Here is the story...

I recently finished rebuilding a new motor for the Rexer, all done to IT specs. It started just fine with around 75-80psi oil pressure during normal running above idle. I put about 250 break in miles and one autocross event on it with everything running just fine.

I hit VIR for some lapping on Friday (nervous as hell about the new motor...my first) and all goes well. 2 hours and 40 minutes of trouble free track time. Even did some dyno pulls at the end of the day with no problems. The only unusual thing that happend was that towards the end of the day, the oil pressure would read high (near 100psi) at startup, but would return to the normal range after things warmed all the way up. I figured this to be a flaky sending unit as everthing felt normal.

When I got home on Sunday and back the car off the trailer, I notice no oil pressure. YIKES.

I dug into it tonight. First I put the idiot light OEM sender back in place to verify if I really don't have pressure...light stays ON. I then drop the pan. Everything looks normal in there...pickup is clean. Next I take the lower plug out of the oil pump along with the spring. I expect the relief valve/piston to drop out also but it stays up in there. I have not had the oil pump apart, so I am not sure what to expect.

Questions:

1. Is the relief valve/piston supposed to come out easily? My guess is yes based on what I see in the shop manual.

2. If this is the mode of failure, has anyone else had this problem.

TIA

 

So I answered my own question tonight. I got the oil pump out and took it apart. Sure enough the relief valve/piston is stuck almost completely closed. I got it freed up and cleaned out the bore. There was some trash in there. After taking the gears out and cleaning everything up, this is what I see:

The gears have some abrasion marks on them. I am not sure what normal wear is supposed to look like on them since I have never had one apart. This looks slightly rough for something that should have gentle wear from clean oil for 140K mi. The piston looks to have normal wear and no abrasions. The bore for the piston has some heavy scratch marks near the top of the travel (probably why it froze up). I plan to replace the pump...mostly because the bore for the piston is not smooth enough for my liking.

I am perplexed as to the cause of the problem since I had a couple hundred of trouble free miles on the new engine. My only thought at this point is that maybe some honing media or trash from the machine shop operations may have been stuck in some passages. (I did wash and use compressed air on the block once i got it back from the machine shop) Maybe the first good thrashing at the track broke something loose.

Any thoughts??? ....anyone...Ferris....Beuler....

 

Perhaps it needed a longer break-in period before taking it throughout the RPM range. (i.e. autox or track days) I've always seen and heard 1k miles or more. But I've also never rebuilt a motor, so take my opinion FWIW. I would say replacing the pump would take care of the problem. Perhaps the track did dislodge some loose particles, etc.

- Ryan

 

I kept it under 5K for the first hundred or so miles, and under 6K for the next hundred. I did not take it to readline untill the autocross at Ericson. I don't think that many race motors get that luxury. There have always been two schools on break in from what I have seen. Break it in like you want to drive it...or go easy at first. Personally I think it is safer to go easy at first.

 

Yeah, I think taking it easy initially would make more sense...

 

I have heard a rare engine is broken in within the first 50 miles....Depends on how it was built I would guess....