Outer Limits 4x4 Board

Gday,
As of late when running on gas, my TB42 Carby/Gas will sometimes play up.
It varies from the car cutting out at lights (rarely occurs), or when im doing 100kmh down the freeway the tacho will drop from ~2200rpm to 1000rpm and quickly back to ~2200rpm.

The major problem im having is when its under load (either accelerating or cruising at constant speed), there will be a bang or clunk coming from the motor that momentarily cuts power for half a second, sends you into your seatbelt and scares the bejesus out of all in the car.
Im guessing this is backfiring?

I also assume this is an ignition based problem. I still have points and will be replacing them with a petronix system soon. Does this sound like a faulty points problem? Or something else like a coil

I have replaced the plugs with colder plugs and I have a GT40 coil.

The motor seems to run fine on petrol.

MAYBE the clunk is actually a solenoid cutting out or even a tachometric relay.(this relay is triggered by the negative side of the coil and supplies power to the solenoids).
Mine has got 3 solenoids:
One at the tank
One at the in side of the converter
One at the out side of the converter.

When it first happened, I thought something in the front diff went bang.
Pretty sure its not coming from the diff
I dont think its a solenoid cutting out

ok thats ignition system

That bang is backfire though the carby, Mine use to to do it quite a bit when the points got worn down, Replace the points with a Crane cam Fireball XD700 Pointless ignition kit and never had that problem again, in fact i got more power and economy out of the old girl when it was fitted.

When under load you will notice it, especially if you labor the engine down.

Check the petronix post, I just put some ignition LPG info there that may help.

Joel

Just got the pertronix fitted. Fixed all problems.

Thought it would fix.

Was told by Williams Bros down here on the Central Coast (best place on the coast for LPG, Paul knows his Shizit) that Points and LPG are asking for more trouble then your even going to know

Petrol it doesn't matter as much, but fitting an after market pointless system makes all the difference. I did it, made things so much better when i had mine. While some people say that they do the Points with a High capacity kit installed does help, points still wear cause they are mechanical, with either Crane cam or Petronix you never have to worry about it again, nothing in there to replace.