Rear Scroll Seal Conversion

Post by **Matt** » Sat Jun 30, 2007 12:22 pm

I know there are conversion kits to replace the rear scroll seal with a "proper" oil seal, but are they effective, how much do they typically cost and where are they avaliable from?

Thanks

Post by **jonathon** » Sat Jun 30, 2007 1:29 pm

In our experience they sometimes work. If the crank has been worked on for performance reasons then the boss that the oil seal should seal onto will have been machined off or to a much smaller diameter. The original spec crank has this boss as a cast part only so the surface is rough. The kits instructions state that you should dress the boss with emery cloth to achieve a smooth surface for the seal to sit on. Fine in theory but in practice this can mean that the boss is undersized, and a good seal impossible. However although not satisfactory it will reduce the oil leak, normally associated with the standard seal.
So in short its 'pot luck'

Post by **Matt** » Sat Jun 30, 2007 1:31 pm

hmm guess I will use the standard arrangement then!!!

Post by **RogerRust** » Sat Jun 30, 2007 2:02 pm

I'm thinking of fitting a drip tray to the bellhouse to catch it before it drops on my drive.

Post by **Matt** » Sat Jun 30, 2007 4:33 pm

funny you should say that, but before I had the engine out I made a little catch tank that went between the sump and backplate to catch my leaking oil... it was then going to get pumped back in!!!

Post by **bmcecosse** » Sat Jun 30, 2007 4:35 pm

It will be filthy - don't do that! Best bet is to have negative pressure (certainly not positive) in the crankcase and this seriously reduces all leaks !

Post by **Matt** » Sat Jun 30, 2007 4:42 pm

BMC...

before I had the engine out I made a little catch tank

notice the past tense ;)

at this point all the breathers were plumbed in to the carb, and oil was being sucked in to the carb!!! The engine had 3 broken rings etc etc it was a bodge so I could get it home without spending more money on oil than petrol!!!

The engine is totally stipped and is at the machine shop as we speak having the crank ground, the block bored and new pistons fitted to the rods!

Post by **dunketh** » Mon Jul 02, 2007 10:34 am

I was put off by the high cost of the oil seal conversion.
There must be an easier DIY/bodge way?

I guess the first step is to make your engine breath as well as possible so as to reduce pressure through the back as much as possible.

Post by **picky** » Mon Jul 02, 2007 1:12 pm

I suppose you could fill the oil collecting groove in the rear main bearing and the other sealing part (held on with 3 small bolts) with a silicone sealant, letting it dry before assembly. I was going to try it but I forgot and now I cant be bothered taking it all apart again. Whatever you do dont simply block up the hole in the bellhousing!! although that is obvious to the average minor owner I think...

Picky

Post by **Packedup** » Mon Jul 02, 2007 2:03 pm

Cost - Around £80 I think!

Where from? Peter May does them, others probably do too.

Effective? I'd have to be leaking a lot of oil before I'd consider it cost effective, even if it was very not leaky effective!

Post by **dunketh** » Mon Jul 02, 2007 2:57 pm

Whatever you do dont simply block up the hole in the bellhousing!! although that is obvious to the average minor owner I think...

lol... I can actually imagine someone really dumb doing this.

Oil bath for the clutch anyone?

Post by **picky** » Mon Jul 02, 2007 9:56 pm

Post by **Matt** » Mon Jul 02, 2007 11:28 pm

well some motorbikes have a wet clutch ;)

Post by **bmcecosse** » Tue Jul 03, 2007 8:31 am

I used to have to do this !! Scrutineers were always worrying about little oil dribbles going on the track - so a small cork was pushed into the hole and all wiped clean. After each run - away from the track - cork removed and small amount of oil allowed to dribble out. Problem solved. Scruts happy.

Post by **picky** » Wed Jul 18, 2007 9:36 pm

<br />has anyone tried this before? the other end of the tubing will connect to the engine vacumm. probably no good for serious leaks - you would just end up with lots of smokey exhaust fumes! but cheaper than fitting the rear scroll seal, AND can be done without removing engine and box.

Picky

Post by **minor_hickup** » Wed Jul 18, 2007 9:59 pm

Surely this would suck in dirty oil with clutch dust and allow too much air in?

Post by **bmcecosse** » Wed Jul 18, 2007 10:10 pm

Certainly innovative!

Post by **picky** » Wed Jul 18, 2007 11:04 pm

well your idle speed would have to be adjusted, but the tubing is only 3mm diameter and it will be quite long to reach the engine, so not much volume of air can be pulled through. the plastic bit restrics the air even more so there is only a very small hole at the end. but ill admit I have not tried it yet, or seen it done before.

Post by **simmitc** » Wed Jul 18, 2007 11:16 pm

Just to reinforce NOT to bother with the "improved" seal. One well known supplier sold it to me as a simple bolt-on item, fit by dropping the sump. Rubbish! Need to remove sump, main bearing cap, and flywheel. The flywheel mounting boss then needs to be machined absolutely smooth, and as Jonathan observes not all of them will have the required tolerance. The main bearing cap also needs to be machined flatm and after all that the kit still uses a load of sealant. Some finished results are OK, some leak worse than ever. To fit one needs the engine out and some specialst machining facilities, definitely NOT a DIY job and NOT worth the cost.

Post by **picky** » Thu Jul 19, 2007 11:36 am

the small bottle would collect oil and clutch dust, and would need emptying occasionally. it could be mounted in the engine bay so it is easy to reach. to be honest I am going to just connect the hose directly without the bottle, and see how it goes.