Rod bearings

I have a kb 526 with a winberg crank 4.5 " stroke and a 3" main,with GRP rods, P&P pump with the large presure side for the 3" crank.
We also have .050 side clearence on the rods and .004 on the bearing.
The problem is that I am taking the babbet off the radus of the bearing ,I have tried narrow bearings and the same thing happens.
The oil presure is 160 when cold and 110 when warm I have 17 quarts in the tank and we drain the oil from the pan after warming and refill the tank before going to the line.
Thanks
Dave Sharp
hydrotherapy715@yahoo.com

 

Hi Mike thanks for the reply. I can,t get more oil in the system,and the oil tank was made by one the the guys that work for Dan Olson,its sits along side the fuel tank,as for the vent its a #12 line that has a one way check valve that goes into the frame and back to the puke tank.
When we drain the tank after the run there 3 gal of oil in the pan,and looking at the data logger at the start of the run the oil presure goes to about 150 ,and as the rpm goes up the oil presure drops to about 110 at the end.
Thanks
Dave Sharp

 

Dave,
I am no expert but have a similar problem. I have a 4.0-inch stroke billet crank with BME rods, wedge head dodge, stage 6 KB block.

The bearing wear was from the crank radius. I sent the crank back and had the side clearance reduced to mid way between min/max allowed by BME. The oiling hole for each rod is located close to the crank radius.

I narrowed the bearings and put a radius on them. The bearing wear from the radius would go away on the bearings but the oil pressure would drop to 50-lbs at idle. The oil pressure would increase over 50-lbs during the run but unsure how much. The pan is full at the end of the run and we must transfer the oil from the pan to the dry sump tank. I also overfill the tank at the start of the run and vent the tank into an overflow reservoir I made out of aluminum (2-gallon capacity) to avoid an overfill condition when the scavenge catches up after the burnout.

I have decided to trim another set of rod bearings that allow for rod side clearance but still cover the exposed oil hole on the crankpin.

I did a trial and ran the minimum side clearance. Cylinder #2, #5, and #8 had the rod bearings contact the crank radius but the amount of oil to scavenge is significantly reduced. However, I am concerned that I will spin a rod bearing even with the bearings being pinned. I also found that increasing the oil to 70wt helped reduce the amount of scavenge and the oil pressure drop. I do not record the oil pressure during a run but I think I need to step up and get this information.

I hope this info helps,

Have you ever spun the rod bearings from contact with the radius?

Dave

 

Hi Mike the oil I've been using is the valvoline 60 and as runs the oil was fresh and only two runs.
Thanks
Dave Sharp

 

How old is the crank ? Is it still round. Sounds like there might be a crack in the crank. Ive had that problem and that my cure for it

 

The crank has 2 passes on it just came back from Marine crankshaft
Thanks
Dave Sharp

 

Can you post any pics of the damage that you are observing? That might help the collective here. What sort of RPM do you turn and do you have any funny business like unloading the prop or hitting rev limiters hard? Is this a new problem since a change, or is it an ongoing historic problem? Pictures will tell the tale but where is the damage located relative to 12:00 o'clock versus 6:00 (as if the rod was standing straight up)? Any weirdness on the backsides of the rod bearings?

 

I got a new set of rods a couple years ago and the dowel was in the wrong location, but only by a little bit, I caught it before running the engine.

 

curious as well, aluminum wont hurt much if anything, copper is what i look for, run the valves, and a oil pan inspection wouldnt hurt, I would run it.

 

This problem has been going on for a long time about 8 sets of different bearings 2 cranks, new oil pump and two sets of rods and the same amount of main bearings, it not hurting the mains ,just changed them to be safe.
The rpm it turns is 8500 and the two step in the 7730 box is set at 4500 for the trans brake.Had the rotating assemble rebalanced to to make sure , and Marine crankshaft gave the crank a clean bill of health
This is in a altered not a boat so no prop to turn, PS all the boats are sitting next to the car ,maybe its rubbing off on the car HA HA
I talked to Winberg and they said the crank has a 157 degree radius just like all fuel cranks and try chanfering the bearing a little more.Then I call GRP and they told me that I could have the bearing moved over .015 and I think that might help.
As soon as I figure how to paste the pictures of the bearing I will.
Thanks
Dave Sharp

 

Bearings

am i reading you are warming the engine and oil, then draining the oil and putting in cold oil in the dry sump tank. So when you go to the line your oil is cold? Cold thick oil, probably is not flowing well, your 160 lbs pressure, through the bearing, which maybe causing your bearing issue.

.004 seems tight, especially with cold oil.

all i can say is what I do with my 3 engines, Try having your bearings coated at Elliot Coatings, and warm your engine and oil, then run the warm oil.

good luck