I have a 1976 f100 with a stock 390. I use it mostly for riding around and hauling wood. It has a 2 barrel intake and carb. I want to put a 4 barrel intake and carb on it, a few people have told me to just put an adapter plate on. I was wondering what would be best.

 

If emissions exempt, first install headers, dual exhaust, and free flowing mufflers. You'll feel added HP and tq.

... then work on the intake side with an Edelbrock Performer or Performer RPM topped by 600 to 650 cfm carb with vacuum secondaries.

2v to 4V adapters suck... don't do it.

 

I've got the dual exhaust and free flowing mufflers taken care of. Next I'll have to check out about getting some headers. Along with the new intake. Thanks HIOSILVER!

 

Then I suggest Sanderson 3/4-length headers (PN FF427)... way easier to install than long tubes. They cost a little more but very much worth less headaches.

 

If you get into the intake manifold on a 390, plan on going all the way down to the block and replacing the head gaskets as well. Once you have the intake off, it's only removing the power steering pump and the exhaust pipe to manifold bolts away from the heads coming off easily. May add a couple hours of work, but you would kick yourself later if your head gasket failed after being so close installing the intake. Remember that the 390 intake requires that you already removed the rockers and push rods, so you're almost down to a short block as it is.

You don't have to do it, but I would suggest removing the water pump to make locating the intake onto the engine a little easier. The seal at the front and rear of the engine where the cylinder head, block and intake all come together is a real tricky one to prevent from leaking. It's also the source of most FE engine leaks, particularly at the rear. If you have to wiggle the intake onto the small hose between the intake and water pump, while also trying to drop the intake on the engine precisely so as to get the best seal, there is a better chance than not that you'll have problems. The FE/390 intake is a tricky one to install, so take the time to get everything out of your way and do it right.

Also, dry fit the intake before installing just to be sure it fits properly. If the block was machined, or if the intake was machined for another engine, they may not mate up right and you could have all kinds of problems.