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Old 02-27-2014, 04:42 PM   #1
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Quadrajet to Fuel injection conversion

Sorry if this is a rehash of old topics, but I could not find any recent reviews about Motorhome conversions from the 454's Quadrajet to a TBI fuel injection.
My Silver Bullet is a 1984 Excella 270 with the stock 454 and 3 speed tranny that I picked up in 2012.
So... retirement days are coming soon and I am about to venture out beyond my local camping spots for the first time. It will be just a 2000 mile wander, but with gas creeping back up to $4 a gallon and this machine getting only 7 MPG, I think my carburetor is due for a full rebuild and I am wondering if going for a fuel injection conversion is worth the extra bucks?
A proper carb rebuild will be around $350 but for about 3X that I see I can get a kit from Affordable Fuel Injection for TBI fuel injection kit.
I see that there are others mentioned in old discussions, but they are either pricy, incomplete or all of the above.

My question is...
Has anyone out there done this conversion to their 454 from this vendor and how well has it worked for you?
OR
What other suggestions do you have?
Thanks
Wayne
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Old 02-27-2014, 04:53 PM   #2
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There has been a lot over the years on the GMC motorhome forums about converting the GMC 455 Olds engine to fuel injection.

My general impression has been that those who have done it are happy up to a point, but it did not change their fuel milage or reliability vs. a properly maintained Quadrajet. And once it is done, it is kinda up to the owner to maintain the new system, as it is not standard and it is hard enough to find someone who knows the Quadrajet, say nothing about the conversion system which has been installed.

Either way you go, maintaining a 40 year old technology engine and accessories is going to keep you involved.
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Old 02-27-2014, 05:43 PM   #3
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Quote: "I think my carburetor is due for a full rebuild..."

Just curious; what is the reason for converting to fuel injection?

* To replace (or repair) a leaking or malfunctioning carburetor?

* To improve fuel economy?

* Some other unstated reason (please specify)?

Your answer may help others address your question more accurately.

==========

My personal comments:

If the existing carburetor doesn't leak fuel, the engine starts reliably, and power is smooth without surging or other problems, I wouldn't rebuild the carburetor or convert to fuel injection just to improve fuel economy.

We had a 454 V8 in a 1978 Chevy crew cab pickup, and there is very little one can do to improve gas mileage for this engine other than to put it in a smaller, light car, like a Corvette and add overdrive. It's basically a truck engine that sucks gas.

We were satisfied with the towing capabilities of our Chevy pickup; but in over 20 years of ownership and several carburetor rebuilds, a couple of new engines with both 3/4 race and RV cams, and a new transmission, we didn't see any improvement in our fuel usage until the Chevy was finally replaced by a Tundra.

When towing, the 454 averaged 7 mpg on the flats, 4-5 mpg on mild grades and 2.5 on steep hill climbs. We never owned a 454 with fuel injection, but I suspect the mileage would be about the same. I'm sure others will share their experiences with TBI models.
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Old 02-27-2014, 05:54 PM   #4
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Our mileage went from 4-5 mpg to 7-8 mpg with a quadrajet rebuild. It was running okay before the rebuild, it just could not pass a gas station.

I will be watching this thread, have had the same thoughts as Wayne and want to knowhow these "new generation" TBI systems are working out. MSD markets one now, in my mind they have the advantage of being an established company that will hopefully still be there when things go wrong.

Is anybody running a smaller carburetor, like a 650 CFM Holley?
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Old 02-27-2014, 05:58 PM   #5
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I have no experience with motorhomes, the 454, or changes to it. However, if I were contemplating such things, I would get in touch with Edlebrock and discuss their system for you application: Edelbrock.com - Electronic Fuel Injection - E-Streetâ„¢ - Introduction

They have been building aftermarket EFI systems for a good while, and should be able to tell you if their system will help.
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Old 02-27-2014, 06:27 PM   #6
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See what Summit Racing Has to offer. A good TB fuel injection system should work better than a carb and compensate for altitude changes and temp changes etc. I believe you can tune the thing with a laptop and add an O2 sensor to put things in a feedback loop and monitor the fuel/air ratio. You should have the ability to retune the system as you change things or the engine ages. A local hotrod shop might be able to advise you or go to some 454 specific engine hop up forums. Putting in a gear vendors overdrive might also help.

Perry
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Old 02-27-2014, 09:20 PM   #7
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FAST fuel injection has a simple easy to install product that seems to work with ANY fuel injection hardware for less than $1,000.

My son and I installed it on a Ford 302 with stock 90s Ford hardware. Easy to instal and easy to tune.
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Old 02-27-2014, 09:24 PM   #8
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I have also bought and installed Edelbrock's Pro-Flow II on a 408 Ford.

This is a top notch injection setup that works perfectly for fuel and spark.

The FAST system I mentioned above does not control spark, but it is less than 1/3 the price, and the HEI on your 454 will work fine.
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Old 02-27-2014, 09:30 PM   #9
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Both are great products in my opinion, one is a Chevy the other a Cadillac.


Mind you, the FAST setup will require some kind of stock hardware for your engine, but this stuff is usually fairly cheap to get. The Pro Flow is totally inclusive bolt on from the fuel pump to every last wire.

You will however need to make bro vision for a return line port in your fuel tank regardless of whatever F/I you install.
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Old 02-28-2014, 11:02 AM   #10
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Thanks for all the fast replies, I as still hoping someone has used the Affordable Fuel Injection system On their Motorhome and can report their experiance before i plunge into this project.
The Qjet on this motor works "OK" but it is leaking fuel, and the secondaries stick occasionally, so a proper rebuild is one option. It also takes forever pumping the throttle before it it fires.
If I go the carb route, I want to keep my original. I have had bad results buying rebuilts from local parts stores. I regret giving them my original cab only to find the rebuilt one is a banged up poorly rebuilt mess. I prefer to send the original to a trustworthy shop.
On my 77 20' Argosy, I had sent in the carb to Savas Tuning for a proper rebuild, and it worked great. I have not been able to get Savas to answer the phone so, I am looking into the fuel injection as an alternative.

For TBI systems, I looked at Edelbrock and Summit and a few others, most were too expensive to justify or were incomplete solutions.
AFI should be around $1200 for everything, and I will still need to add a port on the exhaust pipe for the O2 sensor. I think swapping the stock HEI distributor for a EFI will be desirable for proper timing.

As for the fuel lines and pump, I think this one has a return line at the mechanical pump, if it does, I would just need to extend it to injector assembly along with the main fuel line. I will have to see how easy it is to mount the electric fuel pump near the tank, mine is in the back and hopefully I can find a spot on the frame.
I would also like to eliminate the unneeded Carb related emission gear, I am not sure if the air pump will be needed? I am also guessing the exhaust bypass valve may be able to be locked out.
I am also considering putting on a Banks exhaust system sometime in the future (Maybe after I win the lottery)
One problem I can see with the AFI system is that if you need a PROM update, you have to go through them. Good points for their system is that other than the harness and their PROM chip, everything is stock GM parts, so getting replacements should be easy.
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Old 02-28-2014, 11:10 AM   #11
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Quote:
Originally Posted by WayneG View Post
I am also considering putting on a Banks exhaust system sometime in the future (Maybe after I win the lottery)
On my 83 310 (long since sold) the biggest improvement I made was a set of Thorly RV headers and a decent sized exhaust pipe and muffler system.

That reduced the engine temps considerably, reduced vapor lock issues, and gave me a LOT more power. The original CI headers and exhaust system on mine apparently was very restrictive.
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Old 03-02-2014, 08:11 AM   #12
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Again, Thanks for everyone's input, it is great to have a place where we can compare experiences, problems and solutions!

I am considering headers for a future upgrade, at the moment I need to make a decision on either spending $350 for a rebuilt carb or about a thousand more to install fuel injection.

I guess nobody reading here has used Affordable Fuel System's kit so I guess I will be the guinea pig and report back the results.

It looks like everything should be strait forward. Since the Qjet air cleaner probably wont work, I am a bit concerned on if there will be proper clearances for an air cleaner in the dog house, and where I can get one that will fit the GM TBI?

If I can work that out and they can build the harness and ship by the end of March, I will order a kit this week.

BTW, Being a cold weather shut in gave me time to take the receipts that came with this 1984 Airstream from its previous 2 owners and put them in a spreadsheet. The receipts go back to 1990 at 42K miles. It now has 100K miles on it and the receipts add up to almost $22K before it was my turn!
So far in my 2 year and 2000 miles of ownership, I have put $6K into it, but much of that is upgrades and not repairs. whats another grand anyway? I will spend that on fuel on my first wander to Kentucky in June.
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Old 03-02-2014, 08:51 AM   #13
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Did GM ever offer this engine as fuel injected? Any chance to convert to the GM system from a used engine?

Sorry no hands on info on your question.
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Old 03-02-2014, 09:21 AM   #14
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Quote:
Originally Posted by GCinSC2 View Post
Did GM ever offer this engine as fuel injected? Any chance to convert to the GM system from a used engine?

Sorry no hands on info on your question.
There are mentions of some folks taking this route. I believe GM started in the late 80's with TBI systems. You need to pull the entire harness, computer, TBI, sensors, and distributor. But there will be a problem that the computer is programmed for the engine, trany, and other vehicle specs you acquire the parts from.
Basically this company (AFI) is using GM parts either new or refurbished with a custom wiring harness and computer programmed for your specific application.
If I was adventurous, I could try the junkyard/ebay method for probably about 1/3 the price, but I am betting that the extra cash spent .vs. the extra problems and work is worth it.
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