Triumph listers please offer advice...
I have an unusual -nagging- problem as I continue to fine tune my TR4A. When
accelerating through the gears at full throttle - pedal to the floor - I have a
flat spot between 4050 and 4200 RPM. This occurs only in 2nd, 3rd and 4th gear.
If I get it revved through 4200 RPM, it goes away. This flat spot is
characterized by an inability for the car to rev higher as if one or more
cylinders are mis-firing. The odd thing is that if I back off the throttle just
a hair - maybe an 1/4 - 1/2 inch - the miss goes away and revs right through
this RPM range with no flat spot though accelerating a bit less vigorously. Once
past this range, I can put it to the floor again with no problem with vigorous
acceleration. Other than this, it's running great.
I'm stumped. I've double checked and triple checked. I feel like I've done 5
tune-ups and can't make it go away. I must be missing something.
Engine is stock with tube headers, new Falcon exhaust, SU HS6 with new re-bushed
shafts, 20w 3in1 blue in the dashpots, new pertronix, new plugs (currently
gapped at .025 but same flat spot at .035) & new plug wires, new distributor cap
and rotor, new battery, new Lucas Sports Coil. Static timed and adjusted while
running using vacuum advance micrometer. Mixture correct as observed by spark
plugs on cyl 3 & 4. Slightly rich on 1 & 2 but I'm getting there by leaning the
jet adjuster nut one flat at a time. Idles great at about 900 RPM. Valves
adjusted but slightly noisy. New oil that is still transparent. 200 miles on the
odo in the last week. Did I miss anything?
Other than the flat spot mentioned, I can't remember it ever running better.
Any ideas?
TIA
Mark A. Evans
1966 TR4A IRS CTC63970 LO 'Tressy'
Acworth, Georgia - USA
mark.evans@anheuser-busch.com
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