Have a stock 283 in a Model A Tudor,350 Turbo, 3.0 9" rear. 31 x 10.50 x 15 rear tires with a Holly four barrel. It now gets alittle over 12 MPG driving at 60 MPH on the highway. Looking for a more economical carb, either 2 or 4 barrel, and estimated MPG you may have experienced. Thanks for any advice.
get a 700R4 transmission. the TH350 doesn't have a lockup convertor OR overdrive,and without either of those the power loss through the torque convertor is more of a problem than the carburetor.
Holley is great,as long as you're only going 1/4 mile at a time. Rochester 4GC is what your engine would have come with,and is a good compromise between power and economy.
12 MPG seams low for that combination...my `36 ford 3 -window coupe (much heavier car) with a 283 , th350 and 2.79 gears gets 17-18 on the road driving 65-70. it has an Edelbrock 500 CFM carb my `28 tudor with a 350/350 with 3.00 gears , 600 CFM Edelbrock gets around 14....my theory is that even though it is a much lighter car , it is a lot less aerodynamic ..at 60 MPH you are pushing a lot of air
A 3.0 gear and 31 inch tire might be droppin your rpm's below efficiency level. Sometimes too low an rpm can hurt mpg by lugging. If that's not the case I would still replace the Holley with a Edelbrock 500. Small primaries like .86 I think and .95 secondaries?. If that leans it out you can always spend the 7.00 to get the step up spring kit for it and go 1 step up and reset the carb. I'm running 2 of them on a HO 305 with a tunnelram and I'm getting 16-17 with 3:73 rear and 29 inch tire so you should be getting much better
Gotta go with Yorgatron on this one. The little 4gc 4 bbl is perfect for this engine and at the weight of your car should return well over 15 mpg. they used to get that kind of milage pushing full sized Belaires and Impalas. Frank
fab32, I would tend to agree with you BUT years ago I had a 66 Impala with the 283 PG that got 25 mpg so I really think that his should be close to that with the gear and tire combo unless it's dragging the rpm's down too far. Wouldn't that combo result in a mid 2: ratio??
Edelbrock 500 cfm carburetor will solve your problem. 4GCs are fine but the EDL is easier to tune easier to find and will provide max up for your engine size.
If your only getting 12 MPG, something is very wrong with the tune-up. But, to answer your question, I would put a Q-jet on it and never look back except to see all of the gas stations that you passed. Logg on here and have them help you through it: http://cliffshighperformance.com/simplemachinesforum/index.php Glenn
Dual 4s on a 283 that's what you need. It gives you the real vintage hot rod look. I get that kind of mileage and better with my 57.
try to find a wcfb like chevy used on early 283's and power pack 265"s-came on lots of cars--should get one cheap at a swap meet (bought 4 in a box for $$25)--kit it and go--they were about 450CFM I think but not sure--a little easier to kit than a 4gc I think -The little wcfbs on a stock manifold like Bob W are really cool too and ran well when done right but like a very mild or stock GM cam to run their best I've found
Everyone has carb opinions but it's like Chevy vs. Ford vs. Studebaker. No matter what's on it, should do way better than 12 MPG. My big block 1 ton flatbed will do that. I'd start with what vacuum reading does the motor pull at idle? Since you've already got a vacuum gauge on there, adjust air/fuel ratio to highest vacuum/idle speed obtainable. You said stock motor but if it's a Holley, probably not a stock intake. What manifold under there? Single plane is a mileage killer. If it's a power valve equipped carb, make sure it's not blown out and it's rated at least 2 inches less than your idle vacuum reading. what size carb? double pumper? small or large accelerator pump(s)? accelerator pump & some pump cams are adjustable If you change from a Holley (depending on funds) I'd recommend an old school style Rochester tri-power with progressive linkage. Good mileage if you can keep your foot out and has a big kool factor. WHAT THESE GUYS SAID TOO..... gas pumper: Vacuum advance working? Ya need it for good mileage. Solidaxel: tried changing the main jets to TWO sizes smaller?
For what it's worth, I get 17-18 MPG with my dual-quad-Coupe all the time..... and that's with a tiny 9" torque converter and 3.55 rear gears.....and my heavy-foot. I know that if I changed to a tight 2000 RPM converter mileage will improve to 21+........but I just can't bring myself to do that !
Jets and gaskets are cheap for a holly = $3.50 fpr gal. gas. There many solutions if money is no object!
I run into this alot. Over carbing an engine. The cutomers have problems with emissions or poor performance. Most of the time too many cfm's for the motor. Most of the time with a stock sbc or slightly modified a 500cfm Edelbrock Performer card is a plenty.
hey Bob W, is that the ever elusive, rare as hens teeth, DRIVER quality 57 vette??? if so, my hat's off to you
I had a 283 in a 50 Plymouth. T-10 tranny and first, the original 3.90 rear and later, a 3.08 Camaro rear. L78x15 tires. Used an Edelbrock C4B manifold (old school; still had a separate oil tube) and a Rochester '4 Jet' carburetor (circa '56 Olds, maybe later). Was a terrific highway cruiser with mileage over 20 mpg on the highway. THis was not a drag strip setup, obviously, but was still a whole lot better than that original flathead. Moral: the little Chevy motors like the little ROchester 4 Jet carb. Note: this is NOT a Quadrajet. Those came later. The 4 Jets had equal sized primaries and secondaries.
got a 327 tripower and proabbly 3.5 gears [s10 rear]running 50 mph get 17 to 20 MPG hard to calculate spedometer reads 10% fast crank the plugs open to 80 thou to give a good flame front, find a gas analyzer to set up idel jets, yes they affect mileage and crank the timing till it kicks back starting and retard it till it starts got to have good spark output and good advance mechinism, keep on top of points as they move[wear] and change timing I had a 71 impala 307 w 2 barrel aND PULLED 20 mpg , BUT NOT PERFECT DRIVEABILITY WE MAY HAVE TO GO TO SMALLER ENGINES TO GET BETTER mpg SOON did the same w a 307 impala 1968 had the small 2 barell and put 55 chev emulsion tube and jets in it and pulled 20 MPG and boy do I have a lot more training and knowledge now that i had in 1968 but back from Nam I thought I was on top of the world being poor has the effect of causing a lot of tinkering and it can take a couple days to fix some of those driveability problems, keep tinkering and switching parts in a logical manner and test it will pay off trust me I know I learned building race bikes for 2 year and 18 year stock cars and yes it is a steep learning curve to learn , surrond yourself with some good Knowledgeble people and work together TRAIN YOUR FRIENDS to do some of this work and they will become experts and come back and help you out
turbo 350 trans had an overdrive option later on (have one in my monte carlo, runs great). the 283 had either rochester 4gc or carter afb, something to the tune of 400-450cfm depending on whether not it was stick. holley makes power, not efficiency (unless you got lots of time to set it up and fiddle with it). easiest thing to due would be get a small edelbrock 4 barrel (good combination of effeciency and power for the street). if you are just worried about effeciency the quadrajet is king with those tiny primaries (can make decent power too if you set up the secondary tension right). jetting will be fun for that one, and you'd either need to knock the plugs out of the base or find an older adjustable base for the idle mixture (DO NOT run the factory setting--one adjusted all the way in, the other one out so it would pass emisions).
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