Worn distributor drive gear - cause or effect?

rincewind23 · Post by **rincewind23** » Thu May 14, 2015 1:24 pm

Hi all,

I am building a kit car with the 3.5 v8 from a Discovery 1, with a MegaSquirt system (so the distributor is only used to drive the oil pump and doesn't have the cap on). I did a full rebuild and after finishing the new wiring loom, managed to get the engine to run for about 30 seconds.

Long story short, I eventually discovered it was a lubrication issue. WD40 into the cylinders, fuel pump relay removed and the engine cranks. However, I noticed that the distributor rotation was erratic - it would turn 1/8 turn, then the shaft moved outwards slightly, then in, then nothing, then a bit more turn.. very strange.

I took the distributor out and noticed that there was about a 1mm vertical play in the shaft through the housing:

You may also be able to see the gear was slightly worn. I took the timing cover off and the teeth on the drive gear seem to be pretty stripped:

So, the question is: Is this a cause of the lubrication problem? Or would it be the consequence of the lubrication problem? I'm happy to buy another drive gear but I don't want to fit it just to have it destroyed the same way. I've also ordered an interim timing cover and water pump, but was hoping that upgrade was a way away since it requires the crankshaft to be removed and engineered to fit a larger woodruff key (so I've read).

Thanks,
Kev.

kiwicar · Post by **kiwicar** » Thu May 14, 2015 2:15 pm

Hi
I think you need to strip the engine and have a proper clean and investigate. Do you have a high pressure oil pump relief spring in the pump? Did it have the correct oil filter? One that works with the rover bypass? Has a foreign object got jammed in the oil pump? Are the oil galleries free of blockage. Something has caused the rapid wear of those gears, this is often as a result of extra load from the oil pump from increased pressure or restricted flow hence my questions, however it needs proper investigation.
The description of the distributor not turning means the oil pump has also not been turning, this has serious implications for main and rod bearings so they will need investigating. The teeth on those gears have been turned into metal swarf, that in turn has got into your oil and back into the oil galleries so the engine will need a proper clean. I would have a good look at the cam lobs and tappets because they usually suffer very quickly in the event of swarf in the oil and reduced oil flow.
Sorry to be a misery guts but if you just replace parts without cleaning the galleries then you will just make more swarf.
best regards
Mike

rincewind23 · Post by **rincewind23** » Thu May 14, 2015 2:31 pm

Thanks for the reply.
The relief spring in the pump is the original as it came out of the Disco - I can only assume that the previous owner did not swap it from the original.

I bought the oil filter as a Disco 1 filter, so again I assume it is correct. The original problem with oil flow was that I have a Mocal remote fitted, and it is higher than the original filter location. When rebuilding I packed the oil pump with vaseline, but I didn't fill the remote pipes with oil so there were still big air bubbles in the system i.e. both pipes.

I think what you're telling me is that I have made a big booboo and need to rebuild the engine again, to make sure it's not full of swarf?

DaveEFI · Post by **DaveEFI** » Thu May 14, 2015 2:37 pm

The thrust when running pushes the dizzy gear upwards. The play might be caused by a worn plastic washer on the other end of the dizzy shaft which isn't really needed when running - many stumpies don't have the shaft secured at the top at all.

I'm surprised the gears were 'jumping' - even when worn. Unless teeth are totally missing. Are you certain the dizzy was located on the oil pump drive and fully home?

Other thing is the oil pumps are notorious for draining, and not priming afterwards. It's recommended to pack them with Vaseline for the first start if you're not sure how things were before. Some also spin up the pump using an electric drill and drive adaptor to make sure there is oil pressure before attempting a start.

rincewind23 · Post by **rincewind23** » Thu May 14, 2015 2:54 pm

Hey Dave,

The teeth on the drive gear look pretty flat compared to images I found through google. I'm pretty sure the dizzy was located correctly - the lip on the housing was right up against the block and the bolt was fully tightened.

On the positive side, Since the remote filter housing is above the pump now, I can prime the pump by removing the hoses and filling them with oil rather than removing the pump cover and packing it with vaseline

bigaldart · Post by **bigaldart** » Fri May 15, 2015 7:54 am

This is a fairly common problem at high RPM and or excessive load. We fitted an oil feed pipe from the pump cover to spray into the nip between the gears, this was a fairly common mod in the rover V8 drag race series days, there used to be an off the shelf kit for it, don't know who made it as we made our own.

Alan

DaveEFI · Post by **DaveEFI** » Fri May 15, 2015 8:55 am

Yes - I've read lubrication can be a problem if you raise the rev limit.
But never seen wear that bad even on a high miles standard engine.
So would guess the normal lubrication system is faulty in some way? Which would need sorting before replacing the gears?

ged · Post by **ged** » Fri May 15, 2015 9:52 am

A couple of things I don't think have been mentioned.

Did you check that the cam key was parallel to the cam axis when it was fitted? If not it can restrict oil to the distributor drive gear.

Did you have the cam gear spacers flange facing forward & the cam gears oil groove facing it? Again this can restrict oil flow to the gears if you get it wrong.

rincewind23 · Post by **rincewind23** » Fri May 15, 2015 3:46 pm

Dave:
Yes there was a problem with the lubrication system - mounting the oil filter remote meant that even though I packed the pump with vaseline, I forgot that I would need to fill the hoses to the remote so I had two huge air bubbles in the system, so the pump de-primed itself when it started.

Ged:
I will check the key and the spacer flange when I refit the new drive gear. I originally did the rebuilt ages ago so I don't remember if the rebuild guide I was following pointed those things out (the one I have now does!)

Thanks again for all the replies.. Hopefully I have found all the issues now and will successfully get it running..

DaveEFI · Post by **DaveEFI** » Fri May 15, 2015 5:01 pm

Those gears haven't worn like that in a short time. IMHO, there's been an ongoing lack of proper lubrication for ages.

mgbv8 · Post by **mgbv8** » Fri May 15, 2015 10:10 pm

That looks a bit odd to me. The dissy drive cog should not be worn like that? The cam cog can wear down in quick time as I have had a good few let go and cause the dissy to jump teeth. From my own experiences the dissy cog remains ok while the cam cog can wear so far that it lets the dissy cog jump a tooth on each rpm.

rincewind23 · Post by **rincewind23** » Tue May 19, 2015 12:51 pm

I have ordered a new drive gear and when I get back from a work trip, I'm going to refit, triple-check the key parallel-ness and gear orientation, prime the pump and the remote hoses, and spin the engine with a drill to check everything is ok.

Should I be able to get the oil pressure high enough with a drill to open the pressure switch (to turn the oil light off)? Or is that only possible at running rpm?

DaveEFI · Post by **DaveEFI** » Tue May 19, 2015 1:40 pm

Yes - the oil light will go off even with a fairly slow drill speed.

rincewind23 · Post by **rincewind23** » Tue May 19, 2015 2:03 pm

I think with my level of skill it's "should go off" not "will go off"

DaveEFI · Post by **DaveEFI** » Tue May 19, 2015 2:38 pm

Well, I'd expect the oil light never to come on at idle with a good engine. Even more so with cold oil.

Engine will idle at perhaps 600 rpm and oil pump speed is half that.
So a drill speed of about 300 rpm will give the same sort of thing.