Question guys. I guess what i'm considering doing is pretty obvious, going old school and loosing the EFI. I'm thinking throw a Vac-sec 600 and a performer or whatever intake on after i delete smog gear and get headers and a 3.73 rear.(I know theres more to it that that i've read the tech article many many times) Granted I know i'll loose a bit of highway MPG from the gears, but my daily commute to/from school and work only puts me on the highway about 20 minutes a day total so i'm not real worried there.
I guess my 2 main questions are:

1. Power increase? I'll assume noticable, changing the 2bbl carb to a 4bbl on a freind of mine's 72 LeMans made a world of difference.
2. MPG decrease? How bad?

I'm averaging about 180-220 miles per tank depending on how my right foot feels that week. The way i figure it, if i get it all converted to carb, it will be much easier to upgrade to a 350 later not to mention changing cams. Burning chips just sounds like a band aid to keep a restrictive 2BBl EFI unit on the car , I'm sure a 4bbl carb would out power a TBI on the same engine any day if its tuned right. I'm not looking for challenge or originality, I'm looking for performance on a budget with minimal headaches




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88 Camaro (The mighty LO3 SC!)
305TBI/700R4/2.73/123,XXX miles
14" Open Element and Flowmaster 80 seires

Next up: headers and gears

 

I, too, am sure a carb would outperform TBI for all-out peak hp/tq but if you can get an easy 300+hp out of that stock TBI unit, whats wrong with that? Yeah, if you don't want to deal with it and the associated work, don't! If you have the patience and ability, take the time to get better mileage, driveability, altitude/temperature compatibility, enough HP/ Up to you.


My bet is that you'll spend almost as much $$ and MAYBE half the time to get what you want with what you already have...

 

This is true i do agree that i could get the power i'll be wanting with the TBI, which is why i've been debating it so much. But, from the research i've done I've pretty much decided on goin carb. Like i said, I'm kinda still stuck on the thought that identical engines, one with a TBI and one with a 600-650 carb, the carb'd one will make more power. Theres lotsa good carb tuners in this area and i've seen them run good year round, plus altitue dosen't vary much in Illinois its all pretty flat, and i don't travel ever. There are benefits to a major circle track scene in your hometown afterall... lotsa good engine builders and tuners

 

When I made the swap from TBI to a Holley 600, I gained a crap load of power and lost 1-2 mpg. That probably could have been made up with leaner tuning.

 

I get about 200 miles/ tank easy now with my set up.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

i challenge anybody who says they are getting 300 horsepower out of a stock tbi unit on a 305. are you talking about the aftermarket tbi setups from holley?

 

"I get about 200 miles/ tank easy now with my set up"

Dang, thats about exactly what i get when i keep my foot out of it, and mine's a 16 second car! What a ripoff!

 

Heck, I used to get 20-25mpg when I still had the Q-jet on it (with the 350c.i. and 3.27 gears). At 10 gallons, that's 250 miles... and my tank holds more than just 10 gallons! TBIs suck And I'm a little faster than 16 seconds in the 1/4...


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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Biochem, what is your actual mileage per gallon????? City and highway, if ya' got 'em.

 

That was about 20 in the city and 25+ on the highway. With the Holley, you can subtract about 2-4mpg off those numbers.


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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Thats pretty good considering you can't tune a Holley to save your life

 

Do you realize that "about" completely negates "exactly" and vice versa? I'm just messing with you...

I don't think it's worth keeping TBI if you ever plan to make a real racer out of a car... you can do the swap relatively cheaply (under 1k easy) compared to the mods required for the TBI and you should lose 2 MPG or so... not much more than that. I don't think the direct swap is a great difference in power... probably gains you 10 or so, but it will greatly improve throttle response... I don't think there are enough carbs on the road, we need to fight EFI!


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1984 Firebird - Daily driver, 305 LG4, T5 - Hurst short shifter, Edelbrock 600 CFM Performer Carb + Intake - Edelbrock Pro-Flow air filter, gutted cat, IROC 16x8 Wheels, AIWA bargain basement (from Sears of course) CD player, Eight-ball shift ****
Check out my ride here - My $1300 Toy

"IT'S SNOWING! TO THE HIGH SCHOOL PARKING LOT!" - The Mustang and Firebird face off in the dead of winter.

 

At least I can install a MSD box and still have my aftermarket tachometer work. Ever find that filter? It's next to the blinker fluid tank! Take off them hairdryers and I'll race you now! I drive my car to work every day... do you? NO

[This message has been edited by Biochem (edited October 10, 2001).]

 

my suggestion would be to keep the tbi i'm using a holley and all it has boiled down to is headaches and horriable gas miles i'm using a 4160 series 650cfm granted my engine is far from stock (350 .30 over , pm rods ,trickflow twisted wedge heads@pistons ,compcam 292h 501i 501e , edelbrok rpm headman 1 5/8-3"y-pipe and 3in-out flowmaster t-5 with 410s) so the stock tpi i had would have been far out of my reach to use and have it run correctly from what it seems your car is fairly stock i'd look other places to try to gain power just my opinion

 

I did the godly swap from T.B.I.>>>> (Terribly.Badly.Inferior)
recently and I didn't change anything except what was needed for the swap...performer rpm intake, afpr, 750cfm carb, msd pro billet hei...all for around $900. Same motor but carbed + no lousy computer = a HELL of alot more power. Like I was told when I was considering the swap, I will NEVER go back.

 

Speedluvr, can you give me any input on any mileage change that you may have noticed??? Highway AND city?? thx

 

If you can afford the $900 dollars to do it, the fuel milage CAN'T be a concern. If you lose 2 mpg, that comes to about 1 gallon per tank (10% in a 10 gallon tank) and if we nuke the entire eastern world, gas will go up to 2 bucks. You're looking at 4 bucks a week, or 16 dollars a month. Time to get your hands dirty, boy. And I didn't say Roy.

 

I can afford the 900bucks... I was just curious about any mileage change.

I run TBI in a BIG Wrangler and get only 15mpg on the highway and 11 city, so changes in mileage are larger, percentage-wise, for me... Not really a concern, though... Just another piece of the decision process.



[This message has been edited by fast_broker (edited October 19, 2001).]

 

I would say city (since I only drive around town) mileage is right at or better than with TBI. I think it is because of the fact the you can truly control the leanness or richness that you want to run with a carb. When you have chip controlled fuel infecton, unless you program it yourself which sounds like a pain in the a$$, you can adjust fuel pressure up and down all day and if the chip doesn't like it, it's all for naught.

 

Heres a thought. My rich running 355 with a radical cam and a 3800 stall coverter was getting 9 MPG on a good day with its old muncie 4-speed. it has a tricked out 600 HOlley converter for square jetting with 2 powervalves, 4 equal jets. the trick with that car is the more CFM the faster you go. As it was, I would hit 12.4 @ 115, and get this: at WOT the secondaries would never even open, it was all primary. (Mechanical Carb) reason? Not enough pedal throw. imagine what it would do with full secondaries? Ill know Sunday if that huricane dont hit.

 

HrdRock,

If you decide to ditch the TBI I'd be interested in buying the complete computer setup. Would like to swap it on to my offroad v8 s-10 blazer so I can get it emissions legal.

email me: fabi3714@kettering.edu

Thanks.