Still A Misfire

Neilr

Member
I have gone through and managed to get car running better. However I still cannot get it to rev over 2000 rpm
and then it rises and falls. To get this far I have reset points gap which improved it greatly, reset timing to 6 degrees btdc as per manual. When I try to set 2,4,6,8 carb nothing appears to change. I have taken off dashpots and cleaned insides with carb cleaner. I am now wondering about condenser or coil. I can now detect difference when pulling leads off. Any Ideas please. Thanks
 
If its hunting around over a certain rpm I would suspect fuel starvation. Is the pump working ok, and are any filters nice and clean?

However can you elaborate on what you mean by

"When I try to set 2,4,6,8 carb nothing appears to change" ?

If you mean that making changes to the carb on the drivers side has no impact to the running of the engine then it is possible that you have some crud in the jet and its not really fuelling at all.

A simple way to test this is to pull the leads one by one with the engine running and note which ones make a difference to the engine note. Each carb feeds two cylinders on each bank, the end ones on the side it is mounted on, and the middle two cylinders on the opposite bank.

If your drivers side carb is not working properly then you would expect that pulling the leads on cylinders 2,8,3,5 would have a fairly dramatic impact.

Another test you can do with a cold engine is to spray a bit of water on the exhaust manifold close to the ports on the head. When you start the car the cylinders that are not working will take longer to evaporate off the water. A more high tech version of this is to point one of those infrared temperature guns at each one to see which ones are running hotter/cooler.

If you do pinpoint the bad running to a particular carb then I'd check that the dashpot is rising a falling freely and easily, without getting stuck. If that is all ok, then as I mentioned earlier its probably a blocked jet. Just remove the carb, whip the bottom off and see what you find.

Apologies, that was a lot more rambling a reply than I had intended!

Good luck!
 
Thanks for reply. I should have said when trying to alter mixture screw whether fully in or out the engine note does not alter. I know dashpot is working have taken out both and cleaned inside with carb cleaner. Also refilled with oil. I believe my most noticeable lack of difference is numbers 4,6.
 
Also fuel is pumping strongly and fuel is flowing through fuel filter. The carb that I suspect is on the left of engine as you look from front of car.
 
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