I was autocrossing my car a couple of weeks ago and watched my oil pressure gauge go to zero after a couple of laps. I've replaced the sending unit, the pump, the pump driveshaft, and the pickup. I finally got to take it for a drive yesterday, and after I got it warmed up, the oil pressure still fell way down (it was back at zero when I pulled back into my garage ). I could not hear anything out of the ordinary as far as the engine is concerened (ie, no sound from the valve train). A friend told me that the cam bearings may be worn. I have used it at a few autocrosses and a couple of track day events, so I guess it has seen some pretty hard use. Is this a common occurence with 350s? I've searched the threads here and have seen where others have had problems with their oiling system. Could it be just a bad gauge, or am I looking at a rebuild? If I am looking at a rebuild, would you go with an aftermarket block? What would be required to use my stock block if the cam bearings are worn? Thanks for your help.

Russell

 

Check your oil pressure with a mechanical gauge.

When cam bearings go bad, they leak oil. Usually at real high miles (100k plus). I had low oil pressure, hot and at idle (10#). Changed rod, main bearings and put in new stock oil pump. Oil pressure was better (15# not great). When I tore down engine for a complete rebuild, cam bearings were shot, down to copper. At speed 2000 rpm you will hardly notice (40#)

BTW a typical idiot light comes on at 6# and by then the rods are knocking.

 

When you checked a main bearing and a rod bearing as part of your normal check-out procedure while you had the pan off, what did they look like?

Of all the possible causes for an oil pressure problem, cam bearings, while possible, are WAY down at the bottom of the list. Once a motor gets past about the first 30 minutes of running, if they haven't failed yet, they aren't going to. I don't think I've ever seen them fail in ANY motor unless they were improperly installed (in which case it was more or less immediate at initial startup), or unless something else failed first.

Possibly; although since you've already replaced the sending unit, which is the part that usually goes bad, I'd again describe it as possible, but highly unlikely. You are at the point where if you suspect the gauge, about all you can do, is hook up some other gauge to verify it. Probably worthwhile to do so, but don't be surprised if it comes back that you really do have an oil pressure problem.

More than likely, yes.

Sure; if somebody else was paying the bill. Whether all of that $$$$$ is of any value to you, however, depends on what the motor is, what you use it for, etc. I'm guessing, by the questions you're asking, probably not; rebuilding a stock block, either yours or some other equivalent core, would be fine.

Being replaced. Cam bearings are always replaced anyway as part of a normal rebuild.

 

Thanks for the advice guys. When I had the pan off, I didn't notice anything abnormal, but then again, I'm not an expert either. I'm at 122K miles now, so a rebuild would probably not be a bad idea. Just out of curiosity, if you were using the car like I am, how would you go about rebuilding the engine? It usually sees duty at several autocross events each year, and starting last year, I ran it in a couple of track day events (this is likely to continue). The only real modification to the engine itself are the aluminum L98 heads I put on a couple of months ago. I would probably retain the stock TPI system for now, but what about the cam? Would it be ok to reuse my stock crank too? Sorry to ask so many questions, but I've never done anything like this before. Again, thanks for your help.

 

What did the bearings look like?

Find out what's wrong with it first, and go from there.

If thhe rings are good (no smoking, good compression) and there's nothing else really wrong with the motor, and it turns out that bearings are bad, you might want to just crank-kit it. (crank & bearings) Which you could re-use your stock crank, and just get it turned, and replace the bearings. OTOH, it's usually alot quicker and easier, and about the same cost, to just buy a replacement crank with bearings to match ("kit"), and do the work all at once. Compare to, tear the car down, haul the crank somewhere, wait a few days while walking or riding the bus or something and paying cherry-picker rent by the day, haul the crank back, THEN re-assemble the car. It would be different if the crank was somehow unique or special, but it's not. It's as common as dirt, so there's no particular reason to be concerned about hanging onto the one in your motor.

As far as modding the engine, consult with your class rulebook to see what is allowed, before jumping.