He just bought a brand new carb, so lets keep going down that path. I would check the timing. Clean the damper off really good, and then check the timing with the vacuum line to the dist unplugged. After you check/set the timing, then rev the engine with the vacuum line off. The timing mark should move up the scale when you rev the engine.

Then take the vacuum line, and increase the speed of the engine till you feel vacuum on the line with your finger. Then while looking at the damper with the timing light, plug the line into the dist, and then unplug it. Everytime you do this, you should see the timing mark jump up the scale.

 

one backfire on start-up with that holley could blow out the pwr vlve and cause the problem described

 

all holleys built since '92 have backfire blowout preventers,I'm sure rebuilds do also

 

wouldn't bet on it...found out hard way last summer, then I bought a motorcraft .....again

 

Motorcraft uses power valves that can and do blow out also.

 

I have run holley carbs for 45+ years and have yet to have a power valve malfuntion
I have however had probly a half dozen with motorcraft
guess the are a lot of people who don't like and or understand the function of a holley carb,I could care less

 

the reason why is the difference in the RPM range that 302's run as apposed to 300's, ford used that size carb on many applications of their small-blocks with great success, as a matter of fact a 600cfm 4v is more suited to the 302 than a 400cfm 2v b/c the secondaries are only in use when the engine wants them

 

As for the carb size calculator (street carb), if you plug in 5500rpm with a 351, you end up with a 475cfm carb...then why did ford trucks on the mid/late '80's come with a 600cfm holley ??? BTW I owned a '87 351 4v stock and it pulled like a *******, not the least bit over-carbed..so I guess that throws that theory out the window eh?

 

A Ford truck with the relatively small 302 V-8 engine NEVER came stock with a 600cfm Holley buddy. In fact, a 302 NEVER left the factory with a 4V; it was always a 2V, and most of them were a small 287cfm carburetor.

Engine cubic inches X Max. RPMs / 3456 = ___cfm carburetor

This formula works assuming that your engine operates at 100% volumetric efficiency. Most stock engines operate at only 85% volumetric efficiency, and a well-built engine is usually around the 90-95% range. In which case you would multiply the end result above by 0.85 (or 0.90 or 0.95) for 85% volumetric efficiency.

As for the 351...well that is a full 51 cubic inches MORE than a 302. And, according to the formula, assuming 100% volumetric efficiency, that would make a 559cfm carburetor IDEAL for the 351 engine running 5500rpm. (How often do you plan on running the engine HIGHER than 5,500 rpms?) Well guess what, no manufacturer I know makes a 559cfm carburetor. BUT, Ford/Motorcraft did have a 600cfm carb already in use for the 5.0 Ford Mustangs during the mid/late '80s, AND the F-Series with the big block 460 V-8 used (only) the 600cfm carburetor as well.

So now you know WHY that carburetor was used.

 

according to the calculator, which is the point I'm questioning, a 351 would need a 475cfm carb...what I'm trying to say is the theory is flawed in such simple form, ask anybody that actually put a 600 on a stock 5l

 

I have ran holleys, edelbrocks,motorcrafts, qaudra jets, on everything from chevys to fords 2barrels and 4 barrels, 500 cfm-750 cfm, stock motors to built motors. and One of my favorite carbureators is the holley 500 cfm 2 barrel, I had one I put on a stock 390, I liked the fact they were easy to get parts for, and with a little knowledge you can tune them to get the performance You want we experimented with different jets, and accelarator pumps until I got the performance and mileage that I wanted, and holley has a really good website with alot of info as to considerations when choosing a carb, I had one complaint about holleys and that was offraod the floats would stick, but now they have a kit to eliminate that issue.

 

I have seen the calculators also, and they are in the theoretical world, while like to stay in the practical real world.

The #1850 Holley 600cfm with manual choke is the cheapest, simplest carb they make, and I have had very good success with them on several 302's. No black smoke, no little dead spots or hesitation, really a pretty boring install, since it drives just like factory, though when you get on it, the engine seems more willing to rev up. The 390 cfm is way more expensive.

The vacuum secondary carbs are more forgiving, since they will automatically size themselves to the engine you put it on. If the engine can't take the full output of the carb, then the secondaries will not open up till it can.

I believe some of the factories also went with the real world theory, since most chevrolets from a 305 up to a 454 came from the factory with a 750cfm or larger quadrajet. It also has a "self sizing feature with the air door on top of the secondaries.

Of course we all know the 302 did come from the factory with a 4bbl, but not in a 80-up pickup. Most of the time Ford did seem to use an oddball cfm rated carb, and a lot of them where in the 500 cfm range. They never used a stock off the shelf Holley carb that I know of, they always modified them to suit what they were doing. They also where jetted very lean. I have a Ford/Holley carb, and it's very close to 600 cfm, but it has #62 jets in the primaries. Most #1850 Holley's come with #66 jets in the primaries.

 

You are correct. NEVER in an '80 and up pickup.

I will agree with that statement. Which is why a 600cfm carburetor WILL WORK with a 302 engine. A 650 double pumper WILL WORK also, although it won't be as efficient.

Thing is, most stock and midly modified 302 truck engines CAN NOT "take the full output" of a 600cfm carburetor, which is why I said that a 600cfm carburetor is too big. Again, it will still work, but you will probably be over-carbureting your engine.

In addition, you will be WASTING GAS and sacrifice throttle response (and low end torque - essential for moving a HEAVY F-Series truck with a little 302) running on the bigger primaries of a 600cfm carburetor, vs. running on smaller primaries on a smaller carburetor.

 

BigDave check to see that you are getting a good stream of fuel upon moving the throtle lever about 1/4 stroke. A lean condition off idle will cause this hesitation. Do this with the engine off looking right down the carb(with a mirror if ya wanta be safe). It should happen almost instantly. If not this is your bog. New or not you could have a bad or stuck accellerator pump check ball or valve, letting fuel back into the carb fuel bowl instead of the air stream.

 

I have a 1986 ford f150. It came with and has in it a 2bbl carb. I want to switch it to a 4bbl carb. What intake manifold should I go with or could I even find one from a used truck and just put it on there or would I have to switch a couple of things as well as the intake manifold. I found a stock 351w intake manifold for $30. Just what else what I have to do or need?