Author Topic: 1989 Winnebago SuperChief 454 7.4L Smog Delete  (Read 67 times)

Offline Winterbagel68

  • *
  • Posts: 2
  • Member since: 2020
  • I own: a Motor Home
  • Year: 1989
  • Make: Winnebago
  • Model: Super Chief
  • Chassis: Chevy P30
  • Engine: 454 7.4L
1989 Winnebago SuperChief 454 7.4L Smog Delete
« on: June 28, 2020, 03:45 PM »
Hi I’m new to the site and am so appreciative of all the good info I picked up here over the years.  Well here it goes I have Super Chief P30 454 7.4L Gen IV and just raced the engine by myself with a bit of help from my wife who moved some levers on the forklift I rented to get it in through the door.  I removed all the air boxes and air pumps, purchased the cast mounting brackets for Gen V engine, passenger side alternator and driver side air conditioning (top) steering pump (below), new reverse water pump, all appropriate pulleys and tensioner that’s sits below the alternator.  All this to eliminate the smog air pumps and use one serpentine belt for the system.  I still have the air boxes if needed still. How do I rework the system to to use an Edelbrock carburetor and distributor? Any suggestions on the carburetor and distributor? I also purchased Doug Thorley ceramic coated headers. So as you can see I’m committed at this point but I’m so lost how to rework the system without the smog pumps and boxes to achieve the proper vacuum timing as well how do I deal with the air hose that came off the air canister to return air to the fuel tank?  As well the Edelbrock Performer air intake manifold sits higher and the carburetor as well air cleaner may not fit properly under the shroud? Use the old air intake manifold? Buy the low rise air intake that fits properly, which I’m having a difficult time locating online. 
I am committed but am a bit over my head on these fixes any help would be appreciated. 
Yep I know very needy.
Once again thanks for the help, this is a fun project and I’m learning tons but it needs finished to enjoy some road time.
Thanks Doug Winterbagel

Online Rickf1985

  • 6 year member
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  • Posts: 5927
  • Member since: 2013
  • I own: a Motor Home
  • Year: 1989
  • Make: Winnebago
  • Model: Chieftain
  • Chassis: Chevy
  • Engine: 454
Re: 1989 Winnebago SuperChief 454 7.4L Smog Delete
« Reply #1 on: June 28, 2020, 07:05 PM »
Welcome Doug, You certainly have gotten right into it. I am a firm believer in the Edelbrock intake products. I always go with the Performer series carb and manifold but the fact that you are working with a GenV I would suggest you call Edelbrock directly and see what they suggest. I am not sure if the Gen IV manifolds will cross over. I am pretty sure the performer manifold is about the same height as the stock steel manifold. The Edelbrock carb is a bit shorter than the Quadrajet. If you do not need the emissions equipment then there is not much to worry about but you are going to have to find a way to get the carbon filters vented into the air filter or you will have a lot of gas vapor from the tank. Air back to the tank is part of those canisters mounted to the radiator support. Distributor I would strongly suggest contacting Performance distributors.  https://performancedistributors.com/


Now, with all of that out of the way let me ask this. You are about to sink a LOT of money into carburetor and manifold and distributor. Why don't you go with fuel injection? It is much more efficient, no adjustments for altitude, no choke in the morning. 1200.00 would get you everything you need to do the job and you use your original manifold and air cleaner. Therefore original positioning and original hookup for vapor canister.

Offline Winterbagel68

  • *
  • Posts: 2
  • Member since: 2020
  • I own: a Motor Home
  • Year: 1989
  • Make: Winnebago
  • Model: Super Chief
  • Chassis: Chevy P30
  • Engine: 454 7.4L
Re: 1989 Winnebago SuperChief 454 7.4L Smog Delete
« Reply #2 on: June 28, 2020, 08:04 PM »
Thank you so much for responding, I’ve been reading your posts for about three years now and from what I can tell you and jimitaska are the best knowledge base out there and appreciate what you’ve shared with people.  The web is a place of varying opinions as well just tons of information to sift through.  So thank you again for sharing.
Once again here it goes.  My wife just asked me who I was talking to and when I responded she said we’re spending more money on this thing?!
Holley Scorpion, put lots of thought into that even had a line on a gen V motor with all the trimmings.  Opted out on that engine, it needed rebuilt too so I went with this option. 
Already have Edelbrock air intake on the engine Performer 2.0 still have the original air intake (shorter profile I measured) I was thinking it would be the best to put it back on.  Is the original as efficient as aftermarket? I like the sound of better gas mileage for sure so injected is an option, Scorpion or EItech?
Big questions;
How do I deal with all my vacuum lines for cruise control, heater and what ever I just yanked out that was the spaghetti that took up the whole right side of the engine?
How to deal with the canister reattach conveniently this time what else will need to attach to the canister?
Electrical; from what I’ve read the Scorpion is not to difficult to wire into the harness?
So $899 to $1200 for fuel injection or $400 carburetor & $250 distributor or use original, not my style?
How much better gas mileage will I see with injection?


Yep I bit off a bit but I’m having fun, the wife wants it done and on the road at least not in front of the house and can be stored for the winter.  So solid advice would be greatly appreciated.


Thanks again The Bagel

Online Rickf1985

  • 6 year member
  • *
  • Posts: 5927
  • Member since: 2013
  • I own: a Motor Home
  • Year: 1989
  • Make: Winnebago
  • Model: Chieftain
  • Chassis: Chevy
  • Engine: 454
Re: 1989 Winnebago SuperChief 454 7.4L Smog Delete
« Reply #3 on: June 29, 2020, 09:28 AM »
You do mention the size of your unit but since it is a Super I am guessing it is at least a 33 foot. You ar looking at anywhere from 6-10 MPG depending on driving style, wind conditions against or behind, hills or flat ground and whether you are towing. Physics states that it takes a certain amount of energy to move a certain amount of weight a certain distance. There is no changing that. So all these claims of 34 foot RV's getting 15 MPG on gasoline ore total BS! If you have an inline computer fuel sensor then yes, at coast and light throttle it will read fantastic mileage but climbing a hill it will be in the .25-.5 MPG range. Yes, you read that right, picture pouring a gallon jug of gasoline directly into the carb at a steady pour at full throttle! These engines are very thirsty and there is no getting around it. What fuel injection does for you is that it senses the air/fuel ratio hundreds of times a second and adjusts the fuel mixture as needed to keep that ratio right where it needs to be. A carburetor cannot do that and all it can do is pour gas in at set rates mechanically, at everything but cruise it is going to be giving you more than you need for the most part. So OVERALL gas mileage will be better with fuel injection, driveability will definitely be better with fuel injection. No more pumping the gas to start, no matter what the temperature is. Just turn the key and it starts. As far as hooking all the vacuum stuff back up most of it works off of manifold vacuum and you can tap the manifold port at the rear of the manifold where the transmission port is or the injection units have most of the same ports as the carbs they are replacing for the ported lines. I suggest you go to Summit Racing and look at what they have for injection units. The FITech is a good unit, the Scorpion I am not familiar with. I know of the Holley Sniper and they are a very good unit but you are paying for the name. One of the more expensive parts of the EFI systems is the frame mounted fuel pumps and they do not last all that long for some reason. Here is an option to look at when looking at the fuel injection, It would mount up front and be fed from your original fuel system and in turn this feeds the injection system. No other mods are made to the stock system.  https://www.summitracing.com/parts/hpf-40004   Also, when looking at the injection systems do not make the mistake of thinking that a bigger system will give you more Horsepower, it will not. It would take a lot more mods on the engine for that.The fuel injection and a high quality set of headers would be the best modifications you could make. Most of these injection systems can control timing also. It pays to call the company that you want to go with and ask them what they suggest as far as distributor, consider that these systems are designed as direct replacements for carbs so most are designed to work well without changing a lot of other stuff.