Misc: Everything Else 1951 Black Shadow Restoration

oexing

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A liquid sealant or any other seal has to transmit forces from the crankshaft or gear shafts within the engine block , so I would not want to have anything rubberlike between case halves. You don´t want fretting in the system. So for that reason you don´t find slicone in aircraft engines, they use Loctite like 518 or 574 curing types, no thinners in these. Same types I take for cylinder base seals or other covers, no cometics for me. For cleaning you need seal removers from Loctite or paint removers at lower price , no big deal.

Vic
 

greg brillus

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Black Threebond 1207B..........Best stuff by far.......You don't see Jap engines leaking. Good luck using any type of anaerobic sealants like the ones Vic suggests.......If the cases are not bolted up quickly once the 2 come together, the stuff starts to go off and the cases will never be fully together. The brown Loctite aviation stuff in a bottle with a brush, is fine on cylinder base gaskets and when installing the oil pump sleeve into the case.........The reason they don't use these later sealants on aircraft engines is they don't like to upgrade anything due to the massive paperwork involved..........Just look at the sealants that modern engine manufacturers use, most modern engines are primarily alloy. Just use a fine bead of the stuff, not the entire contents of the tube like some do..........I just had a barrel and head that i had to remove as a unit because someone used some loctite 518 or similar to bond the 2 together because they did not get the barrel to head joint set up correctly........In the end I had to use some heat, and a fine woodworking chisel to split the 2 apart.......A total mess really........just poor workmanship.
 

oexing

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Greg,
Lycoming approve Loctite 515 for sealing crank case halves when not having POB No. 4 plus silk thread on there. You certainly keep any studs free from sealant and apply only a very fine bead of sealant as you don´t need more than a minimal film to seal all imperfections. Loctite 515 is roughly same as 518, low strength sealant and not hard to break - provided nobody had overdone it on all sorts of places you don´t want to fill. So your troubles were started not from just the cylinder base faces but by sealant filling most other gaps at same time from exessive use .
Fretting between crank case halves is a problem in aero engines so my idea definitely no silicon seals to be used there. Loctite types 510, 518, 574 , 515 typically need min. 5 minutes for initial low strength so no, not a resaon to worry about when you got most bolts and nuts ready for assembly. In some places I want to open occasionally like simple covers I get Hylomar as it is easy to clean with acetone . Sometimes rubber (NBR) gaskets for simple places can be reused. But I do not plan to go inside any engine when on the road - a shame to the mechanic I´d say in that kind of "accident " . You would not be prepared to look inside your car engine on holyday trips , any time waiting for technical holdups - or would you ?

Vic
 

greg brillus

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As most know, the trick to preventing oil leaks is preparation and care of assembly........Good to go over all the mating faces with a large broad file, or a surface plate if you have one.........Good to lightly chamfer the holes, and double check on all parts to make sure it all goes fully home without anything "hanging up" as it were........ I had an engine not long ago that had the lipped type bearings on both sides of the flywheels.........after some repairs and upon assembly I found the cases would not fully bolt together, the width of the crank was slightly too wide for the bearings......... I had to heat one case half and replace one roller bearing with a standard 5/8 width one so I could assembly it correctly........Not the best thing to find once you have sealant on and everything ready to bolt it together.
 

vibrac

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Gregs right about 3 Bond being good stuff I am getting some alternative grade 3 Bond for my Scott Cylinder head as recommended by Scott gurus and joints dont get more difficult than that baby! (unless you include my Comets lower push rods tubes:))
 

Bill Cannon

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I don't think it's been mentioned on the forum before, but I suspect Dow Corning sealer as recommended by BMW would be a good choice as their engines are stress bearing members like Vincents.
Cheers Bill
 

Monkeypants

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There are likely several correct answers to the OP's question.
I've had very good luck with Loctite 518 anaerobic sealer, one of the products Vic mentioned.
I first used it on a very leaky cylinder base. After lifting the cylinder as high as possible with the bottom ring still in the bore, I tore off the base gasket and cleaned the metal surfaces with laquer thinner.
A coat of 518 was somewhat awkwardly applied and that fixed the leak. It's been dry for about 30,000 miles now.
I also used it on the 1360 cases.
That sealed perfectly as well, but that engine had to come apart for a crank rebalance.
The 518 glues the cases together like cement, but it is low strength cement. On disassembly things were looking grim at first. It seemed the cases were welded together. After a few good wallops with a heavy rubber mallet, the 518 let go with a pop.
On reassembly , after scraping the faces clean, I used 518 again with the same result, a bone dry case joint.
Recently, for any surface needing a gasket, including the cylinder base I've used Cometics. They just work.
They are particularly helpful on the intakes flanges. These joints can leak and cause poor engine performance. Slight overtightening only makes things worse as it warps things, especially the carb flange. This can cause the slide to stick.
With the Cometic gasket the seal occurs with very little squeeze required. I put a drop of blue loctite on those nuts, since they are just barely snugged up.

I also had a complete set made for the BSA Super Rocket and let the A10 group know about this product. Now Cometic has all the A10 shapes on file, so they can reproduce them at any time, same as with the Vincent gaskets.
The response was pretty negative, a lot of " What's wrong with using paper gaskets?", " My bike doesn't leak a drop now" etc. Yeah right.
Oh well, horse successfully led to water...

Glen
 
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greg brillus

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Well there are 2 issues there Glen, and this is not a dig at anyone, but...........First a lot of people don't like change...........one reason why these old bikes never changed from year to year.........and second (and more importantly) most all bike people are tight with their money.........That's one reason why I don't and prefer not to work for blokes that own triumph's, BSA's and Norton's and similar, because they all complain about spending money on their bikes........"We don't all own a Vincent you know".........That's the usual response. That suits me fine..........
 
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