1641 with dual Del 40s- Timing?

[Stuster]

Hi people

I have just built a 1641, Engle 100, 009 with Twin Dell 40s. I've run the cam in but there is a fair bit of popping etc from what sounds like No 3 Cyl. I've dialled the timing in at 5 degs after TDC- but I'm wondering what the best timing point is for an engine like this? Anyone got any hints and tips. I need to move to tuning the carbs and want to get it as best I can.

Stu

 

[K@rlos]

30-32 degree's at full advance

 

[Stuster]

Ok done that! Seems to only come back to 15 degree BTDC at idle0 that does not seem right... maybe the 009 is kaput? The DRLA on No 3 seems to also be popping..

 

[sparkywig]

The 009 is mechanical advance only, and is difficult to static time. So you need to set it maximum advance at 3000rpm, usually between 28-32 degrees.
The popping on no. 3 could be carb synchronisation issues. See if there's any difference between chokes using an airflow meter.

 

[K@rlos]

Ok done that! Seems to only come back to 15 degree BTDC at idle0 that does not seem right... maybe the 009 is kaput? The DRLA on No 3 seems to also be popping..

Did you do it at full advance? Which is at 3000rpm on an 009. As for popping could be an air leak, blocked jet or carb balance is out

 

[Tofufi]

As above. But you'd be better off with a combined vacuum/mechanical advance (SVDA) distributor

 

[Stuster]

Out of interest- I got the Dell 40s used and had a strip down and clean, replace seals etc. However, on the manifold for no 3 cylinder there is a vac take off for the servo brakes. I'm assuming this may well be causing the issue? If so, what is the normal route for vac take off from the brakes if you can't do this. I'm new to twin carb and trying to learn quickly!! Also, I'm assuming all the vac ports need blocking off on the carbs?

What is the best starting settings for the Dells I have the Dell VW book and started with idle screws 3 turns out. What about any of the other screws?

 

[atafonso]

The brake servo can be connected to n.3 only and works well.
There is a bypass screw on each corner for fine tuning, most people leave them fully closed as they can be adjusted only by the more advanced tuners/mechanics. I adjust them using my carb flow meter, but normally they are pretty close, so if i were you i would not touch them.
You might have a blocked idle jet as others have said, try unscrewing slightly the idle jet with the engine running and see if the pop stops. If it does, you know there is a blockage on that idle circuit.
The vac take offs at the bottom are for tuning or for vaccum gauges, they work when you unscrew them about half a turn. Keep them all closed if you not using a vac gauge.
On the left carb, there is one extra vac port on cyl4, that is for the vaccum distributor. If you using a 009, blank that as it will leak vac if not blocked.

Abel

 

[smokehouse]

this is why i only run single carbs so much easier.