Those of you who have switched from TPI to a non computer controlled four barrel.. did you notice any significant change in gas mileage? What about those with a larger displacement small block (377+ CID). What kind of gas mileage are ya'll getting and with what cam/heads/gears?

I'm basing my engine buildup around a set of AFR's, but I'm having a hard time deciding between a four barrel carb and a Miniram. Obviously which intake I use will have a big effect on my choice of cam, compression ratio, etc. I'm shooting for 11.90 at around 15 mpg. It seems like a lot of boost is the best (perhaps only) way to get there, but if I could go all-motor with a four barrel that would certainly save some cash.

Gas mileage is only one consideration, but it IS a consideration. If fuel injection were to perform enough better in this area to pay for itself over the course of a few years, it might be worth the added buy-in/headache.

Okay, well enough rambling. Let the carb-related advice commence.

Willie C.

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86 Trans Am WS6

It takes some ***** to do your quarter-miling on foot.
Recent ET's:
@Atlanta 50.80
@Southeastern 50.62
@Mtn Laurel 50.04
Future mods: More endurance workouts and some 300 meter repeats. Projected E.T., 49.8

 

I personaly would rater have a tpi setup than a 4bbl.
Gas milage is 50% tunning and 50% driver.
With a mildly built 350 most people avarage 15 or so city. There are some people with 383's claming 18mpg city. So if you have everything tunned properly and have a light foot look for 14-20mpg city. I get 23mpg city but its a 305.
SSC

 

Yea.. I've been pleasantly surprised by the gas mileage I'm currently getting. The car (305 TPI) got about 18 when I bought it. After the addition of headers and full exhaust (admittedly the exhaust is way way too big, because I put it in in anticipation of a much more powerful engine) it was pulling about 21 mpg on the road. This summer I finished installing a complete ignition system, and now I get about 20 mpg around town and a little over 23 on the interstate. I certainly don't forsee that continuing, but I don't want an engine that drinks gas like a big block. :P I've no doubt that it can be done if I'm willing to spend enough $$, but I'm still working out how to go about it.

Willie C.

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86 Trans Am WS6

It takes some ***** to do your quarter-miling on foot.
Recent ET's:
@Atlanta 50.80
@Southeastern 50.62
@Mtn Laurel 50.04
Future mods: More endurance workouts and some 300 meter repeats. Projected E.T., 49.8

[This message has been edited by WillDC7 (edited September 19, 2001).]

 

A properly tuned caburator will give you good gas mileage. It's when you intall a carb that's out of tune that you are going to have real bad fuel mileage.

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383 86 Camaro Z28 ---1/4 mile et>13.65@103mph,,
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:224/234 at 050 525/525 lift,3500 stall converter,shift kit,4.10 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.ALSO SECOND GEN Z28---mods:454 BBC,.546 max lift(doug herbert cam ) 750 Holley vac sec. ,Edelbrock Performer manifold,Holley electric fuel pump,Hooker headers,Flowmaster mufflers,beefed up 700r4 tranny, 3.90 gears, powertrax unit, B&M console shifter.

 

My 305 QJet gets between 18 and 19 mpg around town. Not sure on the highway; I haven't done any of that lately.

I don't drive with a light foot either. If I did, I suppose it would be up around 20 mpg in town

 

yeah i found that the tpi gets better gas mileage the only real reason i have found to switch one to carb is cheaper performance

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86 IROC-Z
305 TPI/ TH350

 

I switched from a 305 tpi to a holley 4bbl on a 350. The 305 got around 20 mpg on the highway and the 350 now gets 17mpg. It is a new motor and I'm having trouble tuning the carb. My goal is 20 mpg.

 

Tim, what is your 350 combo (cam/carb/intake/headers?) and what gears/tranny you got and what rpm do you cruise at on the highway???