Ok, my 302 originally came with a 2bbl carb and intake. I found an original 4bbl intake for the 302 and purchased a Holley 600 CFM electric choke carb. All I did is bolt this on and did a little adjusting to the carb. Still seems to run a little rough. Is it possible to just bolt on the 4bbl intake and carb without changing anything else in the motor? Just curious if I will need to do anything else. It is just a casual driver but wanted a little more pep when I felt like getting on it.

 

There is no such thing as a bolt-on aftermarket carb. It's likely you'll need to do some moderate tuning to get that carb to run properly for you, especially since it's larger than ideal for your motor.

First thing I'd check, though, is the timing. What did you set it at after you put everything back together? What's the total mechanical advance?

 

I did not check any timing yet. I will do that. All I did was adjust the mixture screws a little. Would it just be best to leave the original 2bbl carb and intake on it since you mentioned that it is larger than ideal for the motor? It should not hurt the motor, correct?

 

It won't hurt anything unless it's stupid rich and washing oil off the cylinder walls, but that's tune related, not intake related. Hack you checked for vacuum leaks? With it running spray some brake cleaner along the edge of the manifold where it mates to the heads, if the idle changes then you have a vacuum leak there.

 

First off, yes it is possible to bolt on an aftermarket 4bbl carb and make NO other mods or adjustments to your engine. however you may/most definitly absolutly nececesarily must will have to make adjustments to the carb. when you say the car is running poor what does that mean. at idle, off idle, at cruise? your carb is on the verge of too big for your engine, if it has vacuum secendaries you can get away with it more becase the vacuume tends to only open the secs as much as you need them. holley makes a 465cfm o.e.m replacment carb for sb fords. I don't like them because I think the casting looks low quality so I have never used them. another opeion is a 480cfm autolite 4100 or 500cfm edelbrock. to my knowlege holley does not make a decent 500cfm carb. but I have heard good things about the 570 street avenger carbs. after instalation and setting the idle mixture and speed for the highest vacuum. let us know how it is running poorly (i.s. hesitation, bogging, surging, stalling, etc.) and where in the power band (i.e. at what rps) it is doing it. then we can maybe help you a little more. also keep in mind though it is possible to bolt on an intake and carb you can get significantly more power gains from making minor adjustments to your timing and other things. but you should be able to not have to if everything was working correctly before. hope this helps.
Kip

 

My concern is that you likely removed and replaced the distributor while changing the intake and didn't time the engine afterwards. This means that, unless you're the luckiest sob on the planet, your timing has changed. Small changes in timing can drastically affect engine performance. Start there, then worry about vacuum leaks and carb tune. If you're timing's not right, you're not going to be able to diagnose anything else very well.