DINO: Sudden power lost

Dave> I get the pops when cruising or decelerating. no pop when accelerating, just the stumble and misfire.

Phil> what are the symptoms of poor valve clearance? how often do I need to service the distributor if I run on points?

 

That sure sounds like carbs, although you should be able to tell if the noise is coming from directly behind your head (carbs) or at the tail end of the car (exhaust).

 

Seems to me you need a different mechanic. Someone familliar with 246's in particular. Engine tuning is tricky sometimes for an amature but it's not rocket science for a pro.

Ken

 

There's not enough info to guess yet.

Valve clearances too tight can hold them open slightly, making carbs spit and pop and engine misfire when hot if it's an inlet valve, or making the exhaust pop, crackle and bang and engine misfire when hot if it's an exhaust valve.

It won't take long with tight clearances for a valve to burn out, meaning heads off and all new etc. And with 246 you can't re-cut the seats much if at all without reducing the tappet shims to below range, so you'll need to fit all new seats and valves to get the clearance range back and correct fitted lengths of the springs.

A compression test when hot may reveal this, but a cylinder leakage test is always a MUCH more accurate test.

 

New points need to checked and re-set after about 1 hour of running, as the heel often settles in, reducing the gap, increasing the dwell and retarding the timing. But once they are settled in, they won't need to be touched for 3000 miles, and then may not need anything anyway. A new condensor will also reduce arcing at the point contact area.

When I fit new points, I run the dizzy on the bench flat out at 3000rpm (6000rpm engine speed) for about as long as I can bear the noise (~10 mins). This settles the heel before installation and reduces heel settling in the car considerably.....meaning I can give it back to the customer and not see him again for a year

The last few sets I've fitted have not settled after the first hour of running, but I still check anyway.