[TR] TR4A carburetors woes

Jeff piggerp at comcast.net
Tue Jul 29 15:31:53 MDT 2014

I replaced the Grose float valves with needle valves.  I also put in new
fixed floats.  I used a color tune and set the carbs to the proper mixture
(I think) The Colortune goes yellow at high RPM but is blue at idle.  I
checked the mechanical fuel pump which seams to pump a good flow of gas.  It
ran great and I thought I was done, but after going up a hill for about a
mile it started to stutter.  I noticed if I pull out the choke it runs
better.  Any suggestions?  Could the gas be bad?  It's been in the car for
about 6 months.

-----Original Message-----
From: greg at gelhar.com [mailto:greg at gelhar.com] 
Sent: Sunday, July 06, 2014 7:51 PM
To: Jeff
Cc: 'Randall'; triumphs at autox.team.net
Subject: Re: [TR] TR4A carburetors woes

A while back, I rebuilt the fuel pump on my TR6. I got to wondering why
with over a hundred horsepower powering the pump what kept it from
delivering sky high pressures. After I had it apart, I realized the
engine's cam only moves the pumps diaphragm to suck in fuel. It is the
spring on the diaphragm that pushes the fuel to the carbs. So no, I don't
think the pump can overpower the carb's float valves.

Greg G.
Osseo, MN

> Thanks for the input.  I'm ordering the viton tip needle.  My fuel pump is
> the stock mechanical pump.  Can that put out to much pressure?
> -----Original Message-----
> From: Randall [mailto:TR3driver at ca.rr.com]
> Sent: Saturday, July 05, 2014 6:40 PM
> To: 'Jeff'; triumphs at autox.team.net
> Subject: RE: [TR] TR4A carburetors woes
>> When I take it for a spin though I can only get about 2
>> blocks and it starts
>> missing badly.  I get it home and pull the plugs and they are
>> really sooty.
> Others will disagree, I'm sure.  But my first step would be to replace the
> Grose Jets with the proper needle valves.  I don't fully
> understand why, but I've fixed several cars with similar symptoms that
> way.
> Or if you happen to have an adjustable fuel pressure regulator installed,
> try turning it down a bit.
> Randall
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