Jeep Strokers

lafrad wrote:I have a slight-offset grind crank using the 0.040" under bearings. Pushed the piston up on the hole 0.012" (0.023" more stroke overall), just enough so a "cleanup" cut on the head for a good mating surface set the quench to about 0.045".

Its been started and cam breakin has been done, but I haven't gotten it on the road yet... still getting the front clip back together.

That is how my stroker went together. Eagle rods and Diamond made up the pistons for a zero deck after the block was skimmed.
No worries

What about having the crankshaft nitrated? Usually around $150 supposed to reduce some stress..

if you do anything that may increase the stress in the crank, heat cycles in a controlled manner are the only way to DE-stress it. There are very specific procedures that need to be followed to heat/cool/heat/cool a *crankshaft* when cycling it. during that process, you must consistently straighten it, as relieving the stress can cause it to warp.

After the whole process is finished, you STILL must put a finish grind on, as grinding it is the only way to get it *truly* straight.

its a whole helluva-lotta-work to weld a crank... especially with as many journals as the I6 has.

StroktWJ wrote:What about having the crankshaft nitrated? Usually around $150 supposed to reduce some stress..

Nitriding is only a surface-hardening treatment for the crank journals. Good but doesn't have the same effect as cryogenic treatment. Here's some useful reading:

http://www.crankshaftco.com/steel-crank ... ening.html
http://www.nitrofreeze.com/racing.html

I know this is an old thread, but talked to my machine shop the other day,about the slightly narrower chevy rods. he said its not much to worry about with a little larger radius and filleted bearings, especially using a pressed rod. that will keep it pretty centered.

Good to know. I still want to do this, but it's on the back burner for now. Other obligations are taking precedence...not enough money right now.

Only *real* thing to worry about would be a making SURE you have good oiling. the tight fit keeps more oil in the rod bearing... your machinest is right... they will naturally keep themselves centered... and there is no "other rod" sharing the journal, so there is nothing really for it to interfere with.

I do know that if the crank is radiused correctly and the bearings match, you can go down quite a bit, almost .155 on a rod journal. The hemi guys went from 2.375 down to 2.20 and used chevy rods. The smaller journal had less friction and weight for increased RPM's like....in a 6000 rpm 1500 HP normally aspirated motor. The most you will probably get from stroke'n the 4.0 is 400 hp in normally aspirated configuration. In that horsepower range the chevy rods with ARP bolts and pressed pins and the right bearings will be no problem. Tim

The crank can be welded. Shops around the country weld cast Mopar 440 cranks and stuff them in the Mopar 400 and make a 500ci stroker good for 528 hp. Its all in how its welded and cooled. The cast only gets brittle if over heated. This is not a 600hp motor being built. As long as its done right I don't see a problem with it.