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I Have a 1979 barth 454 just can't leave it alone. I would like some input on converting from Q-Jet to TBI Do you think there would be a fair gas mileage increase? or would i do a bunch of work for no gain.I can do the work and i have a donor truck so the cost will be minimal.I also have some thorley tri-y headers.Any and all opinions are welcome. I also went to Blue Springs yesterday and they are full for the get together I was most disapointed i would sure like to meet some fl.Barth folks Thanks!!!
Richard & Robin
I don't know about tbi, but go to SEARCH - "Tech Talk" - "Ceramic Headers" - for some ideas on the Thorleys. (I am a Doug Thorley believer - since 1967).
"You are what you drive" - Clint Eastwood
Can't help with the tech stuff, and probably not much with Blue Springs either, but if you want to PM me a contact number I'll check any availability when we get there Fri morning the 14th and maybe we can slide you in.
79 Barth Classic
Some good discussion on carb/TBI swaps:
TBI needs a bunch of electronics to make it happen, but the results should be a bit better fuel economy. BTW, the concept has been around since the '50s; my '55 F-35 Beechcraft Bonanza had a pressurized carb (fuel pressure was around 14psi instead of the usual 4-5psi); the claim was fuel would atomize more efficiently. I don't know if it did, but I got 17-18 mpg @185mph True).
'94 28' Breakaway: MilSpec AMG 6.5L TD 230HP
Nelson and Chester, not-spoiled Golden Retrievers
Sometimes I think we're alone in the universe, and sometimes I think we're not.
In either case the idea is quite staggering. - Arthur C. Clarke
It was a woman who drove me to drink, and I've been searching thirty years to find her and thank her - W. C. Fields
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I have had 454 pickups, and have noticed that TBI will give slightly better economy and better power at altitude. As in climbing up to 12,000 feet, where the air is thin. .
You would probably best with a donor vehicle that would supply the TBI, transmission, instruments and electronics. The GM TBI package includes the 4L80E tranny, which has the advantage of an overdrive, but the disadvantage of being less strong than the TH400. It is also way more expensive to repair and more difficult to get parts for. A GV can be added to the TH400 to provide OD.
When I did my remotor, I looked at TBI, and after considering the whole package, stayed with the Qjet on my 502.
In the grand scheme of things, the amount of money saved on fuel is just a little blip on the radar. We find that, even though fuel is a considerable expense, the amount saved by this or that scheme is not a lot after all the numbers are entered into a spreadsheet and analyzed by my CPA.
84 30T PeeThirty-Something, 502 powered
do you think i would be better to add a performer intake and stay with the Q_Jet? I will be staying with the turbo 400 as they are bullet prof and i just had it rebuilt. although i have considered the gear vendor overdrive but i can't justify the expense for the savings in mileage as i have heard is is only good for about 2 more miles to the gallon. but i don't know anyone who actually has one to to be able to give me real numbers. Thanks for your reply,
Richard & Robin
|The Old Man and No Barth|
Much as those of us who tinker & tweak might wish, there's no economic justification for anything beyond a proper tune-up & a sweet running engine. A TBI conversion sounds like fun, but odds are in the end you'd find it more costly & more trouble than it was worth.
Thorleys, a Performer, & a well-tuned Q-jet are relatively easy, relatively inexpensive, & relatively pain-free for the do-it-yourselfer. Done right, any of these mods will give you a little performance increase. Done together, you'll know you've done something good.
Bill H has a favorite Q-jet guy, though a good book on Q-jets might lead you to some self-experimentation. In any event, you've got some distributor tuning to do as well.
As Bill says, though, trying to justify any of it on the basis of fuel mileage, is a lost cause.
We're dealing with fun, & fun with automotive devices costs money, even if we turn the wrenches ourselves.
I made a major change to my SOB before I bought the Barth for the same reasons you are considering it. The first two things to do are change to a Edelbrock Performer intake manifold and install Headman or Thorley Headers. Make the exhaust system a full dual with large free flow mufflers and individual tailpipes. Then get the Q-Jet blueprinted by a race shop of a tuner so the fuel flow is smooth and progressive. That raised my miserable 6 mpg to 8mpg on a 15,000 lb 26 footer. The next and best is get an overdrive, either an add-on unit to the TH-400 or the manual kick-down version of the 4 speed GM 460 with a locking converter. These are used in larger trucks, not the car versions and you will have to have a new driveshaft made. That will cost about $500 with the universals. That package got me to 10.5 mpg on trips both north (elevation rising) and south with elevations dropping. All in all you would spend $3 to $5 k to gain 4 to 5 mpg or about $.40 per mile savings. At that rate it will take 12,000 miles to break even, with no maintenance.
I made several trips across the eastern US and was very pleased but then the Bart appeared - better coach, no leaks, all aluminum, bigger and it already got 8.5 mpg. Grabbed the Barth Regency with a big diesel and never looked back. In regard to the 460 tranny - it will work if properly overhauled to put in Corvette clutches but you will have to be careful if you tow anything and downshift out of overdrive on hills greater than 3-4 percent grades.
Good luck. If you need a source for the carb work I can send you a shop in Texas that does the NASCAR spec carbs for racing.
1993 32' Regency Wide Body, 4 speed Allison Trans, Front Entry door, Diamond Plate aluminum roof &
1981 Euro 22' w Chevy 350 engine and TH 400 tranny
TBI really is just a glorified carb. With a MAP sensor the TBI can make fuel corrections based on O2 data, throttle position, engine temp, altitude and engine load. Drivability will improve, but a well tuned carbed engine will give you almost the same fuel economy.
If I had the time and money I'd run a sequential port fuel injection system. That's a real fuel injection set-up. But, it's really complicated.
I would leave the carb, tune it up and enjoy it's simplicity.
Not sure if you where trying to say a noncomputer controlled 4l60 aka 700r4 but if you where i'll have you know a 700r4 would last maybe 100 miles in these big beast , gm made no heavy duty noncomputer controlled 4 speed overdrive , tbi is a simple system that takes very little to swap over , dont let ignorance scare you , do your reserch, stand along systems only need 2 power wires , and the upgraded pump, you only need 12-14 psi so you dont need fancy hard lines made up or expensive briaded line and A/N fittings.
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