Converting to Fuel Injection
This is by far the most popular thing on my web site. I get e-mail questions
almost every other day on this, and I'm happy to answer them. I've had the unit
for almost 2 years now, and all is well. I also added more technical info to the
last page on how to tune the ECU, wire with MSD ignition, and combat the infamous "CB interference monster"
as well as other FAQ.
Click here to skip to FAQ page
Click Here to see Installation Manual pages
My Jeep has a AMC 304 V8 engine with a 2 barrel carburetor on it. It's as it was
from the factory. It works well for "normal" driving, but has the usual
problems that carbs. are known to have. It likes to kill when you bounce the
Jeep too much, and sputters going up steep grades. Although these are bad
things, the driving force (pun intended) behind doing this conversion is the
need to cross the Rocky Mountains for my annual pilgrimage to Moab! I've gone
there in two different vehicles before, but both were newer, with fuel
injection. If you've never crossed the mountains before, let me tell you, It's
HELL on your truck! If your vehicle has reasonable power at low altitudes, it will
feel like a Yugo at 12,000 feet. I live at 740 feet above sea level, so when
I took my 4.0 Liter Explorer over those big hills, it was all I could do to
keep 50 MPH sometimes! Certainly, the altitude change would cause major havok
with my carbureted motor, and since I'm no expert at fiddling with carb
adjustments, I don't want to spend three days playing with the thing as I try
to get out west. My solution is to convert to fuel injection using a Holley
Choosing a brand of Fuel Injection.
I chose to use the Holley ProJection system, simply because I have used their
stuff before, and have always been satisfied. I didn't compare features or
anything else worthwhile, I just trust that they have a good product
that will function properly. I did read stuff on the internet about people who
converted their 6 cylinders with a Howell brand TBI and had less than good
results. I have also seen articles in which people have used the Holley system and
have had problems with CB interference and after-market ignition systems. I thought,
I'll be the judge of that.
Selecting the Model.
In the Holley catalog, they list a unit designed to work with the AMC small block. The
model number is #502-20. It has a 2bbl throttle body for engines with up to
275 horsepower. They also offer a Closed Loop Thingy that uses an oxygen sensor
to regulate the fuel mixture when conditions change. I want that too,
that way, when I cross the Rockys I don't have to continualy adjust my
settings. Unfortunatly, the Holley ProJection unit doesn't just bolt onto
my factory two barrel intake manifold. It requires a 4 barrel intake manifold,
and the Holley catalog suggests using a dual plane design for best results.
Well, "best results" is what it's all about, so I went in-search-of.
Here's what the #502-20 consists of.
I checked prices at Blakely Auto Parts, a local parts store that's only a couple
of blocks from my work. Their price for the TBI (Holley #502-20) is $1,075.00
optional Closed Loop Thingy or CLT (Holley #534-54) is $123.75. I also
checked with Jeg's and their prices were
much better. The TBI and Closed Loop Thingy was $650.00 together! Now I
like to buy stuff locally when I can, but as you can see, the price
difference was too great. I ordered the stuff from Jegs and got it in a couple
The Intake Manifold Search.
This has turned out to be the toughest part of the whole deal so far. When I
talked to a guy at Holley, he suggested I contact Offenhauser. Their phone
number is (213)225-1307. Offenhauser offers a Dual Port
intake (Cat #6057-DP) that is a dual plane design and accepts a four barrel
carb. They also offer a EquaFlow
intake (Cat #5917) that is a single plane design. Since Holley suggests I use a dual
plane design, the EqualFlow is out. That leaves the Dual Port. The Dual Port
design has completely isolated airways between the main and the secondary airways
of the carb. Since I'm putting a two barrel throttle body on it, I don't think
the Dual Port design will allow much fuel to reach the secondary airways,
so it's out too. (See Dual Port picture)
Now I turned to Summit Racing. The guy there suggests an Edelbrock
intake, Cat #2131. Summit
quoted me a price of $165.95, but they were out. I went to Edelbrock's
Web Site and checked it out. It's
perfect! It's a dual plane, and it shares airways for main and secondary.
It's all mine. Click Here
to see the info. I then called JEG'S mail order, and they had the intake
in stock at $163.00 (including freight :-). Just to confirm your suspisions, I
need a four barrel intake,
and I'm putting a two barrel throttle body on it! Go figure.
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