Holley Carb
10-21-15, 08:01 PM
#27
carb whisperer
Yeah I looked at some superchargers last night. The camdens, while easy to install, are VERY expensive. and the eton's are very big and I dunno if they would easily fit on the right side of the engine (M45 might work). The Mazda millinia Miller supercharger might work, but it doesn't look very powerful (I suspect its just the factory kind of helper amount of boost)
I had the chance recently to poke and hold (similar to share and tell) a Q-jet. and its surprisingly similar to the nikki, only spread bore and 750 cfm. From what I've read and been told the Q-jet has issues, at least early models, with warping. You wrote draw through, but couldn't you blow through it with the same ease of blowing through a nikki. Or would the warping GM carb not withstand pressure?
I had the chance recently to poke and hold (similar to share and tell) a Q-jet. and its surprisingly similar to the nikki, only spread bore and 750 cfm. From what I've read and been told the Q-jet has issues, at least early models, with warping. You wrote draw through, but couldn't you blow through it with the same ease of blowing through a nikki. Or would the warping GM carb not withstand pressure?
The air door and rod calibration (and accel pump) design wouldnt work well with air being forced through it.
If it were draw through though, it still works. Its been done many times with great success...
10-21-15, 08:54 PM
#28
Wasn't there some Chevy creation in the early 80's that used a turbo and a Q-jet****? I dunno I wasn't even a glimmer in my father's eye at that point in history 
I started thinking about it, and I've come to the conclusion. Want moderate turbo power just use the nikki; want N/A power do a PP engine and use webbers or some other 2 barrel carb.
Still wanna see someone do it.
*** with some searching its called a Pontiac firebird turbo 301. and its a drawthrough. :P
I started thinking about it, and I've come to the conclusion. Want moderate turbo power just use the nikki; want N/A power do a PP engine and use webbers or some other 2 barrel carb.
Still wanna see someone do it.
*** with some searching its called a Pontiac firebird turbo 301. and its a drawthrough. :P
Last edited by Qingdao; 10-21-15 at 09:03 PM.
10-22-15, 05:13 AM
#29
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Let's analyze the problem.
Holley carbs are designed to run on a multi cylinder engine with multiple cylinders feeding off of each barrel (or rather, each primary and secondary). The vacuum signal to the venturis in the carb is nice and smooth because there's always at least one cylinder sucking air.
Our stock intake manifolds are semi-independent runner - each primary and secondary barrel sees only ONE rotor. At low RPM the vacuum signal is very staccato - suck-stop-suck-stop etc. At high RPM this smooths out.
What happens when you slam a stock Holley on a stock-type intake manifold? You have to richen up the mixture a lot for the engine to run right at low RPM because the vacuum signal sucks. At high RPM the engine will run EXTREMELY rich. You can fix this in two ways - dick around with the air bleeds and jets to correct the fuel curve for operating conditions that Holley never intended... OR... use an intake manifold that allows the barrels to see the vacuum signals from BOTH rotors!
A fellow rotorhead on the Mazspeed forum stuffed an Edelbrock carb on his half bridge ported 12A and the engine didn't want to run past about 6500. At some nameless dude's suggestion ( ) he decided to cut a passageway between the two secondary barrels so they see a smoother vacuum signal. Instant success - the engine no longer choked on excess fuel and it screamed to dizzying RPMs like a bridge port should.
FWIW a 650cfm is just right for a built 13B *if* you keep the manifold independent runner... once you go to a plenum type setup it will be WAY too big. Probably a 390cfm or 450cfm carb would be best. 390cfm double-pumpers are rare as hen's teeth though, they're only good for dual carb setups on small-blocks, and for people racing 2.3l Fords... so not many people want them, so there aren't many around, so finding a used one is difficult (and buying a new one is out of the question!) still looking for my 390 tho!
- PJ (duuh, what if I put my 750cfm vac-sec on my engine and lock out the secondaries, so it's just like a 375cfm two-barrel?)
Holley carbs are designed to run on a multi cylinder engine with multiple cylinders feeding off of each barrel (or rather, each primary and secondary). The vacuum signal to the venturis in the carb is nice and smooth because there's always at least one cylinder sucking air.
Our stock intake manifolds are semi-independent runner - each primary and secondary barrel sees only ONE rotor. At low RPM the vacuum signal is very staccato - suck-stop-suck-stop etc. At high RPM this smooths out.
What happens when you slam a stock Holley on a stock-type intake manifold? You have to richen up the mixture a lot for the engine to run right at low RPM because the vacuum signal sucks. At high RPM the engine will run EXTREMELY rich. You can fix this in two ways - dick around with the air bleeds and jets to correct the fuel curve for operating conditions that Holley never intended... OR... use an intake manifold that allows the barrels to see the vacuum signals from BOTH rotors!
A fellow rotorhead on the Mazspeed forum stuffed an Edelbrock carb on his half bridge ported 12A and the engine didn't want to run past about 6500. At some nameless dude's suggestion (
) he decided to cut a passageway between the two secondary barrels so they see a smoother vacuum signal. Instant success - the engine no longer choked on excess fuel and it screamed to dizzying RPMs like a bridge port should.FWIW a 650cfm is just right for a built 13B *if* you keep the manifold independent runner... once you go to a plenum type setup it will be WAY too big. Probably a 390cfm or 450cfm carb would be best. 390cfm double-pumpers are rare as hen's teeth though, they're only good for dual carb setups on small-blocks, and for people racing 2.3l Fords... so not many people want them, so there aren't many around, so finding a used one is difficult (and buying a new one is out of the question!) still looking for my 390 tho!
- PJ (duuh, what if I put my 750cfm vac-sec on my engine and lock out the secondaries, so it's just like a 375cfm two-barrel?)
and yeah, if you go holley on a 12a try to stay under 450cfm =P. Asking for more, you might as well get a 13b and turbo it for the desired horsepower.
10-22-15, 05:30 AM
#30
carb whisperer
Wasn't there some Chevy creation in the early 80's that used a turbo and a Q-jet****? I dunno I wasn't even a glimmer in my father's eye at that point in history
I started thinking about it, and I've come to the conclusion. Want moderate turbo power just use the nikki; want N/A power do a PP engine and use webbers or some other 2 barrel carb.
Still wanna see someone do it.
*** with some searching its called a Pontiac firebird turbo 301. and its a drawthrough. :P
I started thinking about it, and I've come to the conclusion. Want moderate turbo power just use the nikki; want N/A power do a PP engine and use webbers or some other 2 barrel carb.
Still wanna see someone do it.
*** with some searching its called a Pontiac firebird turbo 301. and its a drawthrough. :P
Not a qjet, but :http://detroitdemigod.deviantart.com...cket-204694751
215 ci turbo v8! And it was water/meth injected. in 1962, lol.
Last edited by wankel=awesome; 10-22-15 at 05:39 AM.
11-24-19, 10:55 AM
#31
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What adaptor plate use on 12a stock intake for holley
[QUOTE=Jeff20B;8752299]I like where peejay mentioned to cut a channel connecting both secondary barrels. I have a Holley carb adaptor to fit stock 12A and 13B manifolds with a channel connecting both primaries. What the part number for Holley adaptor thanks Kyle
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