[Kelvin Poe]

Hey guys,

I'm in the process of freshening my motor and I'm running GRP aluminum rods. I got it apart and after popping the bearings out, I found 4 rods that had cracks in them. I've never seen aluminum rods crack in this area before and was wondering if anyone else has run into this. I have no clue how long they've been like this, I had it apart last winter to check the bearings, but just pulled the caps and looked at them. They looked perfect, so I never popped the bearing out, I just bolted it back together and ran it all last year.
Granted, I do have 350+ runs on them in the 5 seasons since I put them in, but still, I think I'm pretty easy on them. I'm only shifting it at 6800 and go through the 1/4 at around 7400. All the rod bearings still looked perfect with no signs of any wear. The mains, on the other hand were showing some wear, but nothing too excessive.
So, needless to say, looks like I'll be getting a new set of rods. Just need to decide if I will go back with aluminum or switch to steel.

[cgeise]

WOW -- Id say you hit the lottery finding it when you did -

[Tom Vaught]

Kelvin, I say, for the rpm that you are turning, put good steel rods into the engine and forget about them.

GRP rods are supposed to be the best aluminum rods, no issues with that deal but you are running rods for 5 years between replacement. You might have run the things 6 years if you had not found the cracks. LOL!

So you got your moneys worth.

You are such a consistent racer, will it really matter at the end of the day if you are a slight bit slower in et?

Tom Vaught

[67cruiser]

Mind if i ask, what crank you running??? Forged, maybe crank flexing on you a tad???

[Kelvin Poe]

Originally Posted by Tom Vaught

Kelvin, I say, for the rpm that you are turning, put good steel rods into the engine and forget about them.

GRP rods are supposed to be the best aluminum rods, no issues with that deal but you are running rods for 5 years between replacement. You might have run the things 6 years if you had not found the cracks. LOL!

So you got your moneys worth.

You are such a consistent racer, will it really matter at the end of the day if you are a slight bit slower in et?

Tom Vaught

Yeah, you're right Tom, I do think I got my moneys worth out of them, lol, and I am leaning towards steel rods this time.

[Kelvin Poe]

Originally Posted by 67cruiser

Mind if i ask, what crank you running??? Forged, maybe crank flexing on you a tad???

Yeah, I am running a forged crank from Butler.

[BruceWilkie]

Originally Posted by 67cruiser

Mind if i ask, what crank you running??? Forged, maybe crank flexing on you a tad???

Aluminum rods do a bunch more expanding/contracting stretching/compressing than steel rods. They do have a cycle life then they reach their limits and reliability drops off fast.

Kelvin caught this in time. I saw a Venolia rod fail on a under 600 hp 427 Chevy with far less(half?) racing than Kelvin. My friend built a 540 to replace the 427 and went with Oliver rods(steel) and they have gone many seasons. (10+)

Dont get me wrong... a GRP is a superior rod to the standard Venolia(IMO). However Aluminum rods arent the best choice in many applications while in other applications they are a "must" have.

Doubtful the crank or material its made of had anything to do with the cracks in the rods.

[chiefbigb]

Years ago there was a racer named Brinson Parcher that had a set fail just like that.He was also freshening up his engine when he found it.Im not sure if he still runs pontiacs or races anymore.

[taff2]

Yeah,that seems like a strange place to develope cracks.

[Tom Vaught]

I remember that name.

Well Kelvin, you and your family have a good year and say hello to your brother for me.

Tom Vaught

[grnmnstr]

Originally Posted by BruceWilkie

However Aluminum rods arent the best choice in many applications while in other applications they are a "must" have.

Bruce, could you expound on this please??


We just had my motor apart and it is possible my forged steel crank was flexing. The mains were showing black on only half of mains 2 and 3. I bit the bullet and bought a billet.

[Chipped Tooth]

Was the car ever stored in a unheated storage?
I have herd Aluminium rods crack if left torqued up in a engine over winter

[Dragncar]

A engine will not make any more power with aluminum rods vs steel. ET will not change hardly at all either.
Might live longer in very high HP engines where some 'cushion" is needed but many a bracket type engine has had a block windowed because of them.

[taff2]

I've seen far more blocks windowed because a steel rod has let go than an ali rod. The trick I believe with using ali rods, is to buy an ali rod suitable for 1000hp to go in your 600hp engine,you've just significantly increased your safety margin.

[Hooter]

Originally Posted by Dragncar

A engine will not make any more power with aluminum rods vs steel. ET will not change hardly at all either.
Might live longer in very high HP engines where some 'cushion" is needed but many a bracket type engine has had a block windowed because of them.

My experience has been the opposite. I've seen 2 engines with aluminum rods have a rod break and do no damage to either the block or crank. Just lots of aluminum pieces scattered about.

[Dragncar]

The comment was more about the power and ET difference then blowing a hole in the side of your block.
Engines make exactly the same power on a dyno going from aluminum to steel with everything else the same. It 'could" ET quicker because of the lighter rotating mass but the guys I know who have done it the ET was the same.
Why someone would install 1000HP aluminum rods on a 600HP engine. I know people that do it but whats the point. They still need to change them every 400 runs or so. Just because they are aluminum and work harden means they are unreliable after a certain point.
I have a 600 or so horsepower engine and run cheap 4340 CAT steel rods and am in the 1000 pass range.
Now, just what would aluminum rods have gotten me except that I would have had to buy them 3 times ANY worry bout them breaking.
Not worth it unless you are making enough power to warrant it.

[XSIVPWR]

I have GRP's in my 474 with over 500 runs, but I will say the last half of the season I grit my teeth going down the track. I am going to replace them with the same rods since it's a easy switch and keep it as a back up engine. But my new 535 will have Oliver Billet's.

[Marty Palbykin]

[QUOTE=Kelvin Poe;4836175]Hey guys,

I'm in the process of freshening my motor and I'm running GRP aluminum rods. I got it apart and after popping the bearings out, I found 4 rods that had cracks in them. I've never seen aluminum rods crack in this area before and was wondering if anyone else has run into this. I have no clue how long they've been like this, I had it apart last winter to check the bearings, but just pulled the caps and looked at them. They looked perfect, so I never popped the bearing out, I just bolted it back together and ran it all last year.
Granted, I do have 350+ runs on them in the 5 seasons since I put them in, but still, I think I'm pretty easy on them. I'm only shifting it at 6800 and go through the 1/4 at around 7400. All the rod bearings still looked perfect with no signs of any wear. The mains, on the other hand were showing some wear, but nothing too excessive.
So, needless to say, looks like I'll be getting a new set of rods. Just need to decide if I will go back with aluminum or switch to steel.

Wow in a promod we change them at 25 passes.
Most ADRL guy at 15 to 20.
If you don't need aluminum rods why bother.
We have no choice.
BTW GRP is the best I my opinion.
Sounds like a good steel rod would work fine in your app.
I would recommend Carrello (sp)
Marty P

[Kelvin Poe]

Thanks for all the input, guys. I know I don't really need aluminum rods in my application, but I've run them in past engines and never had a rod or bearing failure, so I've stuck with them. I guess I just like the idea of having the lightest rotating assy possible. I even ran a set of the old Super Rods 10-15 years ago and had 600+ passes on them before I finally decided to retire them and they still checked out ok. But, I will probably just go back together with steel rods on this one. The only problem is, or that I don't really like, is that they will have to put weight back in my crank to balance everything. But, the guys at the machine shop didn't think that would be any problem.

[Kelvin Poe]

Originally Posted by grnmnstr

Bruce, could you expound on this please??


We just had my motor apart and it is possible my forged steel crank was flexing. The mains were showing black on only half of mains 2 and 3. I bit the bullet and bought a billet.

Is it really possible that the forged crank could be flexing causing excessive wear to the mains or could it be something else? I ask this because the top of my 2 and 3 mains were showing more wear then the rest also. If that is the case, then maybe I should look into a billet as well.