Small back fire

The motor idles and runs great. But when I slow down I get a SMALL
Back fire. Things I have done to correct this.
1-cleaned idle jets
2-replaced intake metal gasket and torque to 12 ft lbs.
3-replaced plugs
4-replaced plug wires
5-replaced rotor
6-replaced distributor cap
7-adjusted values and rechecked
Thanks for the help

I had the same problem and it was an exhaust leak.

Dick

I agree with Dick. Check your exhaust.
Ron

SOUNDS good to me

are we talking about the gasket at the head?

If the exhaust doesn't have a leak, try richening up your idle circuit,too lean idle mixture can cause back firing on deceleration. Eddie

Yes, most of the time it is a small exhaust leak but you will hear thiis at idle as a erratic pop but sometimes and especially lately it is bad gas leaving deposits on the valves, set the valves loose at 8 and run a couple of tanks of gas with fuel system cleaner. Also you can use the Italian tune-up method of running in third at 4500 RPM for a few miles. These things will help to clear deposits off of the valves.

If not an exhaust leak your idle jets could be too rich.

It sounds that your mixture might be a little rich. Unburned fuel gets into the exhaust and gives you that little "pop" when downshifting.

Is this a small "burble" or bonafide "backfire"?
Did this occur after something was recently altered?
It's probably just a little richness during decel, if its just
a "burble" I say enjoy it. If it's a "backfire", I would guess
[go along with] the rich idle circuit theory. Did you recently alter
the exhaust? Good luck.

I think I'd start with John's noted "Italian" method. John kills me, but it sure beats crawling under there 8 times to adjust the valves twice. Quicker, easier and generally more fun.

On the subject of Italian tune ups.....

Think you may have dirt in a carb jet ? Run it up the 4500 RPM and witt he air cleaner off, put your hand flat down on the top of the car ( shop rag recommeded ) choking off the air supply till the engine almost quits ....run it back up to 4500 RPM's and repeat this a few time ...you'll be surprised at how well this can cure the problem !

Alan M