289 Rebuild, Low Oil Pressure Help!!!!!

kyudizky · Aug 3, 2008

Hello, love this forum and everyones willingness to help newbies like myself!!

My Problem:

My dad and I rebuilt my a-code 289 (which I found out is bored .060 over), replaced all main and rod bearings, rear main seal, all piston rings, oil pump, all gaskets, totally rebuilt stock heads except for rocker arms and spring retainers. Everything stock expect for a little stiffer valve springs. I did prime the oil pump. Got the motor back in the car and it fired right up. My problem is that I''m only getting about 10 lbs. of oil pressure at idle, it will build to about 20 lbs. when i rev the engine and then go back to 10 lbs. Is this typical of a rebuild till the bearings condition themselves and the rings seat themselves. Replaced the oil pump with a Melling bought at AutoZone, could this be an insufficient pump. Scared to drive it. What else could cause this, should I do??? Your help is very appreciated!!!!

Thanks for your help!!!!!

Kyle

woodsnake · Aug 3, 2008

Did you check your clearances? It sounds like loose bearings at least. On a fresh motor when cold you should do way better than 10 lbs.....

D.Hearne · Aug 4, 2008

Don't run it any more, somethings not right. Could be the relief valve in the oilpump is sticking, could be missing oil gallery plugs. Could be many things. Engine's going to need to come out and torn down to diagnose the problem.

spirockp · Aug 4, 2008

D.Hearne said:
Don't run it any more, somethings not right. Could be the relief valve in the oilpump is sticking, could be missing oil gallery plugs. Could be many things. Engine's going to need to come out and torn down to diagnose the problem.

+ 1

zookeeper · Aug 4, 2008

Are you sure the gauge and sending unit are accurate? It would be a shame to yank the motor only to find that guage was wrong.

kyudizky · Aug 4, 2008

The electric guage wasn't working, we bought a new one with no better luck ( i think its a wiring short) so we bought a mechanical guage, it is what gave us the 10 lbs. read out. We didn't remove any of the oil gallery plugs during the rebuild.
With the block being .060 over, chances are the crank has been turned. We didn't mic. the crank to see if it was .010 under. and don't have the old bearing to see if they were oversized, unfortunatly. Would the loose bearings make any noise?? THe few time the engine was rev'd, we didn't hear anything. The car was never put into drive. We are not running the car anymore, and will begin pulling it back out. Not being able to drive my stang for about two months now, and at least not for a couple of weeks more is killing me!!!

Any other thoughts before we tear it down again??

Thanks for everyones help!

Kyle

zookeeper · Aug 4, 2008

That's the problem right there. You simply cannot "guess" when it comes to bearing sizes. You need to KNOW what size it is, then at the very least, use something like Plasti-Gauge to verify that the bearing clearances are what you need. If the bearings are standard, and the crank has been turned .010 under, then you are waaay out the the ballpark of acceptable clearances. You have just learned a lesson in engine building.

truck90278 · Aug 4, 2008

When assy the engine, did you use Plasti-gauge to check bearing clearances. I assume new cam bearings were installed. Assuming the oil pump was replaced, is it a standard or hi-volume pump? Assuming clearances are in spec, I would expect at least 35 lbs cold at idle. I would also expect to see 45-60 lbs off-idle. When rebuilding, you should ALWAYS mic the crank AND get matching bearings.

time to get it out and tear down Check all the clearances - loose clearances = low oil pressure

fvike · Aug 6, 2008

Another option - the oil pump pickup gasket might be blocking the oil flow. I did this on my rebuild, had to replace the rod bearings. Got lucky, the crank survived, probably because I have a HV pump, so I got some oil up circulating.

kyudizky · Sep 24, 2008

Thanks for everyone's help!

Back to rebuilding my 289. Since, I have had the block vated, cylinders honed, and the crank polished. Had crank mic'edand its .020 under. Upon reassembly, with the main caps installed and torqued and the timing sprockets and chains installed, it turns with little effort. Great. As we began to insert the pistons, the crank got harder and harder to turn until after the last cylinder in, the crank would not turn at all, took all but one out and it still wouldn't turn, took it out and installed another (only 1) to see if the last piston taken out was the problem, it would turn but it was extremely hard. Main end clearances were good. The rod bearings showed wear from one end to the other, mainly the dull finish had been worn. We used STP oil treatment, the really thick stuff, to lubricate everything. We are going to plastigage the rod bearings and purchace a micrometer. What are the clearances supposed to be for a stock street application? Also, what should the journals mic at? What else could be our problem??? Very frustrating!!!

Kyle

D.Hearne · Sep 24, 2008

bearing clearances should be at .001-002" Look at the undersize stamped on the backside of the bearings to verify they're correct. The journal diameter should be .020 less than 2.123-2.124.

Rapid · Sep 24, 2008

I had the same problem and found that the rods and bearings have to be turned "the right way". I don't remember what the sequence is. Do a search for hard to turn and see what shows up.

kyudizky said:
Thanks for everyone's help!

Back to rebuilding my 289. Since, I have had the block vated, cylinders honed, and the crank polished. Had crank mic'edand its .020 under. Upon reassembly, with the main caps installed and torqued and the timing sprockets and chains installed, it turns with little effort. Great. As we began to insert the pistons, the crank got harder and harder to turn until after the last cylinder in, the crank would not turn at all, took all but one out and it still wouldn't turn, took it out and installed another (only 1) to see if the last piston taken out was the problem, it would turn but it was extremely hard. Main end clearances were good. The rod bearings showed wear from one end to the other, mainly the dull finish had been worn. We used STP oil treatment, the really thick stuff, to lubricate everything. We are going to plastigage the rod bearings and purchace a micrometer. What are the clearances supposed to be for a stock street application? Also, what should the journals mic at? What else could be our problem??? Very frustrating!!!

Kyle

D.Hearne · Sep 24, 2008

The rods are oriented so that the bearings are offset to one side. The open side faces toward the journal fillet Check the rods so that the chamfered side of the rods face the fillets of the journal The outer edges of the journal have a curve leading onto the counterweight material, this needs the gap in the rod created by the offset bearing. When all is right, the oiling hole in the cap and rod faces outside of that rod's cylinder bank. This is also the side wwhere the rod's cylinder number is stamped.

289 Rebuild, Low Oil Pressure Help!!!!!

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