AFAIK, the only thing those marks do is designate what rod and main bearings need to be used.
Last edited:
Crankshaft issues
- Thread starter IdahoRob
- Start date
Attachments
Last edited:
Now if someone would only exert the time and expense of building a billet crankshaft.
3 years ago I set out to build a billet crank in response to these same types of failures. I didn't set out to build a stroker crank, but it occurred to me along the way that the cost of the crank would be the same whether or not it was a stock stroke or increased stroke. It turns out that +.250 in stroke would fit in the block with out any surgery. So we built 20 stroker cranks and 6 stock stroke cranks. We sold out of the strokers and still had 3 stockers left so I built 20 more strokers. By the time the 40th stroker left we finally sold the last stock stroke.
I won't keep any of the stock stroke on the shelf as it is just too slow of a mover. However if anyone wants one I can slip it in with the next run of strokers. Usually takes about 10 -12 weeks.
Guy
Guy , does the stroker require different rods or does it just use standard rods and move the wrist pin requiring new pistons ? if i can re-use my rods i may move to a stroker when i switch to forged pistons
and i agree with the choice if your going to replace the crank anyways it makes sence to stroke it in the process .
Guy , does the stroker require different rods or does it just use standard rods and move the wrist pin requiring new pistons ? if i can re-use my rods i may move to a stroker when i switch to forged pistons
I talk to Guy last week about the stroker crank and he told me i can use my crower rods but if i had wanted to use my stock pistons i would have to get custom shorten rods to make it work. So I bit the bullet and bought the crank and 0.040" over forged piston from him.
If I were worried about it and wanted to run a stock crank, I'd start with a used crank and magnaflux it (magnetic particle inspection for cracks). If it passes, then this is one case where I'd try cryogenic treatment. Cryo is where they cold cycle the metal to try and reduce internal stresses locked into the metal. I'm currently running a SoCal billet crank with no problems.
Concerning where the cranks normally break (first throw) and accessory drive load? We don't have any really serious drive load up front. Maybe 30-40HP including cam. Supercharged engines run several times that.
If you think about it, when 1 or 2 fires off, it's at the far end of the load. It could be simply leverage.
I'd be curious to find out if anyone had magnafluxed a stock crank and had a rejection, and where the reject area was.
Concerning where the cranks normally break (first throw) and accessory drive load? We don't have any really serious drive load up front. Maybe 30-40HP including cam. Supercharged engines run several times that.
If you think about it, when 1 or 2 fires off, it's at the far end of the load. It could be simply leverage.
I'd be curious to find out if anyone had magnafluxed a stock crank and had a rejection, and where the reject area was.
probably a newb question here but what order does the cylinders fire off? Could in high rpm motors could 1 and 2 be firing and trying to counter act each other?
Just a thought.
Just a thought.
Has anyone broken the LBZ/LMM crank yet? I wonder if GM perhaps did any updates to the processing for the LBZ.
1-2-7-8-4-5-6-3
So yes, there is some torque overlap on the 1-2 rod journal, but so is 5-6 & 7-8. Only the 3-4 journal has no torque overlap.
cranks
Every picture I have seen the crack goes into the radius. How big is the radius in Guy's cranks? I will bet .125 to .140.
Every picture I have seen the crack goes into the radius. How big is the radius in Guy's cranks? I will bet .125 to .140.
yes, IIRC Rhall's was an LBZ, and a guy named gary (Mr.YFZ450) on dieselplace. there were more that i found when i searched it but those two are on the top of my mind
Attachments
Last edited:
just to update this thread, Empire Diesel has released a new Cam that has a different firing order - i believe it swaps 2 and 7 if i read correctly- they say they have found it not only increases hp all things being equal, but it could be the fix for breaking cranks. thoughts?
How do they test for that? How do they prove it? I am not saying they are wrong. Nor am I saying they are right. Just very hard to point your finger at just one thing. In a performance build many things need to be accounted for. Very bold things to say with out data to back it up.
Personally I think Jeff hit a the nail on the head in this post.
Gear drives are great at transferring harmonics. Plus add the helical cut of the gear that creates a lot of load that contributes to crank walk. I look at what my tractor pulling buddies have done. They had issues with helical cut gears tearing up parts and thrashing thrust surfaces. Now they all run straight cut gears. Helps alot. Two me the ultimate would be a belt drive for the cam. You need to have the cam custom ground because the rotation would be opposite of stock. Also the CP3 would need to be removed from the valley and driven some other way. Going to a Gilmore belt drive and low mounting the CP3 would be slick.
Personally I think Jeff hit a the nail on the head in this post.