17 replies to this topic

[carbon]

Although unlikely, it could be failure of the oil pump drive. I have never sen this in a spade drive pump, but I was told that if a 998 pump is fitted to a 1275, the engagement of the spade into the slot is very small and the pump spindle could fail.

With early engines with a pin-drive oil pump it was not unheard of for the pin to shear if the engine was started in extremely cold weather with thick oil.

I once thought I had the latter failure in a 970 'S', but after taking the engine out it turned out that the pump was draining down due to the manufacturing tolerances being on the limit. A new pump cured that.

When I rebuilt my 1275 S motor quite a few years back I replaced the pin drive Piper 270 cam with a star drive MD266. The old pin-drive oil pump looked to be in good condition, so it was put on the shelf as a spare.

 

Then about 2 years ago I was rebuilding a spare unit to 'original' spec. So I pulled the 'S' pin-drive oil pump off the shelf and to my surprise noticed that it was a 'small-bore' type pump with the shorter shaft. Luckily there must have been just enough engagement to keep the oil pump turning...

[Cooperman]

I recall a pin-drive pump which failed when a rally car was started on morning in Winter after being parked outside all night. It fired up, but because of the 'hot' cam it had to be kept at around 4000 rpm to warm it up. The oil was a 40 grade and the pin sheared due to the high load and thick oil.

 

The short-shaft pumps were still listed as correct for the 1275 back in the late 1990's with pin-drive pumps and I measured the engagement and it was about 3/16". The suppliers now all list different pin-drive pumps for the 1275 engine.

 

Another tip is if you have a block which has been modified to go from a 3-bolt oil pump to a 4-bolt and you subsequently go to a 2-bolt pump, plug the 4th hole to prevent the oil from getting into the coolant. I had this happen and it was very difficult to diagnose. 

[carbon]

I recall a pin-drive pump which failed when a rally car was started on morning in Winter after being parked outside all night. It fired up, but because of the 'hot' cam it had to be kept at around 4000 rpm to warm it up. The oil was a 40 grade and the pin sheared due to the high load and thick oil.

 

The short-shaft pumps were still listed as correct for the 1275 back in the late 1990's with pin-drive pumps and I measured the engagement and it was about 3/16". The suppliers now all list different pin-drive pumps for the 1275 engine.

 

Another tip is if you have a block which has been modified to go from a 3-bolt oil pump to a 4-bolt and you subsequently go to a 2-bolt pump, plug the 4th hole to prevent the oil from getting into the coolant. I had this happen and it was very difficult to diagnose. 

Out of interest did this engine use the modified oil pressure relief valve with large ball bearing instead of the thimble?

 

I used to run this ball bearing set-up until one very cold morning when I started the engine the oil pressure went around the gauge. When it got up about 125psi the pressure suddenly dropped back to zero. The main oil gallery plug at the flywheel end had popped out.

 

I suppose at least it did not shear the oil pump drive (star type).