primary gear bush!!!

[Dean]

Hello again

i did have another post on here about my clutch slowing the engine when pressed and not getting enough throw. well thats all sorted and find,
but one thing i did find was i had oil running down the inside of my primary and coming out by the C washer not a lot but it was getting there.

i put it down to only running the fresh built engine at first on the starter so the oil was not being forced out,

WELL!!!!

all has been well, i just had it set up on the rollers, got it home to find that the split pin at the bottom on the flywheel housing have oil dripping from it,

i am sure i have a lot of pressure inside the engine case, as its also got oil dripping from the bottom flywheel housing where it bolts to the gearbox.
i have now removed the flywheel and primary and it looks like its been forcing its self past the seal and down the outside of the primary, the seal is undamaged.

but after looking at the front bush its for some reason is starting to show sights of wear, when it was fine before refitting the last time it was off not so long ago. ( see photo )
it looks like more to do with lack of oil???? maybe. all clearances are fine and with in tolerance,

i will be replacing the bush with a floating bush, but its on a 1071 S engine , but on the mini spare instruction, it says that it won't fit mk1 S primarys as the internal where the bush goes is 0.030" bigger. so fingers crossed,
anyone know the internal size of a no mk1 S primary with out the bush???

the other big question is why.?????
could i of pushed the seal in too far, (it was fitted with the correct tool), but could it of gone in too far and covering the oil holes on the primary?

i sure the oil leak is down to pressure but what else could it be.

i need to get this sorted quick, as i have got to get it to beaulieu, but i need to work out why its happening before i can do something to fix it, so it does not happen again.

i give mini spares north a call and get a floating bush and seal ordered tomorrow, if i wait i will run out of time!!!!

so for the long winded ness, but i know there are some very helpful people on here,
i also have so many ideas and questions in my head about this and this is the best place to air them are help work out my problem

Dean

[Spider]

One thing that does grab my eye right away is the black bits. Burnt Oil?

It also appears something's not parallel or the back bush (the top hat one at the other end) has way too much running clearance.

I wrote up how I do mine here;-

viewtopic.php?f=3&t=7645

and there's also some factory info as well. Been doing them that way for a very long time.

There is no pressure oil feed to the Primary Gear Bushes, not since the very easy 60's at least! and never in the big bore blocks.

As these are all spinning parts, Oil gets thrown out from them so it's not until clearances get on the bigger side that oil will actually pass from one end through and out the other. What ever Oil Pressure the engine may have will have next to no bearing on how much oil may get through the Primary Gear.

If, on assembly, there's too much oil in the primary gear, it can come out of the back bush and the black spots on the photo of your bush ^ suggest to me that it may have been over-lubricated on assembly.

<Edit: If you are mad keen to use a floating bush, the Mini Spares ones for the 1275 Primary Gears should fit.

https://www.minispares.com/product/Clas ... o%20search

I'm sure Rich can confirm>

[Dean]

thanks for your reply.

when i said pressure i was more on about crank case pressure, i think i worded a bit wrong.
as it looks like the oil has forced out around the seal. as it has also blown a gasket as well

is there a chance that the seal can be pressed in too far and block the holes on the primary , not allowing oil out???
it is fitted with the correct tool so its goes in squarely

i will be removing the transfer case as i need to replace the gasket. i can then have a better look and measure the crank.
i already know the rear bush ( top hat ) is at 1.502", what running size should it be

i have also ordered a floating bush just in case, if its need replacing i change it if not i clean this one up and make dead certain its correct. i already have a top hat, and i know a very good machinist who can do the work.

thanks

[Spider]

Yeah if the clearances are right, the pressure in the crankcase would have to be reaching astronomical levels to push oil out between the bushes and the crank tail.

I feel that 0.002" running clearance maybe too tight though, the factory spec is 0.003 to 0.0045". Also, just lately I have been putting a slight taper (4 deg) for the last 0.125" of the top hat bush as it appears that due to the extra material of the built in thrust face of the top hat bush, they appear to expand a tad more here and can grab the crank. I'm still trialling this, so not something I would (yet) suggest as a matter of course.

I was actually going to ask if in fact the oil maybe getting through the seal. If you've used the proper tool for fitting the seal, then it should be right as far as covering the holes goes, though the only way to know for sure is to check as the time of assembly (fit the transfer housing up to the block with THE gasket and without the gearbox). Some seals though are better than others, I've been using these for a while now;-

https://www.minispares.com/product/Clas ... |Back%20to

only had one that didn't seem to work as well as it should.

Though, if it is the seal, you'd see the oil on the clutch face, if it's from the primary gear bushes, you'll find it in the centre of the flywheel and in the extreme on the outer side of the flywheel and inside the diaphragm.

[Dean]

spider you were correct.

i have now removed the engine and have it on the bench and checked and measured everything.

the top hat bush is at 1.503, but the crack is at 1.497.5, so too much running clearance

the front bush was 1.628 but the crack is at 1.6235, so yet again at the limit of tolerance

i bought a floating bush ( which is at 1.625), so i going to use that, and i already had a top hat bush in my tool chest, so i be fitting that and going to see a friend of mine to size it. then dump it in a frier to get oil in the bush

i think i have got to the bottom of my oil problem , when i split the clutch from the flywheel, and there was no oil on the inside of the flywheel, i did not real see any on the top hat bush. or in the C washer.
the clutch plate has had very little use, but i can see oil on the plate, and around the clutch, so its the seal that failed.
i had taken it off and on 3 time even with the correct tools, i really should of replaced it when i had it off , lesson learnt.
i also bought a new seal, which is the same one as above

i check to see if the seal was covering the oil hoses on the primary and can now say they don't, the seal lip sits a few mm infant of the holes so thats not a problem

but i am sure i have too much crank case pressure, i also think its part of the oil leak on my seal and the oil leak at the bottom of the transfer casing.

so i will open up the hole in the top of the cover that later cars use and make up some kind of breather, there is also one on the rocker cover and the tappet chest cover, so i will make up some kind of catch tank
fingers crossed that will solve the problem

my next thing is to get it all back together, before next weekend for beaulieu, plus i still have other bits to finish off, so its going to be a mad week.

[Dean]

i been looking for oil to use the soak the primary in, you say in another post us a non friction modified oil.

i am finding it hard to find an oil which states this, i have found a lot of transmission oil come up when i search, but i can't see that to be true???

or should i just just use normal 20/50 mineral oil.
my engine is running on castrol R40, i don't want to use that as i rather buy a cheap oil as its only going in a frier then deposed of

[GraemeC]

If you're running R40, I would use that - mixing it with mineral oil could cause issues.

[Dean]

true,true.

but it is only for the top hat primary that does not come in any contact with any oil, so the reason to soak it in hot oil before fitting .so its self lubricated, it will be dried when fitted.

but i could be use it, i do have a few litres spare but seems a waste of good oil.

[Spider]

Good that you seem to be getting at the bottom of it.

Even with the running clearances you have, if no oil is passing through the bushes, I might be temped to leave them and run with it as is, but also could end up being one of those things at the back of my mind too. With bigger clearance, possible Oil leakage problems aside, there is a risk of clutch shudder (judder) and even tearing the centre from the clutch, though it would need considerably more clearance than a few thou before that becomes a potential issue.

In regards to the Oil for the Hot soak, I just use an ordinary 15W40 Grade Engine Oil, I wouldn't suggest using anything but engine oil for this in fact. While that is what I use on the Primary Gear Bushes, I do run with a 20W50 in the engine (Penrite HPR30).

To a point, with Lip Type Oil Seals like those for the Primary Gear, the more pressure on the Oil Side, the tighter they seal - in theory!