300 cid , best stock exhaust
 

Started playing with my '66 resto project again yesterday, and thought I may set my 390 on the engine stand for this project and go with the 300 that came with my parts truck. The parts truck is a '66 F-250 2wd 4 spd. It is my understanding Ford made a better flowing exhaust on some HD truck engines, what do I need to look for to find one of these gems? And does anyone have a decent blueprint for a torque y dailey driver?

From what I have seen posted the HD exh manifold should flow better than the stock every day one.
IIRC the HD one does not have butterfly valve that helps heat the stock intake manifold.
I don't know how easy it is to find an HD manifold and matching head pipe?


You would be better off using the EFI exh manifolds and Y pipe, they are like mini headers.
http://cars.grantskingdom.com/var/re...121_082911.jpg
I don't know what manifold you would be using but there is a plate that bolts to the bottom of the stock intake and uses water to heat the intake.
I had to grind part of the intake divider to clear the weld on the plate so it would sit flat and seal.
http://cars.grantskingdom.com/var/re...128_104032.jpg
Installed on motor in truck
http://cars.grantskingdom.com/var/re...201_174106.jpg
http://cars.grantskingdom.com/var/re...201_174124.jpg
Dave ----

What years are those dual EFI manifolds? I kinda like that, could run dual exhaust with an X pipe.

I ran the stock duals back to a 2 into 1 muffler. Everything I used came out of a pull a pull a part. I love the power and the sound.

1987-1996.

There is not a lot of room to run duels let alone and X pipe like you would on a v8.


You can do like Brian did below, duel pipes (side by side) to a 2 in to 1 out muffler.


I ran the Y pipe into the stock single pipe/muffler tail pipe out behind the rear tire.
Thank you for posting the years.
You can find them in the junk yards or get them new thru Dorman at any parts store.
Dave ----

No problem.:-X22



They do sell a narrow X-pipe set up that would work with side by side pipes. That being said there isn't much to gain by running the X-pipe on the inline 6. But if someone wants to run one they can.

And in a truck( depending on the year and fuel tank set up ) there is plenty of room to run dual exhaust. The space all depends on your fuel system, exhaust pipe size, muffler choice and how you want to run the exhaust. On trucks that I want true duals on I usually run both pipes down the pass. side of the truck. And I run two mufflers stood up side by side. Then run the tail pipes out over the axle and then either both out the pass rear 1/4 behind the tire. Or once over the axle split them and run out out the back, one on each side.

Looking under the hood of the '66 I have a ton of room for duals. And they do have a narrow x-pipe. and beyond the transfer case I can split and go to opposite sides with the mufflers and tailpipes. I was lead to believe the x-pipe enhances flow in some dual systems, not sure if it's true or not. But I should have the room if they work.
PS. found the Dormans on Rockauto for about 60 bux apiece.

I believe that to be true and my personal experience is that it is true, especially in an exhaust system that has high exhaust backpressure.

Does that hold true for a straight six running a 3 to 2 exh outlet, header or EFI system?


I have heard the X works pretty good on a v8 but have not heard much testing done on a six be it a v6 or straight six.
Dave ----

I just spent about a half hour on a response and my computer crashed before I could submit the response. GRRR. So let me start again and briefly summarize.

When an exhaust valve opens a high pressure wave travels through the exhaust system. This pressure pulse meets resistance to flow at every twist, turn, and obstruction in the exhaust system, reducing the ability of the engine to evacuate all the exhaust gasses, thereby reducing its efficiency. If you have a crossover X or H pipe then that pressure pulse is attenuated, or reduced because the mass of gasses now splits and travels down two pipes, rather than being forced to exit through only one. So there is less pressure rise downstream of the headers.

With more cylinders the pulses come closer together, so a crossover pipe may be of greater benefit on a V 10 or V8 than on a six. I don't know that. I still know it will help the six.

On a race car with open exhaust headers there is no downstream restriction. A crossover pipe is not needed.

4.9 exhaust systems are the base system, are low cost, and are relatively high in backpressure.

I have done WOT dyno testing on small V8s equipped with headers and simulated exhaust system restriction. When an H pipe was added the engine made around five more HP, or around a 2% improvement even though the restriction was the same, as measured at the outlet flange of the header tubes.

Anecdotally, I added a crossover pipe to a 496 ci V8 motorhome that was getting 8.5 mpg on interstate travel. After adding the crossover pipe mileage improved to 9.0 mpg. That is about a 5% improvement. And it sounded a lot better to me.

TY, sounds like a plan. Now I just need to choose a manifold and carb. setup if the engine proves to be repairable without overhauling, If I have to overhaul we'll have to talk about a full blueprint and what I'd like to achieve. I wont waste the money yet if I can get away with minor work to the top end. I should figure that out this week.

It makes good sense that a x-pipe or h-pipe would help a 6 cylinder as well as a v8 or v10. Anything that would help exhaust flow should help. The pulses from each bank or in the case of efi manifolds on the 6 should help pull the other bank.

Are there any negatives to using the complete efi exhaust off of a donor thruck?

EFI exhaust will have Cats. and it's probably single exhaust.