List,
Still don't have the TR6 on the road in it's full splendor and
beauty....nagging running problem....looking for hints from any of you who
have "been there &
done that".....here's the scoop:
1976 TR6 - recently completed body off frame restoration - motor rebuilt with
these specs: .030" over pistons; head milled and combustion chamber grinding
and polishing done; intake ports matched and polished; cam is Kent Cam #TH5
Fast Road; stainless steel headers; triple 175CD Stromberg setup through
Goodparts intake manifolds; ignition is stock; fuel pump is electric Carter
#P4070
72gpm 4-5psi internally regulated and mounted on frame rail behind rear driver
side tire; fuel filter is between tank & pump; fuel delivery from the pump is
via 5/16" stainless tubing to an aluminum billet in the engine bay where
individual <" stainless lines run to each carburetor - an 8 psi pressure gauge
is
attached to the billet.
Problem: from a cold start (fuel pressure gauge reading 4+ psi), the motor
will run strong for approximately 20 minutes with mild pinging under light
load
(timing set at 33 BDTC - 1000 rpm - distributor vac line disconnected &
plugged) then motor begins to cough, buck and spit while under very light
loads
and idle turns very rough.
At this elapsed running time, the fuel pressure gauge shows close to zero psi
but a check of fuel flow at one of the carburetors confirms that fuel flow is
strong (this was accomplished by disconnecting the front carb fuel feed line
and attaching a flex line to the delivery pipe and directing the gas flow into
an empty bottle. I clamped the rubber flex line to the bottle with small
vice grips and released and tightened the clamp to check flow from the pump.
Each time the clamp was released, fuel surged into the bottle and the fuel
pressure gauge jumped up to about 3 psi. When the clamp was again tightened,
pressure went down to zero psi.
At this elapsed running time (30+ minutes), adjusting timing either way
(retard or advance) doesn't have any affect on the bucking/coughing, etc.
I reconnected the fuel line to the carb and, just out of curiosity, let the
motor idle for a few minutes then I shut off the fuel pump while the engine
was
running - it took about 3 minutes before the engine began to stumble and die.
As a test for fuel delivery, I bypassed my Carter fuel pump with another
electric fuel pump and got the same results. Voltage at the fuel pump remains
constant and proper throughout the entire running time. Ignition dwell is 35
degrees, engine temp is normal; carb mixture is spot on, there's oil in the
dashpots, etc.
A penny for your thoughts!
TIA
Chip Krout
Skippack, PA USA
1976 TR6 #CF57822U - one of the last 500 built!
1970 Spitfire Mk3 #FDU78512L - ready for spring
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