Hi Lawrie, I checked the gear end clearances with feeler gauges while
building the oil pump. Yes, the new gears were too long and I had to
machine some off. I aimed for 0.002" clearance. The book says 0.0016" to
0.0035" so I thought 0.002" was safe. When I installed the pump I checked
the installed clearance with plasti-gauge and it was 0.002".
After the failure I re-installed the oil pump and the clearance is still a
full 0.002" using plasti-gauge.
It is possible that after a high speed run between 4,500 rpm and 6,000 rpm
on the road the gears expanded and made slight contact with the cover.
However only the driven gear shows any marks on the cover and this only
less than half way round and some of this mark was present when assembled.
I don't think it was a clearance problem but more an oiling to the gear
problem.
The information is still coming.
So far, nobody has suggested a new race cam, any suggestions???
Bob
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><mg-t@autox.team.net>
> Did you fit new oil pump gears when you were building the engine? Did you
> take the time to measure the end clearance between the new gears and the
oil
> pump cap?
>
> The problem you describe has happened on several engines with which I'm
> familiar (though, thankfully, not ones I built!) The gears are just a
skosh
> too long and, when they heat up, they bind in the housing. The weak link
is
> the gear on the shaft, so this shears off. In one instance, it then
jammed
> between one lobe of the camshaft and the inner wall of the block. Room
was
> made for it by a large piece of the block exploding
outwards..............
>
> When fitting new gears in an XPAG or XPEG oil pump, it is imperative to
make
> sure there is 3 thou clearance between the ends of the gears and the
cover.
>
> Just a possiblity..........
>
> Lawrie
> British Sportscar Center
>
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