Another Backfiring Issue!

[CPBerry2011]

Hi.
Any help much appreciated on this. Got my bus engine in after resto. Changed a few things since it was last running. Bus is running rough and intermittently backfires. I have checked the tappets and adjusted to tdc (my pulley has three notes and a dimple - I believe tdc is the dimple?). The exhaust has black sooty deposits where the fumes exit the pipe. I timed the engine with a strobe to 5 deg atdc (left notch of three). The changes to my engine included;

- Pertronix Elec ignition, new pertronix leads, new dizzy cap.
- New fuel pump, oil pump, oil cooler.
- Changed to Alternator (from Dynamo)
New pushrods seals and tubes, new main seal, new seals at top end I.e. Manifold, Alternator Stand etc).

I have altered the idle mixture screw but scared to mess about with the carb too much. Should I just take it to a pro mechanic? Any recommendations in Warrington or Cheshire area? Don't want to travel far with the running issue.

Anyone able to offer potential diagnosis/help?

Thanks

 

[Trikky2]

Yes the dimple is tdc.
5 atdc is for engines with the dual vac dissy and is done with hoses on at tickover.
If you have a normal single vac dissy then it's 7.5 btdc.

 

[CPBerry2011]

Yes the dimple is tdc.
5 atdc is for engines with the dual vac dissy and is done with hoses on at tickover.
If you have a normal single vac dissy then it's 7.5 btdc.

Thanks Trikky2!

So if I have one vac line into the centre of the dizzy cap then I'm 7.5 btdc.

That may explain things!

Cheers.

Chris.

 

[CPBerry2011]

Yes the dimple is tdc.
5 atdc is for engines with the dual vac dissy and is done with hoses on at tickover.
If you have a normal single vac dissy then it's 7.5 btdc.

I think I have the normal single vac dissy. Is there a surefire way I can tell which I have. Just strobed it to 7.5 btdc and the engine is still a bit rough and occasionally cuts out. There is still backfiring though not as bad.

 

[CPBerry2011]

Yes the dimple is tdc.
5 atdc is for engines with the dual vac dissy and is done with hoses on at tickover.
If you have a normal single vac dissy then it's 7.5 btdc.

I think I have the normal single vac dissy. Is there a surefire way I can tell which I have. Just strobed it to 7.5 btdc and the engine is still a bit rough and occasionally cuts out. There is still backfiring though not as bad.

I should also state that my engine is a stock for the most part twin port 1600 and my bus was registered Jan 1971. It's a US bus also.