I recently noticed that when I ref the engine in my 1965 Ford F250, the engines backfires. The engine size is a 429 Big Block v-8.

I just bought the truck and the exhaust is removed from the muffler back to the tailpipe...is this the problem? What are all possible problems?

 

Backfiring from exhaust or intake?

 

I believe it's from the exhaust...

 

Is it doing it when you are revving it or when you let off?

 

Backfiring can be caused by any number of issues. Most will be basic tune up issues. I did say most, but not all.

I usually go back to the basics. Rule out the simple items before you start looking for the deeper problems.

Check the engine's tune. Confirm the dwell (if it has points )and timing. Check the condition of the spark plugs and plug wires, cap and rotor, etc. and replace as necessary. Make sure the carb is correct for the application, in decent shape and working correctly. Make sure there are no vacuum leaks. When the plugs are out run a compression check and record the readings.

If the backfire still persists post your results and settings and specifics and we will have a place to start. Once you know all is where it should be and have established a baseline we can help you can start digging deeper.

Good luck.

 

Hmmm! Good question and I'm not at the house to check ... However I do believe the backfire occurs as I push the accelerator peddle... Can you give me both scenarios?

 

Backfiring as you let off is semi-normal. Not much to worry about.

However if it is backfiring under acceleration, I'd say your distributor is not advancing properly. Retarded timing would cause this too.

What is your timing set at?

 

Perhaps running little too rich, does not sound like any thing major, but then again not an authority on the 429. Seem to recall there is quite a variation on timing on the 429 depending on yr. and source of engine; passenger, or truck. If I am stumped usually start off by pulling #1 plug and rotate engine w/ ign. off and place finger in plug opening as compression forces finger out of the plug opening then immediately stop and check rotor position to the positing of the timing mark, should be w/in manual spec's. Open the fuel bowl site screw, fuel level should be just below the threads. I then close the idle mixture and open approx. 1 1/2 turns. I use this procedure only as a reference point, once the engine is running adjust and fine tune accordingly, keeping in mind any adjust on either the idle mixture or timing need to go back and adjust the other. I have a Holley which operates off secondary vacuum, if it were to operate off primary then I would block the dizzy vac. advance when adj. timing. Not recommended using a vac. gauge for tune up purposes, but if there's a vac. gauge available connect the line to a primary source and should be drawing between 18-21 hg, if not, then may want to see if able to rotate dizzy until within limits, if unable then possible vac leak???. Interested in outcome??

 

what should the timing be set at? for a 429 bb v8

 

Somewhere between 6 and 16 degrees. Best usually around 10-12-14. But it all depends on the engine.