I don't know what the reasoning is behind the high IFR. Part of me thinks its just monkey see monkey do engineering.
Along with 4-5-6 emulsions...
I don't know what the reasoning is behind the high IFR. Part of me thinks its just monkey see monkey do engineering.
Along with 4-5-6 emulsions...
FWIW.... That is 'for real' useful engineering, that has been going on for over 60 years, at least. Weber had a lot of different emulsion tube patterns for their performance carbs by the 60's... the DCOE sidedrafts that I messed with in the early 80's had at least 10 different emulsion tube patterns to choose from. Changing them makes a big difference in how the carb mixes the mains AFR up through the RPM range. See here and the old emulsion tube page that shows 14 different ones:Along with 4-5-6 emulsions...
FWIW.... That is 'for real' useful engineering, that has been going on for over 60 years, at least. Weber had a lot of different emulsion tube patterns for their performance carbs by the 60's... the DCOE sidedrafts that I messed with in the early 80's had at least 10 different emulsion tube patterns to choose from. Changing them makes a big difference in how the carb mixes the mains AFR up through the RPM range. See here and the old emulsion tube page that shows 14 different ones:
TheSamba.com :: Performance/Engines/Transmissions - View topic - Emulsion Tube Break Down.. F-7's/F-11's
I find it encouraging that the American hot rod market carbs finally caught up to this idea.
I know the feeling.... My advice to the younguns is get your stuff done by age 55...View attachment 1715200105 View attachment 1715200106
(275) 10.5 heads up build. Age and knee condition have caused a near stop but I will get moving. I could finish the engine in three hours and I have the transmission almost done
LAMO! Danm true!I know the feeling.... My advice to the younguns is get your stuff done by age 55...
The higher locations allows air to get on the other side of the IFR when manifold vac is low enough.Interesting.... What do you guys think causes this? Maybe too much air above the emulsion holes? (Oops the idles may not have a real 'tube'..)Or something unstable in the airstream higher up? Just curious....
Does seem that way. I've seen a few of these builders occassionaly post explanations. Maybe I'll find them and start a thread just on that.I don't know what the reasoning is behind the high IFR. Part of me thinks its just monkey see monkey do engineering.
One use of a high idle position is providing a shot of extra fuel from the idle up-well. When the throttle is opened wide flow changes direction and goes from the idle upwell into the mainwell. This seems to be the reason secondary metering plates have the restriction up high. Maybe you have a situation where that extra shot is just what is needed. Mark Whitner's mentioned this, and Tuner explains it in post #23 here: Secondary metering plate vs Secondary Metering Block?I have one of the queer applications because every time I lower the IFR the car doesn't idle nearly as well. I have spent enough time on it that I gave up and moved them back up and let it go. Everyone I know moves them down, but for whatever reason, mine want to be up.
I like pictures.The higher locations allows air to get on the other side of the IFR when manifold vac is low enough.
Flow tested a few carbs the other day, thought I'd share my findings. The Ultra HP carbs are the older design from around 2005 they are no longer sold.
Holley Ultra HP 750 part#80675
1.375 venturi / 1.687 base plate
819 cfm
Holley Ultra HP 950 part#80676
1.375 venturi / 1.75 base plate
825 cfm
Holley 850 "old style main body" part# 9380
Choke horn milled off, slabbed throttle shafts, annular boosters
1.58 venturi / 1.75 base plate
945 cfm
I'll be replacing the 1.375 main body of the 950 with a 1.45 main body and retesting in the coming weeks.
This test backed my suspicions about the true flow of the 950, as it was only able to make about 5 more HP than the 750 on an upper 500 HP 360 motor. 950 my *** lol, I know Holley took a lot of **** over that carb and the new XP950 has a 1.6 venturi because of it.
I hear ya. Always a gaggle of “know it all you don’t know **** don’t you read the internet and car rags!”Whooah buddy....you can't just throw out cold hard facts that disrupt the "bigger is always better" crowed, LOL!
For some reason whenever I tell folks that I run a home built "750" Holley I get SOOOO much crap from the bigger is better folks (sure I would love a bigger carb, but I don't want to drop $1000 for a few hundredths of a second)....Kudos to you sir.
Flow tested a few carbs the other day, thought I'd share my findings. The Ultra HP carbs are the older design from around 2005 they are no longer sold.
Holley Ultra HP 750 part#80675
1.375 venturi / 1.687 base plate
819 cfm
Holley Ultra HP 950 part#80676
1.375 venturi / 1.75 base plate
825 cfm
Holley 850 "old style main body" part# 9380
Choke horn milled off, slabbed throttle shafts, annular boosters
1.58 venturi / 1.75 base plate
945 cfm
I'll be replacing the 1.375 main body of the 950 with a 1.45 main body and retesting in the coming weeks.
This test backed my suspicions about the true flow of the 950, as it was only able to make about 5 more HP than the 750 on an upper 500 HP 360 motor. 950 my *** lol, I know Holley took a lot of **** over that carb and the new XP950 has a 1.6 venturi because of it.
I suspect the blade angle was goofy on the 950. Maybe opening too far?
My 950 flows 1011cfm after adjusting blade opening...
What are the venturi and base plate bore diameters of your 950? Is it an HP Holley or different brand carb? Part #?I suspect the blade angle was goofy on the 950. Maybe opening too far?
My 950 flows 1011cfm after adjusting blade opening...
I'll give that a try when I get the 1.45 main body carb on the bench.I understand. But you will find they flow better when the throttle blade is arked over the shaft about 7° or so. Depending upon the shaft width, of coarse.
Do the primaries and secondaries separately. vary throttle opening and watch the manometer.
So you're opening the throttle blade to about 7° before 90° ?
I have used the China base plates, and they are poor quality. The last one I used had different length transition slots, and the vacuum port nipples were so crooked they looked as if Ray Charles put them in with his feet. I won't use the China knock off base plates anymore, too many issues to fix for little money saved.
The engineers 50 or 60 years ago had the holley style carbs right.
Anyone ever flowed a 650 or 750 Mighty Demon?
Thanks for the info. The Mighty Demon I have came with downlegs, no choke and 1.69 throttle plate.I did a 650 a while back for a rules class that had to maintain the OE look. So the air horn had to say on, but the choke valve was removed. Flowed 709 that way, otherwise stock.
I swapped out the OE boosters for AED dog legs, 850 base plate = 792cfm
I have heard of people swapping boosters and pictures coming up 40-50hp on the dyno.