deceleration backfire

[Duckhnter83]

I recently adjusted my valves on my car which is new to me but the lash is suppose to be set at .016 hot. before I adjusted them the car ran great. After now I have a backfire on deceleration and a little blue flame out the right header. Could this come from my lash being to tight maybe? Or would adjusting my lash cause the car to run lean? Any help would be great. I used the exhaust opening intake closing method.

[twisterf5]

I recently adjusted my valves on my car which is new to me but the lash is suppose to be set at .016 hot. before I adjusted them the car ran great. After now I have a backfire on deceleration and a little blue flame out the right header. Could this come from my lash being to tight maybe? Or would adjusting my lash cause the car to run lean? Any help would be great. I used the exhaust opening intake closing method.

most times it a header gasket leaking letting in air.

[Duckhnter83]

I would agree to that but what i don't understand is how one weekend it runs without popping or backfiring then I adjust valves and it starts backfiring. My gut tells me to loosen the valves up a little but I don't know if this would be right. I'll check the exhaust gaskets.

[Egoracing]

Did you happen to lean on the header while doing the adjustments?

[Duckhnter83]

Not that I recall.

[StuckInReverse]

Sounds like an cracked header or bad header gasket. Probably just a coincidence that it occurred the same week you adjusted valves.

[powerslide]

Header bolts need to be checked weekly. They tend to loosen themselves

[Duckhnter83]

I will definatly check the exhaust gaskets. My thought was I got an exhaust valve to tight and it was opening to soon and letting unburned fuel in the header causing the car to pop or backfire on deceleration.

[9car]

pop the valve cover off and run the valves again, 15 min you'll know if thats it or not

[Bubstr]

A little tip, if you don't already know it. Mark your Balancer at Top dead center and at every 90 degrees. put your pointer on the mark and follow the firing order, moving to the next mark and you will never be unsure if you set a valve on a ramp. It makes it fast too so all valves are set at close to the same temps. It's a good time for a plug check and that makes it easy to turn the crank with a ratchet. Write down if you have to tighten up a valve, it can be an early sign of wear in the valve train. It's also a good time to do a leak down test and record it. It will not only give you a progress report on your ring and valves, it gives you a baseline in case something happens internally. They don't all wear the same and if you feel something down on power, you know what it was and what it is now. The best part is it's only a couple minutes when all the plugs are out. Do it as you do the lash check. An ounce of prevention is worth a pound of cure. If you find one with too much leakage, listen to carb, exhaust and crank case to find what is leaking. If a valve tap with plastic hammer to dislodge any carbon if there and check again.

Another thing, all leak down testers are not the same. I could get mine to blow 2% on a tight cylinder and a friends registered 8% on the same hole. Use the same one all the time at the same incoming pressure.

Add checking oil for metal and sooner or later it will save you a lot of cash.

[Duckhnter83]

I checked the header gaskets last night and they weren't leaking so I took the headers off and inspected for cracks all good. Replaced header gaskets and put them back on. Still popping on decel and blue flames when it pops out both sides. Tonight I'm double checking my valve lasj again. If that doesn't cure it I guess I'll try making it run richer.

[crateracer16]

I had that happen to me last year and it ended up being a loose wire in my ignition system. It was always popping out of both pipes on decel.

[Duckhnter83]

What wire did you find loose

[merc123]

I had that happen last year. It took us a little while to track it down. Finally found the header was leaking out of the top on the middle ports. It was almost impossible to feel because of the air coming off the fan but we could hear it. Sounded like valves tapping. Resealed it and it stopped.

It would also do it in the shop if you reved it up and let it go real quick.

[jedclampit]

I recently adjusted my valves on my car which is new to me but the lash is suppose to be set at .016 hot. before I adjusted them the car ran great. After now I have a backfire on deceleration and a little blue flame out the right header. Could this come from my lash being to tight maybe? Or would adjusting my lash cause the car to run lean? Any help would be great. I used the exhaust opening intake closing method.

Will it do this in the garage or only when there is decel load on the engine?

If you have/had an exhaust valve too tight, it won't be long before you have, if you don't already , a poorly seating valve from the heat buildup @ valve head.Leakdown test as mentioned above will show if this is the case.

You may have an idle mixture screw open too far or a plugged/restricted air bleed on top of carb.