Holley 1900/1901 3-Barrel Carburetor

[1970FuryConv]

I was looking for a small 4 barrel carburetor for mounting on a 1971 small block spread bore intake, 351-2100. I came across the Holley 1900/1901.

The 1st thing that leaps out at me, as the article says, is that it is a 3 barrel carburetor not a 4 barrel carburetor. https://documents.holley.com/streetdemonarticle.pdf

Question: has anyone installed one of these on a factory dual plane intake? How tall a gasket did you have to use to get clearance for the secondary throttle valve to open? Or did you have to use a spacer?

I guess the other question is: what was your experience with a single secondary barrel?

I don’t know how the throttle valves open and Holley carburetor tech support never seems to pick up when I call. I just hold on hold forever. I am concerned that a carburetor like this, particularly if the fat side of the secondary valve opens down, would significantly dampen vacuum signal and affect streetability. I realize that Holley recommends a three-quarter inch height spacer to install this on a spread bore carburetor intake. I don’t like that it raises the position of the carburetor versus the throttle linkage. I'm wondering if you could install it with a shorter gasket.

Thanks for your thoughts, Ben

 

[CBODY67]

The original Holley 3bbl carb was a modified 4150 4bbl with the secondaries hogged out to allow an oblong secondary throttle plate. It was rated at 950cfm, as I recall.

What you reference it the Street Demon carb with its "goggle valve" secondary throttle plate. Holley bought the old Demon Carburetor company, which was drag-race and higher-performance oriented. What is shown is their Street Demon carb, which is a very close reproduction of the old Carter ThermoQuad carb. They've been out for approx 5 years or more, at this time.

It is unique in the secondary side's throttle valve. That configuration allows more total airflow while also fitting onto either a square-bore or spread-bore manifold. Basic calibrations seem to be for a Chevy 350 (as usual), but items similar to the old Carter Strip Kits (metering rods, jets, power valve springs) are available from Holley. Either electric choke or manual choke models. AND their pricing has typically been more friendly that a similar Holley 4175 spread-bore, by observation.

Many YouTube videos, plus some in the Holley website, too.

Just some thoughts,
CBODY67

 

[MacLebaron]

I was looking for a small 4 barrel carburetor for mounting on a 1971 small block spread bore intake, 351-2100. I came across the Holley 1900/1901.

The 1st thing that leaps out at me, as the article says, is that it is a 3 barrel carburetor not a 4 barrel carburetor. https://documents.holley.com/streetdemonarticle.pdf
View attachment 452620
Question: has anyone installed one of these on a factory dual plane intake? How tall a gasket did you have to use to get clearance for the secondary throttle valve to open? Or did you have to use a spacer?

I guess the other question is: what was your experience with a single secondary barrel?

I don’t know how the throttle valves open and Holley carburetor tech support never seems to pick up when I call. I just hold on hold forever. I am concerned that a carburetor like this, particularly if the fat side of the secondary valve opens down, would significantly dampen vacuum signal and affect streetability. I realize that Holley recommends a three-quarter inch height spacer to install this on a spread bore carburetor intake. I don’t like that it raises the position of the carburetor versus the throttle linkage. I'm wondering if you could install it with a shorter gasket.

Thanks for your thoughts, Ben

In addition to what CBody67 has already said Holley also made a 1050 cfm version of their original 3-barrel carburetor. The only difference was the 1050 just had straight tubes without any boosters on the secondary side. These were actually the precursor to the Dominator carburetors.
Plus, some of the dealers like Baldwin-Motion, Nickey Chevrolet, etc. used these carbs on their hotrods. Just thought somebody may be interested to know this. I actually have one of the 1050 carburetors.

 

[1970FuryConv]

@CBODY67

So Willis
It looks like the primary bores in a factory spread bore intake have a much wider separation than the Demon. Would you use this on a factory intake or would the narrow gap between the bores and the gasket/adapter required to compensate mess up the vacuum signal and rob the carb of some of it's crisp throttle response? Thanks, Ben

 

[Big_John]

To use that carb, or anything besides a spread bore carb on that manifold, you'll need an adapter.

Per the Holley site "This model of carburetor has the square bore flange bolt pattern. It can replace Holley, Edelbrock, Carter AFB, and Autolite style carburetors with 5 3/16" x 5 5/8" bolt pattern. If you have a spreadbore style intake manifold, you will need an adapter to install this carburetor. Similar to the Mr. Gasket #1932."

IMHO, any performance gains from the carb with that manifold with an adapter are going to be negligible at best, probably negative.

 

[1970FuryConv]

IMHO, any performance gains from the carb with that manifold with an adapter are going to be negligible at best, probably negative.

I agree 100% Time to sell that 3512100 manifold to someone who is building a 71 340 for stock restoration. Maybe on FEBO. I'm having it cleaned up at NAPA. Maybe I can get some good money for it.