hello, my 1969 ford f100, 360 bib block is backfiring through the carb, new taylor high energy plug wires, motorcraft plugs, new points, new accel super stock coil, new starter solonoid, it is timed, i have no idea what would be causing this! its really agravating! i need help, what could it be?

 

Provided your 100% sure of the timing accuracy, damper hasn't slipped, spark plug wiring sequence is 100% CORRECT (COUNTER CLOCKWISE on the dist routing AS SEEN ON THE BACK OF THE INTAKE 15426378 iirc ) 1-4 are the pass side of the engine 5-8 are the driver side, front to rear of the engine.

First I'd look for a huge vac leak.. like the brake booster or the PCV hose that goes to the carb base phenolic spacer etc..

If nothing turns up, plop a comp tester on it suspecting for issues with an intake valve. if you find low comp on one cyl, bring that cyl to TDC on the comp stroke and push air into it, using a compressor & the comp tester hose minus the petcock valve on the spark plug end. Listening to the carb for sounds of air making it's way through.

Weak intake valve spring, or stuck valve due to valve to guide tolerance,

that would be a starting point for me.

 

thanks i will see what i can do, i was wondering if the fuel mixture being too lean or the fuel bowl setting being wrong could cause this?

 

i gapped the points today at .017" also today the timing is set at 10 degrees btc, being an automatic transmission the rotor is also pointing to the 1 on the cap when the 1st cylinder is on compression stroke

 

Damper might have slipped and thrown your marks off. Maybe advance it till it runs better and then read what your timing is at. If its a little off then id guess your damper slipped. If you cant see the marks maybe your timing is 180'd and your firing on TDC of the exhaust stroke. But it sounds like your one step ahead of me on that one.

 

Did you verify that the accelerator pump in the carb. is functioning properly. You didn't state when it is backfiring.

 

Thanks for the info, the truck only does it if you floor the throttle, or really put your foot in it

 

Besides the accelerator pump which can cause the backfire under sudden acceleration you also need to check the vacum advance mechanism.

 

thanks 69cj. how to i check the accelerator pump? the advance when vaccum is hooked up does advance the timing.

 

When looking down the front barrels of the carb, hit the acceterator. You should see two strong streams of gas squirt. One in each barrel. You do this with the engine not running. If the gas just dribbles the pump is bad.

 

alright bud, i will let u know what i find.

 

Hello all, i think i have narrowed it down to points, the, points were new, 2 days old and have burned up already, i am runnin a accel performance coil and i think its to hot for the stock points, what do yall think?

 

You may have to high of voltage going to the coil, should be about 9 volts max not 12v You may need a resistor block to lower it. Put a volt meter on the coil wire coming from you key switch let motor run a few minutes so it's at regular idel about 600 rpm b4 checking voltage...
orich