LOOKING FOR SOME HELP.I PICKED UP A DONOR CAR FOR THE MOTOR AND TRANS.ITS A 1971 383 DODGE ,DROVE IT HOME RAN A LITTLE ROUGH BUT DIDNT OVER HEAT OR SMOKE OR DO ANYTHING WIERD.. PULLED IN THE DRIVEWAY SHUT IT OFF AND GOT THE LOUDEST BACKFIRE I HAVE EVER HEARD..FROM THAT POINT ON .. NO OIL PRESSURE.. I MEAN ZERO. THE CAR HAD BEEN SITTING FOR A LONG TIME BUT A LITTLE GAS IN THE CARB AND A NEW BATTERY AND IT FIRED RIGHT UP..NOW I THOUGHT IT MIGHT BE THE A CLOGGED PICK UP TUBE ,DROPPED THE PAN ,IT WAS CLEAR...NEXT PULLED THE PUMP , CHECKED IT OUT SEEMS TO BE WORKING FINE..ADDED NEW OIL AND FILTER.. NEXT PULLED THE DISTRUBITOR HOOKED UP A HEX ROD TO MY DRILL AND RAN IT WITH A NEW GAUGE AND RAN IT FOR 5 MIN ,, STILL NO OIL PRESSURE,IVE RUN OUT OF THINGS TO TRY ... AT THIS POINT I AM ASKING FOR HELP FROM ANYONE THAT CAN HELP ME OUT... THANKS
Not sure what the backfire thing is, but check for a blown out galley plug. I was breaking in the sbf for my 27 and the oil pressure went from 60 to zero in a second. Found out a galley plug in the oil circuit had blown out. Now I only use screw in plugs. Not familiar with Mopars, but I bet they have them too. Don
When I got my '52 Chevy, the seller said the oil pressure gauge never worked. Called the builder and he said it never worked. The previous owner put a new motor in and it never worked with the new engine. Turns out, the sending unit wire was bad. Replaced it and discovered the oil pressure was low. Replaced the oil pump and now she runs fine.
i think that you might be right cause when i had the oil pump off i ran air through the out port of the oil pump flange and the only place i could hear the air come out was behind the timing cover and there are 2 plugs behind it where they had to cross drill the block to connect the oil passages.. Thats my next step .. Thanks for the 411
Sounds as though a lifter may have come out of one of the bores?? This would explain both the loud "pop" and the low (zero) oil pressure! Thanks, Gary in N.Y. P.S. You can do a "visual" on this with the Mopars by looking at all the lifters with the valve covers removed. Using a flashlight you should be able to see all 16 lifters down past the pushrods, one of which will be missing if this be the problem.
When you ran the oil pump with a drill via the hex rod, did you have your drill set to reverse? You have to spin the pump in reverse on a BB Mopar to get oil pressure. Stan
The pump is on the outside, oull the bypass spring out and make sure that there isn't a piece of crap holding the by pass open. You have a donor engine, which is an unkown entity. You have no way of knowing what you have until you open it up.
Ok you said zero oil pressure. Then you must have started it after the big bang backfire. If it ran smooth, and just ticky then a lifter didn't pop out of the bore. If it ran real bacd and was popping then could be a lifter. There are oil treaded galley plus in the rear of the engine also but if one of those cam out then you would have a big puddle. I have never seen these come loose unless the engine has been rebuilt and someone forgot to insert them, seal or tighten them. A couple of things to keep in mind is big block Mopar spin the oil shaft counter clockwise so make sure when you are running the primer with a drill you spin it CCW. Another thing did you change the pump? I built a 383 once and forgot to seal the front plugs. After about 1000 miles the plug came out and my oil pressure dropped to almost 0 psi at idle but would come up and gain about 10 psi with every 1000 rpm. Now I was running a melling HV pump with 20w50 so before the plug came out I would run about 30 at idle and peg the gauge at 3000 RPM. If I was running as stock pump I prob wouldn't have seen any pressure at all. One side note is big block Mopars run low pressure at idle. I had a 440 that had about 100K on the bottom end and with a HV pump the oil pressure light would come on if it was hot and at idle for more than 5 min. If it was me I'd toss on a HV pump drop in some 30 straight weight oil check it again with a drill (turning CCW). if still no pressure then pull the front cover and check oil plugs.
Same thing happened to me back in the day in a 383 Roadrunner.....Spun a cam bearing...immediately lost oil pressure. Bearing spun blocking the oil passage. I'm sure loss of oil pressure could be caused for many other reasons, including an indicator or sending unit failure, as mentioned, but it my case, it was the cam bearing. Hope thats not the case for you.
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