crank/rod question

[2dumb2kwit]

Crower stock plus crank, and C&A rods. If they check out ok,(mag and measure), how long would you run them? (<500hp, 355, 7000 rpm)

[Lizardracing]

Check em every season, gasket's arepretty cheap, maybe sooner if it hooked up hard.

[2dumb2kwit]

If they keep checking good, at what point would you no longer use them, or would you use them until they don't check good?

[claybuster]

If they keep checking good, at what point would you no longer use them, or would you use them until they don't check good?

Good question, we have 2 Lunati cranks/rods that were bought in '94, and 1 crank/rod combo bought in '97. All three of them are still std. journals never turned. I know its not your brand but, I guess its hard to say. Unless you got mucho $$ to just replace them, I guess you run'em till,yah know. . .
I guess that wasnt a lot of help, huh?

[2dumb2kwit]

You kinda said what I was thinking,.........it comes down to money vs luck. Problem is........I don't seem to have much of either.

[billetbirdcage]

Isn't that crower stock plus just a GM cast core or is it a steel core? I can't remember anymore.

Anyway, I personally wouldn't use a steel GM core in anything and would use a factory cast core before the steel ones. I've seen the steel ones break far to easy as they seem to be not as flexiable as the cast ones and crack and break faster then a cast one. I was using the 3.25" strokes so the choice was a cast 307 or 327 crank or a steel 327 crank and the steel ones were the worst about breaking around the 5/6 journal. They seemed to break after about 5 or 6 races as many people did break them.

I used to use in limited LM's a cast crank and turn them 8300 in a 311 at 480HP and 391 TQ (Now my dyno is very stingy compaired to others byat least 40 HP). I'd run then about 18 to 22 races a year (one season) and replace the crank as part of the freshening. If you had them Zyglo tested (A form of wet maging them with a ultraviolet dye and look at them with a microscope type machine -- aircaft testing proceedure) you could see very, very small cracks all over the place. I had some come up in just a few races so they will show up farly quickly and how far you could run them I really didn't want to find out. I do know that any cast crank that was used in a race engine would show these small cracks. How ever they would run a long time with these but they just made me nervis.

Back then I could get 307 cranks for pretty much free as nobody wanted them so they were alot cheaper then a steel crank that people wanted 150.00 or more for. An index grind back then was 150.00 and to respin/balance just the crank was 100.00 after I trimed the counter wieghts down in a lathe to remove excess weight for the light rods and pistons. So it wasn't to costly to replace the crank every freshen.

If it was a good aftermarket core then I would run it if it passed a good mag process not one a smaller shop would do. However If that is a stock core I'd think about replacing it. At that power range I'd either use a stock cast crank (not a import after market one) and replace yearly or step up and buy a better 4340 crank and be done with it. While I'm not a big fan of the import stuff, the eagles do hold up very well at that power level but the grinding is somethng to be desired as you will likley end up with taper in the journals or have to use over or under size bearings or mix match shells to get the proper clearance for a crank that isn't ground on size. You can pretty much plan on having to grind the mains or the rod or both so unless you wish to wait for eagle to OK that to be done and then reimburst you, you are probably ahead to just buy a compustar or something that is machined correctly.

[2dumb2kwit]

Billet, I think you and I see things the same way. The reason I haven't built a new motor yet, is the cost of building a "good" motor, and I just can't see spending money on a "cheap" motor.

[billetbirdcage]

I forget are you 2 barrel racing? With the right machine work, you would be surprised how well stock parts will hold up in those lower power ranges.

Heck, I still got that 311 and a 335 while they no longer have stock rods in them they do both have stock cast cranks in them. The 311 was 480 and the 335 was 515 on my stingy dyno. The 335 has only 4 races on it and I have my machinist drive it in one of my cars at a fair grounds 1/2 mile race track with NCRA Late models which usually rubbers up. He was running 3rd well he pushes slightly and got passed and ended up 4th. Not bad on a completely rubbered one lane track with a bunch of 400+ CID open engines. We were turning the piss out of it though ran a 6.28 gear on a long 1/2 mile.

The 311 ran the first 2 years with stock rods (heavily worked) and took them out after then and maged them to see if they were ok just out of curiousity and they were fine. They are now in a friends street rod since 1999 and still running in his 510 hp 406 that he doesn't cut much slack.

Engines can be done with a budger if the parts are chosen correctly.

[profab00]

I run an engine with the Eagle cranks and rods, as you said Billett, they had to be turned. But they ran 54 nights two years ago and 19 nights after a rebuild this last year. May blow first night out this year but I was impressed a 400 or 500 dollar crank lasting this long. I used to run GM steel, I blew at least one engine a year in those days. Never again.......or at least, as long as I can afford different, never again.