Hey guys, i need some help. I've read till i'm blue in the face (or maybe RED at this point)...
1978 ford F100, 3 speed standard
Newly rebuilt 300 I6 (4.9)
Offenhauser DP Intake
Edelbrock Performer 500 CFM
Hedman Headers (with Raso heat plate)

The question is, how is the carb supposed to be orientated? I've seen about every post on this, but it's still unclear to me. Primary towards valve cover seems to be the most popular. throttle linkage nearest the firewall..... but then i see images of the opposite, and even sideways.....sigh...

sitting the carb directly on the intake with linkage nearest the firewall, looks like i need a spacer to bring throttle linkage up above valve cover, or if reversed, to clear the carb linkage from touching the intake manifold (nearest the radiator).

Any GOOD pics you guys can send, or advice to offer? kind of new at this, so don't be too harsh.....

And just to make sure i'm on the right page, when looking at the car b from bottom, the smaller ports are the primaries? right?

 

You may be looking at pictures of 4bbls on the C series intake, or the Clifford intake. Both of those are open plenum (the opening to the intake) which allows the carb to be mounted any way you want.

With the DP series intake, you have it correct. The primaries (the smaller ones on the Edelbrock) face toward the valve cover, and the throttle linkage is toward the firewall.

Also, a good spacer can help with not only with the throtte linkage, but fuel atomization since it can help reduce turbulence.

I have a Holley on mine, but the idea is the same:


(You can see the outer ports are darker, due to them being the secondaries)


I have a nice, 1" spacer I got off of Summit Racing on mine


The primaries have the choke cover over them, which are toward the valve cover.

 

Awesome. Thank you so much!!

 

how did your throttle linkage work out?

 

Just to summarize, there are at least six reasons to place the carb primaries on the inside, as Abandoned Bronco recommended:

The primaries will feed the lower, smaller runner section. This will keep a high velocity at part throttle.

It will also place most of the exhaust heat on the primary side, improving atomization of the fuel.

The runner will be nearer to the short side radius of the port which will be the most direct path into the cylinder when the valve opens at low mass flow.

The secondaries will open into the larger runners for max airflow during WOT operation.

The upper runner will place the high flowing secondary at the top of the valve bowl where there will be more laminar flow at a high rate of flow.

Flow from the secondaries will be cooler than the bottom of the intake, making the charge cooler at WOT and thus more dense.

 

Thank you guys for setting me straight!

 

For mine, I purchased Lokar's throttle bracket and cable. The bracket worked really well but I wasn't super pleased with the cable.
Granted, I don't know if it's the cable's fault.

I don't know how it is on the '78, so you may not have to deal with it, but on my '81, the firewall where the throttle cable exists is at an angle. The stock cable had a curved end on it to point it back toward the gas pedal. The replacement cable didn't have that, so it came into the cab at an angle, and then took a sharp bend so it could line up with the gas pedal. It made it really bind.

I put some angled washer shims on the cable where it came into the firewall to try to straighten it back out. It works pretty well.