I have seen some adaptors that will allow me to mount a 2 bbl carb to my stock 1 bbl manifold. I have access to a 2bbl carb in good working order. Would bolting the 2bbl onto my six give me any performance gains over the 1 bbl carb, or will the 1 bbl manifold restrict the flow too much? I am gonna add some headers, but a new 4bbl intake and new holly just isn't in the budget right now.

 

The one barrel intake manifold and 2bbl carb will be just like forcing a baseball though a golf ball size hole. If the one barrel runs good, I would just hold out and wait for a 4bbl intake, the 2bbl carb would work good on the 4bbl. intake with a adapter.

 

Thats what i was afraid the response would be. Good point though. Will the headers increase my performance while keeping the 1 bbl?

 

Yes, the headers will increase the performance of your engine with the 1bbl. When you can get the 4bbl intake and bigger carb. is when the headers will really produce for you, because the more air that is coming in the engine, the more air that has to get out of it. Go for the header, it is a good start.

 

Thanks for the advice

 

I put a Holley 2 brl on my stock intake ('79 F150) using an adaptor and it made a HUGE difference. Definitely worthwhile if you can do it! I put on a 4brl intake with the 2 brl adaptor later and it ran better with the stock intake. I don't have the budget for a new 4brl so I'm not using the 4 brl intake but I will bolt it back on when I can.

 

How bad did it hurt your mileage?

 

It didn't lower my mileage at all. In fact, I think it actually raised my mpg by about 1 to 2 on long trips. My around town mileage didn't improve but it definitely didn't drop. Overall, it was an improvement in throttle response, acceleration and overall power. Quite a noticeable change in my case and that was with an engine that had 201,000 miles. If you have the 2 brl carb, go for it, the adaptor was only $35. with shipping when I bought it.

 

Well i have a couple of 2bbl Holleys laying around that probably only need to be cleaned up and rebuilt. Is it definately worth the investment? I saw a couple adapters in a Cliffords catalog, they say you have to drill the holes to mount it to the stock manifold. How difficult was it to drill the holes in the adapter, also what did you do about the smaller hole in the top of the carb mounting surface? Also I heard that EFI manifolds off a newer 300 flow almost as good as headers.

 

It was easy to drill the holes in the adaptor, my truck had an EGR on it so I just pulled the EGR plate off and used that as a template. It worked well. If I remember right, the hole in the adaptor necked down so it fit the stock intake fine. To me, it was well worth the $35 I spent on getting the adaptor to my PO Box. My carb was free, long story, so I just bought a Holley rebuild kit for it. My truck starts easier, runs better, has less "difficult" moments, and has more usable power. Well worth the small monetary and time investment. Biggest problem was remounting the throttle cable bracket to work with the Holley. I cut, bent, and formed some 1/8" steel, drilled some holes and mounted it to the intake with one of the intake/exhaust bolts. It worked well. I don't know if the EFI exhaust manifolds flow as well as headers or not, either one calls for a big money investment, though the EFI manifolds are generally the cheaper route. I put the EFI manifolds on my truck but didn't notice much of an improvement over the stock setup. I used 2 1/2" pipe for a set of true duals but it didn't seem to make much of a difference. HOWEVER, others on this site will say they have noticed a big difference with the EFI setup.

 

I may or may not convert to different manifolds or headers, still deciding on that one. I forgot to ask did you have to add a higher output fuel pump? Or does the stocker provide enough juice? If you did change it out what did you use?

 

I just used the stock pump, I looked everywhere and couldn't find an aftermarket high volume pump. In fact, when I rebuilt the engine, I bought a new pump from NAPA, it was built by Carter (Federal Mogul,??) and it didn't work. So, I put my original 200,000 mile pump back on and I'm still using it. Knock on wood! Of course, I bought another new pump and keep it in my truck as a spare. I don't think I mentioned it before but I used my 2 brl on my open plenum Offy intake with a 4 to 2 brl adaptor, it didn't work as well as the stock intake with my 2 brl. Others will have different experiences though, I am sure.

 

One problem I have had with my 300 is when I am towing a decent sized load up a grade my truck would lose speed conciderably. Sometimes I would have to down shift to maintain what little speed I had with a big load. Do you think converting my 1bbl to a 2bbl will help with the lack of mid-high end power?

 

My best GUESS would be that it would help but who knows for certain until you try it. All I can say is that it made a noticeable difference for me but I don't tow any thing with my truck and the heaviest thing I haul in it is a couple of dirtbikes.

 

I just put in my order for the 2bbl adapter this morning, I am gonna give it a try. Did you have any hood clearance problems after installing the new carb and adapter? Also even though you don't haul or tow really heavy loads did you still feel a difference in power when going up a grade as opposed to the stock set up? Just curious, it would only make sense that it would help.