John Veninger

I think your sugar coating using the word "suspect"

marton

I think that asking the people who bought these cranks about the technical details is like asking someone drinking a coke "what is the secret formula".

You have to ask the guy who drilled the crank

Marton

John Veninger

It's quite simple. Take a Chevy 350 crankshaft and drill it the same way.

Stan.Shaw@Excell.Net

Happy to sell this slightly used Devek drilled crank to someone who can use it....

GregBBRD

Here's my 2 cents, for what it is worth.

Any crankshaft with damage that caused distortion needs to be thrown away. Repaired, welded, chromed cranks usually break into two pieces fairly quickly. This is "used car lot" repair proceedures. Most cranks that are ground undersize have flaws in the radius and they will also break. A very good crank grinder will radius their stones and not get this "chatter" in the radius. "Good" crank grinders are expensive, as it takes longer to do things this way. Most people don't know the difference, so "good" crank grinders are very rare! If you have a crank ground and it has "chatter" marks on the radius, throw it away and smile.

Your crank was not drilled anywhere near correctly. One of the problems with the 928 is that #2 and #6get their oil last....not first! To improve the oiling, you need to drill the #3 main bearing to supply oil to these rods. The main bearings need to be modified to supply oil to the rods throughout the rotation of the crankshaft.

What rod bearings were used? I'm betting a set of "aftermarket" Glyco bearings. Nice price. Not enough oil clearance.

Jay Steele at Taylor Engine has a guy that knows how to do this. I had him do the very first one to my specifications and he's done many of them since. Jay is a "world class" machinist. He's also very busy. The two go hand in hand, in my opinion.

John Veninger

Yes, one of the factors to the failure is the foam oil.


Hmm... then why did Porsche decide to place a 6600rpm rev limiter. To protect warranty claims?

maybe, but they raced the 944, which has the SAME design problem. The 944 guys deal with the same issue.

marton

Exactly my thoughts; it is too simple & easy to be a true solution.

Marton

John Veninger

Kevin wrote:
So Yes, 6600 is less than 7000, but you indicated this engine should run PAST 7K.

John Veninger

If your talking factory changes, then they still seem to fail......

GlenL

928 oiling problems:

The sump is in the front
The pan is too close to the crank
The pan doesn't slope steeply enough
Early pump sucked air through shaft seal
Separator sized for low blow-by volumes, not for 100000 mile engines

Oil ejection is a symptom of the foaming problem. Combine foam with blow-by and that creates ejection.

The rev limiter is obviously set to produce a 200000 mile engine. You want a 2000 mile engine? Rev it higher. Don't float the valves, though.

The key is to keep liquid oil over the pick-up or, more specifically, coming out of the pump. Drilled cranks, reworked ladders, accumulators and dry sumps are all addressing that basic failure.

Lemme add: All reports are that the full I-J windage set provides clear improvements in oiling behavior.

Something to consider is that the crank drilling scheme may not be optimal for higher-revving engines. If you want to go to 7000+ it might be better to have the drilling and grooved bearings. It could be the combination that provides the benefit.

Why not do a main bearing mod alone to get more pressure to the rods? Sounds like a whole less money.

BC

So you would put that pump on and through a separator - but were would you draw from? The oil filler area? In through cam covers, up through oil filler area?

BC

There are three holes in the V. All are about 3/4 inch or so. Two are used for knock sensors. I suppose new holes could be drilled, but I would be concerned since the originals look cast and then tapped.

BC

The other is the 4x2 hole that is the oil filler area - that looks directly at the main crank case area.

Vilhuer

Porsche saw need for thicker casting in rear block area which they used to drill breather holes in GTS block before blocking them with freeze plugs. There prrobably aren't many places in block where factory would feel comfortable making new holes without any reinforcements.

Vilhuer

Heads drain oil practically directly into path of rotating crank.

Many of these problem areas would have been easy to avoid if they would have been thought off in original design. Later on it become financially virtually impossible to fix them.