View Full Version : holley 2 brl

04-22-2012, 12:24 PM
I just bought a 1991 16. it has a holley 2brl on a 5.0 ford that needs work. any sugestions? it seems to run fine just stumbles coming off idle. like the acc pumps are not working

Dr. David Fleming
04-22-2012, 07:20 PM

Holley 2bbl carbs for performance were generally the 2300 Series which is half of the famous 4150 Holley 4bbl carb. Holley also made a 2200 series carb which is entirely different non performance carb.

Story goes that Smokey Yunick the famous engine tuner from Daytona Beach developed the 4150 for racing and that Holley picked up the design. 2300 Series two barrel is half of the 4bbl.

First you got to figure what series carb it is.

Most "off idle stumble" is from the carb going lean - too much air and not enough fuel. Too much fuel will blow black smoke out the exhaust and also cause a different acceleration stubmle.

The accelerator pump system on the carburator is generally the first tuning circuit on the carb to examine. This is a small mechanical pump that squirts the gasoline into the engine. This system has a rubber diaphram inside the pump chamber that can rupture, and also a couple of check valves to flow the gas in and out that can give problems. The input valve is a small rubber flap that is replacable the output valve is a ball bearing or brass needle that can get hung up on dirt or get lost.

The 2300 Series has a number of performance parts for the accelerator pump system. Different cams and on some carbs a larger pump chamber. Check Carburators Unlimited they have most of this stuff for under $50. On a functional carb you should be able to look into the carb throat, work the throttle and see the fuel stream squirt into the barrels.

Holley also had a power enrichment system called the "power valve" that basically increased the fuel flow under load. These were also rubber diaphram parts that if not working would allow the engine to go lean. This is more difficult to inspect. Power valve controls the fuel supply under full throttle.

Fuel supply - the entire carburator can go lean if for some reason the supply to the carb is insufficient - fuel filter and pump output are considerations here.

Holley carbs are fairly easy to pull down and repair if you take your time and know what you are doing. Most can be repaired with a repair kit and a good cleaning in lacquer thinner. I would avoid adjusting things you do not understand. The float in some carburators is adjustable from the outside with the engine running. Some require bending and this can be tricky. Some of the brass soldered floats can develop small leaks and then become sinker floats with a small amount of gas inside the float - test by shaking. The plastic floats can do weird things if chemicals attack the plastic sometimes they absorb this and do not float properly. This upsets the fuel supply to the carb.

04-22-2012, 11:54 PM
Nice write up Dr. D

I too think the off idle stumble would be from being too lean but because of varnishing in the pilot jets, off idle circuit and the jets with the smallest I.D.
Ethanol varnishes up pretty nasty and it also eats rubber so after looking at the pilots, check the rubber diaphrams as Dr. D wrote.

joseph m. hahnl
04-23-2012, 09:49 PM
Holly are notorious for blown powervalves.

04-23-2012, 11:25 PM
Newer Holley carbs have a built-in check valve to prevent an engine intake backfire from blowing-out the carb's power valve.

Jegs, & other speed shops , sell a Holley check valve retrofit kit to add this backfire check valve in older Holley carbs.
It's an easy install & works very well.
I have installed a few in Holley carb's metering blocks with great results.

Holley power valves & acceleration pump diaphrams dry-out over winter storage and the valve's rubber diaphram then cracks & fails.

Ethanol also attacks these rubber Holley power valves & acceleration pump diaphrams.

This is why I prefer the Edelbrock/ Webber performer AFB/AVS four barrel Carter carb clones.
These carbs have no rubber power valve & acceleration pump diaphrams.
Instead they use power circuit main jet enrichment stepped rods & pistons; along with a plunger style acceleration pumps.

04-27-2012, 11:21 AM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]
what carb unlimited are you referring to

Just Say N20
04-27-2012, 12:08 PM

As you can see, for some reason the QUOTE function does not work correctly on the site.

Probably the easiest work around is to highlight the text that you want to refer to, copy it and then paste it in your response.

Then the original poster will know you are asking them something about their post.

Just Say N20
04-27-2012, 12:10 PM
what carb unlimited are you referring to

You can make it work, but it is a bit of a pain.

04-27-2012, 03:28 PM
thanks all you guys for the info. should i just trash the 2 brl, change out the intake and go with a 4brl? what might i loose in fuel consumption vs hp and mph? thanks again for the advice

04-27-2012, 03:45 PM
An intake and a good carb will run about 700-900 bucks. It will be money well spent. Fuel consumption will go up a little if your into the secondaries all the time but the fun factor will be greater also maybe a mph or so Just make sure the intake and carb will fit under the hatch I just got a weiand stealth intake for my 302 was very reasonable at summit or jegs and had Holley 4 bbl rebuilt. The new stealth was an inch higher than the old stealth so watch the height for a 16. Was not an issue in my hornet

04-27-2012, 05:01 PM
mattboy, what gains will i get with the 4brl and what size carb would be good?

04-28-2012, 06:35 AM
You have another option I had the same year 302 16, toss the stock two barrel for a 500cfm two barrel. I did it and gained nearly a mile an hour, I had no stumble with either the old 350 or the 500. It is a simple bolt on the 500 externally is identical to the 350, the newer carb will have the updated power valve.


04-28-2012, 11:26 AM
I think the base 5.0 was in the 185 ish HP range and the HO or higher model was around 200-210 ish HP range. I would think a good intake and a 500-600 4bbl would show the same increase. The highest rating for the 5.0 was around 225 HP in the marine version

04-28-2012, 04:48 PM
of the 3 options, what do you guys think ,my carb is ethanol damaged, not sure if it is rebuildable / cost wise
1 buy a new 300cfm and install a larger acc pump
2 buy a 500 cfm
3 buy a intake and 500 cfm 4 brl
i am a porsche mechanic so the work is easy
Thanks for all your help

joseph m. hahnl
04-28-2012, 06:15 PM
You Know you'll never be happy with out the 4 barrel and manifold:yes:. There will always be that what if ?,if you don't :confused:.

04-28-2012, 06:26 PM
I would think you could rebuild it just fine, and that would be your cheapest option by far unless you really want to add power. (Don't know if it'd fit any of your potential ideas on increasing the HP, but on the off-chance it'd help, I have a virtually new 600cfm Holley 4160 for cheap. My guess is one of your 3 options makes more sense instead.)

Dr. David Fleming
04-29-2012, 12:42 AM

Porshe mechanic - come on - 4bbl is the "sine qua non" of performance.

The Holley 4150 was made in increasingly larger sizes from the small 500 to 850 cfm and larger. Some had smaller primary barrels but the big carbs were I believe 1 3/4 throttle plates on all four barrels. Mercruiser swore by them in their Mercury Racing program in the 1990'a until the advent of fuel injection. They got close to 500 hp on one 4150 Holley.

Of course you will have to tune a different carb.

Usually an aftermarket - speed shop Holley Marine carburator is set up with a general jetting program for the average use. This tuning should be fairly close and you could probably use it out of the box and have it run pretty good.

Holley 4bbl uses vacume operated secondary barrels and the engine only really uses them on demand. The engine self opens the rear barrels never opening them beyond the vacume draw in its secondary operating chamber diaphram. Hard to over carburate with this design. Big primary barrels however can cause an intake vacume drop that is significant if the driver pops open the front two barrels and they are too big for the engine. This causes the "bog" or "stumble" from "over lean" you are already complaining about - the condition that the 50cc accellerator pump is designed to cure.

Chrysler and Chevrolet used the 2bbl carbs in triplicate for their 6 pack or tri power setups. Throttle was only connected to the center 2bbl - the outer two opened by vacume on engine demand. I think GM and Chrysler used a smaller 2bbl in the center - outers were 500 cfm and inner was 350 cfm - total was a whopping 1350 cfm. Course the Street Hemi Chrysler used two Carter 4bbl carbs. I am guessing 650 cfm each for about the same 1300 cfm rating for the 425 hp the Chrysler and Chevy put out in 1970.

You probably wouldn't go wrong taking Ghost up on his used 600 cfm carb. 4bbl was standard on any small block Ford performance package.

By the way - somewhere - in someone's garrage is the ultimate exotic Holley 4150 - back in the day of NASCAR racing they came up with a 4bbl that had the rear two barrels opened into one giant oval barrel - the Holley 3bbl - 950 cfm carb. Hot rodders used it on about everything - had a large unusual secondary chamber diaphram and would not open beyond what the engine could use. Interesting carb had one on a 440 Chrysler in 1977 - ran pretty fast and wished I hadn't sold it - just for the novelty of owning such a unique Holley 4150.

04-29-2012, 10:53 AM
I had an original '70 440-6 Road Runner, the inner was 500 and the outer's were 350, pretty sure the tri-power Vette was the same, the Pontiac's used a different thinking altogether and probably worked better than the Mopar or GM setups, I had a '62 Grand Prix with a 389 tripower and it moved that sled surprisngly well

if someone is interested, I have a complete 348-409 tripower setup including intake and a spare set of carbs, I would like to sell it....

04-29-2012, 11:11 AM
If the carb has ethanol damage it might be wise to check the rest of the fuel system. Since this is a new boat to you I would get it running as is with a new or rebuilt 2 bbl like fixx suggested
Better to get get her running then make a list if repairs or improvements are needed