Ongoing backfire

[Jhonno]

87 Classic, gas only.

B2 Converter, Impco 200 mixer

This problem has been bugging me for sometime.

Have changed to bosch 024 module, new cap and rotor (lucas) spiral wound stainless leads, GT40 coil, (not new, came off a gas powered county that performed perfectly) replaced a lucas as the final attempt at solving the problem. Removed distributor, stripped, checked for bush wear, weight freedom, vacuum movement and diaphragm integrity

Have re-kitted the converter, diaphragm in the mixer is in good condition, replaced about 18 months ago, have searched high and low looking for air leaks to no avail.

The problem started quite a while ago, noticed a starving symptom when at low revs under load (increase/decrease in engine speed as in intermittent delivery/restriction of fuel) resulting in backfire, thought maybe it was a hardening of the converter diaphragm (did post re this at the time, thanks bee-utey for the heads up on where to source.) replaced and seemed to get a little improvement for a while, all the other mods had been done (except the coil) prior to the problem becoming evident.

This has driven me to distraction, parked her in the shed, (have acquired my daughters 93:D:D) but would now like to sell the 87 so must sort the problem before this can take place.

Any ideas regarding this problem would be greatly appreciated

jhonno

[33chinacars]

May or may not be LPG related. Could be a worn camshaft as I found out on my Holden 308 V8 recently. Was missing & back fire-ring through the carby. Just something else to check.

Gary

[bee utey]

The GT40 points coil is NOT the right coil to use on electronic ignition. Get a Bosch MEC723 or genuine (used) LR Bosch coil.

Make sure your ignition leads are separated as much as possible, the less they get near to each other the better. Plug gaps at 0.7mm max. Ignition timing 10 degrees BTDC at idle.

PM me your phone number if you want a chat, text explanations don't always work.