backfiring

[Mike Cardwell]

Help. I'm running dual 34ICTs on my 1.7 and I can't seem to get it running smoothly. Does anyone know if there are any adjustments to the timing that I need to make due to the FI cam? Would advancing the timing help eliminate the extra fuel not being burnt. Also, could the fact that I'm not running a fuel pressure regulator contribute to the backfiring problem? I've set the timing, dwell, and valves according to the Haynes book. What is the actual dwell angle? Thanks.

[jmcleod]

since you mention a fuel pressure regulator in the same post as carburetors, then maybe you still have the fuel pump for the fuel injection system hooked up to the carbs. the fi fuel pump puts out about 30 psi which is too much for carbs which needs about 5 psi (to the best of my memory). is this the case??

[Mike Cardwell]

I am running an electric fuel pump but I had read about people also using a regulator to regulate the pressure to 4.5 lbs. I thought that someone said that carbs do not run as well with the pressure varying as does with a facet type pump.

thats right..the needle and seat in carbs like to see a consistent pressure, i have my regulator set on 4.5lbs, the car engine ran better when i set it on 4.5lbs, although..i dont know if that was coincedence, as i had no compression on one cylinder, and my rings were starting to go, ( i just pulled the heads the other day), you know..you always find something else wrong when you go in to fix something simple..oh well..also, while on the subjects on fuel pumps, its good for the pump to mount it low, as close to the bottom of the car as possible, so it is gravity fed by the tank and only has to push the gas to the carbs, not pull it from the tank and then push it to the carbs as it would have to do if it was mounted up high..good luck

[John Rogers]

Dwell angle is 47 +- 3 degrees. That is for the Fuel injection system on the FI cam. I checked with the people that built our 2.0 and they said that if you just change the FI to carbs w/o a cam change, it will not run as good? Does it backfire on acceleration or when letting off? Acceleraton backfire is usually caused by timing/dwell/carb mixture. Backfire when letting off the gas can be caused by flooding, valves out of adjustment or retarded timing.

[Conrad W Peden]

The backfire when coasting(with your foot off the accelerator)can also be caused by a leak at the intake manifold. Carbs need a good anti-vibration intake gasket. I use Dellortos and have discarded the original gasket(the thick plasticy type one, I think they call it bakellite) and made my own. This has helped me in the past.

Good luck.