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Hey all. This is a bit of a hairy one. I am living in the philippines and drive what is known as an "OWNER TYPE JEEP". These things are built in the jungle and nearly al are made with the mighty 4k engine under the hood. Mine was bought second hand and has been nothing but trouble. I got myself a 4k carby to replace the forklift carburettor some monkey had retrofitted but this carby that i bought is the most simple f all the 4k carbies i have seen online. It simply has one vacuum port from just next to the fuel inlet which I have taken apart and confirmed is connected to the vacuum port just above (before) the throttle plate, There is also one well below the throttle in the rubbery adaptor plate between the carby and the manifold. (manifold vacuum). I can not get my vacuum advance to work properly. Now, I have myself an electronic distributor with working mechanical advance and 2 vacuum advance ports, my research tells me one is for ported and one is for manifold. Other research revealed that most people simply block one of these ports off and simply connect the other to their vacuum port of choice. This makes no sense to me and I want to do it properly. I suspect this lack of vacuum advance is giving me economy issues; as my Jeep is using about 13L/100k, when I should be getting at worst, 10L/100ks. Based on tests with my timing light, I have come to the conclusion that the vacuum supplied from the manifold port (under the carby) is too much and never varies. With the mechanical advance jammed (ziptied shut) the timing stays at a solid ~40 degrees BTC with the vacuum from this port. attached. When opening the throttle, this does not change. This indicates to my brain, that either a. this carburettor is too sensitive to vacuum advance, or b. I'm not testing it properly. Now moving on to the ported advance. This has the opposite problem. I know there is meant to be nill vacuum at idle and a blip of the throttle should cause a blip on the timing (more advance). I am seeing the opposite of this, and at very most I'm seeing a 0.5 degree retard when i blip the throttle. Nothing i can do with the ported vacuum will make any advance happen. This indicates to my brain that either: a. this distributor is not compatible with this carburettor, (not enough vacuum to operate it) or b. the carburettor is ill manufactured and the ported vacuum port is to small to generate enough vacuum. So my general consensus, which I would love if someone knowledgeable could verify: I need to increase the ability of the ported vacuum source to supply vacuum when the throttle is just open, by drilling out the external aluminium plug behind the port and drilling out the port to a larger size and the re plugging the external plug. I then need to increase the spring tension in the dizzy advance to overcome what appears to be an oversupply of vacuum. other info There are no other vacuum systems in operation other than the brake booster and PCV valve. The carburettor is clean and rebuilt by me (3 times with a bit more effort each time) and I can 100% guarantee it is at factory condition and is producing as much ported vacuum as it possibly can in its currently engineered state. I have no idea if the dizzy is a 4k or 5k dizzy, I only know it is electronic, has 2 vacuum advance ports, both are definitely advance ports and it produces a great spark. I can not determine what the difference is between my carburettor: and this common variant: or this other variant with numerous vacuum ports Anyone able to shed some light on this for me?
