Do you have the stock exhaust run or is your header running closer to the
drivers side frame rail? If the coil situation checks out you should take a
look at how close your exhaust (manifold or leader pipe off the manifold) is
running to the metal fuel portion. Very possible you are getting fuel
evaporation. Try shielding the line and see what happens...
Josh
'76 TR6
Chip19474@aol.com wrote:
This is sort of a continuation of the "diminishing fuel pressure from my
Carter fuel pump" thread I started 2 weeks ago.....
It's my '76 TR6 - just completed 3+ year restoration - engine rebuilt with
mild lift cam, .030" over pistons, head shaved, ports matched & polished,
stainless steel headers, Richard Goodparts 3 Stromberg carb setup, lightened
flywheel, Carter electric fuel pump....
My original concern a few weeks ago was the diminishing fuel pressure from a
starting point of 5 pounds to zero psi on the in-line fuel pressure gauge
after 20 minutes...during this time the engine the gradually ran worse (bucked
&
spit at cruise and upshift throttle) and idle dropped considerably and got
rougher. BUT - I replaced the electric pump with a stock TR6 mechanical pump
and
I still have the same problem.
Whatever is going on with this engine appears to be "time and/or temperature"
dependent. I cleaned the spark plugs 2 weeks ago and with less than 2 hours
of running time on the engine, they're black again. I checked the carb mixture
with 3 colortunes....one on cyl #1, one on #3 and one on #6. I have the
carbs adjusted for the correct blue corona which quickly turns yellow when the
throttle is blipped then back to blueish when the throttle is constant at 2500
rpm. I double checked the mixture by using the "lift the air valve slightly"
method....rpms momentarily decrease very slightly upon lift which is okay. The
carbs are TR4 175CD's....no emission control razzle dazzles.
So, just for kicks, I replaced the condenser with one that I know works and
no change. BUT - by sheer accident I happened to touch the coil after 15
minutes of running time....my Lucas Sport Coil gets too hot to touch (this
doesn't
seem normal but it's hard to compare with, say, the Spitfire, because the
Spitfire's Lucas Sport Coil is mounted on the bulkhead). If I pull a plug wire
and check for spark quality after 20 minutes, there is a spark but I can't tell
if it's strong or steady. Tomorrow I'll swap the TR6 coil out with the sport
coil I have on the Spitfire and see if that makes a difference...maybe it's
opening internally with "time & temperature"???
Can anyone give me some other options to look at? Moving the ign timing
around from 10BTDC to 20 or 25BTDC changes idle speed as expected but it
doesn't
stop the bucking/spitting.....point dwell is right where it should be. I guess
the bottom line is I've been chasing a fuel problem which may be an ignition
problem but I'm not totally ready to rule out either....I can't explain the
zero fuel pressure on the gauge because the carbs are getting fuel (I checked
by
removing the line at the carbs)....and if the floats were sticking, the
colortunes would be showing yellow....I'm getting stumped!!!
Thanks for whatever ideas you may have.
Chip Krout
Skippack, PA USA
1976 TR6 #CF57822U - one of the last 500 built!
1970 Spitfire Mk3 #FDU78512L - on the road again - 33 years young!
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