I just had a rather interesting conversation with the machine shop that is doing the block work on my 388. I was discussing crank and balancing options and he had some info that kind of concerned me. This shop builds primarily drag and circle track engines, not so much street engines. He told me that these cast steel cranks like Scat and others have been known to literally explode in a dirt track car. He said they are made of better material than OEM cast cranks but are still cast and are not a good choice for any semi-serious engine. He said that Scat was about top of the line as far as low dollar cranks go (no experience with Eagle), but they have quite using anything not made in the USA. He also said they have had a few experiences with cheap crank engines wiping bearings because the metal they are made of expands more as it gets up to operating temps than any OEM or good aftermarket crank. I have never heard of this, but he gave several examples of this with some of the local dirt track and drag cars around here. He also said that on these circle/dirt track cars that an external balanced low end seems to break balancers quite often. Their theory is that the offset balance of a typical 400sbc style balancer and flywheel causes a lot of vibration on the ends of the cranks to keep the internals running smoothly. This guy has me worried now...the low end kit I am getting uses a Scat 9000 series cast steel crank and is externally balanced. Should I not be concerned since this is not going to be a constant high rpm engine, or should I rethink my low end plans?

Well, dirt track and an ocassional 1/4 mile blasts are entirely 2 different things. Sustained high RPM is murder on parts and I can see how a cast crank of any type would explode when used at 7000 RPM for 20 minutes!

I think the bearing stuff is either BS or something the really high end race guys have to worry about. My Eagle cast crank has held up quite nicely for 2-1/2 years now --- that's 12,000 street miles and probably 150 quarter miles passes.

If you want to read more in depth about the metalurgy of cast vs forged vs billet check out this months Hot Rod (or maybe Chevy High Perf?). They ran an excellent article that really laid out when to use forged pieces and when cast is OK - it was a metalurgy article with graphs showing when various materials should be used in pistons, cranks and rods. Street strip was way on the left of the graph and the roundy-rounders were way on the right --- OEM cast stuff was at the low end and 4340 and billet parts to the right.

My question is, what do you consider high RPM? Sustained high RPM is a killer on valvetrain parts more than anything else. Cranks? No....not if the balance of the assembly was done correctly and attention to the overall bob weight.

With the engine experience that I have gained over the years dealing with the cast cranks being discussed, I havent seen or heard of these cranks exploding. I have alot of 'Left Hand' turn friends that use these cranks at 7500-7800 RPM for 2 to 3 seasons before they consider replacing them and when they pull them out, they are fine.....they normally put them into their kids street cars. SCAT or Eagle. I use ALOT of Eagle stuff.......

As for the comment on the bearings, the damage they describe sounds associated to main cap problems.

The balancer issue is a known problem with SCAT cranks. That is why they will even tell you not to run a FluidDamper. It will brake the snout off sooner than later.....

I wouldnt sweat the rhetoric. As long as you dont use a FluidDamper on a 9000 crank you should be more than happy with what you have.

i agree with the rest of the guy's, that crank you have should be just fine. my machinist ran the eagle cast steel rotating assembly in his 406 blazer, ran 11's on the motor and he regularly squeezed 250 horse on it. never a problem. he also builds a ton of roundy round motors with them. i'm running an eagle crank in my 406 and all is well so far (knock on wood). heck, for that matter, my buddy has a 406 w/ stock rods and crank, yes stock, and a ross forged piston (the light piston helps), and ran 10.80's on the motor, in a 70 nova. he regularly went through the traps at 7500! has run it for two seasons this way. yes i know, this is not an advised combo, but as chicane stated, alot has to do with the balance, bob weight, and set up of the motor. on a funny side note, he called n.o.s. and asked him how much squeeze they thought he could get away with on it, and they said please step away from the bottle, i think they thought he was running a 100 horse kit on himself. now he's starting a new combo, building an sb2 motor, thats gonna be a screamer. sorry to get off track there, but the point is, a cast steel crank can take a lot of abuse, when set up properly, and keeping the bob weight as light as possible. i also think the bearing failure described would be due to main cap "walk", or a poorly balanced assembly. also, i thought i read somewhere that the scat 9000 was a foreign casting? (not that it should matter) anyway, good luck with the motor

I agree Travis. I wouldn't worry to much about it...I have heard horror stories, and long term stories out of both SCAT and Eagle. I think for a driver on street, with some occasional 1/4 times, you will be fine.

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406, Dart Pro 1 aluminum heads, Comp 294s solid,Eagle rotating assembly with 6.0" rods,JE forged pistons,Edelbrock RPM intake with Holley 750 HP, all MSD ignition

Tracy, hows that new motor running?

Chicane, tell me more about this fluidamper/Scat crank issue...I have never heard of this. I haven't gotten a balancer yet and was looking at the FD's. At what point is an SFI balancer and flywheel/flexplate needed? What would be a good quality balancer (400sbc style) that doesn't cost an arm and a leg.

Well, this is good to hear that the cranks are ok. Maybe the dirt track guys where over revving them in the loose stuff or something. I am looking at no more than 6500 rpms.

Here is a link to a discussion on another site about the Scat/fluidampr issue:
http://www.thirdgen.org/techbb2/showthread.php?s=1a7edde87c03a62f5ed72b30dc4c2338&threadid=140852&highlight=scat+cast+crank

At what point is SFI needed? When the rules say it.....and if your primarily a streeter you really dont need it....but if you are going to pound on it, it may be worth the extra insurance on some parts. A stock GM balancer isnt a bad thing, nor is the affordable Summit SFI approved unit.

Ya know, if your not going to be spending a considerable amount of time at 6500 RPM, I think either of these will do just fine.

<BLOCKQUOTE>quote:</font><HR>Originally posted by travis:
Tracy, hows that new motor running?

<HR></BLOCKQUOTE>Travis...awesome! I love the added TQ from this thing. The bad thing, is that Holley is still BO'd on my carb. So they said they should ship this next week or so. But I will know once I get that on, and dial the timing up. It only has a small 650 VS with a total of 34 timing. So I think I can play with it...but pulls great.

Morton's got me I think it's a Pioneer balancer. Nice unit, cost just a tad more than stock. Said they liked them better than stock, and they have spun them to 6500 quite often, no problems. I think they ordered it from Arrowspeed over in Tulsa...I have an account there if you need something. http://www.camaros.net/forum/wink.gif



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406, Dart Pro 1 aluminum heads, Comp 294s solid,Eagle rotating assembly with 6.0" rods,JE forged pistons,Edelbrock RPM intake with Holley 750 HP, all MSD ignition

I think mine is a Pioneer too.

Glad to hear its running strong Tracy. Do ya'll get to run 'em in the winter down thar? We had a high temp of 9* today http://www.camaros.net/forum/eek.gif can't wait until spring.

Travis,

Don't go anal on this stuff b/c I think the operative words are "cast steel" vs "ductile cast-iron"!!

Sure if you are going to lug your engine like in a dump-truck hauling 24 tons of rock up a ten mile hill or run it in an off shore boat at full throttle for hours on end, I WOULD get the best there is!!! But you are just playing with the sucker so should be FINE!!!

As for thermal expansion stuff, figure it out by using change in temperature times the thermal expansion rate times the diameter of the main or journal!!!

Figure ductile iron and cast steel as well as forged steel, then figure aluminum and I bet there ain't a schosh a difference in any of them b/c delta temp. is going to be from about 75 degrees to what 350 degrees if your engine gets good and hot!!! Any hotter and the oil starts ta go AWAY!!!

Think it over and get back... pdq67

<BLOCKQUOTE>quote:</font><HR>Originally posted by Eric68:
I think mine is a Pioneer too.

Glad to hear its running strong Tracy. Do ya'll get to run 'em in the winter down thar? We had a high temp of 9* today http://www.camaros.net/forum/eek.gif can't wait until spring.<HR></BLOCKQUOTE>Yea, the tracks pretty much open, but it was 28 degrees yesterday, and wind gust up to 40 MPH...bet my 'rearend' was inside where it's warm! http://www.camaros.net/forum/smile.gif

But 58 tomorrow...so I have high hopes for an early spring, then I'll take her to tulsa track.
http://www.camaros.net/forum/smile.gif



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406, Dart Pro 1 aluminum heads, Comp 294s solid,Eagle rotating assembly with 6.0" rods,JE forged pistons,Edelbrock RPM intake with Holley 750 HP, all MSD ignition

Not much to add here except that I am running a Summit SFI balancer on my SB, it is a really nice piece. Made in Australia, it just looks like a really high quality piece. I'd recommend one.

Paul, its hard not to be at least a little anal about it when you spend this kind of money on one http://www.camaros.net/forum/wink.gif My second block should be done tomorrow...the 1st one was .060 over but ended up having 2 cracked cylinders (I already knew one was cracked). I found a virgin '73 truck 4 bolt that was pretty rusty. It had to be taken out to .060 over just to clean up the rust pits. They also clearanced the lowend for 5.7" rods, decked it to 9.005, honed for speed-pro moly rings, etc.
I also think I am going to use the speed pro H602P's (-12.5cc dish) instead of the H600P's (-6cc flat top). Calculating with the piston .005 in the hole, .038x4.100 head gaskets (.044 quench), and the vortecs 62cc chambers (mine measured just a hair over 62cc on average), the dished piston comes out at exactly 10.50-1, while the flat top comes out at just over 11-1. The dished piston is also lighter, so that is an advantage too. Per EA3.0, isky's cam recommendation is almost perfect for peak power in the 5500-5800 rpm range. I wonder if the cam companies use this tool also?
Tracy, hopefully we can hook up this spring and go hit the track. I think tulsa closed down early in november...I'll have to recheck their calendar and see when they open back up. Just be forewarned though...I'm spending all my car budget on drivetrain this year so the nova isn't going to be pretty for a while http://www.camaros.net/forum/biggrin.gif

I understand, Travis...

Hang in there, you will get her!!

Good luck with everything... pdq67

<BLOCKQUOTE>quote:</font><HR>Originally posted by travis:
Tracy, hopefully we can hook up this spring and go hit the track. I think tulsa closed down early in november...I'll have to recheck their calendar and see when they open back up. Just be forewarned though...I'm spending all my car budget on drivetrain this year so the nova isn't going to be pretty for a while http://www.camaros.net/forum/biggrin.gif<HR></BLOCKQUOTE>
your spending it in the right places...that's what counts! http://www.camaros.net/forum/biggrin.gif


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406, Dart Pro 1 aluminum heads, Comp 294s solid,Eagle rotating assembly with 6.0" rods,JE forged pistons,Edelbrock RPM intake with Holley 750 HP, all MSD ignition