another fuel injection question

[Cole1986]

so i have a 81 sx4 and a 82 sx4 and i want to make the best of the two. the 82 has the selective drive with the automatic tranny, so the question i have is......if i was to do the 4.0L head swap and put in the fuel injection, will the vacuum on the selective drive still work? i just picked up the 82 so I really dont know to much on how that all works so any input will be much appreciated. thanks

[eaglefreek]

Yes, as long as you hook the vacuum line up.

[IowaEagle]

Yes, like eaglefreek said.  If the front axle in the '81 is the same ratio as the rear in the '82 and the '81 is not select drive then you have want to consider swapping it in.  Or just lock the front disconnect axle on the '82.  Either way you then have shift on the fly capability.

[Amc1320]

X3 , as long butt the vacuum hose that goes to the system is hooked to manifold vacuum your good to go.

[carnuck]

Which trans will you run? OEM 998 needs a CPS hole and flexplate to operate the EFI or harmonic balancer kit (@$300 last I checked). If you go AW4, will you run the Eagle Tcase? If so, you need a '91 up AW4 (23 spline) and 1" spacer ring between trans and case. You can hook up just the front axle to the dash switch if you use a non-vacuum controlled XJ tcase.

[Cole1986]

K thanks guys. I started this weekend on pulling it all apart so the fun has begun. Still throwing the injection idea around but I'm not totally against the carb. So if I kept it carbed what's my best option. I like all the post on gronks kit and I saw I nice set up from Clifford. So let me know, thanks

[eaglebeek]

K thanks guys. I started this weekend on pulling it all apart so the fun has begun. Still throwing the injection idea around but I'm not totally against the carb. So if I kept it carbed what's my best option. I like all the post on gronks kit and I saw I nice set up from Clifford. So let me know, thanks

There seems to be as many opinions on what carb is best as there are people using carbs.

All carbs perform the same function...vaporizing gasoline and mixing that vapor with air, ideally to attain the perfect 14 parts air to one part gasoline mixture. For the engineer that figure is called "stoichiometry". The difference between carbs is how much of this mixture they can produce and how they do it.

Carbs are sized to meet the needs of the engine. They are typically rated at cubic feet per minute, or cfm. The engine's needs are dependent on the displacement of the engine and its volumetric efficiency, or how much power is used  by the engine to move air-fuel mixture in and exhaust gases out. A larger or different carb is not by itself going to allow the engine to produce more power.  What's more, the larger or different carb may not be able to produce a stoichiometric mixture at less airflow.

The original 258 cylinder head was not known for good volumetric efficiency. Many on this forum have installed an improved 4.0 head and intake manifold on their 258s to improve the volumetric efficiency of this engine, therefore making more of the energy produced by burning gasoline available for moving the car. For engines so modified a larger or different carb may make a difference.

I'm not an engineer, and I'm likely guilty of over-simplifying. The point is that improved performance is a multi-faceted proposition. Improving any one facet without attention to the others is likely to produce disappointing results.`

I'm partial to the OEM Carter, but that's because I've worked on them, understand them and am able to make them work. Are they trouble-free? No, but neither is any other completely trouble-free. The later feedback carbs are certainly more troublesome than the earlier models, but that's what happens when you add more features. 

[Baskinator]

If you want to buy a new carb, I'd recommend just getting an original Carter brand new from eBay. It's about the same price as the Motorcraft, or less for a non-feedback, and you won't have to figure out how to hook it all up correctly. A properly tuned Carter BBD will run just as well as the Motorcraft with similar mpg numbers, so long as everything else in your engine is working properly. It's not too difficult to tune if you know what you're doing, plus you don't need an intake adapter or modified throttle linkage.

If you're looking to eliminate the computer and get rid of vacuum lines, a non-feedback Carter can be run just as easily.