Hello just rebuilt the carb on my 67-A-100 ,1 bbl holley 3398 ,ran it but it had a lean surge under light load,then I rememberd that I had leaned it out with a #55 jet when this carb was on our 74 scamp,had to in order to pass our local emissions test.I replaced the #55 with a #58 now it runs great (a little too good when cold,with no choke) .Does any one know what the original jet size would have been ,I think it may have been a #57..is this correct ? thanks .... Dee...

The original jet in your Holley model 1920 type 3398 would probably have been a 57, yes, but one jet size will not generally make the difference between "needs the choke and gets good gas mileage" and "doesn't need the choke and gets poor gas mileage".

I've posted before about a Holley 1920 I once had on my '65 that exhibited strange behavior: The engine ran very well and had fine power, but was suspiciously easy to start and drive from cold (zero choke required, just hop in, turn the key and drive off without any stalling or gasping...even with the choke disconnected!) and the car was getting under 10 mpg. Turned out the brass seat ring that retains the power valve check ball, had fallen out of the metering block. Result was that the power valve was always WIDE open. I put the metering valve back together and restaked the seat ring, and things went back to normal (20mpg, choke and careful cold driving required). That metering block inside the Holley 1920 has all kinds of tiny passages and check balls that can make problems without any outward signs...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan.I checked it out again ,and all looks well.The float level is not high and the power valve ball is in place and sealing.will run it to get an idea on milage.If the original jet is a 57 then the 58 should be fine as I live at sea level and run a cold air hose to the filter,long reach plugs and have 2 1/4 exhaust front to back.did'nt know if the original jet was indeed a 55 and the 58 was masking another problem.This engine is a 74 and when i bought the van it was running on 4 cyl due to tight valves.rebuilt the head and replaced the timing chain.it's run great for the last 2 years but always had a choppy idle.I run my valves on the tight side and attributed some of the rough idle to that.got tired of the base to main body screws coming loose on the Carter and decided on the holley's one piece body.I've gone back to factory specs on the valves and run an early steel pvc valve(later plastic one had larger hole) and manifold vacuum to the distributor.was getting 22-24mpg (imp)highway before.(4200lbs,833OD,3.91 ) have to see now.The thing idles so much better now,it scared me ..lol ..thanks for listening ..

I just tore down the OEM carb on my 'beater valiant project'...the Holley 1920 had a #56 jet in it and looks like she's never been opened in her life...

I just laid my hands on a 1966 1920 and haven't opened it up yet. It's interesting to see the change in venturi boosters over the years...


-D.Idiot

Thanks Duster.took the van out this weekend and without a proper milage check, things seemed on par with before.will try a #57 for fun anyway. thanks Dan and Duster........Dee......

Manifold vacuum to the distributor will make your vacuum advance work improperly. Hook the vacuum advance back up to the proper port on the carb.

...except on those applications intended for the distributor vacuum advance to see manifold vacuum!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.