. There has to be a way to figure this out better than just telling everyone a certain number of runs based on pretty limited info on thier use. My question would be beyond piston weight stroke, rpm and power level/type of power adder are there any other factors that play a large part in determining life cycle? Probably running temperature of the rods?

I ran my BME 426Forgings for 300 passes. Never had an issue. Bearings still look new. 7100 shift bobweight was22xx grams,4.500" stroke. Still have them in the box 7.150x 2.200x.990
Doug

I have always tried to be in the 300-350 area. My last set of GRP's in the Cuda were replaced at 404 passes, in a points championship and just time fell in the middle of it. Bearing looked new as they always had. That was the longest I have ever gone. 1080hp B1MC low deck 525" deal, 1900 bobweight, shifted it at 8500 running all out but mainly a throttle stop car.

Power level is a very minor factor, it's to get you to let Buffy-the-phone-girl be your engineering go-to, and buy a more $$ rod.
The relationship between rod tension (what breaks them) and reciprocating weight is linear (500 grams is 25% more than 400).
But it varies as the square of the RPM (and worse if the rod ratio goes down). 6,000 vs. 8,000 isn't 33% more (8 ÷ 6) but 78% more (8^2 ÷ 6^2)

IIRC Bill Jenkins said 300 passes 45 years ago (SBC), but he anticipated that there is a tendency to say "just one more time", so he advised hitting each rod with a big hammer and into the dumpster to stop anyone from doing that...

Aluminum rods are not inherently unsafe, they were used in 750 Hondas forever, and lasted 70,000 in Triumph 750 triples.

GRP had a article on this someplace .
But with that said if you send GRP your rods they will check them for free . ( 2 to 4 weeks I think )

What exactly do they check for? Center-to-center distance? X-rays for flaws?

From BME's website: http://bmeltd.com/rods.htm

"In a hot street application, using the aluminum rod is a no brainer," BME President, Bill Miller, said in an interview with an automotive magazine. "I don't know how the myth that aluminum rods can't be used on the street got started, but I'll guess that, back in the 60s and early-70s, they weren't making them using the process we're using today. With the material we've got and they way we manufacture the connecting rods, they'll live a couple hundred thousand miles on the street because a street application is, for the most part, low load. Our basic Aluminum Rod is made for an 1000-hp, 10,000 rpm race engine. The design criteria for the connecting rod is way overkill for what it's going see on the street. We been running aluminum rods on the street for more than two decades."

They look for cracks. There are certain places they are prone to cracking. I questioned GRP about street life on rods that had about 100 runs on it. They said they don't worry about street miles, check for cracks and run em. All out race only. If it's high HP with power adder, as other's have stated I wouldn't go more than 300 runs.

I was always told that the rod bolts should screw in and out nicely. If the big end starts to distort, then the rod bolt requires a little effort to undo.

Your mileage may vary, but in a typical bracket motor, they'll live damn near forever.

I have two sets of BME and a set of GRP rods. The BME's have been in two motors each now. When I was building the last engine, I spoke with Bill and he came right out and told me that he cannot make any promises as to the life of the rod, which I totally understand, nor was I asking for that kind of answer. What we did discuss though is that the rods (BME 426 forging) are designed to live their lives in an environment with a few thousand horsepower, where your typical bracket motor is in the 6-700 range, and is only at WOT for about 9-10 seconds. What he did tell me is the key to the longevity with aluminum rods, is keeping them well oiled, and not letting them overheat in the motor. He told me that if either of those two conditions occur, the rods are junk. It's not 1975 anymore, and the aluminum forgings and processes are way better now than they ever were.

i have run them as much as 150 passes. a friend broke one in his BBC, 330 passes.

BUT rods don't usually just break, the bearing goes first, then this makes the rod break. SO usually you looking for distortion on the big end of the rod. Most people have their own ritual based on ?? they replace them at X number of runs or...just roll the dice. I know a lot of people that say, " fix it when it breaks" LOL
You do see some using them in bracket motors and they run them 3-400 passes a season.

Its like "how many licks to the center of a tootsie pop".....LMAO !

There are exceptions either way I’m sure. My buddies 1350 hp, 665 CID BBC broke one at 30 passes, only thing salvageable was top end. R-M said it was a break, not an oiling problem and were very helpful with repairing/replacing it. He has since switched to titanium. Me, I’ll stick with steel. Jim

And don't forget the RV2 compressor.

As several have said a lot of factors go into how long they will last. I have owned two sets of 440 BME rods and I think they are the best brand if you want an aluminum rod. First set I bought used and ran for several years not sure how many runs were on them but way over what they should been run, I am sure, I put 400 runs on them, who knows what the previous owner did. So I replaced them on a freshen 5 years ago, just because I was worried about them, and I put about 600 on that set, and this spring one broke going through the lights. So your answer is how lucky do you feel? Normally aspirated, keeping the RPM's down, and timing back so it don't detonate, they will last a long time, BUT eventually they will break. A steel rod just has a longer fatigue cycle than aluminum. I had one guy tell me that storing your car in a controlled environment over the winter will make them last longer. Might be something to that, as the last two years my car went from a heated garage to the race car trailer for the winter.

Ok how about billet rods? I’m thinking of using them on the street (new) 7.1 long

40-45 runs and Rods are changed along with Bearings.

the blown hemi promod guys change the rods at 20 to 25 passes they break at under or right at 30 passes , i would never run aluminum rods on the street. there is no reason to, ive had the same set of oliver billet steel rod in my motor for 18 yrs , i just change the rod bolts every 5 yrs just my 2 cents