I am close to firing up the engine for my 53 fhc project, and want to consider permanent installation of an electric pre-oiling pump like this one, used on aircraft:
I have already converted the oil filter to an xj6 spin-on with an external cooler. I think that I can add the pump in the line to the cooler, but I am unsure which is supply and which is return, without tearing it off again. I think the front would be feed from the jag pump/oil filter and the rear return to the block/bearings. Does anyone know this off the top of their head, and whether a pump in this line will adequately pressurize the system? My set-up is similar to the one sold by SC Parts Group in the UK, but they don’t offer a pre-oil pump in their setup.
Thanks
We had a long discussion about filters back in Oct '12.
The four holes in the block are:
Lower rear hole is supply from oil pump into filter head
lower rear chamber.
Upper center hole is supply from filter head to oil gallery.
Lower front hole is the dump to the sump. Thus the large
bypass dumps unfiltered oil to the sump through here.
Upper rear hole is a straight drill to bearing 4. It could
have had a brass plug like the other six but I guess since
it was covered by the filter head they didn’t bother.
Related image
Thanks, that’s helpful. I had forgotten exactly how the oil was routed. I don’t know my copy and paste xj6 housing photo is going through.
For the xj6 conversion, the front hole and the small rear hole are blanked. I believe that the oil from the jag pump flows into the lower chamber, through the rear cooler line, returns from the cooler through the front line into the upper chamber filling the outside filter holes and subsequently into the galleys. The valve in the bottom returns excess pressure/oil to the sump, and the valve in the top chamber bypasses to the galleys if the filter is plugged. If I’m right, then I should put the electric pump in the rear line directed to the cooler. If anyone sees this differently, please let me know.
So, I think the only question remaining is whether an external pump can suck oil through the jag pump without the engine in motion.
The original gear pump probably does not have much clearance around the gears to allow oil to suck past. If it did, it would not itself pump very well. We’ve only heard about one failure of a gear pump in 20 years, and that was on a questionable rebuild engine.
An additional pump seems to me unnecessary, but if you really want it, you probably want to rig it up to draw from the sump drain plug and pump into one of the brass gallery plugs on the RH side.
The pump looked fine when I rebuilt the engine, speced out ok then, but it’s over 60 years old and this is at least the third rebuild on this motor. The engine is a bit beefed up, overbored to 3.8 with Terry’s street performance cams, big valves, a little porting and dual 2"SUs. With the spin on and external cooler, I was just a little concerned that the pump might not be up to snuff. Plus, there is the purging of the cooler when the oil is replaced. This is the first engine that I’ve not put a new oil pump on, and I was thinking I might hedge my bets, but maybe I don’t need to. The aircraft pump is attractive because it shuts itself off when it sees system pressure, and turns back on if it drops too low. I know 120s can do ok with low pressures on hot oil, but I still don’t feel good when my gauge reads below 10psi.
I appreciate your suggestion of tapping into the galley - I have the filter housing return plumbed into the blanking plate on the side of the pan, but I could add a “T” and switch the pump manually.
Thanks
I looked that up, because I wasn’t familiar with that brand name, and I find that it’s an accumulator. I can see how this could be useful for pre-oiling and for short periods of oil pressure drop, like during hard cornering on a race track, combined with a pump that usually has good output. I’m not sure that it’s a better solution to the problem (or anticipated possible problem) of a low output oil pump. Seems like the accumulated charge might not last very long, like when one is idling in heavy traffic. If you have low pressure and a depleted charge on the accumulator when you shut off, you wouldn’t have much pre-oiling the the next time. Plus, you have to have a manual or electric valve to hold the charge on shut-down. I don’t see that it’s a better solution than the electric pump that I’m considering, but thanks for making me think about it.
You said it was to be used for PRE-OILING. Charge will only last 10 seconds
Further if Your engine has such a low pressure at tickover,there are other problems to be resolved.
Dirk
Yes, of course you are right. The rebuilt engine has not run yet, so the real question is whether the used, but within specifications, 120 oil pump is adequate considering the performance modifications of the engine that I mentioned. Provided that I get adequate pressures on spinning up with the starter, I think I’m going to take a wait-and-see attitude on a pre-oiler. Please correct me if I am wrong, but I think that nobody offers a new or up-rated oil pump for the 120.
Correct, I am not aware of any new pumps for XK120, but there doesn’t seem to be a crying need in the market. Plus the Mark VII used the same pump for about 13,300 cars, and the pump from the next 10,400 cars can be modified to use on a 120 by taking out a check valve, so there are still enough used ones around.
The main thing is to be sure you have done the filter head mods correctly. I don’t quite follow why the front hole and small rear hole would be blanked. Perhaps you should draw yourself a diagram of all the oil chambers and passages and be sure you understand the flow in all conditions.
Hopefully, mine is fine and I don’t have to seek another used one. I’m probably overthinking this one, but the discourse is useful to me in being sure that I’m not missing something.
Your earlier note helped me to remember how the conversion works. For clarification, the filter head for the XJ6 is different from the 120 in that the lower chamber doesn’t have a central partition. If one does not blank the front hole, oil from the pump simply dumps to the sump. With this hole blocked, oil travels to the cooler, back to the filter, then out to the galleys. The cooler is not optional on the model I have, although I think oil would flow through the rear housing internal bypass if the pump is strong enough.
You pointed out in the earlier email that the small rear hole is just an unplugged galley passage, and this one connects only to a blind chamber on the 120.
It’s easy to make an aluminum blanking plate that only has the larger holes in the lower rear and upper center, the former accepting flow from the pump, the latter out to the engine. As on the xj6, excess oil in the lower front bypass goes externally to the pan. I hope that is more clear. Thanks again for your input.
Well,in the lower rev range one does’t need much pressure. As long as there
is direct pressure rise when revving up,no problem.The accusump is a good
solution for engines which have the oil dripping down to the sump woith
time,causing a delay in the rise.
Your electric pump will need a prefilter as well as it draws from the sump.
More complications…
Dirk
I hadn’t thought about the need for filtering the sump oil - that’s a good point. One other possibility comes to mind if I don’t like the pressure on spin-up. The upper xj6 filter housing could be tapped for an oil fitting, fed from the electric pump, drawing from the sump. This would send the oil out through the spin-on filter. Like I said earlier, my plan after considering all this is to see what the pressure is before fixing something that may not be broken.
