Oil for racing an old MG?

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I "vintage race" a 1957 MG, this is road racing, and we actually race pretty hard. The biggest problem with this engine is the oil pump drive gear -- they often fail, typically right after an engine rebuild.

This gear is a little crossed-helical gear, driven off a mating gear on the camshaft. They work fine in street cars, but often fail when run under racing conditions, i.e. 7000 RPM redline, with 70 psi oil pressure. The pump requires more power at this speed & pressure, putting more stress on the gears, and they sometimes fail. Normally, they either fail "right away" (within a few hours of start-up) or they last "forever" (until the next routine rebuild).

So the basic question is, what is the best oil to use to help prevent early failure of these gears?

No, I can't easily re-design the whole gear system. No, new ones aren't available -- so we have to re-use old ones. Yes, we have tried custom-made bronze gears (running against steel camshaft gear), they last about 3 race weekends. So I'd like to stick to the basic question here, WHAT OIL, rather than how to re-design the engine, thank you.

Some more background: if you're not familiar with crossed-helical gears -- they have a VERY small area of contact, so the contact stress is relatively high, and there is lots of sliding motion, so it is similar to the flat tappet/cam interface. The gear mesh is lubricated by engine oil, there is a small passageway drilled in the block, so some pressurized oil "kinda/sorta" squirts in the general direction of the mesh.

I have used Castrol GTX 20w-50 in my MG race engines for years, without problems. However, I just rebuilt a race engine and the oil pump drive gear failed after about 3 hours of run time -- first time it has happened to me. I followed the usual recommended break-in procedure for flat-tappet cams, i.e. I used Isky cam lube on lifters & lobes and also on the skew gears, ran 1 hour at 2000 - 2500 RPM in the driveway, etc etc. Always worked before. Haven't looked at the cam & tappets yet but I think they're OK. Thankfully I saw the low oil pressure and shut down before anything broke (I think).

Since this was the first time I've had a skew gear failure I am wondering what may have been different this time around (versus 4 or 5 previous engine rebuilds with no problems). Last time I rebuilt, was 1999 and everything went fine on that one. So:

1) Do you think zinc is the answer -- i.e. would an oil with zinc in the additive package, help to save my drive gears?

2) Anybody know when the API spec changed and they took the zinc out of most passenger-car oils? Was it after 1999? Maybe my Castrol 20w-50 isn't the same as it was in 1999?

3) Lots of guys recommend Rotella. I can't find a Rotella RACING oil, I can only find Rotella T multi-grades and Rotella T Synthetic, primarily intended for commercial/diesel use. Do they make a racing version of Rotella? If not, is the "regular" multi-grade still a good oil for racing? The answer man on the Shell site is evasive about racing questions.

4) Should I use an oil with zinc for break-in only? Or continue to use a zinc-rich oil long term for racing?

5) Is zinc the same as ZDDP? Or are they different?

6) Have read about GM EOS, I guess it has lots of zinc, why not just use a good quality passenger-car oil and add EOS to get the zinc content?

7) How do I find out the zinc percentage in various brands of oil? Shell won't tell me the zinc percentage in Rotella. Do I have to send all the candidates out for VOA to find out?

8) Valvoline Racing oil is readily available but I get the sense (from this Forum and others) that there are "better" oils out there. Is Valvo Racing out of date?

9) I'm not cheap but I don't like spending money on things I don't need ... so do I really need a synthetic? Typical oil temp peak is around 220-230 deg F. These old engines leak a LOT, and I change frequently, so I use a fair amount of oil in a year of racing. And of course the engine wasn't designed with synthetic in mind back in 1957. So I'm tempted to stick with dinosaur oil -- agree?

Any learned advice from you experts will be MUCH appreciated!
 
How does the gear fail? wear, teeth breaking? Is there a way to set the teeth engagement distance maybe shim the pump
body? Cryo, high tech coatings have helped stuff like this?

Rotella is Shell commercial oil line, no race. ZDDP or zinc phos levels can easily be seen at the virgin oil sample section on this site. Would more solve this problem? couldn't hurt but may not do anything at all? Thinner oil, or preheated oil may put less load on the gears?
 
70psi seems a lot for an engine of that age.

It's prolly not that topical, but when they race Holden "grey" motors (1948 though '65 or so) they limit oil pressure to the low 40s to prevent failure of the pump drive.
 
WileyE,

Teeth wear drastically and eventually don't engage any more. Teeth do not break off. Only small slivers of teeth found in pan, no broken teeth. This is a fairly common problem on MG engines in racing.

Will check out the VOA section on web site, didn't know there was one but I'll find it -- sounds useful. Thanks for your input.

MG185
 
Shannow,

YES it's topical! Very interesting ... do you know what the pump drive looks like onthe Holden? Is it crossed helical gears?

MG185
 
I'd use a different oil. I don't see anything special with the Castrol GTX. Maybe its too thick or isn't protection as well you hope.

Hows the mating gear on the camshaft holding up?

Consider shotpeening, mikronite, cryo treating, and gear coatings.

Castrol GTX isn't a racing oil. Why not just use the Rotella or any other HDEO?

A 15w40 or 10w30 would also be easier to pump.

I'd consider using a full synthetic also.

Make sure that during engine assemble, that everything gets a good coating of the assembly lube. Try other assembly lubes.

Some additives to run:
GM EOS
Molyslip-E
CD2 streetlegaloilboost
SpecialtyFormulation SX-UP
PowerService extender
Torco MPZ
 
I'd un 5w30 Redline. The Moly and ZDP should help protect the gear and a thinner oil should unload the gear some.
 
MG185, the old grey motors have a crossed helical distibutor drive, and the oil pump is driven off the bottom of that.

If the dizzy drive breaks, the motor stops without problems. If the oil puump drive shears, then it's toast before the operator knows it.

The later red motors have their own crossed helical drive, and it seems to behave itself pretty well.
 
Call Red Line, they have some experience with vintage racing and it's their racing oil you want to look at. You might get a complete package in the oil and not have to experiment on your own. They might know more about the oil, since they put it all together. Ask for Roy, the head chemist.
 
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