Does it always have to be like this? I finally get on the road after rewiring the entire care, and after my first tim out this year I have a problem...

O.K. - Now I have vented. Enough complaining...

'68 Camaro with a '68 Corvette 427. The engine history is somewhat unknown, but appears to have been rebuilt recently & all signs lead to a fairly stock rebuild.

I removed my broken console (& mech. oil gauge) while wiring & replacing carpets. I temporarily installed a $40 oil pressure gauge & temp gauge until I buy a new console. I changed the oil & filter using 20/50. I started the car & had oil pressure right away. It would read 40-50 when started & drop o 20-30. It rose some when the RPM's climbed, but never much above 35-40lbs.

I have had a small rear main seal? leak that appears to be getting worse. I have driven about 20-50 miles so far & have watched the oil pressure like a hawk. I also check the oil level before going to shows & before leaving. I have had to add oil due the leak, but the level is O.K.

Tonight the level was O.K. the whole trip. Then I got in my driveway & glanced at the gauge *no oil pressure*. I shut the car down & checked the oil level. It seamed O.K. but I added some oil anyways. I started the car & the pressure came to maybe 15lbs & started to drop - I pulled the car in the garage & shut down again.

What should I check 1st? Could junk plug the plastic line or the mech. gauge, or is that just wishful thinking? No unusual noises of any kind.

Sorry for the long post & thanks in advance for the help. I want to fix the oil leak but would love to carefully cruise 1 summer before pulling the engine.

I'd guess your guage isn't getting a good signal. Perhaps you have a crimp in the line or a bad guage or sealant or something is blocking the way.

Some other possibilities? Broken oil pump drive shaft (or the nylon sleeve failed causing the pump shaft to break off). Or a clogged pick-up,..or separated pick-up,..or a spun bearing.

15 to 10 psi at idle is normal after the motor has warmed up a bit, and 35 to 40 psi going down the road is normal, sometimes after i have gone on a long cruise say 100 mi maybe 50 mi with normal conditions weather wise and 10w 30 it is normal for my oil psi at idle to be any where from 8 to 10 psi which may not even register.

I have had a similar problem. The oil pump pickup cracked at the weld. You can check this somewhat by overfilling the oil some and checking to see if it has better pressure.

Too many possibilities here, some simple others rather treacherous. Start with the basics and verify your oil level and find out what viscosity the previous owner ran in te engine. 20/50 is somewhat old school unless the engine was built loose. Check that the gauge is functioning, is it electric or mechanical? If mechanical pull the line off the gauge, stick it in a glass jar and crank the engine over. If oil pumps into the jar your lines are fine and you are getting some pressure. Very little can go wrong with the gauge it either works or leaks typically. The numbers are not as important as how steady the pressure is at any given rpm. Cold pressure will be higher than warm so don't confuse warming up for loss of pressure. Next, here any ticking? Check the valve train for oil, pull a valve cover right after running the engine, is it wet or dry? What oil pump is is used? Both high pressure or high volume pumps have been known to suck a pan dry. Speaking of pans, is the pan larger than stock requiring more oil than say 5qts? I've heard of filters causing oil pressure problems. If all else is right it's cheap to swap a filter.

From there if you hold a warm engine at 2000 rpm and you have 40 psi and then it drops until you rev it more it's a good sigh of bearing or oil pump problems. If your pump dropped a pick-up tube, over filling the pan could bring back your pressure.

Hope this helps you get this figured out, I know I may have repeated some of the others advice and I'm sure there are more things to look into but you've got some info to keep you working on this. Get it figured out and report back...

my friend had a problem in his pontiac 455 with the pump was pumping faster then it could drain back thus the oil psi was very high at idle then dropped very low when driven. another thing is, my mechanicl line for the oil gage always leaked alittle bit, try using some good thread sealing tape, maybe invest in some new lines and fittings, they dont usually hold up that long.

If you drain the oil, you may be able to poke a wire in the drain plug hole to check for the pickup falling off. It happens a lot with BB engines. You may try tapping the bottom of the pan and listen for the pickup rattling around.

Low pressure around 40 at cruse is normal BB low perf pump pressure.
I had a cam lobe wipe out and thin smears of metal got stuck in the oil pump relief valve, this caused erratic oil pressure readings, both high and low. A magnetic drain plug would tell you if a cam lobe was going.

If you have hyd lifters, zero pressure would cause them to click and the engine would run very rough.

Check distributor engagement with the oil pump drive shaft.

20/50 oil? never hurd of that? my dad says he has though is it kinda on the thin side and for racing or what?

Last night before moving the car in my garage I over filled by 1/4 quart. (at least that's what it read this morning after draining back to the pan) Started & had some (but not much oil pressure) I moved it in the garage & called it quits.

This morning I started it & get about 40-45lbs. After warming up it dropped to 30-35lbs. It climbs to about 40lbs @ 2k & nears 45lbs but never any higer @ other RPMS.

Did my oil level just drop too low due to my increasing rear main leak? I never heard any knocking or valve ticking (didn't hear anything over the noise of BBC with 3" headers anyway). I tried the 20/50 to try & slow the oil leak a bit.

Is it time to have the engine pulled at least to fix the leak? Can the bearings be checked with the engine in the car to see if any are spun & check clearences? Keep in mind I know little about this engine. The guy who sold it to me (small "dealer") bought it & dropped in a used '68 427 that he knew little about. The engine has been decked & it's freshly painted. I had the valve covers off & the lifters where clean (0 sludge).

The car does stumble at high revs (5k or so) but I don't know if that is related or a carb/timing issue. I have been trying to find a chassis dyno in CT to have it properly tuned.

Pete

20/50 oil? never hurd of that? my dad says he has though is it kinda on the thin side and for racing or what? 20w50 is the modern replacement for 50wt oil and is thicker to a higher heat than say 10w30 or 5w30 oil. Old school thoughts on building performance engines called for larger/looser clearences and you ran 50wt (thicker) oil to fill the clearences and keep pressure up. Also when you bought a high mileage car you often switched from 30wt to 50wt to make up for worn bearings...

This morning I started it & get about 40-45lbs. After warming up it dropped to 30-35lbs. It climbs to about 40lbs @ 2k & nears 45lbs but never any higer @ other RPMS.Sounds like a bad pump or bearings? Did you try anything suggested like changing your filter?


Did my oil level just drop too low due to my increasing rear main leak? I never heard any knocking or valve ticking (didn't hear anything over the noise of BBC with 3" headers anyway). I tried the 20/50 to try & slow the oil leak a bit. Even a very heavy leaks shouldn't cause a oil pressure problem... You would know it if the valves were clattering do to no oil, were the rockers wet when you pulled the valve cover?


Is it time to have the engine pulled at least to fix the leak? Can the bearings be checked with the engine in the car to see if any are spun & check clearences? Keep in mind I know little about this engine. The guy who sold it to me (small "dealer") bought it & dropped in a used '68 427 that he knew little about. The engine has been decked & it's freshly painted. I had the valve covers off & the lifters where clean (0 sludge).

The car does stumble at high revs (5k or so) but I don't know if that is related or a carb/timing issue. I have been trying to find a chassis dyno in CT to have it properly tuned.

Pete

You need to try to figure out what it is before pulling the engine but if you are planning to pull the engine to fix the seal then check the bearings and pump when you have the engine out...

It's sounding like you are not very mechanical (just an observation, no offense meant) and you might be better off finding someone to do some trouble shooting for you.

Only known cure for speculation is to pull the pan. Your seal leak is probably due to the person rebuilding engine not knowing to put a dab of RTV on the rear main cap to seal the oil that flows through the cap and to offset the rear main seal joint a little from the cap parting line.

Yes BBC's drop oil pick ups far to frequently, that is why I weld full circle around all of mine, than weld on a tab to bolt it to the pump (kind of like wearing suspenders with a belt). The bean counter that changed the retainer from steel to plastic should have to pay out of his own personal retirement fund for every blown engine out there (but that is just my opinion, I'm really not that bitter I learned after the first lost engine).


Larger Dave

I had the exact problem a couple of weeks ago and re did the entire line system from the engine to the gauge. Changed the oil, checked the pressure again and it came back. Be careful that the barrings, and lifters are not going bad? In my case, I was 4 quarts low on 20-50 and with like I said it was fixed.

Sounds like a bad pump or bearings? Did you try anything suggested like changing your filter?

Even a very heavy leaks shouldn't cause a oil pressure problem... You would know it if the valves were clattering do to no oil, were the rockers wet when you pulled the valve cover?

I didn't think so - I added 1 quart & ended up 1/4 over, so I wasn't even really low. I didn't here any valve noise - I shut the engine down as soon as I saw it dropped. I had the valve covers off a week ago, not yesterday.



You need to try to figure out what it is before pulling the engine but if you are planning to pull the engine to fix the seal then check the bearings and pump when you have the engine out...



It's sounding like you are not very mechanical (just an observation, no offense meant) and you might be better off finding someone to do some trouble shooting for you.

Thanks, it's always nice to have your ego brought into check. I'm not easily offended, & as Dirty Harry would say "A mans got to know his limitations."

I did just rewire the entire car & have done significant suspension work in the past. I have little experiance other then maintaining Engines/Transmissions though - That I will leave to the experts. Not to mention I have now free time due to my business. Now I just need to find good local guy that knows classic Chevys.

Pete

I ended up tracing the oil leak & indicated pressure problem to the fitting on the block. The guy who installed the engine:

a) didn't use any tape/sealent on the fittings
b) Kinked the oil hose
c) Tie/Wraped it to the clutch!
d) all of the above

You guessed it d, all of the above.

Anyway for $5 & 1hr of work I'm back on the road with no leaks and good pressure.

Thanks for the help.

"In my case, I was 4 quarts low on 20-50 and with like I said it was fixed" How in the world does something like this happen?

Besure To Check Your Oil...again And Again...

That was your quote dukme, not mine. I can assure you that mine has never been an 1/8th of a quart low on oil. Mike