Thread: 391/361 steel crankshaft info

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How strong are these FT cranks? I've heard everything from that they are as strong as the 427 steel cranks to that they are prone to breakage. Whats the real scoop? I have two of them and I was thinking of using one in a genesis block build up. I don't want to risk it if they are questionable to use. Thanks for your input guys!

My experience with the 391 crank is that it is very stout and will take about any abuse. Just remember, you'll have to have the front snout turned down to the FE size if your going to use FE timing chains, front cover, and balancer.

I've had a few 391's break cranks, but it always happens after the bearings go away, so she's screwed anyway! 318 trucks do the same thing, where a cast crank will rattle on for weeks with loose bearings a steel one will break. Had it happen on diesels, too.
By the way, if you are going to use a truck block, bear in mind that the pilot bearing at the bottom of the distributor, where the oil pump drive engages it, is bigger than the car ones. Either bush it down, or use the truck dist. and pump and drive. It's 33/64",I think.

after reading an article a few months ago, in engine builder magazine, about metallurgy... i've decided using 30 year old cranks isn't a good idea, the thing is metal does age and weaken with age, cranks, even more so than things not seeing a lot of pressure... secondly you really dont know how the last owner of that crank drove the vehicle it was in.... 3rdly steel cranks tend to be more brittle anyways, which means it could already have a bunch of microscopic stress fractures running through it.... i've used plenty of old cranks and not had problems, but it does make you wonder sometimes.... personally if it can be fit in the budget, i'd prefer putting a brand new steel crank in there.... i know its expensive but it is some good insurance.... the billet steel cranks are obviously the best but also cost a lot of money, but the forged steel cranks are pretty good as well

Originally Posted by blueoval67

How strong are these FT cranks? I've heard everything from that they are as strong as the 427 steel cranks to that they are prone to breakage. Whats the real scoop? I have two of them and I was thinking of using one in a genesis block build up. I don't want to risk it if they are questionable to use. Thanks for your input guys!

Don't think I'd be putting a 30 year old crank in a brand new block!!! I'm with sals, the extra $$$ for a new crank would be good insurance... Oh yeah, even a new crank can be flawed.... A quick magnaflux and maybe shot peening before assembly might be some good added insurance. The 4340 cranks will take a lot of pounding and hang together....

i'd be scared to check the rockwell hardness of some of the cranks i've used in the past

Originally Posted by Dave Severson

Don't think I'd be putting a 30 year old crank in a brand new block!!! I'm with sals, the extra $$$ for a new crank would be good insurance. The 4340 cranks will take a lot of pounding and hang together....

Are you guys the voices in my head?

I'm afraid I'm at the same crossroad. I have a new block and I keep staring at the fresh .010/.010 IUB 428 crank and rebuilt LeMans rods in the corner. I know the history on both but....40 year old parts I keep thinking. And you just never know. I had planned on using them to get my 452" in by the end of the summer. So I'm toiling with the idea to sell them and look into a better assy. Barry R from Survival MS (I'm sure some of you guys know him) bought a few of those new forged 4.250" stroker cranks. He had to true each up a bit at the crank shop. And he noted that Scat although cast steel not forged was a much better product out of the box. I found this interesting and refects the high and low prices I see on these. Now you can buy these new forged cranks direct thru Condor on ebay for $800. But I'll bet your still looking at another $200-250+ at the shop. So your looking at $1000+ for a new 4.250 forged unit ready to use sans balance with the other bits. In my case I'm looking for a little more rpm up top and was happy with the 3.98 stroke. A forged 4.250 arm, Oliver BBC rods and I'll possibly need custom Diamond slugs are in the $2400 range balanced. With the tunnelport heads 82-83 cc chambers I need a good dome piston but I'm working with a 4.250 bore which helps on selection possibly. At best I can get $600-700 for my crank and rods. And I'm only$1000 away (custom pistons and balance job) from having everything done to assemble it with what I have. So close..... It would be at least another year maybe longer before I'd be able to afford the new parts and the extra $1400+. But I'd have a 482" What to do??


G..

Yea Denny tough choice for sure!! Take a look at these forged cranks. They are getting cheaper!! Now $699 and they were $799 a few weeks ago.
Ebay item # 270137726693 FE forged 4.250 crank.

Good points Denny. I sent them a email and asked what they are packed in. My UPS guy already hates coming to my house. I guess I'm being over cautious with this build. I think I'll proceed as planned. Thanks for your input!

I hear what your saying about the 40 year old parts, that thought has crossed my mind. Is anyone running the old LeMans rods? They can be scarey too! I'm cautious about these $800 steel cranks from China, how good can they be? There is also the theory about the seasoned parts. As they go through their life cycle of heating and cooling they become molecularly stablized with age and possible become stronger. I know that this can apply to engine blocks but does it apply to rotating assemblies? Maybe if I wouldn't consider running 40+ year old LeMans rods I shouldn't run an old steel crank as well. Oh boy, I guess it all depends on if I feel like rolling the dice. I think I have raised more questions than answers.

You guys are hitting some good points here. I'd run a 30 yr Ford crank
cast or steel before I'd run a Chinese POS for sure. Be careful not to get
the reciprocating weight to heavy with a 2 bolt block, Lemans rods are
heavy. I have raced a 427 with cast cranks for over 20 yrs and never
had a crankshaft problem. My 390 I ran 7000 and the 427 a little more.
I blew one up at 8500 (stupid) ,broke a rod, ruined a block, but did not
hurt the crank. I did see one in a Stock race car (Calverts 428 CJ) with a
heavy bottom end pull the block webbing and destroy everything. Very rare.
Of course with the longer crank throw on a non race motor you don't
want to turn the RPM's of the shorter arm. Good Luck with the parts. These
are definetly tough old motors.
Ron

Yep got a set of LeMans rods ready to use. Bought them new years ago and have since been rebushed, sized and tapped for ARP capscrews. And yes they are heavy at 845 grams each! Those and the crank I've had for years.

Denny thanks! I'll check that out. I think I'm going to stick with and run what I have. I wanna drive this hotrod and not stare at a pile of parts!! I'm going to assemble at my buds engine shop. We are going to final check and mag everything and then internal balance the assy. Hopefully I won't be staring at a pile of parts under the car!! Time will tell....

Thanks for the input guys.

Blueoval sorry to invade your thread. But this topic came up at a good time with some interesting thoughts.

G.

There is a interesting current disscussion on these new forged cranks on the net54 forum. www.fordfe.com see the "What is the story on these cranks" thread on pg 1. Even with that good BIN price I'd still be leary not knowing the origin or history on these other than the fact they are forged overseas.

G.

No problem FFR everyone in this forum has a wealth of info and I'm just glad they are willing to share it. Not too may people run FE's anymore so its kind of a lost art. I'm guilty of switching out my FE for a Boss 351 in my Fairlane. I ran that engine for years on the street and at the drags. It was basically stock with 1 point higher compression and a well matched roller cam. I tuned it to run 11.50 to 11.40 in street trim. Then I went to a 514 which was a beast behind the 4 speed but weighed a ton. Now I'm back to the FE. Now that there is a growing aftermarket support for these great engines it makes it easier to build a great running engine. The FE is maybe the best engine Ford ever designed for all out performance. Super strength with light weight is a great combination. Thanks again to all the guys on this forum. The knowledge shared between us makes things easier for all of us and, our hobby better.