My friend buys a 750 Vacuum secondary carb... ok so we open it up to jet it... and we find...

THIS!!!!!!!!!!!

 

Thats a metering plate. ALot of VS carbs have that.

 

A metering plate? but wheres the jets? how do i change the amount of fuel going into the venturies when the secondaries open? My other 750VS carb doesnt have that thing, it has a metering block...

what should I do?

 

If you need to adjust the secondaries, either drill out the metering plate or install the conversion kit.

 

now were getting somwhere... whats the conversion kit?

 

it basically allows you to put a metering block like what is on the primary side, onto the secondary side so you can adjust fuel for the secondaries.
i think its like fifty bucks through summit.


adam

 

the 4160 holley. you can either use different plates for tuning it, or get the conversioin kit the others were talking about.

I prefer having jets in the rear, but the plate system is funcional.

 

<b>but the plate system is funcional.</b>

ok so does this PLATE thing I have, have a number so i can tell what Jet Size worth of fuel it will be adding when the secondaries open up?

 

I have the same carb. I also was thinking of getting the conversion kit.

 

"4160 to 4150 Conversion Kit", Summit p/n HLY-34-6, $39.95 (add "S" suffix if you want "shiny" rather than chromate finish).

"Holley Jet Assortment Pack", Summit p/n HLY-36-181, 2 ea #64 to #99 jets, $37.95.

 

Don't bother changing the plates, if you really have to tune it the block conversion is worth it.

But, get a good ways into tuning it first. A good lot of the time the stock plate is close enough that you don't even have to mess with it.

 

okay well I suppose ill either sell it or try it as is. its going onto a 383 with a blower if i keep it...

i dunno if it will be able to keep up?

 

its called a metering plate... just get the conversion kit which is a metering block which will give you 2 more idles screws and will let you use jets

 

The metering block in the conversion kit does not have idle mixture screws.

 

I didn't think they were called "idle adjustment screws". I thought they were "idle air bleed adjustments". Then again, I don't know squat about them. My idea of "tuning" a Holley is a quick trip under a Bomag hot pavement roller with the vibration turnned on FULL. (Maybe I'll catch the pavers this spring and try that.) By then I'll probably have acquired an improved design doorstop anyway.

BTW - You can "fool" the metering plates a little with secondary float level adjustment, too. Whatever you do to the secondary jets and/or plate orifices, you need to consider the secondary throttle diaphragm spring rate as well. Damn - Carters are just so much more flexible and easier to tune precisely.

 

http://www.holley.com/HiOctn/TechSer...fo/TI-219.html 2nd paragraph, 1st sentence:

"Most Holley Street Performance, O.E. Muscle Car, Competition and Pro-Series HP carburetors utilize idle mixture screws, located on the sides of the primary metering block." (emphasis added)

 

ah, i sold it on ebay for $202. what the heck right?

i already have a good carb anyways...

hehe thanks for the help tho guys.

 

Okay, I bit the bait. I was laughing all the way in, thinking it was going to be something like "The tuner has to have more intelligence than the die casting" or something like that.

I've got quite a few of the older BBCs to run with Holley 4150s and a few Fords with mechanical secondaries, but like I said, I don't stay current on them. I alway understood the old factory 4150s on BBCs had idle air bleed adjustments, not strictly liquid fuel metering (like most real carburetors) or mixture volume controls, as the instructions imply.

Told you I don't know squat about them. I rather like the old updrafts and mechanical injection systems, or EFI, but not much in between. Hell, a fat wick in a jar of gas is about all I can handle some days. That might explain a lot of my tuning issues. Naaaahh.

 

There is a consistent retelling of a myth that on Holley idle mixture screws, "in" is rich, "out" is lean.

Maybe in some time gone by, but not today.

Hey, welcome to the fuky world of old-time technology with new-fangled twists.

"Third generation F-body - the first muscle car with a brain."

Think that'd fly?