QuestionI hope you can help me, I know that you specialize in hundai engines, however hundai engines are not that much diffrent with misubishi engines.
mine is a 4G63, 1985 model SOHC 8 valves 2.0 litter engine
naturaly aspirated, cross flow.middle east market
my problem is with the proper porting for the vacumm advancer from the carb to the distributor.
I have rebiult my engine, but the carburator is a replacement from one of the dealers here in KSA, and the ported tube for the vacumm advancer is only one.
this port exhibits no vacumm at idling and produces manifold vacumm proportional once the trottle opens up.
I remember from my corolla back home that my advance setting for the 4KU engine is that the ported tube exhibits manifold vacumm in idling and lesser to no vacumm once the trotlle opens up, thus the timing setting for the distributor is 10° BTC vacumm hose removed and pluged, and once un-pluged and reconnected produces 0° or TDC and then advances once the engines starts to rev up due to function that manifold vacumm releases the advance diaprahm.
but for my 4G63 it is the exact opposite, the ported tube exhibits no vacumm at idling and manifold vacumm at trotle up, thus my timing setting is 10° idling and more than 10° when the engine starts to rev up.
if I set it at TDC idling then at rev up it becomes retarded.
If I set my timing advance to TDC on idling and leave it to the vacumm to advance, my timing, then the advance timing is way beyond 25°when the engines revs up beyond 3000 RPM producing a rough engine roar.
secondly the engine is sluggish at this settings and lack the agressiveness during hi-way runs.
follow on question
is the carburator ported port function correct for my 4G63,? where no vacumm at idling and manifold vacumm at trotle up. or is it the other way around, like my corolla?
is there a vacumm valve that reverses no vacumm at idling to full vacumm at idling and vice versa when the trotle opens up?
thank you
AnswerHi, Cezar. I don't have any experience with the particular engine you describe, but I'll go over some more generic items with you.
You're correct to expect vacuum at idle and none off idle for a vacuum advance system. To my knowledge, there is no valve you can purchase and install that will reverse the vacuum.
The first place to start is to look at your old carburetor. It's possible that there was some sort of vacuum bleeder or other valving that would limit the vacuum. It's also possible the carburetor you've installed is not correct for your vehicle. You're likely to be able to figure this out only by comparing with the old carburetor.
