mark kibort

and Todd and Tim built my engine that has lasted 6 racing seasons, and these are full racing seasons by the way....... not just WCGT race weekends with 3 times on track. . sure, his engines were subjected to much higher G loading for the PCA weekends due to slicks, but he didn't do that many of them.
my engine and the stock holbert engine (as far as the block goes) lasted over 8 racing seasons, and had NO issues.
again, let the times speak for themselves as to far as what the engine was subjected too.
1:36.1 at laguna on DOTs and 1:36 to 1:37 for many years with 372rwhp
Anderson 1:35 On DOTs and 520rwhp with WCGT, 1:31 with slicks
1:40.1 on DOTs when he had only 420rwhp.

point is, ive subjected the car to greater forces, which is not a driver comparison, just a time comparison to show the engine can survive and survive a very long time, racing, not just DE'ing.

Casper's engine was a 4.5L with the smaller oiling hole crank. Never should have been expected to last. PERIOD. Nuff , said there

mark kibort

the smaller oiling hole crank IS what your Casper was using, its not your crank, but it shows the difference of what will work and what theoretically shouldn't work. yours lasted much longer than it should have.

heinrich

Guys great discussion but how is oil in water related to rod bearing failure?

mark kibort

I didn't know this. and Gregs description makes sense too.

does this mean that crank and its 180 degree off set holes, acts like a peristaltic, or piston pump, where the pressure builds, then its released, builds, released, etc???

anyway, it works if you have a good engine, and you use the right oil and are smart about the RPM you run the engine at, and where on the track you are. again..... watch my video. I take no regard for limiting RPM down the straights, only the turns, where you don't need power at the apex, only the exits.

ptuomov

Cross drilling and minimum radius are different things. You can cross drill (in theory, not in practice) in a way that the passage stays close to the surface. You can cross drill the straight shot passage with an additional channel.

As far as I understand, the pulsing is of no significance. The single hole straight shot pulses. Cross-drilling pulses differently. I think it doesn't matter. That's an opinion.

The minimum radius of the oil passage matters to how much oil pressure you have to run. Once the oil pressure is set high enough, both drilling schemes work well. The straight shot allows you to save a little bit of power by requiring a lower oil pressure. Both kinds of cranks fail if the supply pressure drop below the critical threshold. The crank drilling isn't going to cure a problem caused by a pickup uncovering in the turn.

atb

Mark,

I think you were confusing the terms "cross drilled" and "drilled like a chevy".
Stockers are cross drilled. The strokers and Taylor-modified are drilled like a chevy.

GregBBRD

I don't recall seeing this mentioned.....what kind of oil was Casper using?

GregBBRD

I actually do not know the answer to this, nor have enough of a background to have a theory. All I've got is what I've taken apart and what I see and hear. I am just repeating what I have been told, by engine people that are far, far smarter about this stuff than me.

Not to keep concentrating on one source (there are very few engine people that have written books on "how" to do things), but Reher Morrision is adamant about not cross drilling cranks....they consider a cross drilled crankshaft to be scrap metal (keep in mind that their engines probably all exceed the 6,500 rpm limits that we are talking about.)

Bill Dailey (Dailey Dry Sump Pumps) sat down one day and took the time to explain the different crankshaft oiling problems theories, to me. He's forgotten more about oiling problems and their solutions than I could ever hope to know. I consider him to be a genius about this subject. He's the one that explained the drillings acting like a pump.

I approached my crankshaft builder about redrilling cranks to have Chevy "surface" passages, much like my good friend Jay Steel (RIP) used to do for the 928 cranks. He refused. He said that unless we could plug the existing holes (which isn't practical) it was a waste of time to add more holes to a crankshaft that already had "very confused" oiling.

Instead, I had stock stroke (5.0 and 5.4) liter crankshafts built, from billet, to have improved oil passages, be stiffer, lighter, and have different bearing sizes (to be able to use a larger selection of bearings.)

GregBBRD

I doubt that this is an issue. Those holes are plenty big to supply oil to the rod bearings.

One thing that is worth mentioning is that all of the early 928 engines with these cranks were supplied with main bearings that had 360 degree oiling.

The benefit of 360 degree oiling is that both oil holes in the cross drilled main bearing are subjected to oil pressure, at the same time....and continuously.

Porsche superceeded these bearings to the current style, ungrooved bearings, presumably because the crankshaft loads increased as the power output grew.

I have built race engines with both fully grooved and partially grooved main bearings, before I went to my current crankshaft design.

ptuomov

My logic says that for a cross-drilled crankshaft where the passage to rod bearings intersects the crankshaft centerline, the required oil pressure is proportional to main journal diameter times the rpm squared. That is, if we go from 60mm mains to 70mm mains, we need 17% higher oil pressure. If we go from 6000 rpm to 9000 rpm, we need to more than double the oil pressure by increasing it by 125%.

Given that Reher Morrison builds racing engines where winning and losing are determined by 1-2% of power, it makes sense that they don't want to use a crankshaft that will unnecessarily lose more power to the oil pump. It makes total sense that a crank in which the oil passage to the mains goes from the main journal surface to the crank centerline is junk to them.

For our engines, the oil pressure is already so high that I personally don't think the crank drilling is a binding constraint anytime soon. One respected 944 engine builder runs dry sumped 944's with modified stock cranks but with the stock oil passages at 7500 rpms and appear to be using oil pressures lower than the 928 stock oil pressure. My opinion (not a fact) is that if we could reliably get clean pressurized oil all the mains, the 928 engine with stock crankshaft oil passages would live happily ever after.

GregBBRD

Reference crankshaft cross drilling and Reher Morrison comes up pretty quickly. They are not connected with anything I do, but I was doing some online crankshaft "data" collecting and ran across them, years ago. They were not concerned about the loss of horsepower, but had problems with the connecting rods flying out of the engines.....just like ours do.

I understand your theory and appreciate that you are entitled to your own ideas.

However, you would be hard pressed to find a crankshaft maker than would agree with you. I've talked to dozens of crankshaft builders, in this country, and have yet to find anyone that would put anything but the current high speed oiling into any high performance crankshaft, built from scratch. Note that I'm not talking about crankshaft builders that build crankshafts to the exact specifications of obsolete crankshafts, but strictly brand new high performance crankshafts. And, because you seem to get "lost" in the tiniest little details.....I'm not saying that they would not build a crankshaft with any drilling method you desire....smart people build whatever the customer insists on....I'm strictly talking about what they would recommend.

ptuomov

For others, here's what the good people at Reher-Morrison think: http://rehermorrison.com/tech-talk-5...calls-part-ii/

If you're asking me if I would drill a 928 style oiling passages in a new crank, the answer is no. If you're asking if any racing crankshaft maker would drill it that way by default, the answer is also no. Why would I or why would they? There's no logical reason for the oil passage of a main-fed, high performance (read rpm) crankshaft to go thru the crankshaft centerline.

Where we may or may not disagree is whether it's possible or practical to compensate for the passage drilling style for a 928 S4/GT crankshaft. (The GTS crankshaft is an abomination and I wouldn't want to be seen anywhere near one...) I think we shouldn't give up so easily on those nice, strong, hard S4 cranks just because of the passage scheme.

Todd Tremel is trying to run very high rpms soon with the stock S4 crankshaft. That will be an interesting experiment, custom rods, motorcycle pistons with 1mm rings, and turbos to turn any rpm desired.

GregBBRD

Nor would I.

I install those beautiful stock crankshafts back in engines all the time.

I just would not stick one in a high performance engine, turning 7,000 rpms, that was going to live its life racing.

BC

Last time I spoke to him, it was not motorcycle pistons. I am not even sure what that is.

ptuomov

Custom pistons made from forgings that are usually used for power sports pistons? That's my recollection from talking to him, might remember it completely wrong.