Well I guess with that statment THOSE 29.9 #'s dont add up? MAYBE downhill and in neutral?? 29.9mpg w/ a Q-jet??? at highway speeds? You got alot of factors in that # ie: weight, rolling resistence, CID, wind drag and more.

 

More fuel used thats why your #'s decrease kinda simple aint it?

 

Because a carb is far less efficent than a fuel injection system. Why do you think they quit putting them on cars in the early 80's EPA requirements-for emissions AND fuel economy.

 

with what we know about injection today ,i cant see us going back to carbs.

 

Not here to argue or to BS someone, only to help. I had a 1979 Z-28 camaro, similiar build as on my Vette EXCEPT intake [Edelbrock RPM] and carb of course. It made 394hp @ 402ftlbs of torque ON the DYNO at the crank. It had a little bit hotter cam and 2.02/1.70 valves using a Holley 650 double pumper a bitch to tune hard to start when cold and AT BEST it got about 12mpg on the hwy at 60mph, 350 turbo trans w/3.55 rear. iF you drag race cars as I DO its all about the combination and the REAL gain in hp is all in the heads.

 

I TOTALLY AGREE!!!! I think that one gentleman just wants to argue? I'm here TRYING to share my experince's and learn MORE also.

 

EFI maintains settings for 100,000 miles to meet epa rules. Carbs are infamous for needing slight adjustment each year. That made carbs flunk epa tests
My 61 has 4.11 and NO OD, and gets 15-19 mpg AROUND TOWN going easy on the pedal. Would easily get mid- 20's with a modern OD on the HWY. Only the SPREAD BORE carbs are designed for max mpg and full HP. The public loves square bore carbs which were racing carbs, and they suck gas. SO, compare EFI to square bore carbs, and efi gets more mpg. But against Spread bore carbs, it is too close to call.

 

With a fuel/air ratio meter it seem fuel injection can handle a 14:1 cruising ratio better than a carb but I've seen some Q jets work out close but temp changes and elevation have a big affect on a lean running carb where fuel injection will adjust itself

 

Yes most facory cars are calibrated to that number a lil rich however better rich than to lean. Some combinations like a lil more fuel at WOT my Buick Turbo and intercooled engine was set at about 14.1 from the factory, however I've built that engine to THE ABSOLUTE MAX using the stock 109 block, 0-ringed heads [no head gaskets]you name it I've got it on that engine roller cam,TE-61 Turbo, modified aftercooler [intercooler] ported EVERYTHING, alcohol inj. billet steel main caps, forged rods,crank & pistons, 009 inj. w/ 7 stage chip, etc,etc,etc, any more and i take the risk of blow n the crank through the oil pan. At 25 lbs of boost fuel pressure set at 45psi at idle, alcohol turned all the way up a/f/ratio is at 12.1 on the gauge and egt is about 1500 degrees, BEST pass to date is 10.56 @ 128 mph car is completly STREET LEGAL. I know a lil bit about fuel injectionWONT EVER RETURN TO A CARB SET-UP. UNLESS its an old muscle car.

 

Yes better on mpg's than a square bore however IMHO they still can't match a EFI system for effiency and they can't adjust for altitude[on there own] and still gotta diddle with em, personally I like the Q-jet w/ a lil tuning the'll run w/ a Holley or any other carb for that matter. I"ve gotta buddy that runs a Q-jet on his 1970 LT1 4 speed Vette, he races his car and it runs low 12's in the 1/4, BUT he is a WIZARD w/ carbs. Your 61 a 283? right?

 

It sounds like you do
I remember as a kid working on the older Buick 3.8 turbo with the 4bbl carb. What a PITA. Between turbos seizing and oil pumps loosing pressure from front covers wearing out... Ugh! But the block and heads always held together

 

Yep front cover is a problem on the 3.8 however there are some things to correct that, using a special shim the oil pump gear doesnt ride on the aluminum case. And as far as turbos seizing up ya gotta let em idle about 2-3 mins at least before you shut them off [if you just run it hard], the turbo spins at 10,000-20,000 rpms [depends on set up] AND the ONLY thing that cools the bearings down is the oil flow shut em off after running em hard ya just bought a turbo-COOKED IT! Thats why ya see diesels idle for a lil bit before they shut em off NOT because there a DIESEL because there turbocharged.

 

Love the 61 vette must be nice? Like the 69-70, my favorite is a 66 but my poor *** can't afford those cars. settled for my 82 [bought it in 2000], got sick about 7 years ago developed MS somehow?? and I've got lower lumbar degenerative disc disease. Sucks ta get old however I still do my own thing, just slower at it now.lol. Luckly for me EVERYTHING I own is paid for. hard ta live on $715.00 a month plus FS's. considering before I got sick I was making about $3500 a month, oh well could be worse, now I gotta be careful NOT ta blow nothing up!!! TURN THE BOOST DOWN!!!!

 

please explain how some are getting 2 almost 3 times the mileage GM did without an OD trans and using a carb.

 

my 61 has a 355 since 1994.
But, in 1975 when i bought it with a seized up 327, i put in a $50 283 and used the fulie heads from the 327, 9:1 CR. Went from NJ to FL , averaged 20mpg no OD, just 3.36. Then i put in smaller jets for my next trip, got 22mpg, but it was sluggish so i went back to stock jets. The guys in C1 with OD get mid-20's anything 283-355.
I do agree EFI is superior with large altitude changes, and with knock control. I wouldn't mind a timing computer w/knock sensor with my carb. If i ever put in a LSX, it would have a carb w/timing computer. would get same mpg as EFI, except at altitude.

 

my 2010 articlesome funny stuff in there, be prepared to laugh now and then)
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EFI/MPG? By Matt Gruber

Why EFI is the LAST thing I'd add to a carb car to get better mpg.
Carbs with stick 350's, at 17-24mpg in good tune, make me wonder how much more mpg you can expect from efi. It is the most expensive way to improve mpg! Hopefully, efi helps mpg a bit in a modern car, but it is way less than many think. This article is about a factory built car with a carb, a completely different design. There are many things a carb car owner can do while maintaining a stock or near stock appearance for less money. I've studied LS1 C5 engines to steal mpg secrets. It gets great mpg for many reasons other than efi. And some never get talked about or copied.
1. Low friction, low tension rings. Did you build your engine with them? Well, I didn't either. Next time I get bored, I'll switch to low tension oil rings. Adds mpg and HP due to less friction. My 355 takes 60# to slowly turn the crank. Way too high!
2. Higher compression. Vizard says his SB Chevys gained 15% mpg going from 8 to 10:1
Good way to improve HP too. In summer, cold air induction allows higher CR. I can raise my CR from 9.7 to 10.2 by using a 1094 head gasket. It will tighten the quench from .065 to .040 causing better fuel atomization. Be sure to use a flapper valve on cold air so it gets warm air during cruise, but goes cold on acceleration.. 150-220F air gives best cruising mpg due to superior vaporization.
3. Roller lifters and roller rockers reduce friction, add mpg and HP. My 61 has roller rockers, but NO roller cam.
4. Better spark timing. Set up an old car right at cruise, and watch the mpg go up. A friend tried a MSD under the dash, timing control. On a trip he adjusted the **** until it ran best. MPG was so good I didn't believe him! No, I haven't tried it because I don't have an MSD or HEI system, but it has a lot more appeal to me than efi, because of the logic. There is no way that weights +a vacuum advance can be all that accurate. I've learned how to tune for cruise without a timing control, but it could beat my best tune, Jegs $136 #121-8680 MSD, + or - 15 degrees. But, it only works with MSD 6. If you can find a used MSD8682, it plugs right into a GM HEI. Too bad it is discontinued.
5. Even the oil pump is more efficient. Avoid high volume/ high pressure pumps. My 61 has a high pressure pump, not the best choice.
6. Efficient roller cam helps mpg with wide LSA. Maybe someday I'll make the upgrade.
7. Thin synthetic oil cuts friction. I'm using dino 20w50! Go figure!
8. More efficient exhaust. Still have the original mufflers in my 61.
Other well know mpg improvers:
1. Modest overdrive or a taller rear. But carbs often can't cruise efficiently below 1500-2000 rpm. So don't overdo it.
2. Taller, narrower tires. Taller slows the engine a bit, narrower cuts wind resistance. Even just taller on the rear is a good move. Improves traction too.
Want 1-3 more mpg? Consumer Reports found, in the 11-09 issue, that the best got 3 mpg more than the worst! BFG's are near the bottom. Buy a top tire and get better handling, wet and dry braking, faster acceleration AND 1-3 more mpg!
3. Get rid of old school engine fan and go electric fans that don't turn on until near the C5's temp of 228F. High pressure cap and new hoses to complete the upgrade.
4. Reduce friction losses. Do your brakes drag? The E-brake? Are the half-shafts near level at cruise? Synthetic gear lube in rear? Automatic have a locking converter? Modern high pressure low friction tires?
5. Electronic ignition with vacum advance. Got mine 15 years ago, same great spark as new. Points start out fine new, but before you know it, the mpg goes down.
6. Keep a good stock carb, replace a worn out carb only with a carb that has a good reputation for mpg. Be sure to quiz anyone that gets good mpg about their cruising rpm and make sure it matches yours. Here is my pick in the 1500 rpm and up range http://community-2.webtv.net/MATTGRU/carb/page2.html
7. Advance the cam. I've read that Vizard advances the cam. I thought since CompCams ground my cams already advanced, I didn't need to. A C2 driver advanced the cam an extra 4* and picked up 2 mpg!
8. Trapped Vacuum Spark control for cold starts. Makes it run like it is warmed up, on a cold start. Pull right out no warmup. Uses less gas, Often doesn't need a choke.
So, my 61 gets 19 mpg with a 4.11 and NO OD.
And there are plenty of things left to do to increase mpg: roller cam, low tension rings, more compression, proper quench, a timing control, a 3.36 rear, basic oil pump, advance the cam, synthetic thin oil, turbo mufflers, add warm air valve to cold air induction.
1-10 Added #8 above TVS.
EFI? It is not on my list because EFI really shines at very low rpm, and with a 4.11, I can't benefit. Since a 4.11 is a heck of a lot more fun where I drive, I'm not interested in poking along in an overdrive trying to squeeze a little more mpg. For cross country trips I'd use my 3.36 rear. In the past it has added 3 mpg. So I'd expect 22 mpg. A C5 can get 26 mpg with ALL the tricks it has. How much more is just the EFI worth? You decide. It is your money.
Aerodynamic Drag
Put an EFI C5 engine with overdrive in a C1/2/3 and go on a trip at higher speeds. Go with a friend in a C5. The C5 will get better mpg due to the body design. Corvette Fever Magazine test results http://i237.photobucket.com/albums/f...8new/aero4.jpg I've seen reports of 26-30 mpg in a C5 on trips. Look at the extra RWHP for even 80 MPH compared with a C5. Use more power, get less mpg. My recent mpg tests have been local driving in the 40-50 range. The C5 appears to have no aerodynamic advantage at slower speeds. A C5 owner told me his C5 could not get better mpg around town than my 61. But on the interstate the C5 wins. LOW DRAG is a significant factor.
How do you test mpg? What type of driving?
It is the mpg you get when there is a cop behind you, and you don't want a ticket.
It is 2AM and you are cruising home when you realize all the gas stations are closed, and the gauge just hit empty. 30 miles to go, can you make it?
To find your cars' best mpg, don't start the test until the engine reaches 180F. To find the WORST mpg, make lots of short trips where it doesn't fully warm up. My cars get about HALF the hot mpg when they are cold. Winter starts are even worse.
If you are serious about mpg, read how Bill Jones got over 29 mpg http://speedtalk.com/forum/viewtopic.php?t=2178
I can't get no satisfaction
When automatics first became popular, some guys would joke "I can't drive an automatic".
At first I'd just smirk and shake my head at that comment, but as I got older I found "I didn't LIKE to drive an automatic". It shifted too early. Didn't downshift fast enough. When I bought my 72 vette TH400, I HATED IT. Only after I removed the governor and recalibrated it did my opinion change. NOW, it shifts great! Still not quite the satisfaction of driving a stick, but quite acceptable.
EFI? Same deal. Pre-programed fast idle on cold starts. I HATE THAT! When I start my carb cars up, having no choke, I just let up on the gas, and it gently shifts into gear. I don't warm it up even 3 seconds. I back right out. Sure, being cold it shakes a bit and barely runs, but, it doesn't bang into gear at like 1500 rpm. I do the driving, not a computer nanny.
My carb cars NEVER get a "check engine" light. NO trips to a dealer for service. No calling a hotline for service tips. Maintainence is $9 pump diaphragms not $400 injectors. No 3000 page service manual with 1000 codes like on a c6. Simple to fix compared to any efi. No wires! No laptop needed! Can be swapped out in an hour. No special, expensive fuel pump.
Never got stranded in 35 years. Will still likely work fine 35 years from now. Can you be sure a new efi will stand the test of time? Do you want an expensive nanny driving your car?
The next BIG thing
People don't want to step on the gas to set the choke. They sure don't want to adjust the idle speed or the idle mixture. So we have EFI.
People don't want to shift, so we have automatics.
Roll a window down? Nah. PW. Press hard to stop? Nah. PB
Use muscles to steer? No Way! PS
Pay attention to traffic? What? No way! Rather be on Phone or Text or Surf or Put on makeup or Shave or Eat.
So they are quietly working on it. The next BIG thing: Cars will be computer operated and you just go along for the ride! Then you can do what you really want: SLEEP!
Lexus already has a model that can parallel park itself! And the military has a contest each year to find software clever enough to drive a military vehicle without a driver! This I like. Why put our men/women in harms way? Once it is perfected, new cars will have it! And when I'm 98 and too old to drive, I'll buy one, and tell the car "go to the store and get my groceries" Then I'll go take a nap in the house. Why bother tagging along?
When does EFI make good sense?
1. Tunnel ram. The weak vacuum signal makes things tough for a carb. A friend got 5 mpg with dual quad tunnel ram. Research and solve this or get EFI!
2. Big cams with less than 12" vacuum at idle.
I'd swap the cam, but if you insist, get EFI!
3. Peer pressure. If important people laugh at your carb, like your boss, get EFI!
4. Turbos or blowers. Easier to set up for high boost wth EFI.
5. If someone is too stubborn to try a carb with a good reputation for mpg, get efi. The US economy is weak and somebody has to buy expensive stuff to keep things going.
6. Big Big Blocks. They are so expensive to build, EFI is just part of the fun of blowing a big wad of cash. Are there any carbs that get good mpg, big enough for a BB over 600 HP? If there are, they probably cost plenty. EFI enters the picture against those high prices.
A budget Big BB could use the long discontinued 4165-6211, It is only 800 cfm, but I'd give it a try if you can find one at a swap meet. Don't confuse it with the 6210. Big difference 1 digit can make. Another 150 cfm! It too needs a fuly separated dual plane to make EFI-like mpg numbers.
7. Deep overdrive. Carbs get rich at low rpm. Some automatics may only lock the converter in 4th. So attempts to cruise in a fuel efficient gear cause the converter to unlock! Get it fixed, or get efi.
With a stick some drivers love how quiet it is at low rpm, and shift into OD at a speed too slow for carb efficiency. EFI often beats a carb at low rpm, 1000-1500, so mpg would improve using efi if the driver gets a headache in 4th instead of 5th.
Or it could be the driver ASSUMES lower rpm equals better carb mpg. Some REFUSE to use a lower gear. They should get EFI!

 

Not sure of your ? tuning?? high rear gear [2.87] 2 barrel carb? some claims not caculated correctly maybe? My 1990 SS 454 gets at BEST 10 mpg with a tail-wind @ 55mph! 3.73 rear w/400 turbo trans.

 

turbo 350 or powerglide? curious? whats the curb weight on a 61? Thats believable mpg.............BUT 29.9??? Thats hard too believe however I am an optimist so who knows maybe? I did have an old 67 impala w/ 283, powerglide not sure of the rear gear? I was a kid remember 1st to 2nd shift about 75mph [probably daytona rear gear]. it was good on gas had a 2 barrel.

 

DAAAAANG!!!!!!!! that was alot to digest!! I'm glad I took the tiiiiime to read that post alot of information. Which being a old gear head [me] I agree w/ 99.9 % of that post. [no body is perfect,lol] BTW I did use low friction rings every lil bit helps.

 

I WOULD NOT change a carbed factory car to the EFI either, waste of money HOWEVER if it had it from the factory I'd stick with it.