[Fot] TR3/4 Rear Main Seal

[Jack Wheeler]

Before the Viton seal became available, I used a couple of different approaches to keeping the crankcase sealed at 7,000 RPM's, both involved machining off the scrolling from the rear of the crankshaft.  The first was to use a rope seal, like the E-Type Jaguar.  I took the dimension off the Jag crank, then machined the Triumph crank to the same OD.  I used the stock Triumph aluminum seal to hold the rope seal in place.
My next attempt was a big block Chevy, 2 part neoprene seal.  Again, I machined the Triumph crank surface where the seal rides to the same OD as the Big Block Chevy Crank.  Then I machined a two part aluminum retainer, similar to the stock Triumph rear seal, but with the inside machined to hold the Chevy seal in place.  I think there was a kit available at one time, were you could buy the seal, and the adapter that holds it in place (Moss (?) or someone like that had made up the same aluminum adapter that I had, and were selling it as a kit).  Anyway, this worked pretty well as long as you got the Chevy seal well centered around the crankshaft.
You might go to a junk yard (or speed shop) and find out what the dimension of the big block Chevy crank is, at the point where the rear seal rides against the crank.  If your cranks can be machined to this diameter, then see if you can find one of the old Moss conversion kits.  When I sold my race car to Don Marshall (#11 EP TR-4A - Runoffs winner 1990), there were 2 or 3 of these seal adapters that went with it.  If you can track it down, see if one of these seal adapters is available (out of an engine), and could be used as a sample to have one machined.  Or, you could do like I did.  Buy the big block Chevy seal, and use it as a template, along with a stock Triumph rear seal, to figure the dimensions needed to machine a two part adapter.  This may seem like a lot of work, but if your cranks are good, it might be cheaper than getting a new crank, especially if you have good machining capability available.
Good luck, and let me know what you decide.
Jack


      From: Tony Drews via Fot <fot at autox.team.net>
 To: Joe Boruch <jaboruch at netzero.net>; fot at autox.team.net 
 Sent: Saturday, January 21, 2017 3:12 AM
 Subject: Re: [Fot] TR3/4 Rear Main Seal
  
I did get the message but don't have any alternate suggestions for 
rear seal if the crank is machined for the earlier seal kits.

- Tony Drews

At 06:57 PM 1/20/2017, Joe Boruch via Fot wrote:
>Not sure if this went thru before, since I did not receive it in my 
>inbox and did not receive any replies.  Sorry for the duplication, 
>if it went out previously.
>
>The recent discussion of the valve cover gasket reminded me to ask 
>about TR3/4 rear main seals.  I know that the new improved Viton 
>seals are make to fit cranks that the scroll surface has not been 
>machined.  All my cranks have been machined to fit the earlier seal 
>kits.  Is there an upgraded seal kit to fit machined cranks or would 
>there even be any advantage to using the new seal?  Joe(B)
>
>
>fot at autox.team.net
>
>http://www.fot-racing.com
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