Severe Backfire on Overrun and hesitant cornering acceleration/power out

[Cassios]

Hi Guys,

Can anyone offer some thoughts. I have a 1967 SWB 912 which had the motor and carby's rebuilt in Dec 06. Initially the car felt strong but after 2,000 miles, the car started to become hesitant when taking fast sweeping corners and powering out was fluffy/fluttery. My mechanic who built the motor can't seem to find the problem. To add to insult, the car has developed a severe backfire problem under deceleration when hot (less so when cold) and i am quite worried and annoyed at the same time. This has been apparent now for approx the past 2000- 3000 miles. The car has only done about 10000 miles on the new motor.

Can anyone give me a list of some of the issues it could be. Would be much appreciated.

[Jaems]

I am sure your Mechanic did this. However, first check the valve adjustments. You can burn them pertty quick in less than 2000 miles, then the points, dwell, and timing. Make sure that you are getting a good spark. Also if the exhaust has leaks it can pop and bang quite loud. If everything checks out. Then your carbs are out of adjustment or dirt in the jets and etc. Which probably is the case but check the valve adjustment. If your mechanic is not familiar with Webers or Solexes then that could be the problem.

[fbarrett]

Cassios:

Don't overlook your distributor. If it's old, it may not be firing properly; it may be allowing oil to leak up from the crankcase and foul the points. I had this problem a few years back, and a Pertonix unit solved it completely: better starting, idle, no backfiring, smoother running at all rpm.

Frank