Best 4 barrel for 302 on a 74? I recently bought this Bronco and it lacks power and am thinking of upgrading to 4 barrel. What model should I go with?

[JoefromBC]

As stated previously, my “new” 74 Bronco is lacking power and runs poorly and was thinking of upgrading to a 4 barrel carb. Any advice on what 4 barrel I should go with?

 

[DirtDonk]

I need to review what you said before, but are you sure a different carburetor is going to be enough to help? Did you discuss other options in your other threads?
I ran four different carburetors, five including the original, and none of them had a large increase in overall power. I liked the four barrels better, and they seemed more versatile, but adding a lot of power they did not.
A little bit, yes. But they didn’t set the world on fire.

Your stock engine had probably 145 hp or so. You need to create a more powerful package to make a big difference. Carburetor, camshaft, exhaust, and maybe even cylinder heads.
Or you can make a big difference by lowering the gear ratio.
What are your differential gear ratios, and what is your tire size?

 

[bmc69]

What 4-barrel you go with depends on what other mods (cam change, heads, headers, etc) you do to make any use of the carb change. Carb change alone does almost nothing.

 

[gnpenning]

A poorly running motor on a 46 year old vehicle that was low on hp from the factory can be caused by many things. Yes it could need a carb overhaul, but what condition is the motor and ignition system in? What do you mean by running poorly

Tire size and gear ratio make a huge difference in performance. If you are running 35 with the stock gear ratio it will be lacking in power.

The 2100 series carb is a great carb for a stock to very mild motor.

Paul and you mentioned another thread, maybe it will answer a couple of my questions??

To answer your question either a 4100 series or Quadrajet for both in and off road for on road only your options open up.

 

[Speedrdr]

All REALLY good advice ^^^^^. Too many things will work in concert to develop any significant HP. The 4-bbl carb needs to be on an appropriate designed intake. And even if you don’t ‘heat up’ the camshaft, you really do need to improve the airflow in the heads. All the extra fuel delivery in the world won’t help build HP unless you’re flowing enough air n for it to mix with and combust. Otherwise you’re wasting (in my opinion) fuel and not realizing noticeable gains. But that’s just me and what I’ve been through a couple of times.

Randy

 

[B RON CO]

Hi, start with a compression test. If the engine is worn out a carb and tune up won't help you. Good luck

 

[Lawndart]

I personally like a 4bbl carb.
There was a recent thread - https://classicbroncos.com/forums/threads/intake-and-carb.316600/
As I said in the thread - I played around with a couple combinations; very happy with a 60's iron FoMoCo 4bbl intake and a 390 CFM Holley. I would love a FoMoCo aluminum intake, but have not found one.
Mine is not a garage queen and sees many types of driving (rural, urban, highway, camping) every year and I average a little over 8000 miles per year.
I think 400-450cfm is the best size.

As stated above, you may need a quick tune-up and should be done even if you do not go 4bbl. The stock timing settings will not thrill anyone.
A good set of plug wires, new plugs, confirming the vacuum advance and weighted advances are working and setting initial timing to around 10deg BTDC and confirming good manifold vacuum at idle will be a decent baseline.

 

[nvrstuk]

SOOOooo many variables. Is it still a stock '74 smog special???

You need airflow but without a cam, heads, exhaust, intake you won't gain much hp. Little more rpm but not that much hp.

On a totally stock '69 of my Dad's about 100 yrs ago I talked him into dual exhaust, new set of Ford heads, a new 4bbl manifold, 4 bbl carb and his mileage stayed the same (14mpg) but instead of his engine being dead at 50-52mph in 2nd gear with stock tires, 3.5 gears and 3 speed he could wind it out to 70mph. He couldn't believe it.

AIR in and AIR out equals noticeable power increase

 

[jamesroney]

I personally like a 4bbl carb.
There was a recent thread - https://classicbroncos.com/forums/threads/intake-and-carb.316600/
As I said in the thread - I played around with a couple combinations; very happy with a 60's iron FoMoCo 4bbl intake and a 390 CFM Holley. I would love a FoMoCo aluminum intake, but have not found one.
Mine is not a garage queen and sees many types of driving (rural, urban, highway, camping) every year and I average a little over 8000 miles per year.
I think 400-450cfm is the best size.

As stated above, you may need a quick tune-up and should be done even if you do not go 4bbl. The stock timing settings will not thrill anyone.
A good set of plug wires, new plugs, confirming the vacuum advance and weighted advances are working and setting initial timing to around 10deg BTDC and confirming good manifold vacuum at idle will be a decent baseline.

The Autolite 2100 carburetor has a wide variety of CFM capabilities. The Bronco 2100 with the 1.08 Venturi is rated for 287 CFM. But the 2100 with the 1.33 venturi was available on a 390 and rated for 424 CFM. The 429 was also available with the 2bbl.

So your 2bbl CARB can provide plenty of flow. But it doesn't matter what size your carburetor flows if your engine is breathing thru a straw. That's why @nvrstuk is 100% correct. So many variables.

 

[nvrstuk]

SOOOooo many variables. Is it still a stock '74 smog special???

You need airflow but without a cam, heads, exhaust, intake you won't gain much hp. Little more rpm but not that much hp.

On a totally stock '69 of my Dad's about 100 yrs ago I talked him into dual exhaust, new set of Ford heads, a new 4bbl manifold, 4 bbl carb and his mileage stayed the same (14mpg) but instead of his engine being dead at 50-52mph in 2nd gear with stock tires, 3.5 gears and 3 speed he could wind it out to 70mph. He couldn't believe it.

AIR in and AIR out equals noticeable power increase

I forgot to mention that my '68, 289ci could smoke his '69 302. I got much better mileage than he did and with so much more power he was starting to believe his kid - the hot rodder! lol

It sure was fun driving around BC together in our Broncos with small alum boats on top fly fishing for weeks & months at a time.

 

[Broncobowsher]

As stated previously, my “new” 74 Bronco is lacking power and runs poorly and was thinking of upgrading to a 4 barrel carb. Any advice on what 4 barrel I should go with?

Looks like this is your first post, which "as stated previously" comment are you referring to?
Quite often the lacking power isn't actually the engine lacking power, but the gearing is not matched to the tire size. At which point any engine will feel like a turd.