Serious backfire!!

[palmer]

Hi all since fitting my 1.3 engine i have had some serious backfire. I get flames coming out of the exhaust manifold (still to get rest of the exhaust) when i really put my foot on the gas, i dont think its timing could it be to high fuel mixture?, if so how do i change this.
Any help would be good thanks
Palmer

[Pugsley]

Copied and pasted from the Internet - hope it helps.

Causes for backfiring normally wont change from one car make to another, backfiring in a nutshell: A backfire is when the ignition of fuel doesn't take place in the ignition/combustion chamber, it(a backfire) can take place in the intake or exhaust. It can be caused by a fuel to air ratio not being correct, also if the timing of the spark is not just right that could cause it to back fire. It could be running lean with not enough fuel and too much air, or could have too much fuel and not enough air. It could be because the intake valves are not shut when the combustion takes place, therefore the combustion would take place in the wrong spot. The most likely cause are from: 1. Incorrect timing, the timing issue could be caused by bad wiring/ or bad ignition. 2. Incorrect fuel to air ratio, bad fuel filter, low fuel pressure-caused by weak fuel pump. Most cars will have the same cause for backfiring, as long as it's an internal combustion engine it shouldn't differ... Also another reason cars can be backfiring during accelerating is that when RPMs change so quickly the fuel mixture is wrong for the current situation((but this should be brief/not common), granted it shouldn't be backfiring at all, this is a common reason it will when accelerating.

[Edweird]

It's not that uncommon for cars to occasionally spit flames under sudden, hard acceleration. Is it happening every time or every now and then? Also bear in mind it's an old, detuned, carbureted engine not a severely refined fuel injected one: it will have it's quirks.

When I had a leak at the manifold to front pipe flange on mine it started doing a rally style backfire when I eased off after accelerating. I was half tempted to leave it doing it.

[ScottieJ]

Have you checked that all the HT leads are in the correct order and the timing is correct?

[palmer]

Going to put a timing light on it tomorrow and all the leads are in the right place, i understand that its a old engine and carb and there will be little problems with it. Its every time i give it the beans it back fires, su carb after Christmas i think

[Edweird]

If it's every single time then there might be something wrong. At high revs the valves might not be shutting completely if the valve springs have gone a bit soft.

[palmer]

Is that serious?? I will check timing and hope that its that. Dont fancy taking engine apart

[Edweird]

Well, to be honest, the only things that limit how high a carb fed F10/G13/G16 can rev is how fast it can get the air in, fumes out and how long it takes to shut the valves.

Obviously that's if you keep within reason. If you modified it to rev to silly numbers it would wear out extremely quickly and send a piston to the moon.

[SJ Greg]

if its out the manifold with out the rest of the exhaust system its normal put rest of the system on and check from there