oil pump drive shaft

[marcusclive]

Evening all,
Went out for a drive Saturday and after a fast run along the military road I turned
off and whilst slowing down the oil pressure suddenly dropped. After getting No1 son to bring my truck out and tow me back, found the little octagonal drive shaft for the oil pump had sheared off. It seems to me that this could be either it was weakened when the oil pump over pressured on the way back from Ireland last summer, or it can't take the strain at high speed. When the engine is at high revs(5000rpm plus) the oil pressure seems to top out at 60-70 psi. I know this has been discussed on several occasions but I can't remember what was decided, is this too high or not?

[V Mad]

The way I see it is, normal max pressure is about 50psi. If the pump runs at 70 psi, then this increases the pump drive system load by 40% which is a massive amount. The drive system includes critical parts such as timing chains, the failure of which usually causes serious engine damage (marcus was lucky to only have the pump drive shaft fail!). On the other hand, there is no proven benefit from increasing oil pressure beyond 50 psi.

Just my 2p.

[milothedog]

I asked this question a while ago, this should help. http://www.stag.org.uk/forum/showthr...t=oil+pressure

Ian.

[JesusofCool]

Now I've swapped out the county spring for the "old" one DJT kindly gave me, I've got oil pressure same as Ian (as described in thread) and all the others. I really wasn't happy with 70psi all the time.

[marcusclive]

Now I've swapped out the county spring for the "old" one DJT kindly gave me, I've got oil pressure same as Ian (as described in thread) and all the others. I really wasn't happy with 70psi all the time.

Mine was at over 90 when hot and at high revs after i first had the crank re ground, then after it stripped the jackshaft and distributor gear i swapped the relief spring for the one out of the old oil pump. since then it has been lower but if this is still too much how can i reduce it further?

[V Mad]

Mine was at over 90 when hot and at high revs after i first had the crank re ground, then after it stripped the jackshaft and distributor gear i swapped the relief spring for the one out of the old oil pump. since then it has been lower but if this is still too much how can i reduce it further?

Your old one was probably too high; you need to find another spring.

I wonder if anyone has tried shortening the spring?

[marcusclive]

Your old one was probably too high; you need to find another spring.

I wonder if anyone has tried shortening the spring?

Would shortning the spring work or does it need to be a weaker one?

[JesusofCool]

Or possibly tempering it. Both a bit (a lot?) hit or miss.