Triumph Repair: TR6 hesitation at high RPM, check fuel, british cars

Question
I recently purchased a 76 TR6 and the car has been fully serviced recently. Car has been running very well.  Today, while driving up a long hill, as i got the car up to 3000 RPM in 3rd gear, it started to lose power a bit, started to hesitate.  I pulled over and downshifted.  Restarted and was able to keep driving, but everytime i got the car up to 45mph and ready to shift into 4th, it would lose power if i pushed heavy on the gas.  Any thoughts.  The car had been running very well prior to this.  Seems to be fine in lower gears with high RPM

Answer
HI Jim,

When loosing power under extender load you should test two items depending on if it misses when losing power or just seems like you have eased off on the throttle.

If it just slows as though you have eased off on the throttle even though you have opened the throttle then you need to test exhaust back pressure. I found that most British cars can not handle any higher back pressure while under full throttle then 1.5 to 2.5 PSI. If you see 5,6,7 PSI you have a stopped up exhaust system somewhere.

If it misfires under load you need to test the secondary of the ignition system and check fuel pressure while at the under load condition.

Let me know which it is and I will tell you in detail how to run the tests.

Howard