Oil Pressure

C

charrbq

New member
Scenario...ITC Honda 1500, carb. Fresh, Mobil 1, 5W-30 with new Fram HP1 filter just as I always run, no change. Total capacity with cooler is just shy of 5 quarts. Everything checks out nice and tight with no leaks, etc. Idle pressure is 35-40 lbs, racing is 65-70, temp at race it 210 in 80 degree temps. At full speed, 4th gear, about 6G and climbing, oil pressure light comes on and pressure drops to 40lbs, stays there, then pops back up to 70lbs., stays there the rest of session. Later sessions, same thing happens, sometimes in turns, sometimes in short straights, once for half a lap. Pressure never goes away lower than 40 lbs and always comes back up to 70. Oil level and temperature remain good. Can't get it to repeat in pits.

Ideas...theories...I'm fresh out of spare bottom ends.
 
No mention of whether this is a direct-reading guage. If it's an electrical device, could be your problem. My 2nd question would be... any sort of pressure relief valve in the system that could be acting up?
 
It's an electric gauge. You're right, don't know why I hadn't thought of that. Only pressure relief valve is in the filter. Never had trouble there.
 
There is a pressure relief valve in the oil pump housing on these engines. It is there for cold start purposes . If the spring is getting weak and the valve is starting to stick a little you may have what you are seeing . When I build these engines I typically shim the spring a little to up the relief pressure somewhere about 80psi .

I am assuming this is in an 84-87 civic since it is carbed. I have some bottom ends if you need a core
 
That's something I hadn't checked. The guy that builds my motor does, though. The bottom end hasn't had that much time on it, but I suppose anything's possible. Good to know about a source of blocks. I've only lost one, and it was marginal for a long time (long story), but all it takes is a pressure drop and 7+Grand, and I'm out.
 
I've heard from a few guys that have had an issue with the oil pick-up either working loose or cracking. This would cause you to suck air or cavitate the pump, which might lower your oil pressure. Maybe the pipe or the pick-up is rocking back and forth?

Some oil filters are more restrictive than others. Try an OEM Honda filter (which quite frankly are about the best out there for our cars).
 
Chris:
Inspect electrical wiring to & from gauge, look for chaffing, rubbing etc between sender & Gauge. W/HP1 fram, I'm assuming you are running remote Oil filter assy!! where are you reading oil pressure from, Stock block location or at remote filter? If you're not running sender from stock location, wire up a stock oil pressure switch with a light actuated by the stock Oil Pressure switch. If loight even blinks while driving, shut it down now, get towed back to the pits and start looking. Oil Level OK? If all above yes, time to pull the OIL PAN. It can be done with the engine in the car! Check the oil pan and the Pick-up for blockages, dings around the oil pan, etc. Also check the two nuts that hold the pick-up to the bottom of the oil pump housing. I have had them come loose in the past, so now they get lock-tite blue when engine is being assembled!!
 
Get rid of the Fram oil filter. I have had more than 1 of these do this and I will never use another Fram on anything.

Les Chaney
 
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