The Stovebolt Site Forums The Shop Area Engine Shop what do i do now?

i FINALLY got a zenith carb, but not the correct one obviously! There's no fitting for my vacuum advance! there's a 'mound' where i believe it should go, by the idle screw.
1. can i drill one myself
2. can a machine shop do this
3. can i use the vacuum tap on the intake manifold where i believe the vacuum wipers would have originally connected or does the vacuum for the VA have to come from the carb?
4. or should i just return it?
thanks
tony

Use the one off the manifold. The original one used ported vacuum so it didn,t advance at idle, but it will work fine. Be shure to remove the hose when setting timing.

tony,

http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=007996#000007


Stuart

thanks much for the help guys.
wrenchbender, reading the link atomarc sent, it appears the advance is to save fuel only and possibly not needed at all? am i understanding this correctly?
i thought the advance was to stop off-idle hesitation.
atomarc/wrenchbender, what about it being hard to get the carb to idle with non-ported vacuum; sounds troublesome.
help...

tony,

I put that link there just for your info. I do not know if you would see a difference ported or not. Wrenchbender feels it will be fine and he has been doing this stuff for a long time. If you have the resources to drill and tap the base, and feel comfortable doing it, that would be an option. Is there some reason these carburetors don't come with a factory port?

The obvious options are to try it as is, and change it yourself if not satisfied..or send it back and try to get a ported carb.

I did some online research several days ago on the function of vacuum advance. It was interesting, although I am not 100% sure I understand it. What I do know is that using a manifold port at an idle, you will have maximum engine vacuum and that means maximum vacuum
advance.

I think Hot Rod Lincoln mentioned in his post that this condition might not allow the engine to return to its normal idle RPM... as my dear old dad used to say "take my advice and suit yourself".


Stuart

atomarc, appreciate the info. like your dads advice :-)

wrenchbender, i hope you didn't take offense. your advice is much appreciated as always. I'm really just tring to get a feel for if i even need the vacuum advance is all. if i don't, then i won't fool with it. i don't have the equipment or knowhow to drill and tap the thing myself anyways.
thanks to all for your help.
tony

hehehe showin me age here...but i wish theyd put the advance on the steerin wheel or handlebars like on the old harleys...or model a's i think it was... *S* then you control the advance... not some computer or mechanical vacuum thingy thats a average deal anyway... that way ya can sit it the way ya want it... how many you ol timers know about retardin it to climb a hill... purty amazin stuff how much lug you could get...and for the goin down or no load condition how much you can advance an engine... of course it all depends on relative humidity, ambient air temperature, and also barometric pressure hehehe... in a short sum up... yeah we dont need no stinkin vacuum advance period... and yeah you can set it at manifold vacuum,,, its all kinda relative to to the purpose ya know..??? anything detroit ever built was built for average use ya know..?? but basically you can tune to what you want to do... and for advance... thats all relative too because it actually needs to be set according to altitude, humidity and temperature also... a settin in the book is the average of all those things...soooooooo dont make to big a deal outta it...*S* rambled enuff... but... i still wish and maybe ill do that...make a manual advance adjustment ya can tune from in the cab... it do make a difference....*S*...

Actually, you do want vacuum advance, to keep the valves, sparkplugs, and engine from overheating under part throttle load. It's all part of the combustion chamber design, and is specific to each engine. This engine was designed to have it. It is not just for fuel economy, it is for proper burn. Manifold vacuum is not appropriate for this engine design, either.

It would be a good idea for you to talk to Carbking about setting up the proper vacuum advance or swapping castings to get it.

No offense taken. I,m still learning too. It,s true you will get a faster idle with manifold vacuum to the advance but you adjust the idle speed acordingly. I wouldn,t modify the carb. About 50% of over the counter carbs aren,t good. If you mess with it they won,t take it back. I wouldn,t run without the advance & believe manifold vacuum will work fine but you will have to try it. Sometimes with excessive advance you might get a surge at just off throttle.