Rowdy, most of the trucks that received the hot fuel handling package were sold in the South and all had factory A/C.

 

And, Big Blue has A/C. There's gonna be a ton of heat under the hood in summer. And, all the surface area of those headers doesn't help.

 

Ah ok. I parted out an '85 that came from Texas and was equipped with the hot fuel package, but all of my '86 trucks have the mechanical pump with return.

 

Im confused - mechanical fuel pump and return? So they had a vapor separator and return line, but a mechanical pump?

 

No vapor separator anywhere on them. They have a return line connected to the small port on the pump, directly above the pressure line. You can see it in the picture I linked to. That runs back to the six port valve and to the tanks. None of these trucks have factory air though.

 

Ahhh! I see it. So, basically it puts out more volume than the carb needs and the excess returns to the tank. But the difference is that it has to suck fuel, which can be problematic if it is hot. Instead, the in-tank pump pushes fuel.

 

Gary, that is exactly the point, it keeps the fuel supply under pressure when the engine is running and properly wired and plumbed will purge the system of vapor quickly during a hot restart.

Even in the hottest weather, towing the 5th wheel, the only hot start issue I ever had was the classic Ford starter slow crank. Once it would spin up, always fired right up, even the time I had a DS-II module die going up 7 mountains grade on US 322 West toward State College PA. Once I coasted over to the side, grabbed the spare from behind the rear seat and plugged it in, off we went.

 

Yes, as I think about it, I'm going to stay with the in-tank pump setup. But I'll have to decide if I want to keep the vapor separator and then have a dead-head style regulator, or go with the return-style regulator. And that will be determined by whether or not the pump is developing enough pressure to cause the regulator to return some fuel, thereby eliminating the need for the separator - I think. Y'all's thoughts?

On the DS-II module, Big Blue has that whipped - he has two on the fender apron. But, one of them may not retard the spark when cranking, and I need to figure that out and replace it with one that does if so.

 

Pretty much. I'm not sure why they only used it on the 460 though. I've never seen a return system like that on 300, 302, and 351W trucks. Older 70's era 460s never used a return line either.

 

I think they we looking for a solution to a problem - vapor lock on a 460. The smaller engines didn't generate as much head and/or had more room around the engine to dissipate what was generated. But the big block needed something so they may have tried the mechanical pump first and then moved to the electric pump if that didn't solve the problem. Or, maybe as Bill said, the A/C trucks got the full problem-solving package with in-tank pumps and a separator.

And, since that's what my truck has, meaning A/C and in-tank pumps, I'll keep it.

 

Gary, as you asked me "How high up did they have to drop it from to get it to fit?" the 460 is longer, taller and wider than any of the other gas engines except the 300 including the 351M/400, it also is saddled with the same radiator all the other V8s used instead of the monster one the 1975-79 460s had in the previous trucks. Everything points to Ford not ever planning on using the 460 in the Bullnose. When the 6.9L Diesel was introduced, it took a completely new radiator support and a big downflow radiator, it would have been nice if the 460 had gotten a similar setup.

 

Yes, the 460 is a tight fit. Much tighter than the M-block, and I should know as I have one of each nose to tail in the driveway. And neither have emissions equipment. In fact, both are sporting an Eddy manifold and carb - imagine that.

I wonder if an upgrade would be to go with the diesel's radiator support and radiator. Not that I'm planning to change, but I'd just not thought of that. However, Big Blue has a brand new radiator and massive engine oil cooler, so I'm pretty sure he'll be cool enough this summer. Having said that, I'll have to thin his coolant a bit to get optimal cooling. Right now he's running almost pure antifreeze since I was pouring it into a non-running engine and wanted to ensure there was no chance for freezing. But, with the swapout of the heater core, replacement of the plug on the radiator's neck, and tightening several clamps the cooling system is no longer losing coolant, so I'm ready to do that.

Oh, by the way, I discovered that the water pump says "Edelbrock" on it. So, with the aluminum intake replacing the serious chunk of cast iron, the aluminum carb replacing the pot metal Holley, and the aluminum water pump replacing a cast iron one, the 865 lbs may be down to 800?

 

My thoughts on this matter are;

A) Every bit of pressure helps keep the fuel from boiling. Hence the restriction in the vapor separator, because there is obviously nothing above ambient pressure in the return line to the vented tank.

B) The constantly recirculating excess of fuel means the (relatively) cool fuel from the tank is carrying some of the engine bay heat away with it.

IMO, either put the vapor separator where it belongs (and use the correct in-tank pumps) or put the return regulator where the vapor separator belongs (and plumb it as the separator would be)

The way it is now the line going up to the carb is cooking your fuel supply.

 

.... Note that Subford posted the three orifice sizes available (.045, .065, .090 iirc) these are color coded with a red, blue or white paint dot on the separator.

So, you can have increased pressure at the carb or increased volume returning to the tank, but not both.

 

Jim - Thanks. I think we are in the same page. To me, placing the return regulator on the intake manifold, basically where the separator was, is the way to go. I think the regulator will kill two birds with one stone - constant return and pressure.

Thinking it through, with the separator and no regulator you'll get some return and full pressure at the carb when the engine is off. But with the regulator you'll get the same flow but controlled pressure with the engine off. And with the engine on and just the separator you'll still have higher pressure at the carb - assuming the pump can deliver higher pressure.

So, I see no disadvantage to running just the regulator, and the advantage is a simplified installation and controlled pressure. Agreed?