Cracked oil pump drive worm gear (crankshaft)

[Whittie]

Hey All,

 

Again with the engine building questions:

 

I found the oil pump drive worm gear, the one that sits around the crank shaft and drives the dizzy and the oil pump, was split and the teeth on the shaft were wearing badly. This is the second worm gear to crack on this motor and before i put it back together I want to know why!

 

I suspect it's either due to bad teeth mesh, which I think is unlikely considering it's not adjustable, or too much pressure being put on the gear.

 

Now, when racing the oil guage, which is standard so readings could be suspect, sits right in the upper region of the guage, close enough to 90psi to call it 80psi. When idling, it sits around 40-50 psi. I suspect that this pressure is putting huge force on the gear, stipping engine power and stuffing the drive parts. So, what I was wondering, for the engine experts, what sort of pressure should the oil pump be putting out and why is mine so high?

 

I've heard that 30psi is sufficient at racing revs (7500rpm) provided you have good oil flow rates and can get the oil into all parts of the engine, but what oil pump should I be using and how should I configure it to get these high flow rates at lower pressures? I think I'd like 50psi at race revs, 30+psi idling, just to be safe!. Also, does any internal motor work need to be done to get oil to flow in/on to all components and away again efficiently?

 

Cheers.

[peter mc]

most race engines that i have look at have wear in these parts you need to replace them often. 30psi at 6000rpm =dead motor 60psi is needed at 6000 if you like to drive home. if you have much more than this you will damage the drive in no time look at running a lighter oil .

[Whittie]

Hmm, thanks Peter.

 

So, short of just changing the oil, is there anything I can do to the oil pump to drop the pressure a bit? Is the oil pressure adjustable at all on a standard mechanical oil pump?

[peter mc]

it not rely you can change the pressure relief spring but there is more to it than that. i would check you gage with a master gage to make shore i have not had one with more than 65psi with normal  Clarence and opperating temps 

[NZeder]

So to help answer the question why the gear wears out - well it might not be running true. The dizzy shaft is long and is only guided by an alloy lug and bush combo on the front cover. We have found that on a few front covers this does not run 100% true, which on the road car is not a big deal - they don't see the loads or high RPM that a race car will see.  Also I believe there were some shafts that ran brass?? gears vs steel (I can't recall correctly) so the difference in the shaft gear and drive gear material might also be leading to the wear you have seen.

 

The other thing to remember is those gears need to go on the correct way - again I can't recall of the top of my head but there is flat on one side and curve on the other - one goes towards the engine the other faces the pulley this need to be correct way around - if this was installed incorrectly it might have lead to the slipping??

[Riceburner]

I run an original f54/p90 L28 and have exactly the same oil pressure at idle and revs as you whittie............ Mine is was a secondhand unmodified turbo motor with 8.3-1cr from japan, could it be the turbo oil pump giving the higher oil pressure?

[peter mc]

the turbo oil pump has more pressher and volume .but it is the same pump that i run on all my motors

[dazzed]

what grade oil do you use , too heavy oil could attribute to this, sounds more like alignment problem , do you have the correct thickness cover gaskets, this is a very uncommon problem have you checked the oil pump drive spindle for trueness maybe bent

[Whittie]

I'm not sure what the grade of oil is to be honest, the mechanic looks after it but I think it's a 20-50. I'll confirm but perhaps a 10-40 would be better? I'll check up but that seems the most likely to me. The worm gear and the shaft were both new less than a year ago and are now busted.

 

I'll also check all the gaskets and that the front cover is true. Both the worm gear and the shaft are steel, I have heard of the brass parts but both are steel, so not an issue of one item being harder than the other and so chewing the soft metal out.

 

The gears aren't slipping, they're wearing each other out, much like they are badly alligned. I never considered alignment because it's not adjustable (I'd assumed) and that's why I think it might be oil pressure, but I'll have to check out alignment now.