[Elarson]

We kicked a couple of rods in the Boss Bird this year. First time ever that we've failed connecting rods. It's amazing that the IA-2 iron block contained the rods! We showed the dead pieces to Bill Miller at PRI and got some additional insight as to what happened.

Apparently we had a bit of detonation on our first lap at Bowling Green that went otherwise undetected. Recall that we were racing a well-worked out, high dollar hemi car and stayed right on his back bumper the whole way. So we were pushing it.

The autopsy indicates that we pounded a rod bearing and loosened up the fit in the rod (it HAS to be snug with crush!!!). When the bearing loosens, the little pin isn't strong to hold it in place so it spins, instantly heats the end of the rod, pulls the rod bolt threads out, rips the cap off and now the spinning crank turns into an aluminum-fueled wood chipper.

I was reading another thread and realized that everybody debates rod and bolt strength but nobody ever talks bearing fit. So the lesson of the day...rod bearing fit has to be snug with crush and has to be rechecked whenever there is a suspected detonation event.

Merry Christmas and Happy New Racing Year!

Eric

[charlie66]

Sorry to hear this.. Did you log the 2 runs? What were your air inlet temperatures ? At your level of racing things will happens very fast I would imagine , so the need to figure out how to detect this during a run would be very critical .. Hope you figure it out..

Merry Christmas

[Tom Vaught]

Eric, I have a great deal of respect for Mr Miller and his connecting rods.
The failure obviously happened before Norwalk when you were racing with the new SOLID cast IA-2 Aluminum Block.

Tom V.

[Elarson]

Originally Posted by charlie66

Sorry to hear this.. Did you log the 2 runs? What were your air inlet temperatures ? At your level of racing things will happens very fast I would imagine , so the need to figure out how to detect this during a run would be very critical .. Hope you figure it out..

Merry Christmas

The whole sequence from spun bearings to busted rods to blower backfire to silence took about 0.6 seconds.

Eric

[Elarson]

Originally Posted by Tom Vaught

Eric, I have a great deal of respect for Mr Miller and his connecting rods.
The failure obviously happened before Norwalk when you were racing with the new SOLID cast IA-2 Aluminum Block.

Tom V.

Yes, BG was in June.

Eric

[Half-Inch Stud]

Eric,
Indeed Bill Miller explained to me that their (rather excellent) Aluminum alloy doesn't tolerate the heat from the spun Rod bearing. They hardness checked all my rods and only the spun rod was bad, only good for wall-art and NEVER to be resized or nothing. Luckly the Threads, etc appear perfect.

I griped that the brass pin didn't have the strength to keep the bearing shells from spinning. That the bearings Spun, but did not overlap (and so did not "knock"). So we figured my engine oil starved and no clever pin(s) method was going to hold the friction. Anyway Bill M was helpful.

[PAUL K]

As usual worthwhile information. Thanks for posting.

[charlie66]

Originally Posted by Elarson

The whole sequence from spun bearings to busted rods to blower backfire to silence took about 0.6 seconds.

Eric

Wow ! Yeah that's less then a blink of an eye. I Give you guys a lot of credit ! Im not saying I know what you mean , but when I turn my boost up from 20 to 45 psi its amazing how much faster everything happens . Definitely have to be on your toes !

[steve25]

When you detonate things can come apart faster with Aluminum Rods !
Does Bill size them to be Oval at the parting line as that gives a bit of insurance against the bearings becoming oil film scrapers.

[mgarblik]

BME Rods come new .0002-.0003 wide at the parting line, so almost perfectly round. When/if you send them back for reconditioning, they may get uo to .0005 wide there. Since they recommend only racing bearings that have the dowell hole and the large chamfer, the shells are designed to "thin-out" toward the parting line. The total torqued assembly will measure up to .001 wide at the parting line. For us at least, in 20 years of running BME rods, this is the first failure. Mr. Miller was not the least bit defensive about his rods and discussed our baggie of tiny aluminum shards in the open at PRI with dozens of onlookers. It was quite clear that he has seen this failure scenario many times. In his usual super dry sense of humor, he asked me, "tell me what you check between rounds?". I explained that I remove and check the mains every run and if they look good, I may check a random rod bearing or 2 because that's all the time we have. He said, staring at the baggie of aluminum cole slaw, "looks to me like you better be checking ALL the rod bearings!". Gotta love that.

[taff2]

I prefer ali rods in anything forced induction,from my personal experiences I've found that the ali rod absorbs some of the force transmitted into the bearing shell/crank if you have light detonation, which would usually kill a steel rod engine.

[Tom Vaught]

Bill Miller rods seem to also have a "longer life cycle" -even as an aluminum rod- vs some other aluminum rods. I have friends who have had Miller aluminum rods in "street" engines (9 second capability) that have hundreds of passes and many many street miles with no failures IF the rod is properly brought up to temp on the initial fire-up each morning or restart. Comments?

Tom V.

[potentpontiac]

Tom. Agreed on bringing things up to operating temperature. I have the 396 BM Forgings in my 461 race motor. So far all is good with bearing life and rod life. A very good quality rod. My friend has run his BME rods for 19 years on the street with 0 issues. I think RPM range would also be a factor with longevity, and of course power adders. Good info on this topic.

[Torment]

Yes crush is what holds the bearing in place - not pins or tangs, they're for locating. I see .004"-.006" crush, steel rods, Clevitte bearings. Pan isn't removalbe in the car though... so it only gets checked when I have the opportunity. As such, I don't push timing. Timing kills these things fast - fueling not as much. My last set of rod bearings had 40+ passes on them - still looked new. Testament to a soft tuneup! lol

[Half-Inch Stud]

....could sure use 1 BME 396 rod; 6.625", 2.2 big end and 927 pin. Maybe willing to bush the little end.

[GTOGEORGE]

GRP also make a GREAT Aluminum rod, I've had in in my engine for like forever. Aluminum rods aren't what they use to be!!


GTO George

[Tom Vaught]

You should never hurt a rod with your engine combination George.

Tom V.

[Aaron Quinton]

Great post and truth. Thanks for posting!

Originally Posted by Elarson

We kicked a couple of rods in the Boss Bird this year. First time ever that we've failed connecting rods. It's amazing that the IA-2 iron block contained the rods! We showed the dead pieces to Bill Miller at PRI and got some additional insight as to what happened.

Apparently we had a bit of detonation on our first lap at Bowling Green that went otherwise undetected. Recall that we were racing a well-worked out, high dollar hemi car and stayed right on his back bumper the whole way. So we were pushing it.

The autopsy indicates that we pounded a rod bearing and loosened up the fit in the rod (it HAS to be snug with crush!!!). When the bearing loosens, the little pin isn't strong to hold it in place so it spins, instantly heats the end of the rod, pulls the rod bolt threads out, rips the cap off and now the spinning crank turns into an aluminum-fueled wood chipper.

I was reading another thread and realized that everybody debates rod and bolt strength but nobody ever talks bearing fit. So the lesson of the day...rod bearing fit has to be snug with crush and has to be rechecked whenever there is a suspected detonation event.

Merry Christmas and Happy New Racing Year!

Eric

[GTOGEORGE]

Originally Posted by Tom Vaught

You should never hurt a rod with your engine combination George.

Tom V.

1,100+hp, over 7,000 rpm and a 4.5" stroke, 8.20 in 95 degree temps!
......and it keeps going and going and going!


GTO George

[Tom Vaught]

GRP rods were designed for a Pro Mod race car running 3 SECONDS faster than your deal at a higher rpm with a lot more boost. As was said before, the rods are barely working with your deal but you had the $$$ so they were a smart investment for you.

Tom V.