backfire through the carbs ..., makes for nice fireworks! Options

[SirAndy]

hey, it's me again, the "carb-hater" !!! (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

i've been trying to get this engine to run right for what now, 10 months??? (IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif)

i still have a issue with backfires upwards through the carbs (looks cool at night with the GT-engine lid) !!!

now here's my question:
- i'm still running stock (well, SSI) heat-exchangers and a close to stock (Manta) exhaust.
- i have a cam with a lot of overlap.

could the stock(ish) exhaust setup cause too much backpressure and the engine doesn't flow and belches back through the carbs ????
(IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif) Andy

PS: this happens all over the rpm range, but more often under lower rpm load and higher rpm "cruise" (steady gas) and only sporadically at WOT ...

[Carrera916]

Andy....

The key word you used awhile ago...overlap cam....that can really screw things up when you don't have a good ignition to begin with....

seems that jake hates 050, I haven't use it and I have no idea what it's sweeping curve are alike....when the advance or retard curves aren't smooth, you'll hit a flat spot that the engine speed and timing speed ain't timing right together, that can back fire a bit....

What I'm looking at is the camshaft itself being overlap, it leaves the intake and exhaust valves open at same time at a certain degree setting, now with the ignition spark fired, the flame will travel out of it's combustion chamber via intake sack or exhaust pipe, giving out 'Jumping Flash Flame'....

like brad & jake said, throw out the 050, try a different one...if problem persist, then look closely at the camshaft overlap & it's timing...that's something I would look at..

good luck....