Allegro Club International

Jim Lavery · Joined: 13 Aug 2013 Posts: 32 Location: Stockport

Hi All,
Here i am again with another request for help.
I have spent the last couple of months working on the car and done some work on the engine. The head has been overhauled and has new hardened valve seats and the carb has been overhauled.
Today (Sunday i took the car on a run with my local club and at around 50mph it starts to act up alittle as if it's missing but it dosen't feel like an electrical misfire. I have been told the engine is an early series 3 so i have set the timing at 12 degrees@1000 revs. Is this right? Could it be that it needs more fuel?
I have fitted an electronic ignition but would think if that was faulty it would be cross the rev range.
Any ideas to cure this would be welcome.
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Jim

M. Irvine · Joined: 21 Jan 2007 Posts: 804 Location: Farnham, Surrey.

Hi Jim,

It would be impossible for anyone to say for certain what the fault is but I suggest you start by checking the following. I don't think for one second it is a timing issue, if the car performs OK otherwise.

1) After a run, what colour are the ends of the plugs? If it is too weak they will probably be white in colour.

2) Are the manifold and carburetter nuts all tight?

3) Is the distributor vacuum advance working correctly? This will normally operate under cruise conditions on a light load. Is it any different with the vacuum advance pipe disconnected when being driven? With the engine at idle apply suction to the vacuum advance pipe and see what effect it has, if any.

4) Increase the plug gaps to say 0.030 inch and see if it has any effect. What plugs are you using?

5) Check the resistance of the plug and coil leads. They should not be hgher than 15,000 ohms. Wipe clean the coil tower, distributor cap and rotor arm.

It is probably best to check these things first and let us know what you find.

Merv.
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ALLEGRO = Agile, Lively, Legendary, Economical, Genial, Reliable & Outstanding.

Jim Lavery · Joined: 13 Aug 2013 Posts: 32 Location: Stockport

Thanks for the info Merv.
The plugs are a light brown.Having just done a lot of work with the engine on the bench I'm pretty sure the manifold and carb nuts are all OK. I will check the vacuum advance tomorrow. The ignition coil and leads are all new though i will check the resistance just in case. The plugs are the Bosh equivalent to N9Y's

Will come back when everything has been checked.
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Jim

J Dawson · Posted: Tue Jan 07, 2014 3:46 pm Post subject:

Follow Mervyn's advice. It is hard to tell without experiencing but it sounds like the mixture is too weak. Have you done any work to the carburettor?

Fuel pump should be checked for delivery.

And put the old coil back on.
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Austin - you can DEPEND on it!

1976 Allegro 1100 4-dr saloon

Squeak, rattle & roll

Laurence · Joined: 17 Jul 2007 Posts: 1408 Location: Plymouth

It could be the distributor rotor arm is faulty.

Some rotor arms are of poor quality even though they may be new, they will create random misfire.

You can test it, see if you can get the king-lead to spark when it is held close to the centre of the rotor arm, if it does spark, the rotor arm is duff. But I would fit a red rotor arm from Distributor Doctor to eliminate any chance of the rotor arm causing problems.

As you are using electronic ignition, you will have to make sure that the ignition coil resistance matches the system you are using & there is a 12volt supply from the ignition & not 6volt-8volt which you would have if there is a ballast resistor ignition as used on some Allegros.