Another Carb/Timing Question, I am really not good at this stuff Options

[tornik550]

I have recently gotten my 914 up and running after a rebuild. I have been trying to work on the carbs and timing. The car runs ok but I am shooting black soot out of the exhaust and the exhaust backfires on decel. Engine idles fine. I have been reading and searching for a long time. I have read too much and I am now super confused. I keep reading that the backfiring on decel is from a lean condition and the black soot is from mixture being too rich? I am confused, can anybody help me? To confuse me more, I recently saw some white/blue smoke- I checked my compression and I am getting 150 in all cylinders.

car info
-73' 1.7 liter however I now have 96mm jugs, 78.5mm stroker crank- making engine displacement just under 2.4l.
-the previous owner put in a new camshaft however I do not know the details other than that it is from webcam
-2.0 heads
-cromoly pushrods with clearance set to 0 cold
-timing set at 27 degrees at 3000 rpm
-bosch 050 dizzy with pertronix
-msd 6al

carb info (all the jet/venturi/etc sizes were placed by the previous owner)
-dual weber 40 idf's
-carbs just rebuilt last week
-32 main venturi's
-120 main jets
-f7.5 emulsion tubes
-200 air correction jets

I am so confused.

Your help is greatly appreciated,
Steve

[r_towle]

I would say first fix the exhaust leak.

I had 40mm carbs on a race car with a 2.4 and a very aggresive camshaft.
I had almost no venturis...they were paperthin.
I would fix the exhaust leak first, then call aircooled.net on monday.
they have a list of all known carb setups for motors.
They will offer good advice on what vents you need to lean out your mixture.
For now your carbs are setup nicely for a 2.0 liter motor...so if you are running rich you have small valves and low velocity.
By increasing the inner diameter of the venturis you will add more air.
Aircooled.net is very cool.
They swaped out vents and jets for me till I got it right.
I would agree with Andy..start with bigger vents...
Once you get close you may need to add larger main and idle jets to really get the most from your motor...

Rich