391 truck crank prep.

[fekbmax]

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 ?

[winr1]

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.

[blykins]

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. 

[thatdarncat]

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/

[Posi67]

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. 

[mike7570]

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.

[fekbmax]

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.

[FERoadster]

I do have a FT large snout  balancer if you want it for the cost of shipping.

FERoadster

[fekbmax]

Thanks for the offer but I have a blower hub already opened up for the big snout.

[BigBlueIron]

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.

[fekbmax]

I got a couple covers that take the big seal .

[mike7570]

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)

[fekbmax]

That's a nice looking piece. Care to share where you had it done at ?

[mike7570]

Castillo’s Crankshafts in La Mirada Calif.

[XR7]

I am curious what it weighs? I wonder how much mallory it will need to balance.