At 05:25 PM 6/13/2000 +1000, Neil Cotty wrote:
>Should I replace my existing oil pump with a new one while I'm doing this
rebuild, or if measured up and found to be within tolerance, is it ok to
keep the old one? A new one is $300+. (AUD).
Ouch! Way less here. I dunno what the exchange rate is, but $109.95US
list for 3-main engines and $65.95-US for the 5-main engines.
>I had planned to buy a new one today without even checking my old pump as
(almost) everyone says to do this.
I'm not part of that herd. I make value judgements.
>The reason I'm asking is before the crank went, I had absolutely perfect,
stock oil pressure. 62-65psi running and never below 20 even when very hot.
The primary determining factor is oil pressure, and you seem to have plenty
of that. If it was my engine, and I lived with it daily, and I knew the
pressure was that good, I would probably put it back in without a second
thought.
>So should I measure her up, or just buy the new pump?
Remove bottom extension from the pump. Turn the rotors to where the apex
of one of the lobes of the male rotor is on top of the apex of one of the
inward facing lobes of the female rotor. Measure the space here with a
thickness gauge. If 0.004 inch does not fit you have good clearance. If
0.006 inch does fit in there, then it's time for a new pump.
Also remove the rotor parts and inspect the mating perripheral faces. When
new they have a ground mirror finish. When used they get buffed and
scratched a bit. If the scratches are very minor and the clearance is
still good and the pressure is still good, then you can continue to use the
pump. If it looks like a handfull of sand went through it and made large
scratches, then renew the parts regardless of the clearance. This is the
most common mode of deterioration.
>There are also kits available, but not sure how effective they'd be, I
mean how do you tell what is worn, the impeller or the body? Are there also
other reasons for replacing the pump, ie drive gear wear etc?
Kits are good, but generally not available here for some reason, probably
because the whole pump is cheap enough. Scratches inside of the aluminum
housing are irrelevant as long as you have no measureable latteral motion
between the outer rotor and the housing when bathed in oil. The bottom
extension commonly gets a little worn on the top face. Just put it face
down an a flat surface with a piece of emery paper and some oil and lap it
smooth again.
You may know my web site is "dedicated to the proposition of having obscene
amounts of fun with your LBC". Fortunately this does not have to include
spending obscene amoumts of money on it. Change parts when needed. Save
the money otherwise.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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