Inliners International Forums General Discussion Hi Performance rod length question for 292's

I am about to order pistons and rods for a 292 that I'm going to be leaning on pretty hard. Question is: what is the limit for rod length with respect to cam interference on a 292? I'd like to run a 7.5" rod so I can run off-the-shelf LS1 pistons, but I don't know if that would hit a small base circle cam or not. I'm ordering billet rods from Crower for this engine. I'm trying to get some weight out of the rotating assembly and I only want to waste one child's college education doing it.

Thanks, Rick

Santucci says for most applications standard rod length is fine. For longer rods, especially the length you suggest, a billet roller cam should be ground with .060" clearance between the rods and cam. He suggest if using aluminum rods, a length of 7.000" to 7.350" center to center is applicable.

56er,
I first have a question. Why would you want to spend the money on custom rods and not want to buy the correct fitting custom piston for your engine?
Understood about saving money! Can't blame you there.
The LS pistons are somewhat cheaper, but they have valve location or pockets that are not correct. Maybe buy a 7- 7.25 rod and get a correct custom piston from Venolia, Ross or one of the other custom piston co's.
I also believe the Crower billet rods are much smaller than any alum rod and will clear the cam easier. They should be able to give you rod dimensions.
Tom

The thought process is since I have to spend a billion dollars on a set of rods, to get a set that takes off-the-shelf pistons so that I can use the rods for more than one engine build. While the valve pockets aren't correct I agree, for this engine build I should need flattops so the valve pocket issue should be moot. LS1 pistons weigh in the low 400's, have modern a modern ring pack (1.5 1.5 3mm) and are 2618 for $76 apiece from Wiseco. That's tough to match, valve pockets or no valve pockets.

What kind of use are you going to be using this engine for mostly. You mentioned lightening up some things, the Crower rods are going to be close to 150-200 grams heavier per rod that the stock rods are. So adding a heavier rod to get a lighter piston isn't going to be big benefit. However, the Crower rods will make your wallet lighter(LOL). Also, a set of Venolia flat tops are $72.52 ea., and for that price that can put the valve pocket where it needs to go and any ring spacing and package and compression hgt, you need.

This is a weekend street/strip car. (Drive to track, run car, drive home.) Engine should make around 550 on squeeze. I want to spin it to around 6-6.5K. You pretty much have to run steel rods in a car with license plates, and although I've never ran aluminum, nobody I know has ever had any luck with aluminum rods and nitrous, so that's just a weight I can't get around. I never thought about Venolia. I will call them tomorrow, thanks.

56er,
You may want to check with BME (Bill Miller Engineering?) They say their Al rods withstand street use just fine. Probably cheaper than steel rods also.

Keep in mind with Al rods, you will probably need a billet cam to clear the rods. Tom

Aluminum rods are actually more desirable for nitrous than steel rods. Nitrous typically shocks the rotating assembly with a big jolt of power all at once, and the aluminum rods absorb that shock much better than the steel rods do. For forced induction like blowers and turbos that provide a lot smoother of an increase in power over a broader rpm range, steel rods are fine for most of these applications, even in real high boost situations. There is a little more pre-assembly preparation required for using aluminum rods, but its well worth the effort.

I agree with you that in theory aluminum rods should be better. I just have never seen in proved out in practical application. I have lots of contacts in the 10.5 classes back east and not every guy I know that built an engine with aluminum rods, but a statistically significant amount shoved them all through the pan the first time they hit it with the big shot. While there may definitely have been other factors at work, this is my data pool. I have an engineering brain that tells me aluminum, but my gearhead heart insists on 4340 steel.

I have also assembled and raced quite a few NMCA nitrous engines and a lot for the 10.5 Outlaw class as well with over 400+ shot, and have never had any issues. Aluminum rods do require a little more effort to prep and assemble in an engine, and that is usually where people get tangled up and have problems(and don't realize it until later) if they are going to have any. In most peoples mind, the steel billet type of rods do seem to be the ultimate in strength and service but do have limitations, moreso than aluminum rods do in these applications. If you do select the Crower steel rod, I would proceed cautiously with your build-up, you might not have any issues using steel rods, since your nitrous wont be adding a huge gain of HP to your engine, im guessing maybe a 200-250 HP increase from what you said your HP goal of 550 HP is going to be. You might ask Mighty6 about his engine, he was making over 800 HP with his 292 combo with nitrous, im sure he had a learning curve on his way to 800 HP, and can confirm data already shared here on his way to that point.

I went ahead and ordered a set of Venolia's. They were not 72.00 apiece, however. But, they should be nice pieces. I asked them to push the wristpin up but don't put it in the oil rail, and I ended up with a 1.54" compression height piston I believe, and a 7.263" rod. This will give me a rod/stroke of 1.76, so side loading shouldn't be too big a factor.

The audio of Mighty6's truck is why I'm building a six, although mine definitely won't sound like his!

I didn't think I was still on their WD deal when I mentioned it, how much did they get you for.

680.00 Haven't decided whether I'm going to blame Canada, Obama, or the Chinese I'm going to have more in rods, pistons and rings for this engine than it would have cost to rebuild the blown 355 I took out of this car.....

Chinese pistons, Taiwanese rods, Mexican block, Canadian crank just make sure you get some good ol' American RTV to fill the cracks and you should be OK. Beater