I working on a friend's 92 F-150, with a 4.9 EFI motor that needs complete rebuild. A lot of the vacuum lines are cut/broken, air pump disconnected, basically in shambles from previous hacking. I have a few questions.
1.) Is all the egr stuff required for the EFI to work? ie, can I get rid of the air pump etc?
2.) The forward exhaust manifold is cracked so I was going to put headers on it, but this will obviously require the removal of the one large exhaust gas return line...Problems??
3.) Is it worth changing all this over to a carbureted system, such as from Clifford? What else will need to be changed as far as the computer and all.
Thanks in advance for your help!

 

Hello, and welcome to the forums.

Don't you just love the "overhaul" previous owners give? Unfortunately, so many fail to realize just how much better engines run (especially EFI) when everything is present and in working order.

As such, everything is required for the engine to run right. The computer uses all of the signals from all of the sensors to know the state of the engine and to guide the systems in how they should be working. It's one big harmonious system.

However, people definitely do put headers on the EFI engines, so maybe someone can chime in on how that works. From what I know, it usually has to do with certain aftermarket setups that "trick" the computer into seeing certain systems present when they're not.

As for going carbureted, the big issue with this you have to be aware of is federal emissions. It's illegal to do. That said, whether or not they check in your area is another matter. If they do, you'll never get it to pass. If they don't, the call is yours. But you'll never be able to sell it to someone that needs to be able to pass emissions.

It wouldn't take much though. You'd need a fuel pressure regular to bring down the PSI of the fuel system, then an intake, carb, and an ignition system. The current ignition system would work, but not very well. It'd never advance the timing and leave you with poor mileage and low power. Your best bet would be to go with the DUI ignition (from performancedistributors.com) since it is an all-in-one kit for the whole ignition.

 

my advice:

keep the efi
put everything back to stock including the egr system.
do not use headers - replace the efficient cast exhaust manifold. headers have a lot of down side. install a low restriction muffler system.
hey, i'm an old skool rodder but efi is hard to beat. changing to a carb will be a step backward in many ways except for the simplicity of it.

 

Thanks a lot for the info.
It looks like my best be it to stay with the EFI and try to figure out where everything goes!! LOL
Is there a schematic out there for the vacuum/egr system?
Next decision will be to go with a rebuild, maybe .030 or .060 over and mill the head .030 or so, or just buy a rebuild, say from Jasper or someone like that.
Does anyone have any experience with them?
Also, upgrading form the stock cam to a 264*? Any input? I know it worked well on the slant 6 I rebuilt a few years back.
Thanks again for all the feedback.

 

"...maybe .030 or .060 over and mill the head .030 or so..."

JMO have the head and block milled only enough to true and clean the surfaces...same goes for boring...only as much as necessary to true and clean the cylinders.

 

For some of us, that's a real big "except for," Flyer.

That said, you got good advice, Rhino. Unless you know all the effects of each piece you disconnect (and there's a LOT more to know with a relatively newer machine than for the late-70s smoggers that I have stripped to their essentials), it really is easier to just restore them to original function.

 

Excellent Feedback Y'all. Looks like I'll go back completely stock. Wish me luck figuring out this bag of worms!

 

If you have a junk yard nearby, go find an EFI 4.9, take lots of pictures, and document what's missing. Be a lot easier that way!

 

Just to play devil's advocate, I went from efi to carb on one of my trucks, and I actually like it, so if you decide to go that route lemme know if you need anything. That being said, something to ask yourself is who will be driving the truck? Also, know that an efi will (almost) always start up, while a carb may take some finagling. Granted a well tuned carb can be faithful, just not as much as efi. I can feel myself start to ramble now, so I'll sign off by saying that for me what it came down to was that I have these strange uncontrollable urges to tinker, and a stock efi was never going to satisfy that. If you are thinking about going to a carb because it will be easier in the short term than fixing someone else's hacks, beware that it just might wind up being more work in the long term keeping it going. Anyways, Good Luck!