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Re: [GMCnet] Injection versus Carbs [message #73324 is a reply to message #73323] Tue, 09 February 2010 06:40 Go to previous messageGo to previous message
Jim Bounds is currently offline  Jim Bounds   United States
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Registered: January 2004
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Have not been following this thread, not had time to get up on the net much lately but since it looks like many are putting 2 cent in on this I figured hey, I might be able to shed some light on the subject from this side of the bench.

it really comes down to what you are looking for out of your GMC.  if it is a object of your frustration, something to keep you out of the bars and into the realm of a custom hot rod for your fingers only then TBI or direct port is probably for you.  I have been to this mountian, fell off the other side so to speak and am here to tell the tale.  I build coaches mostly for folks to use not to play with and for that guy-- someone who does not feel the deep seated desire to mess with their machine and make allowances for it time and again, a carb is the way to go.  i know this throws in the face of what many will tell you is an atribute of FI, I tell you now-- for installing an aftermarket FI system on an old war horse motor you are crawling down the wrong hole.

This is where I get dander up-- and i know there are many out there that are pleased as punch with their FI systems but before you string up my ideas please tyake a listen and this is for those out there sitting, thinking about making the plunge-- I just want you to have a full view of what you will be getting into.

One of the huge positives about owning and maintaining a GMC is that it can be looked at as a "pregnant Toronado".  It is really simple to work on, get fixed, find parts for and have someone work on.  Bubby over there on that tractor had his daddy cut his teeth of keeping his Toro on the road and when a stock 455 breaks down there are many people out there qualified to work on it.  there were fifty million Q-jet carbs made and just as many parts made to fix them and people out there who know what to do to fix them.  Complicate the world by throwing in an aftermarket FI system on top of it all and your pool of techs start to dwindel. 

Couple that with the absolute fact that if you do have issues you, yourself will have to be an integral part of the diagnostic tree, the identification and procurment and many times the installation of the unique parts that make the system work.  Make sure you are happy to do that-- and many people are-- before you get involved in any form of FI.

Now it's true all new cars have FI as well as total engine management designed computer systems and it is true these systems are very reliable but look, that is not what you have.  The auto manufacturers spend millions of dollars tayloring those systems to the drive train-- we are only adapting one system at a time.  There is no way you can link together the system you purchase in a box so seemlessly to your old 455 or 403.  You have to sort of wing it in and together.  Some systems seem to work well and of course that is the goal but not only is there no guarantee but chances are there will be time and energy put into adapting any FI system that was not anticipated.  When I work on a coach, folks want to know how much it will cost to do whatever it is we will do.  it is difficult to leave a project open ended and that is exactly what you have to do installing a FI system.  You never know what road block you will run into.  I have installed
enough FI systems, repaired them and got coaches going that had them to know they are like a box of chocolates.  One person says I got a cherry while another one finds they have a pit!

What is the goal--- do you want appreciably more mileage, more torque-- you will not get that from the bucks put into a FI system.  Do you want a faster, smoother start up and no dieseling when it turns off-- that is possible.  Do you want altitude changes to the timing of the motor, OK you can usually get that but hey, it will not effect performance enough to make the move cost effective and that is what my customers seek.  Does it make the motor easier to get fixed-- no, usually you will have to do the job and if not there will be a charge for the tech to understand what is there before they can work-- that costs $.  Is it cheaper to work on-- no -- so what is the reason to do it?  To be cool, OK, I'll give you that but must of my customers just want the motorhome to run reliably and you can get that with a good running, maintained carberator.  Yes, you might have a shorter maintenance cycle before you need to have work done but doing it yeilds a
good running machine almost every time.  Sorry but as I said after climbing the mountain and about having folks upset at me I have to say a carb will do for a GMC all that is expected and it will keep the machine in the realm of reliability and easy of maintenance most look for if they seek a usable coach.

I will not install a FI system, there are other shops that will and if you say-- hey, I still want one of those please seek out those that like and will install and back a FI system, I am not warm and fuzzy abot that leap for mankind anymore.  I have to customer who blew off their direct port FI systems and now have a coach that runds, gets descent mileage and can use it without fear.  Thats enough proof for me.

Some will say, awe-- he doesn;t know how to properly install a FI system-- sorry but nope, thats not the case.  I can install it just fine-- the problem comes in setting up and maintaining the machine of which I -- the installer -- is not responsible for.   Bottom line, if you want to link your personal abilities and labor to yur coach.  If you wanna be the one to keep her running and you like to have someing different then by all means go for a systemm.  I think you might have fun with it but if you want your coach to run now, tomorrow and the future with a minimum of grease under your own fingers-- brother stick with your Q-jet.

Now I know there are many contrasting views and I welcome them to make their proposal to all who want to dive into that deep end of the pool, just know I'll be at the shallow end with a towel.

My opinion--- Jim Bounds
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