Holley carb woes

[427Fastback]

Up until a couple years ago we had "air care" here.I drilled lots of butterflys for air care and I have drilled lots to get the mixture screws to work again..I have never had to undo what I did not have I ever had a engine idle to high because of it..I see no down side to it and as Holley does it in the factory on numerous carbs I don't see it as a last resort...We all have our tricks......JMO

[Drew Pojedinec]

IMG_0652 by Drew Pojedinec, on Flickr

IMG_0656 by Drew Pojedinec, on Flickr


Royce, I'd download the images so you can zoom in, but the calibration is there.
If you need me to scan anything, let me know.
Other thought.... it mentions that List 1848 is a suitable replacement, if you can't make the 1619 work, that would be a decent alternative.

[Royce]

Thanks Drew  That is very helpful.
.I have obtained another 1619 parts carb . I will look it over check the specs and see if installing that primary metering block cures the problems.

[Drew Pojedinec]

IMG_0885 by Drew Pojedinec, on Flickr

IMG_0887 by Drew Pojedinec, on Flickr

IMG_0891 by Drew Pojedinec, on Flickr

I tinkered with this carb for about 5-6 hours.
I got it to idle smoothly in gear at 450rpms on my 390.
There is a slight haze, tho it's 10:30pm, so hard to see to be honest.  Will play with that more in the morning.
I find the primary boosters like to come on SUPER early.

Last photo.... the two core 1619's I have laying about all have the holes drilled above the throttle plates.  On yours they are soldered shut.
I scratched my head about this for a bit.
Main air bleed in the main body is claimed to be .120, I measured it at .109
Typically on a modern carburetor of this venturi size the main air bleed would be .031 for the primaries and around .026-.028 on the secondaries.

Now, a lil carb pressure talkie talk.....
This carb has no lower emulsion bleed, just an upper .028, no angle channel bleed, but a bleed between the idle well and main well @ .028.  This is common on early 4150's and I use a comparable setup on my 2x4's.
However, the large main air bleed puts a ton of air into the main well which pushes fuel out of the boosters.  I think the drilled holes in the venturi above the throttle plates reduce the signal that the boosters see... makes sense, as some of the vacuum will be bleeding out of these holes instead of pulling at the boosters, this combined with the large main air bleed would have the boosters come online at a normal time, but of course, yours are soldered shut.
Yes yes, what does this have to do with idle?  Well there are ALWAYS vapors coming from the boosters, as there is always flow through via the main air bleed, even if all holes are above float level.  Kinda like putting an air gun above a puddle.... it'll still carry vapor/fluid with it.
These carbs do not have emulsion tubes, maybe this was a Holley experiment on over emulsifying via bleed air pressure, and they drilled the bypass holes to delay main circuit activation.
So a solution to try, I could either drill out the old holes in the venturi, or I can drill and tap the main air bleed and install a smaller size, I'll start with .031 and go from there.

Your call Royce, my gut feeling is reducing the main air bleed is the way to go.

[Royce]

Drew,  you are the man.. Do what you think will work best...I noticed those holes.. I figured some previous owner had plugged them. Never have see a carb with holes in that area. As long as it idles cleanly and accelerates smoothly I would be very happy..  It is fascinating that the older Holleys are so much different internally...

[Drew Pojedinec]

Ain't that much different really.  Seems 57-59 they tried out a lot of ideas.  By the time 1960-61 rolled around they settled on one particular way to do things.

Anyway here is it idling at 11pm around the time I knocked off for the day.
https://www.facebook.com/AirFuelSParkTech/videos/294151977990207/

I notice also that despite being no cracks the baseplate needs to be torqued down very evenly, undoing one carb stud results in a hissing sound and some leaked fuel.
I'm leaving Thursday and may or may not have enough time to finish getting this one where I feel it's perfect.  Worst case scenario I'll snag a baseplate from a different core and try it out.

Lotta little tinkering, swapping butterflies, etc trying to kinda get things to simmer down.  Seems on shutdown I still get some fuel out of one of the transfer slots too, either way I'll get it, be it in the next day or when I get home at the end of August.

[Barry_R]

You see those venturi side holes in some of the old carbs.  Something of an oddball deal for sure.  Never learned for certain, but pretty much has to be what Drew surmises - a signal kill for the mains to serve as a delay.  The side holes disappeared pretty fast as Holley went to more modern (as in 1960s modern...) calibrations.  Somebody probably realized that unfiltered air and accumulated dirt and deposits would plug those holes up in service and render the things useless.