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Comet Oil Filter Woes

Martyn Goodwin

Well Known and Active Website User
VOC Member
I have been chasing an elusive oil leak at the front of my Comet for some time – on reflection I recognise it started after I switched from the traditional “RAG” type oil filters over to the new metal/paper units. I use liberal amounts of non-setting sealant(Hylomar) on the oil filter cap and am in the habit (because of the pesky leak) of checking the filter cap after each run to ensure it is really snug and check for leaks. When I got home from a run today it was still feeling snug BUT still leaking so I pulled the oil filter out of my Comet and took the opportunity to perform some measurements.

The depth of the filter chamber from back to front edge is 3.678”
The diameter of the central spigot (at the base of the filter chamber) at its widest point adjacent to the base is 1.005”
The diameter of the central spigot (at the top of the spigot) at its narrowest point is 0.91”
The overall depth of the filter cap including the compressed spring and filter plate (how far it goes into the chamber to make a seal) is 0.41”

SO – with the cap and pressure plate in place, with the spring in the cap fully compressed there is 3.678 – 0.41 = 3.268” available to “house”the filter element; thus to allow for some wriggle room it seems that the absolute maximinum overall length of a metal/paper oil filter element, including seal rubbers must be no more than 3.258”

The “RAG” type element as supplied in the past by VOC Spares, uncompressed is 3.31” long, and with mild compression becomes 3.18” long; so it fits within the available space, allowing the end cover to be screwed downand sealed.
The VOC Paper Element filter metal body alone is 3.27” long and if you include the seal rubbers (which you must) it is then 3.40” long – so there is no way a seal can be achieved, the bugger is AT LEAST 0.133” too long!
Another Paper Filter element, obtained from another source, but stated to be for a “C” series Vincent Comet has a metal body length of 3.18”and if you include the seal rubbers (which you must) it is then 3.32” – so again there is no way a seal can be achieved as this filter is 0.053” to long!

I see that the VOC Spares Company no longer lists the RAG type of oil filter for Comets so I am asking my fellow Cometeers – is my problem unique to my Comet? I am wondering what sort of oil chamber dimensions can be found on other Comets and what are the external dimensions of the Metal Paper oil filters others have received from the VOC?

For now, I have reverted to the RAG type filter and am able to achieve an oil tight seal with the oil filter cap with thread sealant on the threads and Hylomar on the angled flange.


Martyn Goodwin,
 

Matty

Well Known and Active Website User
VOC Member
Thanks VOC spares - this has been a problem for many years and I have been modifying the paper filters by taking one end off, enlarging one end hole to one and a quarter inches and fixing the end back on with a thin rubber ring outside with silicon sealant on the card board side inside.
The total length of the filter is then reduced to a little under three and a half inches and the filter then can be put in with the end cap oil tight and seals hopefully against the end of the filter chamber.
I am not too happy with this "bodge" because even with great care it is possible some bits could get into the filter from the work, but have not had any problems for more than 10 years.
However now the older style felt filters are available I shall use these in future and go back to standard.
Matty
 

Phil Hogg

Website User
VOC Member
Being an infrequent visitor, I have only just caught this thread. I came across this problem last winter when building a 600 Comet motor for my special. Annoyingly I had already put the crank in the cases when I discovered the new type filter canister would not fit. My solution was to machine the boss area to make a nice register for the rubber seal by making a tool that I could drive with a hand drill, I made a spigot that screwed in to the banjo bolt thread to centralise it and it machined very easily. The photos should make it obvious how I did it.Filter housing.jpgFilter housing tool.jpgMachined housing.jpg
 

Peter Holmes

Well Known and Active Website User
VOC Member
Well Phil, what can I say, a perfect engineering solution, I would not expect anything less, my method was more born out of a lifetime of working with wood as apposed to metal, but it kind of achieved the same objective, just not quite so well, so please keep your tool tucked away in a drawer, next time I am up your way with my Comet perhaps you could clean up my bodge up for me.

Cheers Phil, roll on the next Far Far North Rally
PS How was Achiltibuie?
 

Phil Hogg

Website User
VOC Member
Hi Peter, yes the tool is tucked away with all the other Vincent tools so no problem. Achiltibuie was a great weekend, five Vins made the trip. Sue missed out on the swimming it was warmer than Tongue.
 

bmetcalf

Well Known and Active Website User
VOC Member
Peter, will your tooling only cut a round slot the width of the hole saw teeth? Phil's device cuts a wider area, I think. I am lumbered with a mere Rapide and don't know what the Comet details are.
 

Peter Holmes

Well Known and Active Website User
VOC Member
Bruce, yes you are correct, Phil's method is far superior, no doubt, but confronted with my problem, and with zero engineering skills or equipment I came up with the hole saw approach, and because the internal casting on my Comet was sort of an ellipse, probably the wrong terminology, but anyway the casting was rich on one side of the threaded hole, but not so the other, my hole saw just cleaned it up enough of the casting for the filter to slip over the projection, it kinda worked. But when you look into the filter chamber right to the back, the sand casting is pretty rough, it is hard to imagine that the seal between the oil filter and the casting is that good, but in some peoples eyes, better than no filter at all, Bill does not agree.
But before my engine was sorted out many years ago by Tony Maughan, I well remember looking at my metal encrusted felt filter, and thinking to myself, thank god that is not circulating round my engine.
 

A Nut

Website User
VOC Member
I too have come across this problem on Comets before. As stated earlier the casting in the base of the filter chamber on Comets is pretty rough and the boss is sometimes too big. Many years ago a friend helped me make up a hand cutter to clean up not only the boss but the base of the chamber. In doing this I slightly increased the length of the chamber but by how much I cannot remember. I did this not only on the engine in my Victor replica but also on my '47 Comet (HRD cases) Since doing this I have had no leaks on either engine. I use a coating of Wellseal on the tapered seat. My 1954 engined Shadow (die cast cases) has never suffered from this problem. Unfortunately I no longer have the tool as I think it was passed around the section. Best of luck. Brian.
 

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