Low oil pressure on rebuilt engine

sowat · Post by **sowat** » Thu Sep 08, 2011 8:41 pm

Started to run the cam in on my 3.9 v8 rebuild
When it's up to temp, running 2000 rpm, oil pressure reads around 25psi, we let it idle and pressure drops to virtualy nothing, but the oil light didn't come on.

No horrible noise from the engine, but I should have more oil pressure, surely

Where to start looking ?

mgbv8 · Post by **mgbv8** » Thu Sep 08, 2011 8:58 pm

Check that the gauge is accurate and then let it hot idle with the rocker covers off. You may want to place some rags to catch oil splashes.

At idle the rocker gear should just be slowly seeping oil out and not filling the recesses in the heads. If its gushing at idle then the rocker gear is badly worn.

Worn rocker gear is often the cause of low oil pressure.

Ian Anderson · Post by **Ian Anderson** » Thu Sep 08, 2011 9:27 pm

So is running the incorrect oil.

Non serpent unit is20w50

Ian

sowat · Post by **sowat** » Fri Sep 09, 2011 5:45 pm

Thanks guys

Everthing inside the engine is new, except oil pump gears ( just remembered), con rods and reground crank

Oil is Lucas 20/50

stevieturbo · Post by **stevieturbo** » Fri Sep 09, 2011 7:52 pm

Check gauge is correct, then relief plunger and spring.

CastleMGBV8 · Post by **CastleMGBV8** » Sat Sep 10, 2011 11:55 am

If the above advice doesn't cure the problem then as you haven't checked the pump, strip it and check the gears for wear and the base plate for scoring.

New gears are readily available from Real Steel or others and you can have the base plate resurfaced.

Don't be tempted to use high pressure kits as this puts a lot of stress and wear on the distributor gear which is driven of the cam.

Kevin.

mgbv8 · Post by **mgbv8** » Sat Sep 10, 2011 7:25 pm

CastleMGBV8 wrote:If the above advice doesn't cure the problem then as you haven't checked the pump, strip it and check the gears for wear and the base plate for scoring.

New gears are readily available from Real Steel or others and you can have the base plate resurfaced.

Don't be tempted to use high pressure kits as this puts a lot of stress and wear on the distributor gear which is driven of the cam.

Kevin.

I agree with Kev on the high pressure oil pump kit. My car is track only so it only runs 1/4 miles. The HP pump kit on mine cost me 3 dissy cogs in one year ??

Not to mention the crappy 1/4 mile times as it knocked my ign timing out so far that it wouldnt even idle.

Maybe the HP pump kit would be ok with thinner oils. I use 20/50.

sowat · Post by **sowat** » Sun Sep 11, 2011 9:02 pm

Oil pump/gears looks favorite then as it hasen't been changed.

How does scoring of the base plate affect the pump ?

As I have a remote filter the base plate is the take off plate, should I get that resurfaced or get a new one ?

CastleMGBV8 · Post by **CastleMGBV8** » Sun Sep 11, 2011 9:27 pm

Scoring and wear on the base plate increases the tolerances in the pump and reduces efficiency.

Is the remote filter plate reasonably new? in which case it should be ok but scoring would be easily visible.

Kevin.

sowat · Post by **sowat** » Sun Sep 25, 2011 10:31 am

Just been looking on the internet to order new oil pump gears, came across a problem.

I'm running my old P6 front chest and remote filter from my old 3.5 engine, now I find there are different length gears, and ends(dizzy drive)

The gear dizzy drive I have is male, fits straight into my new 3.9 dizzy, happy days I thought, now I've found that I may need shorter female dizzy drive gear for the P6 chest.

If the previous engine ran these longer gears in a P6 chest would that account for the base plate scoring ? There seems to be around a 4 mm differance fron what I have read today.

Would it be a good idea to run shorter gears ? Then I would need to change the drive on the dizzy, is ths straight forward to do ?

sowat · Post by **sowat** » Sun Sep 25, 2011 10:55 am

May have confused myself here

May have a SD1 chest and P6 water pump, chest stamped ERC 0036

In which case new SD1 gears should be o.k ?

DEVONMAN · Post by **DEVONMAN** » Sun Sep 25, 2011 12:34 pm

sowat wrote:May have confused myself here

May have a SD1 chest and P6 water pump, chest stamped ERC 0036

In which case new SD1 gears should be o.k ?

If your cover has not been modified, you can recognise the SD1 type chest by the rubber oil seal at the crank. The earlier chests had a felt/rope oil seal. Also earlier covers had a hole for the mechanical fuel pump.

Denis

sarge · Post by **sarge** » Sat Aug 18, 2012 9:19 pm

Hi did you solve the problem because i have same trouble