problem with timing - 1600 twin port

[Raggles]

Hope someone might have some ideas.

a bit of history to date...

I have a 1600 twin port with SVDA points distributor with dwell checked at 50 degrees( supplied by the guys at Type2Detectives) and 34 pict 3 carb (a rebuilt unit from Tim at Volkzbits).

The engine was dying on idle though it seemed to run fine under load. Valve clearances set, spark plug gaps set, new leads, timed to 7.5degrees BTDC. It was suggested it could be a vacuum leak. I therefore dropped the engine and refitted the manifold with new gaskets and boots to ensure no vacuum leaks - also drilled out the heat riser which is now working. I have an oil bath air filter with the pre-heat hose fitted.

After a run I found that the engine died at the lights/road junctions with a flat spot when trying to rev. The engined fired straight up when cold but when hot it took a while to catch needing to be turned over 6 or 7 times.

It was suggested that given what I had done to date that it might be a problem with the carb flooding and that the pump might be supplying too much pressure at idle.

I have just fitted a new pump.

Coming to re-set the timing following refitting I am now finding I have to retard the ignition to get it to run. If I twist the dizzy until it runs at its sweetest and check the position using a static timing light I find I am at about 10 degrees ATDC rather than 7.5 BTDC ?

Anyone any thoughts or ideas why? Would it cause damage to set the timing at this point (it was roughly 7.5 degree BTDC before the pump change)

Tim

 

[BRAD]

When I was doing mine, 7.5 is fine, I first had a leak from the carb bushes, bought a new one, then I found the vac advance nipple actually appeared ok but had cracked in a perfect circle around it so was leaking, last thing I fund was tube between carb and vac adv was blocked.
Once all that was sorted it now runs fine 8)

 

[Bluesnailman]

Yes, it will 'sound' happier about 10deg atdc but this is not good for it and it I'll be down on power and running too hot. It Could be similar to problems had this year which was the in the carb. I've a 34 pict3 and I had a blocked jet on the RHs of the carb as you look at it. I believe this is the idle air jet and was dirty, meaning with choke on or throttle open it ran ok ish, but wouldn't idle once warm. Suggest you expire a bit of dismantling. Just beware that in removing mine I dislodged more dirt hiding in the float bowl - so success was limited until I cleaned this too. I suspect in messing with timing you're working around a different prob.

 

[smokehouse]

check the idle shut off valve they can go bad causing you to stop at lights and stop signs.

 

[BJ1]

You should not be timing your engine using static timing. Always time with a gun at 28 to 30 degrees BTDC at max advance i.e. around 3000 rpm. That way you know that the engine is correctly timed for when it is doing the most work - cruising at around 55 -60 mph.
If you use static timing you won't know if your advance mechanism is working properly so you could well be running the engine at 3000rpm with the timing retarded - giving a hot engine that will die within 1000 miles. Overheating could be the cause of the engine dying at junctions and being hard to start when hot.