The gasket is a Felpro / Carburetor Base Gasket for a 1976 Olds, Toronado, 455.  You can go to and enter the SKU number 60335 in the product search box and the correct gasket will come up.  Now I have not checked with Howell lately, but they may have changed to a better gasket.

the correct gasket (it is an Advance Auto parts Fel-pro 60335 or one from Autozone #85505)

The fuel pressure gage I bought from Grainger.  They have dozens and I don't remember the part number for the one I bought. It is in a brass T in the fuel line to the throttle body.  It does not read from the O2 sensor.  Richard Waters
By  Eugene Fisher

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I am very happy.  The installation is complete and the performance is amazing.  It is now clear to me that some performance issues I blamed upon the transmission and the engine, were caused by a poorly performing and badly adjusted quadrajet carburetor.

I cannot tell you how happy it makes me to start the GMC cold with out stamping the gas peddle 5 to 10 times to prime the engine and cranking several times to get it started.  The idle is the same cold or warm and I don't have to slam the peddle several times to get off of high idle and drop the choke.

I have been doing a lot of start and stop testing  and there is no more dieseling. The little flashing light says the motor is running closed loop which says it is in control.  I think this is going to work.

Thanks to Mr.C, Jerry, Manny, Emery, and the Howell company, for their help on this project.

Howell web page
    Tom--test person    810-765-5100
    Troy Brown--Tech Sales

Programming link(3/28/05)


        20 Year upgrade in technology
        No more dieseling at shut down
        No more sticking choke and other linkage
        Get rid of the Carb input filter connection
        No more leaking / varnished linkage, floats,  jets, set screws, etc
        Closed loop control of combustion for altitude, gas, engine condition, etc
        Module swap  repair of system, i.e. , injectors, computers, sensors, etc
        Electronic diagnostics
        No new Quadrajet carburetors available, no upgrade possible with old system
        Technology proven in all modern engines since about 1986

I have never had any success with rebuilt carburetors.  The rebuild never seems to last and some of the areas like leaking around linkage and dry gaskets are often not fixable.  I have always had more success with new carburetors, but none are  available and substitutions are controversial. I hate carburetors. This may have something to do with the fact that I cannot understand, fix, adjust or  tune a carb.  They are too complicated, too hard to adjust, and in a difficult place to work on.  I have a new engine, is the old carb still correct for the heavy breather ?  With a closed loop control, this should be adjusted automatically.  I think basically, I hate carburetors.

This is the start of a Howell  TBI installation.

Click for Detail
These are the parts to be added.

Click for Detail Need to get under the wheel wells and do some work so it is suggested to raise the front of the coach.  I feel safer with it up on blocks and this was enough height.  This picture shows that it is necessary to put a block or stand under the rear of the GMC when ever you are under the rear.  There is nothing lower than a GMC if an air line or bag breaks.

click for Detail Time to get rid of some of this clutter.  Ready to remove carb, christmas tree, and gas pump.  It is interesting what you find when you go looking.  I found a bolt on the AC compressor bracket that was finger loose.  I found a vacuum hose that was barely on a source connection that I know was on before.  Might have been blown off by a backfire ??  Reminds me that we should be looking all the time for these sorts of problems.  This is a definition of Maintenance.

Click for Detail This is a picture of the dreaded input filter to the Quadrajet.  Mine was loose ( but not stripped like some).  The pipe connector is shown just to the right of the filter.  Note the nicely rounded corners of the nut from many in-the-field removals by previous owners.  The last person to remove this gas line was a Mechanic in Mexico with the largest vice-grip pliers I have ever seen.  I took a  hint from him and I used the same to remove this for the last time.   Gone, gone forever.

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All cleaned off and ready to install the adapter plate and TBI.

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TBI installed, everything fit great so far.  I had to add some RTV to the lower passenger side of the adapter plate.  This is as per instructions.  Now to crawl under the old gal and install the injector pump and filter.

Click for Detail The object on the left is a spin off filter that is attached to the selector valve.  The next object to the right is the low pressure booster gas pump.  This pump is here because there is a strong feeling in the GMC community that the GMC sucks air at low gas levels in the tanks, and that there is a need for a high volume pump to feed the pressure pump of the quadrajet or the TBI.  The third object to the right is another filter.  This filter is to take out any remaining small particles that might plug an injector and to provide a small reservoir.  Jim Kanomata and others say that when the GMC sucks air from the fuel tanks there needs to be a reservoir to keep the air bubbles out of the injectors.  I hope these two filters will provide enough storage and will let the air bubbles dissipate.  The Howell kit only recommends the one high pressure pump.

Click for Detail This picture could be labeled " why use one when two will do?".  This is the high pressure gas pump for the injectors.  this pump supplies 12 to 20 pounds of pressure.   I might move this pump closer to the engine in the future. It would be a good idea to carry a spare pressure pump,  the pump as a Airtex E8228.  Howell gets $112 for it.  I found it on the net at for $94.52 and if we were to search more we could probably find it for less. Emery.

Here is an alternative install location for the Electric pumps and filters used by Emery Stora

Click for Detail So much for buying a kit with everything there.  My Rostra cruse control needs a bracket also, so I cannot use the one that came with the Howell.  The bright wiggly piece of metal is the bracket I made with the piece sent by Rostra.  Looks like it will work well.

Click for Detail I took  the cruse control ball joint from the Quadrajet and the final assembly looks like it will work.  You can see the difference on my web page under Rostra.

Click for Detail Lets see now, the ankle bone connects to the hip bone,,, no the hip bone connects to the knee bone,,,, well it looks bad but is really easy to route the harness.  I was a little miffed when they said connect the grounds to a bolt on the rear of the head.   But they did not supply the bolt.... 20 minutes scrounging for a bolt and lock washer.  Then they said use 3 ea  1/4 inch washers on the throttle control..... you guessed it, no washers.  Another 20 min. looking for right thickness washers.   Small things but gripe you all the same.

Click for Detail I guess this hole is to let the mice in..... I hope they give me a plug to cover this hole into the cab.  The computer mounts on the end of the cable through this hole..... Dam big hole.

Click for Detail My map sensor was mounted underneath passenger seat.  But I moved it to top
of engine as per Howell.  Troy of Howell said it should be as close to TBI as possible.Jerry

The instructions say to mount the MAP sensor on the rear flange of the engine compartment..... Wire is too short.  The answer seems to be mount the MAP sensor as close to the vacuum source as possible.  I mounted mine with the vac connections down and I used a cable tie to attach the sensor to pipes and cables near the TBI.  I connected the vacuum connection to one of the sources on the front of the TBI.  The instruction sheet is in error when it says to use a vacuum connection on the rear of the TBI.

Click for Detail I chickened out on the O2 sensor,  I had it welded in for me...I hope I don't need headers for a while.

Click for Detail This was the part I did not look forward to installing.  I did not want to punch a hole in the gas fill pipe and put an obstruction in the already slow filler tube.... Sigh, I could find no better place so as per the instructions, I used a punch to make a hole in the pipe and then put in 1/8 pipe threads and the barb fitting.  The hose goes to the return from the TBI.  It went ok, I did not put a spark into the tank and I did not blow up.

Click for Detail Mounted the fuel pump relays to the rear of the fire wall.  Was a good thing I remove the old cruse control, this gave room for these to be mounted.  Now on to the final wiring.  When routing the electrical connections to the TBI, be sure none of them are placed above the old wires.  Space is critical on top of the engine and the new cable harness will get in the way of the air cleaner

Click for Detail It is not clear from the instruction sheet, but the Air Cleaner hold down bolt they supply replaces the bolt that holds down the injectors.  You will have to cut down the threaded rod and I added a Nylock nut at the right height to hold in the injectors.  This is critical since the small bracket that holds in the injectors can fall off when the Air Cleaner is removed and fall into the intake manifold.

Click for Detail The Nylock nut holds down the injectors while the wing nut holds on the Air Cleaner.  I removed the vacuum lines from the Air Cleaner.  The Howell supply's more gas for a cold start so the warm air should not be needed for starting.


My injectors were plugged when I first tried them.  Howell says the goop Holly ships inside the injectors causes this problem and Howell suggested tapping them with a wood screw driver handle.  I tapped every thing in the area and finally one of the injectors started.  I removed the other one and by shaking and tapping I got it to go.  When you replace the injector, it is necessary to seat it into the holder.  This is done by placing a socket over the injector and taping lightly with a hammer.  This will seat the injector and the two O rings.  See the picture below.

Click for Detail You can test to see if pulses are going to the injector by using a 12 volt test light between the two connections in one injector cap.  When you crank the engine you should see the light flash.  The pulse for the injector comes from the tach signal to the computer.  If you do not get pulses at the injector, make sure you are getting a good signal from the tach input.  I used my tach to determine this signal was present.

Fuel Lines

The Howell system comes with rubber fuel lines to and returning from the TBI.  We have never felt comfortable with these rubber lines over the engine.  Emery was the first I know of that put flexible    stainless shielded Teflon lines to  his TBI.  Manny converted his last year and promised to help Mr.C and me to get lines for ours. We had the return flex line made 4 feet long so that it would reach to the fill tube where the return line is attached.  The Feed line is 18 inches long and reaches to the firewall where we attach to the line to the injection pump.

These pictures show the lines we had made a Royal Brass.  Manny found their lines and service to be excellent and Mr.C and I had two sets made.  The rubber return line from my TBI was cracked and getting stiff after less than a year.  This made it clear that the rubber lines are not a good idea.

 I would recommend any one with these systems  replace the Rubber lines with some sort of a metal sheathed flex line.

Hooking up the Vacuum

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The way mine is set up now, and according to troy at howell, is :
    the left front port goes to the MAP sensor
    The center top one goes to the pcv valve etc,
    the center bottom one goes to the distributor, and
    the right one goes to the canister.
Here is a picture of my setup.  It is just like the list above except I have the MAP senson on the manifold

 Click Here for the Picture of the Engine Vacuum Connections

To verify the types of vacuum on your system, connect a vacuum gage.  With the throttle closed, if there is vacuum, you are attached to Manifold Vacuum.  If you only get vacuum when the throttle is open, you are attached to Ported Vacuum.


DO NOT USE the port in the back of the TBI unit  for the MAP vacuum any longer, the best location is in the front of the unit or from a separate manifold vacuum source.Troy

The latest word from Howell is that the TBI left and right vacuum connections are hard vacuum while the lower center one is ported vacuum.  They also say the vacuum advance for the distributor needs to be connected to ported vacuum.  This is different from the included instructions.

The way mine is set up now, and according to troy at howell, is :
    the left front port goes to the MAP sensor
    The center top one goes to the pcv valve etc,
    the center bottom one goes to the distributor, and
    the right one goes to the canister.
Here is a picture of my setup.  It is just like the list above except I have the MAP senson on the manifold

 Click Here for the Picture of the Engine Vacuum Connections

As Emery points out the GMC manual says the original equipment distributor is connected to PORTED VACUUM  when the engine is cold and MANIFOLD VACUUM when the engine is very hot using the TVS valve.
I hate TVS.  Period.  I've eliminated this system on every car I've had that uses it and gone to a ported
vacuum source.

Using ported vacuum, which is from a source located above the throttle plates, the advance mechanism in the distributer is allowed to move to suit the demands of the engine.  When vacuum levels are high, as in part throttle cruising, you have max advance.  When vacuum levels are low, as when the engine is under heavy load, you have  little or no vacuum advance and the engine operates under initial advance, which is what you set with a timing light.

There is an old trick that still works better than anything other than a dyno for setting initial advance, (or timing as it's    etime called), and that is to set your initial advance to the factory setting and test it under maximum load.  Usually a long grade or steep hill.  If you detect engine detonation, retard the timing a degree & try again.  Repeat this until there is no longer any pinging during your testing.  This is the optimum setting for your engine.  The other side of this test is if there is no detonation at the factory setting, add a degree and try again.  Still no pinging?  Add another and so forth.  Bear in mind however, that this method only works when the TVS is by-passed and you are using a ported source of vacuum for the distributer.  Also, take a moment to test the vacuum advance mechanism by using a hand pump (MityVac) or sucking on the vacuum line to the distributer while the engine is idling and note the increase in idle speed.  If there is an increase with the application of vacuum and subsequent decrease when you remove the vacuum, rest assured that the distributer vacuum advance is working properly. It's tough to accomplish more than this without using the costly dyno method.  To answer your original question about the plate movement;  With no vacuum signal present, the mechanism rests spring-loaded against a stop. The vacuum signal overcomes the spring tension and moves the plate. Vacuum applied to the distributer will advance the timing, not retard it.

  There is one other advance mechanism in the distributer that adds into the overall equation and it is called "mechanical" advance.  I won't go into that here since your concern seems to be with the initial and vacuum side of the house and also because working with mechanical advance requires the use of some specialized equipment.

BTW, a quick check for a "ported" source of vacuum is to use a gauge to test all of the ports on the carburetor (above the base plate) while the engine is idling.  When you find one that registers zero at idle & increases as you advance the throttle, you've found your source.HTH,Steve Ferguson

Click on Picture for larger picture

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Is obtained from a passage just above the closed throttle. At idle, no vacuum is   applied this port due to its location. As the throttle is opened, this port is exposed to manifold vacuum, so vacuum at this port begins to increase.

The manifold vacuum signal is high at idle and even higher when decelerating at relatively high engine speed with the throttle valves closed. At sea level, the idle manifold vacuum is usually in excess of 20" HG.


This is a simple but critical adjustment covered briefly in the Howell instructions that at first I did wrong because I did not under stand the sequence of the adjustments.

The computer adjusts the idle depending upon RPM, throttle position, temperature and other conditions.  The computer controls the idle using  a small stepping motor that adjusts the idle air control.  What this procedure does is to run the stepping motor to one end of its' travel and then you  manually set the warm engine idle as a starting point to give the stepping motor enough range of control for all conditions.

The following setup procedure must be followed exactly: ( I did not understand this)

        Warm up the engine
        Turn off the key and stop the engine
        Place the jumper between  the A and B connections on the diagnostic connector.
        Turn on the key but do not start the engine
(the stepping motor will now go all the way to one end of its' travel and you will be able to hear it clicking when it has reached the end)
        Remove the four conductor cable from the idle air control stepping motor
(the stepping motor is now positioned and removing power will let it stay there during adjustment)
        Start the engine
        Adjust the idle speed screw located near the throttle control to set the low idle speed
( set the RPM so the warm engine will idle with out help , should be about 650 RPM)
        Turn off the key and stop the engine
        Replace the stepping motor connector and remove the jumper from the diagnostic connector

The engine should now start and run on idle under computer control.  You should not have to help the computer make the engine idle and the engine should not stall when you remove your foot from the gas peddle.  My engine idles at about 1000 RPM under open loop computer control.


The Air Fuel Gauge has been installed.  The calibration of the instrument shows me the 14.7 to 1 opimum reading should be in the green area of the meter.   I have mounted the CHECK ENGINE LIGHT  on the dash near the meter  with the test switch so that if the light comes on during driving conditions, I can push the switch and "read" the light to see if the computer has gone out of lock.
I am going to use this meter to set the fuel pressure to the injectors as described by Jerry below.


I do have a few suggestions or maybe I should call them observations.

1.  That RTV patch on the adapted plate is critical.  There is nothing under
that area to support the RTV so you have to use quite a bunch in order for
it to seal.

2.  Be sure to also plug the unused mounting holes in that plate with RTV.

3.  I had the cruise control bellows that used a rod instead of chain linked
to the throttle.  I removed that and adapted to chain.  The throttle cable and cruise rod crossed.  Gas pedal was sticky.

4.  Right rear vacuum connection on TBI is ported.  According to Fellow from
Howell, should not be used.  Plug it off.

The port in the back of the TBI unit must not be used for the MAP vacuum any
longer, the best location is in the front of the unit or from a separate
manifold vacuum source.Troy

5.  On the TBI between the injectors is the fuel pressure regulator.  Preset
from Howell at Approx. 12 lbs.  I use a fuel/air ratio monitor permanently
installed .  With it I adjust that pressure to get fairly constant 14.2  of
14.7  (can't remember right now which).

6.  I do not at present have a knock sensor but maybe Santa is listening.  I
adjusted my timing to get a total advance of 36 degrees.  Turns out that is
about 9 degrees fixed on the dist.

7.  When  installed they had to change out my fuel tank switching
valve.  Said the fuel pump kept sucking it open and causing it to suck air.
Never did fully understand that.

8.  This fuel pump returns unused fuel to tank via the fill line.  If I had
known I would have had installed  a line from TBI back to rear instead
a fill tube.  Had no problem just don't like it.

Please let me know if I can be of any help. Jerry


The throttle body and injectors are stock Holley and are the same ones that are on the Holley kit that I installed in 1993.

A couple of suggestions:  I put the gasoline return line into the rubber hose (about 1: in diameter) that leads to the gasoline filler tube.  I used a solder type rigid copper fitting that fit the ID of the hose and that had a small copper stub that the smaller hose would fit on.  This saved me the drilling and tapping of the metal fill tube.

I have never liked fuel hoses.  They crack over time and can cause an engine compartment fire.  I connected to the steel fuel line that runs along the front crossmember and then I ran a 3/8" steel line from the right front frame, along the frame to keep it away from the exhaust and to the right rear
of the motor box and then forward over the engine to the throttle body.  If you remove the injector mechanism you will see how they have a hose barb fittings (inlet and overflow return) screwed into the throttle body injectors.  I replaced the hose barbs with brass fittings that would accommodate direct connection to the metal gasoline lines, thus eliminating the hoses.

I still have a hose going from the rear tanks along the frame rail to the front tube that goes along the front cross member but plan to replace most of this hose next spring.  Most of the rubber deterioration occurs where the heat is.  That is why I didn't want any hose over the engine. My second gasoline filter is a large metal can type that came with the Holley and is at the passenger right front frame and is easily accessible.  It presently has two small sections of hose hooking it to the gas lines, but I am planning to look for a similar high capacity metal filter with fittings so as to eliminate those two short hoses.  I could also just use brass fittings with compression rings on the filter if I don't find a suitable filter with fittings.

To adjust the fuel pressure at the injectors (Holley say about 18 psi) you'll need a fairly accurate fuel pressure gauge.  I have found that you can purchase a relatively inexpensive dial type air pressure gauge (0 to 50 psi) and unscrew the tire gauge fitting on the end and clamp a hose to it.  The one I bought was under $5.00 at Pep Boys.  I tested it for accuracy before using it on the TBI system and it was right on in the range I wanted.

I originally went to the Holley TBI system because I had just moved from the San Francisco bay area (sea level) to Santa Fe (7000 ft.) and my GMC performed terribly.  The TBI took care of all the problems that I was having with the carb at that time and has given me relatively trouble free service over the years.  I have used it across the country several times in all types of temperature, altitude, and terrain and feel that it is the best modification I have made to the GMC (6 wheel disk brakes are a close second).Emery Stora


1.  How far from the end of my exhaust Doug Thorley headers is the oxygen
sensor installed?  My headers are coated with a metallic ceramic coating.
If the sensor can be installed in the short extension tube , running from
the end of the header to the muffler, then I can have it re-coated, since I
assume that the bung will need to be welded in place?

Since the sensor has to see the exhaust from the whole bank I would guess it would mount like on my standard manifolds about 3 inches from where all the exhausts converge.

2.  Is there any advantage to installing an oxygen sensor in each header?

I guess it could, however program in the computer would have to be changed.

3.  What is the make, model, and CFM rating of the throttle body?

675 CFM Holly ProJection 2

What make and model fuel pump comes in the kit??  What psi rating is it??

about 14 to 20 pounds

Does it mount outside the fuel tank?

 on the frame in front of the tank

4.  Where do you recommend locating the:
     a.  Computer?  Any problem with it being located in the engine
compartment?  If inside the interior of the coach, what size hole is needed
to be cut into the floor?

Under the passenger seat and it is a 2 -1/8 inch hole

     b.  Fuel pump fuse holder, relay, and ESC.

on the fire wall

5.  Other than what you told me earlier below about an optional available
knock sensor, et., are there any other optional TBI parts/components
available from you that I may want to consider for my installation?

They have a fuel pressure gauge
Our fuel pressure gauge is for tuned-port injection only. You would have to get one from a parts store, a 15 psi gauge is used in this system and locate the gauge between the TBI unit and the fuel pump anywhere in the line, preferably closest to the TBI unit or extend it out into the Cab.Troy

6.  Do you have anything available that will show the engine check light?
I'd like to do some planning for layout on my instrument panel if I can get
details on its overall size.

They don't supply the light, just say to use a 12 one.  I am going to use one on a switch so I can switch on the diagnostic mode on the fly.

Apparently the alternator used on our coach is thought to be the source of
electrical/RFI problems that's affecting one of the port fuel injection
(PFI) systems a number of people have installed on the GMC Motorhome.
Theory I heard is that unlike ours, the new car alternators have circuitry
that is compatible with the electronics of the fuel injection system?  Are
you aware of any voltage spike and RFI problems caused by the alternator
used on our engine, affecting your kit operation?


7.  Will there be any conflict with the accelerator cable mounting bracket
being in the way of connecting the gas and vacuum lines to the throttle body
in my vehicle application?

Nope they have that taken care of.

8.  Does your kit include:
     a.  Appropriate fittings (e. g. a "T") for both the oil pressure and
the water temperature senders so that I don't have to go out and get them?

Yes they do

     b.  Fuel pump power supply wire, which would need to be routed to the
pump located just in front of the driver side rear wheels.
     c.  Fuel pump fuse holder.
     d.  A wiring harness having adequate length and sufficient slack so
that I can position it to all the components on the engine without
stretching some of the components, which then are hard to mount where they

This seems to be good, they supply all that is needed

     e.  A diagnostic connector??  If so, what type?  Where does it mount?

with the computer under the seat

     f.  PROMs optimized for the GMC Motorhome having a 403 cid engine.


     g.  Vacuum plugs to plug any unused throttle body port.

they seem to use all of them.

     h.  Fittings on the throttle body with sufficient tubing length to
hookup the fuel supply and return lines/hoses.

Yep if you like rubber fuel lines

     i.  Distributor switched power supply wire.

got it

     j.  Terminal to connect wiring to a computer controlled distributor
that matches the type (GM) needed.

No they do not do this on the one I am using

     k.  A "block off" plate to cover up the well opening in the intake
manifold exposed by elimination of the carburetor choke heat pick up pipe.

No, Mine was already covered, I am not sure how this works

     l.  Any items of other than new parts?

nope all seem new,  Maybe the computer ?

9.  What parts will I require in addition to what you supply to hook up the
system on my GMC motorhome?

3 ea 1/4 in washers  and a 3/8 bolt so far

10.  Are there complete, detailed installation instructions, specific for my
vehicle application?  If so, do they address each of the following:
      a.  Hookup to the fuel evaporative canister.


       b.  Existing heat tube from the exhaust manifold-to-air cleaner
housing and the vacuum hose to the air cleaner air entrance throat valve
that controls heat into the carburetor.

not sure yet

       c.  Dimensions, etc., for mounting the accelerator cable to the
throttle body in order to get full throttle opening.

Yes and a bracket

       d.  How to secure the accelerator cable bracket in place.

same as above

       e.  Type and size of hose to use for the gas return line.


       f.  Need to calibrate the system once it's installed?  If so, what
equipment does one need to do that?

See the notes above from Jerry

       g.  Vacuum line connections and plugging.
       h.  Computer controlled distributor wiring.
       i.  Any unused wires found in the wiring harness.
       j.  Bungs for mounting the oxygen sensors.  How many oxygen sensors
are included?


       k.  A complete system wiring schematic, including the distributor.

Nope just the GMC manual

       l.  Where to route and how to connect the fuel return line back to
the gas tank.


11.  Can I use the original engine compartment cover or do I have to raise
it to clear any increase in height from the TBI system.

Same cover

12.  Do you have available an engine analysis of the before and benefits
after installing the TBI kit?  Can I get a copy of it to look at?


From: Troy Brown []

? Any reason I can't furnish the distributor (e. g. a 81-85 Olds V-8 one)?
Are you saying a different Esc module (what does Esc stand for?) is required
with the knock sensor?

You may furnish the distributor if you like, 81-85 Olds V8, computer
controlled distributor.
ESC stands for Electronic Spark Control,  the ESC module from a computer
controlled ignition system is required along with the knock sensor.

? If one opts for a non-vacuum operated distributor, what additional parts are
required??  What would the price be then??
Is there any lights or controls that need to be mounted adjacent to the

The price of the kit is $1200 , $275 for the distributor, coil, and  coil
connector and jumper.  The knock sensor is $45 and the Esc module is $60.
The only light there is, is the check engine light in which you would mount
to the dash.

?Does your system control fuel delivery and control the spark??

Yes our system controls fuel delivery, but it does not control spark.
However, we can control the spark if you would  like to change the

I'm interested to know how your TBI system for a GMC Motorhome with a 403
cid engine, compares/differs from the TBI system that Turbo City

Our system is the same as Turbo City except for; our system allows you to
maintain your HEI vacuum advance distributor.  We have customized the chip
to eliminate the original computer controlled distributor system.  This
system is similar to the 87-90 GM 2 bbl TBI systems using GM parts except
for the throttle body and fuel-pump.  The cost is : $1.200.


If anyone is interested in what is involved with changing over to ESC (electronic spark control) this is where I am at so far.

Had to remove my TBI harness and send it and the ECM back to Howell. They are going to rework the harness and trade out the ECM. I  have to pay $75.00 to burn a new chip for the ECM and $30.00 for new connectors on the harness.

I received a package yesterday containing:
Coil (remote)......$40.00
ESC module......$60.00
Knock Sensor....$45.00

They are all new GM parts. Yup, thats $550 invested minus $225 for the HEI  being sold, so the upgrade is costing me $325 plus tax, shipping,etc. One  could probably shop and find parts cheaper, especially if parts from the salvage yards were used. I just like the idea of all my engine electronics
coming from one source with the comfort of having technical support just in case something goes haywire. When I get my harness and ECM back (shipped out yesterday), I will get it all installed and let you know how it runs.

The engine starts easily without even touching the pedal. It idles as smooth as glass. The throttle response is crisp without even a hint of stumble or hesitation. These features alone made this project
worthwhile for me. Now, if I get a little added economy and / or performance, then that would be an added bonus. I do expect some increase in engine longevity with the electronic controls as well.

The change from HEI to HEI / ESC will end up costing me about $200. If there is a 1/4 MPG increase, then at $1.40 / gal for gas, I figure the ESC  will pay for itself in 70 K miles. The 1/4 MPG is purely speculatory, but the point is, depending on coach usage, I don't think that the change to ESC
alone will have economical pay offs. But, for the benefits mentioned above, I  still recommend the change. Dave Meekhof

Training Manual for an EMIC ESC system

I am happy to report that outstanding customer service is alive and well at Howell Engine Development in Marine City Michigan.  I experienced it last Friday.

After driving all night from Eastern Ohio to Marine City without incident, my brother and I talked with a couple of fellow GMCers while Troy Brown looked over my TBI to find an intermittent problem that I had been unable to locate for some time.  He found it (intermittently faulty ground) and while he was at it, reprogrammed the computer chip to fatten up the mid-range performance and went through the entire system.  This included test drives with a scanner installed to read the system perf ormance under various driving conditions. We then left for the 350-mile return home. South of Detroit, near the I-275/I75 junction, the engine suddenly died and we were unable to restart it.  I called Troy and he went through
several checks over the phone, to no avail.  He then said he would be there in about and hour and a half.  We turned on the roof air, relaxed, and waited. When he arrived, he had with him a box of parts to cover every possible problem.  It turned out to be unrelated to the fuel injection system
itself -- a failed ignition coil.  We took the cap/coil from the complete distributor that he had brought, installed it and were on our way without further incident.  In addition to offering an excellent product, this company is made up of people who do what it takes, and much more, to serve their customers.
Until Friday, I wouldn't have believed it.  Drop me an email if you would like to know more.Terry Wallace

Smog testing
I also have Thorley headers, that does have a California waiver, but there is only one place here in San Diego that I know of, Juan's in San Marcos, that will smog a GMC with both mods. I have had mine smogged there three times.

I would have to sell my GMC out of state if it weren't for Juan's. I don't have the mechanical fuel pump, carb or air cleaner, sure wouldn't be easy to borrow a set up every 2 years. So there are places that will smog GMC's with fuel injection, just ought to
ID them before you install it.
Regards, Gene 76 Eleganza, Vista, CA