6cly backfire

[mickrae]

The old gs series 3 has a bit of a backfire,fuel/air or electrical stock standard 6cly any ideas much appreciated

[ladas]

I normally associate backfires with bad / incorrect timing settings and /or associated compotents - ie rotor arm, distributor etc.,

Or if the heads need a de-coke - do we still do that - apparently the carbon build up continues to glow and causes pre-ignition - does it run on after switching off ?

[100I]

Start with the ignition as Ladas said is most likely.

When we were younger a friend's mum's car was backfiring badly and they had their usual mobile mechanic out to look at it, who diagnosed it as definitely a valve problem on number 3 [say that with a Rainman voice], big quote, mum was worried, all the rest. Of course after I convinced her to let me have a quick look over, basically just wanted points tidied.
Point is, start simple... and wary who you pay for work.

[JDNSW]

Most likely ignition, air leak into intake manifold (carbie or manifold loose or vacuum line off/leaking), possible carburetter problems. (in that order)

But with this engine I would suspect exhaust valve problems and check tappet clearances and run a compression test to rule this out, as continued use with a leaking exhaust valve will get very expensive.

John

[dandlandyman]

Yeah, as above. But also check if you've done a vacuum advance diaphragm. My 2b FC did one recently, and it would not run at all without choke. What made it hard to do was it didn't have a choke cable...

Dan.
69 2a 88" pet4, 74 3 109" pet4, 68 2b FC pet6.