I have an a12 roadrunner and I'm going through the motor in the middle of a restoration. The crank has some pitting between the connecting rod races. The engine builder is recommending a new crank. Would you guys cut and reuse or get a new rotating assembly?

I would listen to your engine builder, besides, those pits look rather deep. If not mistaken, there are plenty of the cranks still around.

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I have an a12 roadrunner and I'm going through the motor in the middle of a restoration. The crank has some pitting between the connecting rod races. The engine builder is recommending a new crank. Would you guys cut and reuse or get a new rotating assembly?

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Pits by themselves are not a problem for sleeve bearings. However, the pits are most likely caused by corrosion and corrosion can cause cracking.

Cracking is what would worry me. The pits look pretty severe so I am with your machinist and replace.......

Don't know the cause of the pitting, but where it's at will cause no problems ( not on a loaded area). If the size is good, I would just polish it and run it. Would be a good idea to have it checked for cracks ,though. Easy way to this is to stand it up leaning off center and tap it with a hammer- being a steel crank, it should ring like a bell.

I've not seen anything like that! What did the bearings look like? Any distress? I wonder if it was an original quality problem? May be OK to run it but I would not personally. New or "new used" crank sounds like a good idea.

Are you wanting to keep all the original major parts in this motor? If so have it magnaflux inspected for cracks, everywhere If it mags good and measures good, within .0005 of the minimum and maximum factory specs. run it If you want to step the performance up some think about having that crankshaft offset ground from the factory 2.375 rod jourbnal size with 3.75 stroke size down to BB Chevy rod size and offset ground to 3.900 or 3.910 stroke, whichever the crank grinder can get out of it and buy a new set of forge H beam rods 6.800 or 7.100 long center to center and a matching set of forge pistons and enjoy the new found HP and torque of the longer stroke I have one of those motors(3.910 offset stroke 440 crank ) sitting in my shop right now waiting for the 1966 Dodge Coronet Deluxe to come back from the paint shop. I hate waiting on paint and body shops that promise two months and take six months

Don't think of them as pits, think of them as oil reservoirs.

The crank looks really good other than the pits that are visible at two different journals. There is no apparent rust anywhere including in the pits. The motor has been built a couple times before me (given the pop up Pistons and strange brown connecting rods) so the crank may have been cleaned up. If I knew for sure that it was the original crank I'd be more inclined to try to keep it together. Under the circumstances, though I think it's time for a new one. Now comes another question. Should I do a mild stroker like a 4.150 or stay stock? Nowadays the cost is almost the same. The Pistons are 11.5:1 or better so I'd like to bring that down to 10:1 or so so may as well get a balanced rotating assembly. Any suggestions? It is a matching number block and I don't plan on doing much on the track and other than possibly the motor going bone stock on the restoration.

As far as the stroker... depends on what your goals for the car are. 4.15" stroke in a 440 block can be a solid reliable combo. Pure stock resto, then maybe avoid it. You want to drive it and want more get up and go then yes. The stroker will benefit from other changes. More cam, better heads, better exhaust. Is that part of the plan? The stroker can be a blast to drive. I love mine!

For what you are trying to accomplish and the unknown's on that crank I would buy a kit with the crank and not look back.

The pits are between the rod bearings. I don't see how that would hurt anything. If you want to run it I would. If you want a stroker for more power I understand. Make it for pump gas.

If you decide against a stroker, stock forged cranks can be had for pretty cheap these days.

If you decide to buy a stroker kit stay away from the old reliable 4.150 stroke cranks with the Mopar size rod journals and look at a 4.25 stroke with the BB Chevy 2.2 rod juornal sizes and a 7.100 long forged H beam rod with a D dish piston to stay under 9.50 to 1 compression ratio to run on pump gas with iron heads, if aluminum heads pump the compression up to 10.50 to 1 ratio Strokers are a kick in the butt to drive

Crank looks like the journal was welded. Those pits look like they're between the 2 rod journals.
Doug

Cab Burge, can you elaborate on the advantages and disadvantages? One of the reasons I was trying to stick to the 4.15 was to minimize or hopefully eliminate clearancing a matching number block and to reduce side wear that the larger strokes see . I was under the impression that any longer stroke would get me in trouble. Maybe it's not worth worrying about? Also, outside of connecting rod cost and availability, what's the advantage of the 2.200 Chevy rods? As for the crank being welded, highly unlikely, this isn't the only place this happens, there's another journal near it that has something similar. In the picture I posted, there's another small pit in the upper right hand corner. I just can't see someone welding this thing from twenty pieces.

There are two advantages to using the Chevy dimension rods:
1. They are inexpensive and it's easy to buy a high quality rod for way less than a 440 rod. I believe as there are so many stroker bigblock chevies, the rods have more thought given to using them in strokers, meaning slightly more compact. The 0.990 pins as well have the advantage that there are many lightweight pins to choose from.

2. Because the rod journal is smaller diameter, the outside of the rod is smaller diameter too.

When you think about the total diameter of the rotating assembly, you can fit more stroke using the smaller rod journal. This also lessens or eliminates the amount of work to be done on the block. Example: A 4.15" stroke using a 440 type rod will have a LARGER rotating diameter than a 4.25" crank using a chevy rod.

SO: You could build a 3.91" offset ground stroker using your existing crank and chevy style rods and it for sure wouldn't hit anywhere.

Or, you could build a 4.25" stroke chevy rod engine that'd fit into your block with very minor clearancing on the lower edges of the bores.

You can never go wrong increasing displacement in a car you intend to drive on the street.

R.

PS: Look up the 440Source webpage on strokers and stroker kits. There's a lot of information there.

Even if the car is going to be restored rather than modified I'd use a 4.25 stroker crank. If the car is going to be driven at all the extra torque just makes it more fun.

A 4.25 stroke crank with Chevy 6.800 long rods and matching pistons with your desired compression ratio are just a VISA card number away. It should all drop into your existing block and use your existing parts.

If the engine was externally balanced originally and you want to keep the factory damper and flywheel then you'll have to have the new assembly balanced the same way. Or do a neutral balance and buy new damper and flywheel.

I also think you could have that crank ground down 020 or 030 and run it as is, but maybe not. Shouldn't be hard to have it checked out either way.

The main advantage of using the BB Chevy type forged steel H beam rods is the better 7/16 rod bolts,much stronger rods than stock, new materials, less cost and weight The longer rods help reduce the side loading on the cylinder walls also I have a 464 C.I. 440 block pump gas motor that I had the stock crank offset ground down to BB Chevy rod sizes and increased the stroke to 3.900 or 3.910, CRS disease I used a 7.100 long BB Chevy type rod in that motor to help reduce the cylinder wall loading and help reduce the weight of the pistons also I'm building another pump gas 440 stroker motor right now that is 4.250 stroke with 6.800 long Eagle BB Chevy type rods, I'm using them because I had them in stock and wanted to use them up. I would have bought 7.100 long rods if I didn't have this set of Eagles on the shelf IHTHs