PDA

View Full Version : Oil pressure when spinning motor on w/ battery



tdskip
02-20-2008, 11:05 AM
Hi guys - I swapped out the oil relief spring and ball bearing. After pulling the plugs and spinning the motor over with the battery, which results in about 500 RPM, I'm seeing about 10 PSI cold now with 20/50. That is after turning the pressure relief mechanism about one turn tighter than it was.

Anyone have a point of reference on a healthy TR3/TR4 motor under similar circumstances?

(be merciful)

Moseso
02-20-2008, 11:52 AM
I can't say for sure what your cranking oil pressure should be, but I can say for sure that what you've done to the pressure relief valve won't change it. It's a pressure RELIEF valve. It LIMITS the oil pressure to a maximum value.

When the engine is cold, and the oil thick, the oil pump is capable of delivering too much pressure, so, when the pressure reaches a certain point (70 PSI is specified) the valve opens allowing some oil to bypass the system, thus LIMITING the pressure to NO MORE THAN 70 PSI. Tightening the spring can, in no way, raise low oil pressure. Tightening the spring raises the upper oil pressure limit your cold engine can achieve, possibly causing damage.

TR3driver
02-20-2008, 11:55 AM
Sorry ... even on my well-worn TR3 motor I could get 60-70 psi cold with the stock starter & the plugs out. IMO you've got something else wrong, like a busted pump or a gallery plug fallen out.

Opa
02-20-2008, 12:09 PM
sounds low to me,according to my TR3 manual and i quote: a satisfactory oil pressure will be 40 to 60 psi. for road speed in top gear between 30 to 40 miles per hour.A worn engine with worn bearings will cause a drop in oil pressure.Other likely causes of oil pressure drop are ,low oil level,need for oil change,It is also possible that dirt is trapped in the relief valve. It goes on to say,do not adjust the relief valve in an attempt to raise low oil pressure due to wear as it will only decrease the amount of oil passing through the bypass causing the total oil to be less filtered.Make sure gauge is accurate as well.Relief valve is preset at 70 psi at 2000 rpm.

Sounds to me like pan removal is in order and a bearing and pump is check done.

tdskip
02-20-2008, 12:51 PM
It's a pressure RELIEF valve. It LIMITS the oil pressure to a maximum value.

Yeah, I was taking a flier on that the existing spring and ball were toast. I think this proves that they aren't.

Oh well....

tdskip
02-20-2008, 12:53 PM
Sorry ... even on my well-worn TR3 motor I could get 60-70 psi cold with the stock starter & the plugs out. IMO you've got something else wrong, like a busted pump or a gallery plug fallen out.

I said be merciful darn it!

Time to pull the pan as you guys suggest. Bugger.

TR3driver
02-20-2008, 01:54 PM
Look on the bright side ... pulling a TRactor motor pan is easy. Could be like my first car, where you had to remove the engine and transmission from the car first.

tdskip
02-20-2008, 02:04 PM
Hi Randall - I'm actually looking forward to doing it but don't have the time now. And I miss driving her...

Oh well.

hondo402000
02-20-2008, 07:29 PM
I think I read some where about a plug on the rear of the rocker arm assembly can fall out? thats on a TR6, I am sure that can cause low oil pressure. if you pull the pan and a main bearing cap off and plastigauge it for clearance and do a rod bearing too, you might need to replace bearings, I read it can be done, Its easy to pull the pan off, might as well replace the thrust washeres too, cheap... I would also replace the oil pump heck when I check mine it had chunks of RTV in the strainer, could it be that simple???

tdskip
02-20-2008, 09:28 PM
You guys are great - I'm really thankful for everyones help and encouragement.

TR3driver
03-25-2008, 07:50 PM
Hey Skip, any update on the low oil pressure problem ?

Enquiring minds ...

DougF
03-25-2008, 10:46 PM
Swapping out main and rod bearings with the engine in the car is do-able. I just did it in my TR6 last weekend.
The mains were a little more difficult since things were a bit tighter. You have to remove all of the main caps to allow the crank to drop a little to install the top half of the bearing.
Make sure to align the bearings properly before torquing.
It can be done in a day and be driven that evening.
I doubled my oil pressure. It won't last long though since the crank needs turned. Just a bandaid until I finish my other engine.
In case you need these numbers, TR3 main caps torque at 85-90 lbs. and rods are at 55-60lbs.

tdskip
03-25-2008, 11:18 PM
Hi guys - thanks for asking

Not much progress on the TR3 except for pulling the gas tank, getting it chemically stripped and the having a weak spot professionally repaired.

I was having fuel contamination issues due to rust in the tank.

I think I'm going to have a local LBC specialist check it out for me since I'm neck deep in project managing the demo/rebuilding of a house we just bought. Assuming of course I have the funds after the work on the house....