Carb

[C.Jett]

1985 F150 4.9 L 2 wd auto, po removed computer and smog equipment. YFA carb remains,was rebuilt by po.  Only gets 11 mpg.  What carb can I replace it with ?  Would like to get 15-16 possible ?  Many thanks for the warm welcome from members, I replied to each but they were undelivered.  Help is on the way, Grandkids and Great Grandkids are on the way this week, they will school me on the computer.  Merry Christmas to all!  C. Jett

[Gary Lewis]

One of our members, David/1986F150six, put a thread together back on FTE where he explained what he did to his truck to get ~20 MPG.  In it he said he used a "Carter YF 4901 S carburetor [from 1970 F350 with 300 engine]; choke converted to manual".  I helped tune the truck a bit and found the carb to be so close to "right" that we left it alone.

As for the computer, I'll bet the kids can help you a bunch.  

[C.Jett]

Thanks Gary,  do I keep the egr spacer and plug it , or is  there something else to use ?  Also, is there a reason not to use electric choke ?  if it comes that way.  What about the heat ?  Haven’t read all the posts yet, sure it’s covered somewhere,  thanks again

[Gary Lewis]

If you do away with the EGR then you really should re-curve the distributor.  That's because admitting inert gas, like exhaust gas, to the mix slows the rate of combustion so they have to significantly increase the advance to account for it.

But that is usually done via the vacuum advance since the exhaust gas is only admitted under relatively high vacuum conditions, so you can probably back off the vacuum advance via the adjustment enough to stop the ping.  If not you might have to go to an aftermarket vacuum advance with less advance.  But that's not hard to do.

If you want to delete EGR, which really isn't causing any problems anyway, you might want to pick up one of the carb adapters from Canada.  They didn't go to EGR nearly as early as we did in the States, so they had an adapter w/o the passage for EGR.  Or you might be able to plug the passage on the existing adapter.

As for the choke, there's no need to go to mechanical.  However, most of the carbs had a combination of hot air via a tube that went through the exhaust manifold and an electric heater, and it takes both to work correctly.  So if you don't have the hot air tube then you might want to go manual.  

[C.Jett]

Gary,  I don’t know how you do it, you always take the time to answer everyone’s questions, you never talk down to anyone and your knowledge is second to none. I am humbled. I will get you photos.and many more questions when grandkids show up.  Again, many thanks and Merry Christmas to you and yours. C. Jett

[ArdWrknTrk]

Gary, if mr. Jett had a 4.9 with EEC would there be any vacuum advance at the distributor?  

It seems to me that this is one of those "revert to DuraSpark or get an HEI" situations.
Certainly if his truck has a PS TFT and no longer has the EEC computer, the timing is locked and everything is running in 'limp home' mode.

But I'm looking at the '86 EVTM and don't want to make an assumption about what 'computer' was there.
Some photos of the distributor and the carburetor with the air cleaner removed would help clear this up.

[Gary Lewis]

Jim - I took his statement of "po removed computer and smog equipment" to mean that a DS-II ignition system had been installed.  But that is an assumption and should be verified, for sure.

C.Jett - The truck originally probably had an EEC-III system with an ECU, feedback carb, and TFI ignition system.  The ECU controlled everything, including the ignition timing, and if anything was removed from the system it got its knickers in a twist and locked the ignition timing to base, also known as "limp home mode".

But if the previous owner did a good job of removing the computer and smog equipment then you should have a distributer with a vacuum advance and an ignition module with a blue grommet.  Do you?

[C.Jett]

Jim, po installed hei w/vacuum advance.  I know I “got the cart before the horse”, but that makes me normal, doesn’t’ it ?  Just could not shut the brain down.  Will get photos and information soon.  You and Gary are “cut of the same cloth” and I value your input.  Many Thanks, C.Jett

[C.Jett]

Gary,  it does have a blue hei, not sure I understand “ Ignition module w/blue grommet”. C.Jett

[C.Jett]

Gary,  The carb has heat tube and electric choke.  No identity tag.  Is there a source for Canadian carb adapter?  Thanks

[Gary Lewis]

You can search the forum for links to the Canadian adapter, but those things sell pretty quickly if reasonably priced so they'll probably be gone.

However, you need to figure out what kind of EGR system you have as you may be able to use pipe plugs to seal it off.  There are several discussions about that on the forum, but this one might be the best of them for you.

As for the ignition, if you have a true HEI distributor then it doesn't matter what color.  And the computer won't be controlling it.

My comment about the blue grommet was regarding a Ford DS-II ignition system.  The ignition module for them has a colored grommet where the wires exit the module, and the one you want for a standalone system has a blue grommet.  But if your distributor is HEI then you don't have the Ford ignition module.

But we still ought to have those pics to ensure we are talking about the same things.

[ArdWrknTrk]

C. Jett,
Thanks for confirming that your truck has an HEI (all in one) ignition system.

 I was just trying to confirm that your truck had a way to control spark advance under varying engine load and speed.

Gary seems to have this well in hand so I will watch from the sidelines.

[C.Jett]

Thanks Jim, jump in anytime.

[C.Jett]

I will do more study, Thanks