I wasn't talking about a full aftermarket EFI swap or a TBI setup, just the throttle body. Run an 85-90mm single hole mustang style TB with the edelbrock elbow on an EFI converted carb intake. Run the whole mess with the stock SD EEC-IV computer.

 

I *think* the idea is to run the heads cooler (in order to stave off detonation) and change the temperature sensor output to fool the computer into thinking it is at operating temperature so it gets out of cold start mode.
I asked here; https://www.ford-trucks.com/forums/1...1997-f350.html Why stay with an SD friendly cam?
The response was that it was fine for the projected 420Hp/570Tq of his engine.

You have no pressure (well, 14.7 psi at sea level) pushing the intake charge.
The piston is *forcing* the exhaust out.
If you put big valves on both sides in that head, they like to crack between, and from the exhaust to the plug hole too.

 

Ahhhh yea I missed that. Would be easy, so long as the eddy piece (or tb) has a provision for iac

 

The problem with the Ford heads is they're so lopsided to the intake to begin with. They need a bigger exhaust valve desperately. Bigger intake; not so much.

And while it's true that the piston forces the exhaust out, it also sucks the intake in. So that's flawed logic thinking you need a bigger intake to help the air in.

As for the thermostat, 195 is there for emissions reasons. 180 will keep the engine out of cold start mode while adding a little pep because cold air is more dense. A 160 degree t-stat will keep it in cold start mode if that's what you're looking for. Fuel economy will go down the drain though.

 

The biggest problem with D3 heads is the thermactor humps and the tight short side radius of the exhaust port.

The piston going down on the intake stroke can only provide 14.7 psi ABSOLUTE, plus whatever inertia is in the intake charge.
(this is why big ports only work at high rpm)

 

Yeah, and?

Years of experimentation has shown that an exhaust flow of approximately 75% of intake flow is ideal. If you have a head that flows 55% of intake in the case of the F3 head then why would you want to put a bigger intake in? That's what I'm trying to get to. I don't care that at most you're have 14.7 PSI pushing in, that's enough. If you don't have enough flow to get the air out you won't get enough air in.

Ford heads always seem to be weak on the exhaust side in general.

The mustang TB has a provision for IAC. An 80mm would be about the same as the twin 56mm one that's stock. BBK makes a nice one.

 

I'm surprised more people aren't running aftermarket heads then. . .doesn't get any easier than the 3849 adapter. even if that adapter didn't exist, it'd still be easy with the carb adapter and probably be about the same price ultimately. I was confused when you said "4 port TB meant for aftermarket EFI".

 

I seem to remember reading one time that the lower temp thermostat was to help with more fuel and get away from lean condition once headers are installed. Can't remember exactly though. Is this similar to the cold start mode you refer too?

 

I was thinking of one of these.



Not sure what it would take to make something like that work, but after I thought about it more I remembered some of the Mustang guys running modified carb intakes with an elbow to mount a round single TB. If you look I'm sure you can find them with oval and dual port TB's too, but an 80mm is roughly the same as the twin 56mm - actually it's just a touch larger. A 79mm would almost exactly equal the inlet area.

I'll put it on my project list... I should be able to get to it in about 8-10 years...

 

I am going to stick with F3 heads for my build. Other heads may have advantages, but for my goal F3's will do just fine. I am definitely going to do at least some porting and I am not opposed to changing valves. What size valves above stock can I use without being in danger of cracking the area between the valves? I want to get all I can get and still drive it 200, 000 miles with no problems.
As for the thermostat, I thought 195* was a must to keep the computer happy. Now that I lnow better, when the weather warms back up I'll change it back to 180*.

 

remember, the exhaust is aided by the combustion itself finding the easiest exit - the exhaust valve as its opening, causing its own scavenging effect. this doesn't change the facts that you've already brought to the table; intake/exhaust ratio and how the ford heads don't meet what is ideal....just a side note.

 

Just noticed while going through some EFI 460 parts there are two different lower intakes. Not sure the differences, but the casting numbers are different. They are: E8TE & F2TE.

 

I understand what you are saying; there are forces getting the exhaust out and forces getting the intake in. For years though it's been known that having the exhaust flow around 75-80% of the intake is a sweet spot for making power. When you're starting with a 55% ratio I can't see the reason behind enlarging the intake and making that ratio worse. The best bang for your buck with most Ford heads is on the exhaust side.

Will enlarging the intake make power? Maybe, but work on the exhaust definitely will.

 

oh I wasn't contesting what you were saying, the standard is to achieve at least 75% of exhaust to intake flow and I recognize(d) that you were saying just that. I was just adding to the discussion, as I cant help myself.


I was just stating the reason the exhaust-intake relationship, even at the acceptable 75% level, works is due to the "help" the exhaust gets. the only reason 2v/cyl heads get smaller exhaust valves/ports is because there isn't enough room to put both at the same size both physically and practically (economically). a lot of 4vpc heads often have the same size valve and a ratio much closer to 1:1. I'd venture to say the reason ford's (and other factory heads for that matter) intake/exhaust ratio is so abysmal is emission requirements, cost, and efficient power simply not being a priority.


i couldn't agree more that the most power to unlock is in the exhaust.