This Englishman has a problem.

I have a superb 1974 Volvo 145 that has a B20 engine, slightly modified as follows :

B20E head with hardened valve seats and new cam followers
Stainless steel timing gear
Volvo K camshaft
Rebuilt SU HS6 carbs on B20B manifold
M410 o/d gearbox

The engine has run well for over 5,000 miles in its current form. It also had excellent compression and leakage results at the last check, less than 2,000 miles ago. Recently, it started to hesitate at anything over 4,000 rpm, and refusing to rev beyond in 3rd and 4th gears. It would pull well up to 4,000, but then da . . . da . . . . da . . . . da . . . . . da hesitation and it would go no farther. It would keep going if you upshifted and the revs dropped (3rd - 4th and 4th - o/d), and I originally thought that the problem would be ignition advance. I replace the points and condensor and checked the timing and still the same problem.

It has started to get worse and the problem now occurs at 4,000 rpm with the car stationary and out of gear. The car also misfires occasionally when pulling away from the lights under load, and has started to get slightly louder. Also, the engine has developed a resonsance / harmonic that shakes the engine at 4,000 rpm so that the carb float chambers start to froth and overflow.

Could this be a broken valve spring or piston ring causing these problems, or could it be still a timing problem.

Any ideas, look forward to hearing from you,

Simon