914-4 2L #3 rod bearing failure Options

[ChrisFoley]

...
In such a situation, what happens to the main bearings at that end? For the bearings to be so galled it almost has to be poor oiling doesn’t it?

The mains can actually take a bit more abuse than a rod bearing considering the multiple supports to the crank, and excess oil from the mains is what feeds the rod bearings.

[Tbrown4x4]

Lots more surface area on the mains too.

Was there a rod knock? What made you look into this? The only (water cooled) engines I've torn down with a knocking noise were in much worse shape.

[914werke]

Aftermarket rods do not have an oil slinger slot that the factory 2.0L ones do.

(IMG:style_emoticons/default/confused24.gif) What oil slinger slot?
here is a doc that details how to cut/file one into the factory rods?

[yeahmag]

Had this happen to my rod bearings twice even while running Brad Penn, a tuna can, and 1/2 quart over. What I found was happening (based on logging oil pressure) was the oil was not draining back fast enough. If you don't want to go dry sump (which I did) you can try blocking off the head vents and enlarging the case vent. The idea is to keep the heads at a higher pressure than the case to increase oil flow (return) back to the case. I run a -10AN line from the chimney to a cheap breather.

[ChrisFoley]

I think getting rid of the windage tray and keeping the rocker boxes as close to atmospheric pressure as possible makes more sense.

[Driver174]

Lots more surface area on the mains too.

Was there a rod knock? What made you look into this? The only (water cooled) engines I've torn down with a knocking noise were in much worse shape.

No rod knock; was simply pulling rods to do the oil slinger modification while I had the top end apart to increase compression ratio.

My friend actually suggested that I should split the case and inspect everything while the jugs were off. I wasn't going to disassemble it this far as it was just completely rebuilt before I purchased the car. Well I should have taken his advise because I could have addressed this quite some time ago while waiting for custom pistons, and an exhaust from Chris.


I have to say THANK YOU CHRIS; that exhaust is definitely an example of fine and skilled workmanship. I cannot wait to get this car assembled, and experience the performance gains from this exhaust!

[Driver174]

Had this happen to my rod bearings twice even while running Brad Penn, a tuna can, and 1/2 quart over. What I found was happening (based on logging oil pressure) was the oil was not draining back fast enough. If you don't want to go dry sump (which I did) you can try blocking off the head vents and enlarging the case vent. The idea is to keep the heads at a higher pressure than the case to increase oil flow (return) back to the case. I run a -10AN line from the chimney to a cheap breather.

I'm using Brad Penn as well in 20W50 viscosity. Is it normal to run this thick of oil in Type IV's?


An AccuSump was suggested in an earlier post, would I benefit from one?

[ChrisFoley]

I'm using Brad Penn as well in 20W50 viscosity. Is it normal to run this thick of oil in Type IV's?


An AccuSump was suggested in an earlier post, would I benefit from one?

20/50 is appropriate in warmer climates.

The downside of an accusump is the recovery period after a long sweeper, where pressure to the bearings is diminished while the accusump refills. They're really only helpful for up to 2-3 seconds of oil pickup exposure.
The oil vs air volume inside the chamber must be carefully balanced or the accusump will be of no benefit.

[brant]

You also need to run a synthetic

Dino oil is going to break down at your temps. It’s too hot

[Driver174]

Did a trial assembly tonight with new main bearings.

Measured clearances of new main bearings and found: #1=0.0027", #2=0.0057", #3=0.0030" & #4=0.0019". I was thinking #2 main bearing clearance should be tighter as it distributes oil to rod journals 2 & 3.

Should I be concerned with #2 bearing clearance?

Thanks,