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FE Power Forums => FE Technical Forum => Topic started by: fekbmax on November 12, 2018, 10:40:24 PM

Title: 391 truck crank prep.
Post by: fekbmax on November 12, 2018, 10:40:24 PM
How much stroke can I get offset grinding a steel truck crank to 2.200 journals ?
Any suggestions on to whom would do the best job at this and balancing ?
Title: Re: 391 truck crank prep.
Post by: winr1 on November 13, 2018, 02:36:16 AM
FE journal, 2.438 minus 2.20 would be .238 off the bottom of the journal

Would raise the center of the journal .119

looks like the stroke would be 4.018

Then a machinist would want a bit of leeway perhaps

Looks as if you would gain around 14 CI



What I have read on this forum and others is you will have more $$ in the stroked 391 crank than buying a steel crank with more stroke

That said, I love old school stuff, keep us informed as to what ya do please


I looked into off set grinding a 428 crank with 352M/400 rods, would gain me 10 CI and custom pistons would be needed


Then again.... my math may be shite ^_^




Ricky.







Title: Re: 391 truck crank prep.
Post by: blykins on November 13, 2018, 05:53:14 AM
Ricky's math is right. 

He's also right in the amount of labor/prep it takes to get a crankshaft cut like that.  The offset grinding is the easy part.  The hard part is widening the journals and a lot of crank grinders don't want to do that, as it either takes a lathe with an offset center, or wasting a lot of grinding wheels....

The snout also has to be turned down and the keyway re-cut.  A special pilot bushing adapter also has to be made.

There are guys that can do it. 

Last one I had done cost me about $1200 but I had to spend several hundred to fix some mistakes, and then about $300 in heavy metal to get it balanced.

You'd be much better off in buying something like a custom steel crank from Scat.  I've had several of those done and you can give them a bobweight ahead of time so that it won't need any metal to balance it.  You're looking at about the same cost, plus or minus a $100 or so. 
Title: Re: 391 truck crank prep.
Post by: thatdarncat on November 13, 2018, 11:06:12 AM

Any suggestions on to whom would do the best job at this and balancing ?

As far as someone who can do the work, Barry R. & others have recommended Adney Brown at Performance Crankshaft in Michigan many times.

http://performancecrankshaft.com/
Title: Re: 391 truck crank prep.
Post by: Posi67 on November 13, 2018, 12:56:04 PM
What Brent said..  There are way too many easy and cheaper options available nowadays to even consider doing a 391 crank. Nothing wrong with a cast crank unless the HP level is getting up there. Past posts on the subject indicated that not many normal shops are willing to touch that kind of work so now you have shipping costs to consider as well. 
Title: Re: 391 truck crank prep.
Post by: mike7570 on November 13, 2018, 01:53:34 PM
I have one being done right now, it was already set up for FE use when I got it. The quote to change to 2.200 wider journal, 3.995 stroke and nitriding was $600.00
I'll let you know what the cost was when I get it back.
Title: Re: 391 truck crank prep.
Post by: fekbmax on November 13, 2018, 09:11:51 PM
I have one being done right now, it was already set up for FE use when I got it. The quote to change to 2.200 wider journal, 3.995 stroke and nitriding was $600.00
I'll let you know what the cost was when I get it back.

I'd deff be interested in hearing how it turns out.
I think I'm just gonna go with reg FE rods from either scat or RPM and just have the crank balanced . I'm not wanting to turn the snout down so just a good balance is all I'll need. It's for a budget blower build so I'm wanting to leave the snout nice and fat and just open up a BBC crank hub to fit.
Title: Re: 391 truck crank prep.
Post by: FERoadster on November 13, 2018, 10:07:40 PM
I do have a FT large snout  balancer if you want it for the cost of shipping.

FERoadster
Title: Re: 391 truck crank prep.
Post by: fekbmax on November 13, 2018, 10:56:14 PM
Thanks for the offer but I have a blower hub already opened up for the big snout.
Title: Re: 391 truck crank prep.
Post by: BigBlueIron on November 14, 2018, 04:37:23 PM
fekbmax,

What are you going to use for a front cover with the big snout? I would think that leaving this area alone would certainly save some coin in crank prep so that helps.
Title: Re: 391 truck crank prep.
Post by: fekbmax on November 14, 2018, 04:45:45 PM
I got a couple covers that take the big seal .
Title: Re: 391 truck crank prep.
Post by: mike7570 on March 07, 2019, 05:17:29 PM
It's been a few months, I got the finished crank back this week. 391 steel was offset ground to 3.99 stroke, 2.20 journal with 1.90 width, flange cut for torque converter, nitrided and polished.
(Discount for cash, it was less than $600)
Title: Re: 391 truck crank prep.
Post by: fekbmax on March 07, 2019, 06:11:44 PM
That's a nice looking piece. Care to share where you had it done at ?
Title: Re: 391 truck crank prep.
Post by: mike7570 on March 07, 2019, 11:27:35 PM
Castillo’s Crankshafts in La Mirada Calif.
Title: Re: 391 truck crank prep.
Post by: XR7 on March 07, 2019, 11:30:37 PM
I am curious what it weighs? I wonder how much mallory it will need to balance.
Title: Re: 391 truck crank prep.
Post by: mike7570 on March 07, 2019, 11:41:20 PM
I was curious, just weighed it on my bathroom scale, it’s 65lbs. In a plastic bag with a coat of oil.
I need rods and pistons before I can get it balanced.
Title: Re: 391 truck crank prep.
Post by: TomP on March 08, 2019, 02:00:57 PM
That looks great. I have a 391 crank turned to FE snout but standard stroke and journal sizes.
Is yours for a SuperStock 428?
Title: Re: 391 truck crank prep.
Post by: mike7570 on March 08, 2019, 04:01:33 PM
Stock eliminator '67 Shelby, been working on it for a while. Slow build but I see some light at the end of the tunnel.
Title: Re: 391 truck crank prep.
Post by: TomP on March 09, 2019, 03:53:35 PM
Can you run BB Chevy journals in Stock now? I thought the only legal rods are the FE crankpin size?