Speed drops away on slight incline !! Help

[parker999]

I have 1600 engine,.
On flat roads it happily goes along at 50 mph 4th gear , how ever on a long incline in the road,. Dual carriageway scenario ,. Foot flat to floor ! The speed drops to 40 mph ,. Even 35mph ,.
Do I have a vac advance problem !!!
Is this a carb issue !!!
I have electronic ignition, new plugs, ht leads,
Only thing carb does is make engine backfire on downhill, no throttle,. I can hear popping noise !!!
Any ideas

 

[sparkywig]

The popping on the overrun is probably caused by an inlet manifold leak/overlean mixture. This might also explain the lack of power and will make the engine overheat.

 

[Trikky2]

Another thing worth checking is pull one plug lead out the cap at a time to check the engine slows down. (Wear gloves and keep your fingers well away from the end). If when you pull one of them and there's no effect you have narrowed the problem down to that cylinder.

 

[parker999]

thanks for replies, i will check air mixture / air leek 1st...
then i think a compretion test

 

[sparkywig]

Compression test is miles away yet, there's plenty of things to try first.
Make sure there's no leaks first, check timing and valve clearances, carb mixture and then Trikky's checks. Could be a dodgy dizzy cap, plug or lead, etc.

 

[Max Power]

Make sure the accelerator cable is adjusted so you get full throttle.This will cause lack of power.