spokewrench

I had mentioned in my last post that all cast cranks "383" come from China, however, Lunati is building a cast crank from australia, but machined in their shop in the south USA. F.Y.I.

robzr

Would that be cast iron? Cast steel? Any hp/rpm ratings? The scat cast steel cranks have a good reputation and are a great value for what they are.

Rob

spokewrench

Its a Nodular crank supposedly 30% stronger than stock, Magnufluxed, shotpeened etc. goto Lunaticamshafts.com for more info.

robzr

I don't believe that nodular iron is as strong as cast steel. You are going to pay 50% more for a crank that is not as strong, but has a more popular namebrand. I've never heard anyone with practical experience say anything bad about the Scat cast steel cranks. They are a great deal.

Rob

tsw71

What would you guys say is the HP/RPM limit of these cast steel 383 cranks?

robzr

I spoke with Scat, and they said they are good for 600 horsepower and 7000 rpms; 7500 rpm is pushing it in the tech's words. David Vizard raves about these cranks in one of his books and said he has built and abused many motors over 500 horsepower with these cranks and never seen a failure. They are cast in China and machined in California. The guy got a little edgy when I asked about the composition of the 'proprietary 9000 steel alloy', but they are calling it a steel alloy and not an iron, which by definition means the carbon content is much lower and I believe chemically structured differently & possibly bound to the Fe differently (?), as well as the metal has far less impurites. Steel also exhibits different properties. Steel is generally much stronger and harder than ductile (nodular) iron. Cast steel is also more expensive to produce than ductile iron. Steel is more desirable for crankshafts. FWIW there are plenty of circle track guys and a few guys on chevelles.com who run stock cast iron chevy 400 SBC cranks to 6500 with no problems.

Scat also said the only stroke larger than 3.750 that they are making for Small Chevy (both mains) is 3.800.

Rob

tsw71

Robzr, Thanks for the info. One more question. Can these cast steel cranks be internaly balanced easily? I would prefer to do this as opposed to having to use the 400 balancer and flywheel.

robzr

No problem. Scat makes a few different cranks designed for use with different rod lengths and internal / external balance. I see there is a 6" rod internal balance 3.750 stroke 350 main stroke crank on ebay from a reseller:
http://cgi.ebay.com/ebaymotors/aw-cg...615618&r=0&t=0

They are asking $199, you can probably email them and get one for that price by saving them the hassles and closing costs of ebay. I don't know anything about that resellers reputation. http://www.Flatlanderracing.com also has Scat cranks, but with a little higher markup ($250 ish). The description on the ebay page is interesting, they go into detail on the crank properties and machining.

Rob

tsw71

Yeah, I saw those on Ebay too. My biggest concern is trusting their sales pitch. A brand new cast crank that can handle that much HP and hopefully speed shifting at 6500-7000 for only $200 just sounds too good to be true. With that said, I run a cast iron crank (3.48 stroke) in my street rod that turns 7800 with no problems, although there is probably a bit of difference since it is in a 2700lb car with an th400 and 4.56 gears. The stress on that crank is much less than it would be in my vette which weighs 800lbs more with a five speed and driver that likes to speed shift at redline. :yesnod: Unfortunately,the price difference between the new cast cranks and the forged ones is :eek: :eek: :eek:

robzr

Well, lying about the products capabilities is probably not in their best interest as they have a reputation to uphold, and more expensive cranks to recommend as well. I've taken mine to 6500 quite a few times and even 7000 on accident once or twice, but nothing sustained. I looked again and those guys on ebay are from pmeracing.com, they are more expensive than flatlander if you look on their website. I'd say that ebay auction is a hell of a deal, that's probably the dealer price. If you are looking at a motor that you shift over 6500 and are making over 500 horses, you might want to start looking into a better crank. But for under that you're probably wasting money. And like a lot of people do, you could probably get away makeing more power and revving higher with the cast steel (or even a cast iron).

Rob

tsw71

Rob, Thanks for the good info You make a strong argument for those cranks. I guess when you really think about any 400-500 hp engine, the weekest link will usually be the rods. Whichever way I end up going on the crank, a good set of eagle rods or chevy pink rods should get me the strength I'm looking for.

Thanks, Tom

robzr

Yah an engine can live at 500+ hp / 6500 revs with GM rods, but that may be a gamble. For 450+ I'd definatley consider something better than stock rods, but they can live (and often do) well beyond that. You can buy Scat 4340 forged I beams for $219 from FlatLander though, so I think that would be cheap insurance (only $10 more than the lesser quality 5140 alloy I beams). GM also makes PM (Powder Metal) rods for ~500 hp applications which are priced reasonably. Flatlander also has a lower quality (?) brand 'Pro Line', who has 5140 I beams for only $160. I think those Scat 4340 I beams are a pretty good deal and some nice insurance for a strong street motor. Good luck with your motor! Have you settled on heads & cam?

Rob
http://ese.dwdata.com/rob/engine.html


[Modified by robzr, 4:56 PM 8/23/2001]

tsw71

I'll definitely check into those rods that you mentioned.

Right now, my cam choice for this engine is either the comp294S, crower 00355 compu-pro, or the crower 00351 compu-pro. All 3 are solids. I run solids in my street rod and find them very reliable and requiring very little maintainance despite all of the negative thing others say about solid cams.
The heads I'm running in the Vette now are S/R torquers which are more than enough for the 350-400hp range, but will not be enough to feed this 383. Since these heads are only a year old, I hate to give up on them so I will probably do some porting.
The only thing still up in the air is my choice of pistons. I have always run forged flat tops in all of the engines that I have built, but am now considering the Hypereutectic pistons. What are your thoughts on these pistons? As far as compression ratio goes, 10:5.1 should work well with the crower cams(105 LSA), but i'm not sure about the comp(110 LSA). I have never had problems with detonation in any of my 350's, but the 383 may cause more of a problem.

robzr

If you don't want to get rid of those S/R Torquer's, check this webpage out. This guy was a regular on VetteNet (email list) a while back, but I've never seen him post here:
http://www.caspeed.com/488hp383.html

He got 488 hp @ 5900 with some ported S/R Torquers on a 383 with a 244/244 @ .05 hydraulic roller. That's pretty impressive. You'd make a bit more with AFR or similar heads, but probalby not enought to justify the expense if you already have the S/R's (maybe up to 20 hp ?). BTW he's running 9.9:1 compression with those heads on pump gas.

I don't have any experience with the hypereutectics personally, but I've heard good things about them. As long as you are not adding boost, spray or making huge horsepower they should do the job pretty well.

later

Rob

jdunne

I guess i'm a crank made in australia....just a little pun intended.......I understood that some of the Eagle cranks were made here then finished in USA.....can't verify that though.....they certainly are expensive enough when they get back here...john :chevy