i have a stock 460 in an 84 F-250 and it has a sort of smog pump, i've been told that its a pump to help reburn exhaust to help fuel economy, currently it has no catalaytic converter, just straight pipe running from the manifold to the muffler, but i was wondering:

1.) What is this pump, and what does it do?
2.) the truck is registered in a county were there are no emmission standards, so i was wondering how you would go about removing it, and
3.) i was thinking of putting a good set of headers, dual 2.5" exhaust and flowmaster mufflers on it for more torque and power, how significantly would just removing the pump increase horsepower? (forgetting about the mileage loss of course)

any info would be appreciated, thanks a lot!

 

I have an `85 F350 w/ 460. Due to its age, when I bought it, I found that all the vacuum hoses and anything else rubber had dry rotted and so I ended up pulling the air pumps and all other emissions equipment off the motor. All the dry rot had caused many vacuum leaks.

The purpose of the air pump is to add oxygen to the exhaust to help further burn the gases and reduce emissions. While it does take some power to run the pumps I suspect you will not see much difference in gas mileage or actual performance. But, if they are not functioning properly then they could cause further problems.

Adding headers should open up the exhaust and allow freer breathing. This will normally require enriching the fuel mixture. If you remove the EGR that too will require enriching the mixture. The stock Holley carb is an emissions carb and thus is very limited on getting it to perform on a motor that has been de-smogged. I replaced my carb with an Edelbrock 1406 which is a pre-emissions unit.

Good luck,

Mark

 

thanks a bunch man, when you removed the pump and got a new carb, did you notice any difference in performance or mileage? what cfm carb did you get, a 750?

when the pump was removed, was there any other conflicts other than the fuel mixture?

and what did you have to do to remove it as far as hoses are concerned?

also, another question, on the same truck, can i get a new air cleaner for it, differing from the stock one where there is just a tube that brings air in to the carb?

Thanks a bunch guys,
~BLaCkSiLo

 

When I got my truck it suffered from many years of minimal attention. The first use of it after we bought it my wife took it on a short run to get a load of sawdust. It consumed a full tank of gas, could not keep up with 60 mph traffic, and could barely idle – wanting to stall when ever the clutch was engaged and a load put on the motor. We could not check the actual miles per gallon of gas used because the speed-o was also broken. It may have been gallons per mile.

That is when I started checking everything under the hood. Found that the choke would not open, all rubber dry rotted and leaking air including the diaphragm in the vacuum advance for the distributor, ignition timing set at 3 degrees ATDC, and so on.

In pulling the air pumps I simply started taking at the pump and removed everything I came to. I ended up with only the metal pipes that attach to the back of the cylinder heads and come together behind the intake manifold. The stainless steel metal tubes that come up from the exhaust manifold in left in place because it was easier then trying to break loose the very rusted tube nuts. There is a diaphragm that keeps exhaust gas from come up and out of the tubes. If you can remove them and simply plug the holes in the exhaust manifold then it would make it easier to work on various different components like removing valve covers and such. Once the air pumps are removed then you will be left with a gigantic bracket that also holds the alternator. You can find alternator brackets on e-bay. If you can find one for a truck it is best but I used one for a car and just made up aluminum spacers to bring the alternator out enough that it does not interfere with the frame and the belt pulley will line up with the crank pulley. I don’t have A/C so I’m not sure how that may impact things.

My EGR was also not functioning so I disconnected it too. I have since removed it when I replaced the carb. Make sure you put caps on all the vacuum sources when you pull vacuum lines. There is a tree in front of the carb on the manifold and ports on the carb. There is a temp switch on t’stat housing that will not need to be blocked once all vacuum lines are disconnected from it.

The stock Holley carb is 600 cfm. I used the same size because I would never be running very high rpm’s. Many people use the 750 and seem to be happy with it too. CFM calculators seem to support what FORD originally spec’ed so I decided not to try and second guess them. I have had to enrich it from the stock setting but on an Edelbrock it is easy to do. Additionally, I have installed the pre `72 cam timing gear set with a new chain.

So with all the work the motor will now idle nicely at 700 rpm, can pull out on flat ground without touching the gas, can break the dual rear tires loose on asphalt, will run any speed we need for it to run, and generally runs pretty good. Still can’t tell you about gas mileage though I now it is better than it was. No matter what is done it is going to be lousy – it’s a 7,000lbs beast.

I’m sure you can put an after market air cleaner on it but that won’t make any significant difference in performance or mileage.

I hope that helps but let me know if you need any other info.

Mark

 

yeah man, that helps a lot, thanks for all the info, it dosent really seem that hard except for plugging all the vacuum lines and such.... as for the carb, i've heard good things about a 750 edelbrock carb as the need for more cfm is on the table for the beast of a 460, so, i'm kinda at a fork in the road there... when this storm passes here in oregon, i'll pop the hood and look at what i have to deal with, i'll keep you guys informed,

THanks a bunch again,

~BLaCkSiLo

 

While there is a snake nest of vacuum hoses there really isn’t anything to tough about getting it all out. When I was done there were two vacuum lines left - one for the PCV and one for the distributor. You will be amazed how much open space there is when it is all out of there. The nipple on the EGR will not need to be blocked, but any open nipples on the carb or the tree(s) on the manifold will be.

The plumbing for the air pumps is rather significant. Many of those lines are an inch or more in diameter. But as you remove it, and all the devices to open and close the lines, much space will open up.

If you remove the EGR plate you will need to plug the exhaust source in the intake manifold. I used JB Weld and it has held up. Plus, use the four hole thick base gasket against the intake otherwise you will not cover all that needs to be covered and there will be a big vacuum leak. I used a two inch spacer when I removed my EGR plate.

Once you have cleared all the stuff out of the way check the torque on the intake manifold bolts. They like to work loose and allow vacuum leaks where the intake mates to the heads.

While pulling all the vacuum lines stick one on the distributor and suck on it. If you can suck air through it then the vacuum advance diaphragm is dry rotted and it will need to be replaced. If you can’t pull any air through the vacuum line then it should be fine.

A 750 cfm carb will probably be fine on your motor. Go with the pre-emissions version. While it will seem that it is running fine out of the box make sure that you check and adjust the fuel mixture as outlined in the Edelbrock manual. I went with an Edelbrcok remanufactured unit and saved some money. I have not had any concerns about the quality of it. Once I have gotten it dialed in it has performed flawlessly.


Mark