Okay orange 442 started a thread on ROP. So i thought why don't we discuss it here also. Can a 455 steel crank be modified for a D/DX block? My thinking is yes and the cast crank as well!

 

How do you mean "modified"?

 

Yes you can physically put that crank in a DX just as you would the 400/425 crank. But why would you want to? You can achieve more stroke than is feasible with the 400/425 crank.

 

Oldsmobile dave claim he has a 4.30 stoke crank in a D diesel block if i have my info correct! Mark cutlassefi can anyone install a 425 crank in D/DX diesel block with out modifying the crank!Answer NO! So that is why i said modify a 455 crank! You should elaborate more on why you ask the question about modifying 455 crank to fit. Please weigh in on this discussion because those who read this thread may learn something. I am sure i will i hope.

 

On any crank with a 4.300 stroke you'll need to cut the counterweights for piston clearance and cut the journals as well. You only have so much deck height so with the 4.300 stroke and the shortest BBC rod available you're still looking at a piston height of about 1.030. The wrist pin will be in the ring pack, why? Imo this is unnecessary.

You could use a SBC rod instead but you may run into an oil hole problem with it moving too far towards the radius. Plus I don't like to see such a short rod to stroke ratio. That's hard on the cyl walls.

Jmo.

 

I was only ref the 4.30 stoke we all know 455 is a 4.25 stroke and wouldn't be changed.Now that is what i like to hear!Sound reasoning for why not to use even if you can fit it in the block after reworking it! Thanks mark i think that should clear it up! Would you mind doing the same info on ROP.

 

In order to use a 4.300 stroke and still have a usable c.h. piston you would be using a 6.125 sb rod or 6.135 bb rod. In order to make a rod and piston combo physically clear the crank counterweights you would have to take the counterweights down to a smaller diameter than what is normally done. You would have to get a second mortgage on your house to be able to afford enough Mallory to even try to balance it. I personally don't think that is something I would want to try. I would build a 4.00 stroke 6.25 rod 1.062 c.h. piston combo. Set the bore size to 4.155 and you have a nice 434.

 

I don't disagree with what you are saying totally. In theory the balance would be done by bob weight. Till you do a attempt with light weight parts how can you say how much Mallory will be used. Go read what Steve81 claims he did when he lighted a 425 crank ROP.The thread was Life span of a BBO. This was in high performance forum of ROP.

 

Yes the balance is done with Bob weights that equal components connected to the crank. My point is by the time you reduce the cranks counter weights enough to clear the short rod combo that long stroke requires the common connecting rods and pistons available will give a Bob weight greater than the counterweight of the crankshaft. In reference the common 4.00 stroke combo using common BBC rods usually requires at least 4 slugs of Mallory to internal balance from what I have found.

 

I got you point and thanks for the replys. This has been a good discussion.I myself would not use a 455 crank for a D/DX even if it could be done $$$$$$ wouldn't be worth the experiment i am sure.Mark gave a good reason for not doing a build that way. I am glad he weighed in on this discussion.I am going to do a D build down the line when money allows. I also have looked at a 434 build real close. Thanks everyone for replys i think this thread is done!