[TR] Randall comes up with the answer again

[Andrew Uprichard]

Randall:  you are amazing.  I bought a $6 in-line booster valve (Ford, I
believe) and no more noise. Thanks again !

Andrew

-----Original Message-----
From: Randall [mailto:TR3driver at ca.rr.com] 
Sent: Sunday, August 26, 2012 11:27 AM
To: 'Andrew Uprichard'; triumphs at autox.team.net
Subject: RE: [TR] Any one have this problem?

> After rebuilding the TR250, I noticed a distinct "click" from around 
> my feet and in sync with engine revs.  Turned out to be the servo 
> non-return valve.

I don't have any experience, but my guess is that there is something odd
going on with the intake manifold vacuum.  That valve should only move when
the inlet vacuum goes above or below the vacuum inside the servo, so I think
the rhythmic click means the inlet vacuum is going up and down.

You should be able to confirm that theory by connecting a vacuum test gauge.

I'll further guess that you have a fair amount of "lope" at idle, caused by
the aggressive cam profile (this is the engine with 170+ bhp, correct?),
which might explain the vacuum variation.

One solution might be to add an in-line check valve in the line leading to
the servo.  Without the direct connection to the servo and firewall, you
probably won't be able to hear it operate.

-- Randall