Club 80-90 Forums

Can anyone give me some advice on on basic settings for my dellorto drla 40s. What's the procedure for setting the idle mixture screws. Any thing else to consider , they are on my van and has run OK previously but don't seem to be as smooth now. I have my van booked in for rolling road in few weeks.

Getting backfiring through my twin dell's on acceleration and sometimes when it's idling. 2ltr cu petrol Aircooled.

Generally caused by lean mixture or bad timing.

That can be ignition timing or valve timing.

Start with a bottoms up tune up. Eliminating the valve clearances etc. look for scatter with your timing light showing wear in the distributor, make sure you don't have a blocked idle jet, set your mixture correctly. Better a little rich than lean..

Ensure the throttles are opening in sync and you have even airflow in all 4 throats.

It will be a process of steps to focus in on whether it is fuel, electrical, airflow or mechanical...

I found this useful book when i was running Dell 36s on my 1776cc type 1.

Every engine is different and really needs an experienced eye on a rolling road to jet correctly.

I.e. what size are the venturis? What is the fuel pressure, inlet manifolds, compression ratio , exhaust system all have an impact.

When you go to the rolling road they will need to know that the engine is in good shape and correct from the other aspects such as ignition, valve timing etc. also let them know what you want? Economy, smooth running, power, driveability.

I'll look through the book and see what it says about basic adjustments. I no longer have dells so strictly don't need the book.

Matt

This may help for starters....

Thank you

How do I set the mixture correctly.