Take a look at the bearings - in pretty dang good shape. Maybe our 'priority main' oiling system kept them happy?
Even though we're running a dry sump and this beast has an extremely tall deck (8.75" rods), there was plenty of oil up in the pins, the skirts looked really good and the Akerly HTD rings showed a really consistent sealing surface all around.
B&D
The stock priority oiling system is very good, no doubt about it. Adding the dry sump and more volume only adds to the success of the design!
Even though we had plenty of oil to the piston pins this year, it doesn't make me feel warm and fuzzy about next year. We're discussing going to vacuum in the engine next year, so any benefit of 'splash oiling' we had will be lost. Even if we have adequate pin oiling, we can still benefit from cooling the pistons with oilers.
I don't agree, however, that we need to run 100 psi in this engine, for it to survive-not even close! I think if we could enlarge our oil ports, thereby increasing volume while decreasing pressure, we would be more successful. It would be better for the engine internals, and take less HP to run the oil pump.
Now, just like Paul Harvey- The Rest Of The Story!
For the amount of runs on the engine, the bearings look good. The front main bearing showed some crank flex, but I attribute that to the blower drive, since the front showed the most.
I'm interested to see if the rod bearing wear is confined to a couple of rods, or the center ones, as Chris suggested.
The pic of the rod bearing shows the effect of geometric irregularities. This could be because of crank flex, but there are other possible causes. A slightly bent rod, detonation, or rod journals ground with a slight 'hourglass' shape can also cause this wear.
There is even more to this story though, and I suspect it probably contributed to the wear- We misused the rev limiter this year. Instead of setting it higher than we needed, and only having it there in an emergency, we ran against the rev limiter, using it to determine the max RPM we hit each run.
Rex was kind enough to point out the error of our ways, and the explanation made perfect sense to me. What we were doing was having some pistons loaded, then randomly unloaded, in no certain order. I can't help believe that this probably added to our crank flex.
The bearing clearances are one of those things that Dale and I have discussed in depth for the past year. I don't believe we can open the clearances up enough to not show wear from crank flex-the flex is bound to be more than the additional .002 or so that we would open them up. Nor do I think that it is necessary. The mains have the following clearances F = .0035, M = .0035, R = .004, and the rods have .025-.075. The Mains are 2.75", and the rods are 2.1"
Increasing bearing clearances are not necessary in my opinion, but finding out why we have that wear is. I truly believe proper use of the rev limiter will help, but I have no doubt that we will still have crank flex with the 3 main bearing setup.
Saltracer1, that's a darn good question! I was told, and under the impression that we were going to run coated bearings. I sent the cam bearings off to get coated, and was told that we would order coated SBC rod, and BBC mains, but I was not there when they were installed. I will be this time, and they will be coated.
Topic: XXO/BVGC '38 Chevy Coupe Build (Read 1031527 times)