MG Sports Cars

Re the "hunting" Ian. You may have the wrong springs in your carb. If they are too strong they lift the metering rods at part throttle and cause a surge. One way to find out is just take them out and run the car without them. Don't drive the car hard this way as you now won't have any enrichment. If the surge goes away then the springs are too strong and need to be replaced with a lighter set.
If the surge persists it could be the vacuum advance or just a lack of adequate timing. Disconnect the vacuum and set the total timing to 36 BTDC and see what happens.
Keep us in the loop and we'll go from there.
Cheers
Fred

Fred, thats along the lines I was starting to wander. I was thinking that at low revs I may just be switching from idle to primary so what you suggest sounds like a good idea.

I am first going to change my primary jet back to .086 and use the 1463 rod which puts me at 1st stage lean power/cruise. I currently have .083 and 1423 which puts me leaner on ist part of needle and then slightly richer on the second part of the needle.

If that has no effect I will try the spring thing. Stock spring is orange so I guess I will try a yellow. However, I will have to buy some springs first so I hope the jet/rod works.

The vacuum pipe is an easy test.

Its only a minor surge but its irritating when you are trying to drive in slow traffic.

Again many thanks.

Ian

Fred, sorted it and she's running real smooth. I was running with jet/rod which was a little too lean on the first stage of the needle and too rich on the second stage. Ran it then reset the idle mixtures. No more hunting/surging and she will cruise in 4th/5th at 30mph.

So, I am now running with .086 primaries and secondaries and using a #1463 (.067*.055) needle.

So all I need now is sunshine.

Cheers Ian



Edited 1 time(s). Last edit at 05/16/2013 12:09PM by hirot.

Good to hear Ian,
These carbs can be tuned to run fantastically well.
It just takes a clear head and some time.
As for the sunshine, I would send you some if I could.
Here on the west coast of Canada we are having some amazing weather this year.
Had some 30'c days already this year.
Cheers
Fred

Fred....and finally....gave up on the Petronix as it just wouldn't work and settled for the original Lucas amplifier module which has been superseeded by part no:- DAB118 and only costs around £25. I looked at making a remote unit as all the official one seems to be is a dummy unit to fasten on the side of the distributor, which gives a wiring connection, and an aluminium bracket where the original amplifier is fastened and connected by thin wires to the dummy unit.

Making a good and secure connection to the distributor is not easy. The irony is I should have kept one of my failed amplifiers....I had three fail one of which did't work out of the box....stripped it down and used it as a dummy wiring connection to the distributor. It seems a bit of a waste of money now to buy one and break it.

30 degrees now that seems a little greedy people over here would pay to get it up and over 20 degrees at the moment.

Cheers Ian