3K Carby

[Ethan#4]

Í've been having trouble with this new engine i put in recently...

After beening started up the engine will run as if the dizzie timing is retarted, until it revs to 2000rpm.

Once above 2000rpm it sounds and runs sweet. So today i thought i would change the cam timing back to standard( as it was set halve way around the cam sprocket) in hope to try and gain some more revs down below 2000rpm, this did not change a thing.

Now after all hope was lost with that, we decided to turn to the carby, which is getting fuel after the engine is shut off??? I am totally stuck now as to what to do with this engine??? and the fuel pump is brand new.

Help please....

[altezzaclub]

Well, its probably one of only three things-

 

Cam timing.. is it a stock cam? Are you certain it is set correctly, which you can check by measuring in degrees when the valves open & shut.

 

Carb- lean lowdown or rich lowdown. Does it idle OK and pull away without any flat spots?? Does altering the idle mixture change the idle speed??

 

Ignition timing- What is it set to at idle, and does it immediately advance when you open the throttle a little??

[Andy43]

Does the carby have the anti dieseling solanoid connected ?

[Ethan#4]

The cam is a tighe which i brought last year, it is set on standard cam now with no difference down low (under 2000rpm)as of yesterday.

The carby i would say is rich low down as it floods until above 2000rpm, it will not idle and it has a huge flat spot until, again, above 2000rpm.

Changing the idle mixture does not change a thing. The ignition timing is set at 28 full advance not sure what at idle, and the engine wont rev immediately until above 2000rpm.

Andy43 i have no idea what the anti dieseling solaniod is but i would say it is not connected as it is a speedway car??

Thanks for replys,

[Andy43]

The anti dieseling solanoid disconnects the idle cct to stop the engine running on when switched off.

If you don't have one, don't worry not all 3k's had them.

If you do have one, replace with a bolt or connect the wire to +12V

 

A quick way to check valve timing is to spin the balancer to TDC on 1 (firing).

Whip the rocker cover off, and look at the rockers for 4 they both should be open a equal amount.

 

Also check your fuel tank is not pressuring, this is due to the fitment of the one way breather vavle requied by the ASCF.

We have had this cause flooding of carby, as the needle and seat cannot withstand more than a few PSI.

I fix is simple just depressurise the tank if the car has been sitting arounf for a few days.

CYA

Andy

 

 

 

The cam is a tighe which i brought last year, it is set on standard cam now with no difference down low (under 2000rpm)as of yesterday.

The carby i would say is rich low down as it floods until above 2000rpm, it will not idle and it has a huge flat spot until, again, above 2000rpm.

Changing the idle mixture does not change a thing. The ignition timing is set at 28 full advance not sure what at idle, and the engine wont rev immediately until above 2000rpm.

Andy43 i have no idea what the anti dieseling solaniod is but i would say it is not connected as it is a speedway car??

Thanks for replys,

[Andy43]

Whats the valve clearance set to ?

As the cam gets bigger the clearances increase.

Also if it says hot set when engine hot

 

 

 

[altezzaclub]

If it has never worked well with that carb, check the size of the idle jet. That actually runs the motor up to about 2000rpm when it hands on to the main jet. The float level could be too high and be flooding it too.

 

Check the timing at idle and 1500 & 2000rpm to make sure you are getting advance as it gets going.

 

What have you changed since the motor was last running sweet??