exhaust poping

[ppyvabw]

Bit difficult to know where to put this.

My car has started spitting back out the exhaust on the over run, like down hills with no throttle etc... It isn't just occasional either. It's pop pop pop pop pop pop pop, and they are big pops. It never use to do this, except on occasion maybe.

Checked ignition and repaired the knackered dizzy, new plugs, jets, floats. have yet to check the compression because Im not at home and don't have a compression tester with me but apart from the poping it runs fine, and doesn't use oil so i don't think it's rings or any thing. Maybe a tappet, but anyway, I know I need to check the compressions.

Apert from that, do you have any other ideas.

Here's the spec. 3.5, gasflowed standard valves, piper 286 9.75 pistons but composite gaskets and polished chambers. sd1 high rev lifters

I have changed nothing on the car and it is normally fine.

[Coops]

leaking exhaust/manifold allowing air to get in?.

[katanaman]

almost certainly leaking exhaust gaskets or cracked, holed headers

[ppyvabw]

How would that make it pop? Now you say that, there is soot accumulating around the exhaust gasket on no 1. I tried tightening the bolts but they weren't loose.

I certainly have a look at that.

[Coops]

the air getting in helps ignite unburnt fuel, thus the poping out the exhaust.

[ppyvabw]

Maybe I should mention that there are also flames coming out the back.

edit: just added that before I read your reply tony. That explains the flames

[Coops]

[ppyvabw]

Cool? You mean the flames?

Haha, yeah the flames are cool. Very impressive in Durham on a Friday night, disrupting the peacefull ambiance.

Except when they blow the back of your old rusty exhaust clean off on your way back from tesco's and the flames are spitting on the fuel tank . Fortunately it doesn't leak.

Fixed that now though

Thanks for your help. I'll check that at the weekend and let you know what I find.

[Coops]

nice one, good luck mate.