My oil pressure seems to be fine in my 66 289 2v with an automatic behind it when I first start the car and while its idling. However, when I start driving on the highway, it sometimes drops to very very low and scares the bejeesus out of me. Any ideas as to what this could be? Oil level is full and looks good...
Got a engine thats worn .
Something in the guts is letting the oil pressure bleed off . My last 302 would do that if I ran Havoline , a tech school buddy of mine suggested the oil he uses because he did not like what I was running . I switched over to Valvoline and have never looked back . The crank ended up being pretty worn in my 302 and it was causing the oil pressure to fall off . The valvoline got me by for a while , until I busted a skirt off one of the pistons . I ran 1 more 302 and broke the skirts on it also
I decided to switch back to 289's and have yet to bust a piston again . But thats all another story
Try switching oil to a different brand and thicker oil (20W50) or straight 40 or 50 w and see if your problem goes away . If you can hook a manual gauge up and drive the car it will show you if your factory gauge is correct or not .
I imagine it is reading correct .
How does the pressur look if you start it up, never go to the highway, and just drive it stop and go locally?
If it stays ok fully warmed in stop and go, the first thing I'd look at is pullling the valve covers and looking for A LOT of trash sitting on top of the heads (A LOT of sludge, trash, maybe pests brought a bunch of crap in there. The oil gets pumped to the heads, then it has to go thru drain holes back to the block.
On the other hand, if the pressure drops really low anytime its fully warmed up, the motor probably needs a rebuild.
This assumes the pressure is truly good when it's cold. A good motor should just about max the pressure guage when it's bone cold.
Ported vacuum IS manifold vacuum ANYTIME the throttle is open on a holley.
On a side note ,
if there is a bunch of sludge/gunk in the top end of the engine .......
LEAVE IT ALONE !
Don't mess with it unless you are ready to build the engine . If you try to remove it , the chunks will drop down to the lifter valley and then to the pan . Once you fire the engine back up it will suck it all to the pickup tube and the engine will have zero oil pressure . If you must play with it , use a shop vac to suck it out while you scratch at it . It will be down under the intake if it's under the valve covers too .
I seriously doubt your problem is gunk , as I said my engine did the same thing but was spotless inside when I tore it open .
I checked the sending unit and, well, the power steering pump was leaking onto it and that ate away at the wire to where there were bare wires showing AND it was loose on the sending unit. Gonna try and remedy this tomorrow and see if there is any improvement.
We had the very same symptoms with our 66 289 oil pressure gauge when be bought the car last September. By looks, the engine had been rebuilt some years in the past but the PO neglected the car and only put on less than 1000 miles in 9 years. The car also had a terible lifter noise clatter on the right side.
When I brought the car home I changed the oil and put in a treatment. The noise diminished noticibly after a few hunfred miles.
I also noticed that the oil presure switch lead wire was worn and changed the switch and lead over the winter.
Because the car is not yet ready for the road I have not yet been able to check out how the gauge works now. Instrument cluster still out.
I figure the engine is possibly sludged and has issues from standing idle for so long, as I get a lot of "blue" smoke and "black" gunk out of the exhuast pipe when I start the car. Could I have both "oil" and "fuel" issues? Probably!
Once I get the car rolling, hopefully this weekend, I can let you know if the new sender/lead helped.
If not I am going to pick up an oil presure gauge and test each cylinder individually. I really think the engine needs an overhaul though.
I might look for another 66 289 to rebuild next winter. I have never done it and sounds like fun. I can then add some performance modifications. Then put this engine in the car while the original is rebuilt to stock.
If not I am going to pick up an oil presure gauge and test each cylinder individually.
Did you mean a compression gauge? The oil pressure cannot be tested at the cylinders.
The condition of the sending unit wire shouldn't affect the reading unless it has most of the wires broken. I am always leary of PO overhauls. Some of them take place on a Saturday afternoon without even pulling the engine. I've known people to just throw in new rod and main inserts, a new set of rings (usually improperly installed), sometimes new gaskets, and that's about it. They often fail to install new camshaft bearings, and the loose cam bearings cause low oil pressure and result in other bearings failing due to poor oiling. PO's also have often failed to install new oil pumps, which can result in low oil pressure if worn. Good Luck to both of you guys! Just don't make the same mistakes when you tear into your respective engines.
"Get your facts straight first, then you can distort them as much as you wish"!!
I'd check the simple stuff first, but that happened on my 68 289. The oild pressure was fine for a couple of years then all of a sudden it went to NOTHING on the freeway. Scared the bejeezus out of me. As soon as I got off the freeway it went back to normal. Back up to 55mph and zero again. I won't describe all the fun I had tracking this down and will skip to the end. There was a small gasket between the oil pump and engine block that had slipped partway out(you can guess what I was getting ready to do when I saw this). I replaced the gasket (and returned the unused new oil pump) and the car was fixed. I can only imagine that this is an extraordinarily rare occurence as I've never heard of it happening to anyone else. So don't place it very high on your troubleshooting list.
11. If thou be not absolutely sure of thy facts, thou shalt Google before posting thine answer.
Do all of the above...but I gotta tell ya. The pictured convertible drove me nuts after purchase for 6 months as the oil pressure was low and less than an 1/8 up at about 40 mph on the guage. I had some heating probs and replaced rad with a 4-row and what a diff....oil pressure now stays from 1/2 to 2/3 on guage. Its called Boyles & Charles Law. Heat and pressure are inversely proportional. Fixed me.
"You need only two tools: WD-40 and Duct Tape. If it doesn't move and it should, use WD-40. If it moves and shouldn't, use the duct tape."
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