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Re: TR3A brake-light switch confusion (and dual exhaust)

To: triumphs@autox.team.net
Subject: Re: TR3A brake-light switch confusion (and dual exhaust)
From: AMfoto1@aol.com
Date: Sun, 1 May 2005 20:35:02 EDT
Hi Paul, 

The other response is correct... it sounds like you already have a five-way 
connector. One of the connections attaches to the *top* of the "funky silver 
nut" thing. In fact, that is the connection for the pipe that goes to the 
master 
cylinder. 

That silver thingy is a one-way pressure valve helps prevent returning brake 
fluid from pulling the caliper pistons too far back into the calipers, which 
would mean you'd need a longer pedal stroke to engage the brakes. My TR4 has 
always had one on it and it works fine. I disassembled it and cleaned it 
exactly 
once in over 25 years owning the car. Some folks take them off and seem to 
get by without. So, it's your choice.

The other four connections are at the base of the brass unit. One is a 1/8" 
NPT thread (tapered), the other three are 3/8" NF thread with a  conical seat 
at the bottom (check them with a 3/8" NF bolt, gently, to decide which is 
which... the bolt won't thread very far into the 1/8 NPT outlet). The 1/8" NPT 
outlet is normally oriented toward the lefthand side of the car (toward the 
exhaust manifold) and that's the one to which the brake light switch connects. 

The front outlet serves the left front brake line. The righthand outlet 
serves the short pipe to the right front caliper. The rear outlet serves the 
single 
line that leads back to the rear brakes, eventually to a flexible hose next 
to the righthand rear shock, and a three-way connector that splits the line to 
feed both right and left rear drum brakes. 

Regarding installing dual exhaust... it can be done. I've seen it and it 
sounds nice. A few major considerations: Too large pipes will reduce back 
pressure 
to almost nil and the car will have little low end torque, but will have more 
top rpm power. That may be fine at Sebring, but might make it hard to drive 
on the street. 

If you decide to install dual exhaust, use a pair of smaller pipes (maybe 
1-1/2" or 1-3/4" max) at least as far as the mufflers. Next, you should "mix" 
the 
exhaust from the two pipes, unless they are fed off a single collector header 
or manifold. (TR4A originally have a dual outlet manifold and Falcon 
stainless headers feed into dual 1-3/4" pipes, probably some other headers do, 
too.) 
If you have a dual arrangement at the header or manifold, it would need to 
first be joined to mix and balance the exhaust. A single 2 or 2-1/4" pipe could 
lead from this (or directly from a single pipe manifold) through the box at the 
center of the frame cruciform, after which it could be split into the two 
smaller pipes using a Y-pipe, leading to two smaller mufflers/tail pipes.  One 
issue might be the parking brake cable on the righthand side. It would need to 
be 
kept clear of the exhaust pipe. 

Cheers

Alan  Myers
San Jose, Calif.

 However, the original one I removed from the car has only three
connections for brake lines (including the line from the master cylinder), the
brake light switch AND a funky octagonal silver 2" tall nut that must act as a
pressure relief valve. 




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