I started with an '85 F150 with the 300, four speed tranny, and the rear end gears are either 3.00 to 1, or 3.09 to 1. The motor had a computer feedback Carter YF carb on it. It got 11 mpg. The motor was swapped for a fresh '84 300. The '84 motor had the old style head, the '85 motor had the EFI style head even though EFI wasn't released until '86.
When I put the '84 motor in, I added a Davis Unified Iginition from Performance Distributors. It's the GM HEI unit on the Ford stem.
Unfortunately, the person that had rebuilt the motor did not add the thrust spacer that goes on the cam snout. This caused the distributor gear to keep being destroyed. I had to swap cams, and used the stock cam from the '85 motor. That's when I discovered the thrust spacer, an item peculiar to the inline big block motor. It cured the problem.
I swapped in a pair of EFI exhaust maqnifolds. I have 2" dual exhaust with stock oval mufflers. The exhaust ends at the mufflers, nice rumble sound under the bed. I hate loud exhaust systems.
The intake is a Clifford water heated. I have both the two barrel and four barrel plates, I'm running the four barrel plate. The carb is a 600 cfm Edelbrock (carter) with the secondaries disconnected. The primaries give me 280 cfm. The motor zings to 4000 rpm, but it has an off idle problem. I'm working on it.
I think the intake plenum in the Clifford is too large for a stock cam and stock intake ports. I'm going to put an intake divider under the carb so that the back half of the carb is isolated from the front half of the intake mainfold, and vice versa. This is based on research and theory.
I'm trying to build a carb more suitable. It an old Carter AVS from a '65 Chevy. It's the smallest AVS ever build, I'm going to make it smaller.
Rodger that on the plug wires. I have a new set of spiral core wires waiting to go on.
I drive this truck less than 1000 miles annually. I keep it to haul stuff. I have a 9" rear end with a Detroit Locker waiting to go in. It's gear too low at 4.56 to 1, but what the hell.
OK. I have a nasty headache so I hope this doesn't get rambly-dumb. IIRC that Carter carb had a duty-cycle solenoid thingy that metered the main jet based on feedback from an oxy sensor in the exaust. I never actually heard anything good about them, although Holley added a similar option to their 450cfm 4bbl that let you change the effective main jet size with the flip of a switch.
I think that you are on the right track regarding carb setup. Unless a person is building a racer overcarbing is really counterproductice on these motors. They are long strokers that spend most of their time under 4000 rpm and everything that I ever worked out showed that the 390cfm Holley 4bbl with vacuum secondaries was the perfect carb setup. 280 on the primaries alone with that Edelbrock is still a bit large for normal driving.
Writing about all of this brings back some things that I had forgotten. Like why I went from the Cliffird intake to the Offy. Short answer, I screwed up. Long answer, the bane of the 300 imo is that with the way the bolt pattern is set up for the intake/exaust manifolds on the pre-EFI motors leaves the #4 exaust port poorly clamped to the head and causes exaust leaks there. Which results in burned #4 exaust valves. The '77 motor that I bought had burned #4 exaust valves and was cracked across the valve seat.
I found that installing the Cliffird intake and Clifford headers on the 240 with no help was an extreme pita, so when I built my 300 I added studs to the head for mounting the manifolds. I also made a long clamp from a piece cut from a leaf spring to reach over from the #5 stud and help clamp down the #4 exaust on the header. This worked pretty well and made mounting all of that a lot easier. But I didn't think it through about how much extra clamping force nuts on studs have and when torquing the nuts I cracked one of the mounting flanges on the intake. Memory dims but I think that in the end I found that about 1/2 to 2/3 of the normal torque values was enough.
So when looking for a replacement intake I heard about the Offy dual port. It makes sence, the primaries feed into the upper port/plane and because of it's reduced area keeps velocities high. The secondaries feed into the larger cross section lower port/plane.
When I was first trying to find some more in depth info about the 300 I called the local Ford dealer service dept and asked who knew anything. This would have been perhaps '91 or '92. I chatted with a fellow and he gave me a telephone number to a different dealer service dept up in Seattle. And he gave me another number. This kept happening and I just worked my way up the food chain. Finally this one guy gave me the number of "an engineer in Detroit that knows something about the 300".
So I called it. The guy on the other end was a bit freaked out and demanded to know how I got his number. So I explained the whole thing and he just calmed down and started chatting with me. Turned out that I had called Fords cheif engineer that had been responsable for developing the EFI motor. He was actually a very friendly man and we talked for over an hour.
He explained that 2 of the most important parts of the new motor (other than the electronics and fuel injection) was the combustion chamber/piston shape and how the heart shaped quench area opposite the valves created what was later called High Swirl that helped promote a more complete fuel burn. The second thing was improved manifold shapes and a new bolt pattern on the manifolds to eliminate the old leaks and burned valves.
This info is what led me to choose the Solvolite quench head pistons. And being hypereutectic they are stronger than plain cast but have very good heat expansion characteristics, so can be fit very tight in the bores, unlike forged pistons.
The Performance Distributors distributer that you have is exactly what I wanted to buy. But money ran low and then I decided to move over here, end of that. Very nice distributer.
I ran my headers straight back to some glass pack mufflers under the bed with long straight pipe extentions out the back, all 2". The truck sat high enough that I didn't need to mess with any curves. It was a little loud but not as much as you might think considering that it was essentially a straight pipe.
I always loved that angry straight six snarl.
Back when I had that truck I was working at an etching company. Before I quit and moved over here I was working on etching an intake/exaust gasket out of 0.32" soft copper. I think that it would have sealed well and the copper would have spread the heat well enough to avoid burnthrough, unlike every other gasket that I ever tried. Another project that fell through.
I would have loved to have a Detroit locker for the rear axle. The 4.56 rear end was great for off road or hauling a full load of wood. but of course you know that it's not going to improve your MPG.
At freeway speeds your motor will be wound tight. Plan on doing a lot of driving at 55-60mph. If you wind that motor regularly over 4500rpm with stock cast pistons don't count on a long life. If you figure 2500fpm as a max sustained safe piston speed with stock cast pistons you will see why Ford set a redline of 3600 (or is it 3800) for the 300. Hypereutectic pistons are safe to around 4500 to 5000rpm sustained use. That long stroke makes for high piston speeds.
Going with a cam of around 256° will give you the best combo of torque and mpg in the rpm range that your truck will be using when carrying a load. That's why I chose the Isky cam that I did.
'gnite,
James
