U20 back fires

toolsnob · Post by **toolsnob** » Tue Feb 15, 2005 9:14 pm

Ok,

I scared the crap out of the wife today! The back fire had so much force it dented the muffler, made me go deaf and loose my balance!

Anyway, I have removed the crane optical system in favor of a new nissan distributor. The issue I am having is the small backfires, I have set the timing to 16 degrees, the idle is only smooth at rpm and back fires at idle and dies.

Any suggestions?

Alexi

Post by **dbrick** » Tue Feb 15, 2005 11:53 pm

I just put in a Crane optical, was yours backfiring on the Crane or Nissan system?

toolsnob · Post by **toolsnob** » Wed Feb 16, 2005 12:06 am

on the Nissan. It didn't idle well with the crane so I went back to stock. It is back firing through the carbs and exhaust.

ambradley · Post by **ambradley** » Wed Feb 16, 2005 12:48 am

toolsnob,

Have you checked valve clearance? Basically they only way this can happen through the carbs is if there's firing in the cylinders that occurs while the intake valve is open, or if it doesn't seat properly or is burned.

For exhaust, it can be due to the smog system if the anti-backfire valve isn't working (if your car isn't desmogged), or I think even holes in the exhaust system can let in air that ignites unburnt gas in the exhaust. It can also happen if the exhaust valves are too tight, burned, or not seating properly.

TR · Post by TR » Wed Feb 16, 2005 2:47 am

Are you sure the timing is correct? Try advancing the timing and see if it runs better. Thinking that maybe it is running better at speed because the advance is kicking in, bringing the timing from a too far retarded condition.

Double checking that your 0 degree mark is exactly at TDC will also help. Given that the car ran before the dizzy change would lead me to think it is something with ign. timing...

toolsnob · Post by **toolsnob** » Wed Feb 16, 2005 10:56 am

ok, my fault. I had the wires going clock wise instead of counter clockwise. Starts right up!

Thanks.

TR · Post by TR » Wed Feb 16, 2005 11:34 am

Well at least you had #1 in the right place!

I once bought a 510 with a just rebuilt engine for $50 because the owner could not get it to start and run. It would run a bit and caugh and sputter. After completely going through the dizzy, points and carb I realized that the plug wires were wrong. I didn't have the heart to tell the guy that the $700 he invested in the rebuild was lost on such a simple mistake. TR