machine work on 440 crank for 451 ?

Posted By: Tom Fox

machine work on 440 crank for 451 ? - 06/07/12 02:02 AM

Guys, I am Getting Ready To Take A 440 Crank To A Machine Shop To Have The Mains/counter weights Cut Down For A 400 Block. I have A Question, Will The New Mains Require Anything Special To Be Done To The Bearings?

Posted By: DrCharles

Re: machine work on 440 crank for 451 ? - 06/07/12 02:25 AM

Mine didn't.

I think the counterweights were turned down by the shop a little too much though, since even with Eagle H-beam rods and relatively light KB280 pistons, it still needed two slugs of Mallory metal (totaling about 170 grams, I think) to internally balance.

Posted By: StealthWedge67

Re: machine work on 440 crank for 451 ? - 06/07/12 02:56 AM

Nope. You'll be buying bearings spec'd for the 400 block. You typically end up needing standard main bearings and .010 under rod bearings (if the crank hasn't already been turned at the rods). The rule of thumb for the counterweights (if I remember correctly) is a 7-1/4" dia.

I had my machininst order the bearings just to be on the positive side of things.

Posted By: Cab_Burge

Re: machine work on 440 crank for 451 ? - 06/07/12 04:42 AM

Quote:

Guys, I am Getting Ready To Take A 440 Crank To A Machine Shop To Have The Mains/counter weights Cut Down For A 400 Block. I have A Question, Will The New Mains Require Anything Special To Be Done To The Bearings?

Are they going to grind in a full raduis on the edges of the mains or a reverse (inverted) radius like the stock Mopars have

It can make a difference on how the bearings fit and on how much end play, thrust clearnances, the motor(crankshaft) will end up with

Posted By: Tom Fox

Re: machine work on 440 crank for 451 ? - 06/07/12 06:20 AM

Quote:

Quote:

Guys, I am Getting Ready To Take A 440 Crank To A Machine Shop To Have The Mains/counter weights Cut Down For A 400 Block. I have A Question, Will The New Mains Require Anything Special To Be Done To The Bearings?

Are they going to grind in a full raduis on the edges of the mains or a reverse (inverted) radius like the stock Mopars have It can make a difference on how the bearings fit and on how much end play, thrust clearnances, the motor(crankshaft) will end up with

I have not Talked To Machine Shop Yet. & Have Never Used This Particular Shop Before. Hopefully They Are Aware Of What Exactly Needs To Be Done, But The More I Know When I Talk To Them The Better. So, What Specifically Do I Need To Make Sure Gets Done To The Main Journals To Be More Or Less Just Like Stock When Done?

Posted By: Cab_Burge

Re: machine work on 440 crank for 451 ? - 06/07/12 07:24 AM

Take a set of main bearings like your going to use and let them use them to determine how wide they make the mains and the final finishh on them. Most non Mopar crank grinder don't realise that mopar cranks are differnent on how Mopar did them, all the other brands I know of have a radius on the mains and rods, not a reverse radius like Ma Mopar did them

Posted By: Oyvind Mopar

Re: machine work on 440 crank for 451 ? - 06/07/12 08:22 AM

I do not think a crank grinder can make the undercut fillet radius like Mopar did. I guess they made the crank this way by turning them, to have control on the radius without grinding it, so they could use a straight grinding wheel finishing the journals and still maintain a radius.
A crank grinder will (hopefully) make the correct radius with the gridning wheel, which is also stronger than the Mopar design if done correctly. The bigger radius the better it is for fatigue strength, but can make interference with the bearings.

Posted By: ZIPPY

Re: machine work on 440 crank for 451 ? - 06/07/12 01:14 PM

Mine didn't require anything done there either, but like yourself I wanted to make sure everything was cool.

Until I had the parts in hand I wasn't clear on the width of the 400 bearing vs width of the journal.

Once I saw the bearings were a skosh narrower than the journals and could not get hung up on the radius/lock up the crank I knew it was good to go.

I'd suggest doing the same thing, just get the bearings and crank you're going to use and have a look.

Posted By: Performance Only

Re: machine work on 440 crank for 451 ? - 06/07/12 02:55 PM

Quote:

Guys, I am Getting Ready To Take A 440 Crank To A Machine Shop To Have The Mains/counter weights Cut Down For A 400 Block. I have A Question, Will The New Mains Require Anything Special To Be Done To The Bearings?

we've done quite a few of those. i prefer to cage the main bearings in the block and take a measurement first. that way we can grind the crank to get the proper oil clearance for the application. it's not absolutely necessary, but it does make for a better finished assembly IMO for a tiny bit more effort.