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RPM brand 4340 sbc crankshaft

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RPM brand 4340 sbc crankshaft

Postby Baprace » Tue Sep 08, 2009 12:43 am

anyone have any experiance with an RPM brand 4340 sbc crankshaft ? How well is it made and where is it from ? thanks.
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Re: RPM brand 4340 sbc crankshaft

Postby trmnatr » Tue Sep 08, 2009 1:38 am

Baprace wrote:anyone have any experiance with an RPM brand 4340 sbc crankshaft ? How well is it made and where is it from ? thanks.


Have not used one that i know of unless that Forged Probe crank we put in a Ford was RPM

Its like any other budget crank, Sometimes they can drop in and work good with balancing and sometimes you need to grind them and correct/balance out the stroke
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Postby revolutionary » Tue Sep 08, 2009 7:43 am

The RPM brand stuff is like most of the import cranks. Good steel that is poorly ground. I just did one for a BBC customer who bought the whole Probe kit (they supply Probe) and you can see where the edges of the mains were chaffing the bearings but the centers weren't touching. Someone hasn't been dressing their stones and/or they were trying to use the polishing belt to get the center of the journal to sizer while neglecting the edges. Ask Mark O'Neil at Probe how he feels about the cranks they've been getting...
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Postby Mark O'Neal » Tue Sep 08, 2009 12:44 pm

Ask Mark O'Neil at Probe how he feels about the cranks they've been getting...



Annoyed...
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Postby Scatstroker » Tue Sep 08, 2009 1:43 pm

They're made and ground in China.

Check the sizing, taper, ect... they haven't been consistant in my experience and I try my best to sell a more consistant brand.
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Postby Mark O'Neal » Tue Sep 08, 2009 6:08 pm

Scatstroker wrote:They're made and ground in China.

Check the sizing, taper, ect... they haven't been consistant in my experience and I try my best to sell a more consistant brand.



None of them have been consistent lately.
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Postby blwilliams » Tue Sep 08, 2009 6:58 pm

None of them have been consistent lately.

so are these cranks ground in the USA of offshore?
If offshore, shame on them.
If here, so much for QC.
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Postby Scatstroker » Tue Sep 08, 2009 7:04 pm

blwilliams wrote:
None of them have been consistent lately.

so are these cranks ground in the USA of offshore?
If offshore, shame on them.
If here, so much for QC.


Sure!

It isn't if, it's how much.

Problem is nobody wants to pay for a $1000 basic crankshaft, or $3000 for a top of the line crank when you can get an RPM/Eagle/Scat for $200 for a casting and $500 for a forging.
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Postby cb1 » Tue Sep 08, 2009 9:05 pm

There is a place on Ebay that sells 4340 cranks for around $375. The name they give is Hawks racing. They sell the cast cranks for around $140. I can't wait to hear about these. CB
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Postby trmnatr » Tue Sep 08, 2009 11:52 pm

Scatstroker wrote:
blwilliams wrote:
None of them have been consistent lately.

so are these cranks ground in the USA of offshore?
If offshore, shame on them.
If here, so much for QC.


Sure!

It isn't if, it's how much.

Problem is nobody wants to pay for a $1000 basic crankshaft, or $3000 for a top of the line crank when you can get an RPM/Eagle/Scat for $200 for a casting and $500 for a forging.


But an Eagle , Probe/RPM crank is good when sized properly

I wouldnt get big on the American crank thing, Took some stuff down to the machine shop and he had sent a Bryant out to get turned on one journal that had too much taper on it

Have seen this with Crower too but it is rare, It can happen to any of them just the cheaper ones seem to be all the time.

The Crower stock GM forging is $1,004.99 and its the same forging as the GM "1182" known as the Crower "Stock Plus"
http://www.jegs.com/i/Crower/258/SP9512 ... Id=1130488

The Crower "Stock 1182" S38 forging for $939.99
http://www.jegs.com/i/Crower/258/P95121 ... Id=1128847

Your typical Crower crank from Jegs runs $1,949.99
http://www.jegs.com/p/Crower/Crower-Sta ... 3/10002/-1

The Crower Maxi Light cranks runs $2,304.99
http://www.jegs.com/p/Crower/Crower-Max ... 3/10002/-1

Here is the way I look at it, The customer has two options for say a typical small block
1) pay at least $1500 for a Crower or more for a billet Crower/Bryant
2) pay $875 ($675 + $200 grind) for an Eagle ready to go (Includes turning crank to balance stroke and to true it up) , One thing you have to give Eagle is its a good steel AND their bob weight seems to be on the money

Also, Ohio Crankshaft seems to have issues with taper but the cranks when corrected seem to hold up just fine, Actually seem to look alot like the Eagle forgings, Maybe they are the same forgings. Say a customer wants a light weight crank on a budget, They can get an Ohio 44-45 pound crank for $550 then have it turned to balance the stroke and true it up for $200 and is cheaper than most std cranks and for sure cheaper than light weight cranks

Would I use them in 2500hp engines, No. I would not be scared to use a small block crank from them up to 8000rpm and 600-650hp (That goes for Scat, Eagle, Ohio, Probe, RPM)

Also they (Ohio) dont just take a slice out of the counter weight like some of the cheaper cranks, They actually do a pendelum undercut like Crower

http://www.ohiocrank.com/chevysb_cranks.html

Have also used Scat 4340 crank out of the box, Some to the high side but clearances fine many times with std bearings and no wear issues and you can pick up a Scat for $630 to $650

http://www.jegs.com/p/Scat/Scat-4340-Fo ... 6/10002/-1

When it comes to budget cast cranks THE ONLY one I have found to be worth $.02 is Scat , I had a few Eagle that was all over the place and I REFUSE to turn a cast crank

I would have no issue using a Probe crank of thats what your looking at, All cheap cranks have issues that need to be corrected. Mark is honest and tells you where they come from, Not many will do that. Mark knows what he is selling and sells them at a good price
http://www.probeindustries.com/Domestic ... s_s/60.htm

For the people whom want a better crank Mark/Probe Industries offers Scat crankshafts as an upgrade
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Postby revolutionary » Wed Sep 09, 2009 7:54 am

Honestly, I've been using a bunch of the Lunati Sledgehammer cranks and have been really happy with those. They are an import forging that is machined here and we've been using them in our mid range engines. Every one I've measured has had .0002-3" or less taper and every journal has not varied more than that either. Balancing gets a little goofy on the one piece sbc cranks to go internal but other than that I've been really happy with that ~$800 crank.
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Postby DCK » Wed Sep 09, 2009 8:30 pm

My student project's Scat crank held to .0002 or better. #4 did have .003 more stroke though.

A fellow student bought some RPM rods for his 302 Ford...poor guy. .003 oversize on the big ends ...and all over the place. He had to try to pull the locating dowels out, cut the caps, and resize. The same guy that was putting down my chinese damper. Ironic.
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