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Greg: Yes, it's a cast crank.
Last year I built the cast crank version short block. Same pistons, a little bigger cam, same rods but narrowed to fit the cast crank, everything else the same as my earlier forged crank engine. I picked up almost 0.20 in the 60ft times. Yes, the cast vs. the forged made that big of a difference. That's almost 30 pounds less rotating mass. The energy to accelerate the 30 lbs. rotating weight can now be spent accelerating the car. The crank is an 84 version, the very lightest I think. Defiantly way lighter than an 83 I recently acquired. In my lightweight dragster, this weight difference is huge. Most dragster owners would have to spend thousands to shave off 30 pounds, little lone rotating weight. 60ft times are 1.40.
I ran that engine last year and made some of the best passes the car has ever made. I was running in the very low 10s. My goal has always been to be in the 9s naturally asperated. Late last year I lost oil pressure and found a wiped out #2 main. Bearing did not spin, but main cap got hot and shrank. Crank was now bent and would only clean up at 0.040 under, and those bearings are not available. Luckily I had yet another crank and acquired another main cap. I put my old forged crank short block back in the car and finished out the season. Block was fixed and new crank was ground 0.020. Put it all back together, added Ricks windage tray over the winter, and then this happened. (Lots of other stuff done to the car like full disassembly to powder coat chassis, reconfigured front end, shaved weight here and there, new steering box and shifter). Note, I never made it to the track. After getting the car running, I made a test hit on the street in front of my house. Fortunately, my neighbors love it. They are all gear heads. One hit and then lots of smoke out the breather, and 20 psi oil pressure.
Other specs. I am running methanol. Slightly higher oil pressure with a shim under spring at 60 psi. Valvoline VR-1 10W-30. Engine ran great and made some awesome passes, even winning at Bandimere before the #2 let go last year.
So, I'm doing something wrong. Wrong oil? Cast crank can't take it? My guess is bearing clearance. I never checked that. I'm a Manufacturing Engineering Manager in a machine shop. We just spent 1.3 million on a horizontal mill. I know better. I even have access to very high dollar gauges. But i never checked the clearance. And neither did my machine shop guy that outsourced the crank grinding. This is engine #4 for me and never had a bearing issue. In fact, that forged crank backup engine is now in dads car. Bearing look like new.
Some other issues: I've been asked by three people if I put the #2 main bearing in wrong. I sure hope I'm better than that, but I didn't film or take pictures, so I guess I could have. If I did, that's pretty amazing that the assembly lube lasted that long. Then there are the rods... As some of you may have noticed, these are Molnar rods, narrowed to fit the cast crank because only the forged crank version is available. No big deal for someone that has access to some nice equipment right? My machine shop guy noticed that the rod caps were not on the right rods. I never noticed, but each rod is actually serialized. I take great care to keep the caps with the respective rods. But during the narrowing process, each cap had to be notch for the bearing tang. I think this is when the caps got mixed. Three rods had the wrong caps, and two of those were the burned bearings.
Now, block is fixed with yet another new #2 main cap (lots of work on the block, so didn't want to start over with another block), rods are fixed with all big ends re-sized. 0.030 under bearings have been bought. We now know what the crank should be ground to in order to have 0.003 clearance. Changing oil to full synthetic designed to be run with methanol. May add an oil heater, defiantly adding an oil temp gauge. I probably could have caught the issue if I had monitored oil temp. Something that just came to mind. The blow-by on this build seemed more than what I'm used to. That was probably the hot rods and main cap burning oil.
So Rick: Cause? Hell if I know! But what I do know is this guy don't give up. I may have to go back to a forged crank, but I'll give it all I got.
Shoot me some ideas or comments. I don't know it all that's for sure.
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