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Re: "phut" noise in a TR4 (long)

Subject: Re: "phut" noise in a TR4 (long)
From: Randall <randallyoung@earthlink.net>
Date: Thu, 04 Oct 2001 07:16:26 -0700
Cc: "Triumph (E-mail)" <triumphs@autox.team.net>
References: <41E306B582FA924E97D68F1A891419D1061443@BCSRV4.baincapital.l lc>
Noah :

Your "phuts" are likely misfires, which could have all sorts of causes.

Unless you are actually seeing black smoke, I would start with a "full
Monty" tune-up : replace the points, plugs, and condensor; also the
rotor, cap and wires if they are the least bit suspect.  (All of these
things are good to carry as spares, so put the old ones in a baggie and
throw them in with the spare tire.)  Plug gap is .025", point gap is
.015", timing is 4 degrees BTDC.  (You really should have a book with
this info, contact me off-list if you can't find one.)  Might as well
lube the dizzy while you're in there (smear a very little oil or light
grease on the point cam, a few drops of engine oil or "3-in-1" under the
rotor, and a single drop on the point pivot and on the post for the
advance spring).  The "book" timing method is to set the vernier to the
center of it's range (large mark), set the static timing to TDC (pointer
on timing cover aligns with hole in pulley when points open), then
advance the vernier one division (4 degrees).

Now set the valve lash to .010" cold.  (Valve lash will affect the carb
adjustment, so do it first.)

If you've got H6 carbs, first check for any signs of leaks.  If the
lower jet gland is leaking, likely the upper one is too, which will
throw off the mixture adjustment.  Check the float level and clean any
crud out of the bottom of the float chambers while you're in there. 
Check that the carb pistons fall smoothly and evenly with no signs of
any hangup, and a soft but distinct 'click' when they land.

Now start the engine and let it idle.  As soon as it will idle smoothly
with no choke, you can check the carb synchronization using the tools in
your kit.  Then take a short drive, to get everything to operating
temperature, and set the idle mixture using the "lift the piston" test. 
(Another approach is to take the drive first, and use the
synchronization tools from the kit as an easy way to lift the pistons.)

Now, you can retest for your "phuts", and begin troubleshooting if
necessary.

As a side comment, don't be too concerned if the inside of your tailpipe
stays black.  It's tough to never get the mixture rich enough to smoke
when starting, and on today's unleaded fuel, it will take forever for
the black in the tailpipe to go away.  Not like the old days, where the
lead in the fuel would coat the tailpipe with lead oxide, basically
white paint, in fairly short order.  If you look around, I think you'll
find that most cars, even those with computerized fuel injection, have
black tailpipes.

Randall

"Freeman, Noah" wrote:
> 
> At 3.5K rpm, (when revving in
> the garage) i begin to hear occasional "phut" noises in teh exhaust
> note...as I increase RPM to 4.5Krpm, the exhuast can be characterized as
> "mostly 'phuts'"...(a phut is a little noise sort of like a really light
> cough)...the engine doesnt hesitate after each phut (its not in danger
> of stalling or anything) but I have a suspicion that its loosing
> power...(its not like these phuts are very loud...just loud enough to
> hear over/in teh exhaust)

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