QuestionQUESTION: 1964 Buick Riviera 425.Rebuilt the engine,still has points,edelbrock carb,Magnecor plug wires,well maintained.I am getting 9 mpg!!!!!I have went through everything.What the hell do you think is going on?I should at least get 12 mpg.Checked for leaks,cant find a thing.Could you email me at multiplu@hotmail.com if you have any ideas.Cheers
ANSWER: The list of things to discuss is as long as my arm.
1. What type of driving do you do? If it is mostly around town and stop/go driving, 9 MPG isn't all that unusual for that car.
2. How is the car equipped and geared (rear axle ratio, exhaust system etc.?
3. How much do you like to enjoy the power of the engine (meaning, how heavy is your foot )?
3. Have you had the engine on an analyzer to determine what the idle vacuum reading is? If not, at least get a vacuum gauge and see what it reads. Intake manifold vacuum should be at least 19 In. Hg. at idle, if you live at sea level or near to it, somewhat less at higher elevations, but if it is below that, you have a need to get it to a tune-up shop that is equipped with a complete engine analyzer, where they will check for fuel/air ratio, timing at idle and timing advance, (centrifugal and vacuum), point dwell and variation with speed and vacuum, exhaust restriction.
Since the carburetor has been changed, you need to verify that the right CFM was chosen. If someone thought putting a bigger carburetor on it (650 CFM for example) "would make it run better", there's your problem right there. If you can find an original carburetor, put it back on, or at least get an Edlebrock with the same CFM as the original - I don't know for sure, but I'd guess 430 CFM.
Last, I have to ask how you determine your MPG. There is only one accurate way to do it, that is: top off the tank, drive a known distance but at least 200 miles (and don't trust the odometer, use mile markers on the roadway), then top it off again, and divide the miles you went by the gallons it took.
From your first name and your "cheers" I perceive that you are either from down under or a cousin from across the other pond (the UK) - if so, you are aware that our little weenie gallons are a lot smaller than what you are used to, right?
Let me know what your response is to any of the above with a "follow up" question. I can't get back to you via e-mail, sorry.
Cheers back to you, and G'day also,
Dick
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QUESTION: Thankyou so much for your response.
1-mainly around town driving,mostly light on the foot
2-exhaust 2 into 1 Magnavox
3-have not had the engine analized-will do
4-what does CFM stand for
5-tank holds 19 gallon,I have ran it dry and get 140 miles on a full tank.
6-I am indeed a cousin from across the pond-Scotland,now live in LA.
Take care
ANSWER: OK, Thanks for the response;
Around town driving, especially in LA traffic, is a big reason for the low MPG - I have a similar sized engine (440 Cu in) in my 67 Imperial, which weighs about the same as your Riviera, and it gets about the same mileage - perhaps slightly better, but we also live in a much less congested area.
CFM stands for Cubic Feet per Minute - -it is the main specification on a carburetor. It is a very common misconception that putting a carburetor with a higher CFM rating will improve the performance (power or acceleration) of the vehicle. This idea grows out of the fact that higher performance vehicles are designed to make use of a higher CFM rating, but one cannot simply do the carburetor portion of the performance upgrade without doing all the other engine modifications that are needed to take advantage of the higher flow capability. The person who chose the substitute carburetor for your car may have been (I'd go so far as to say very likely was) affected by this idea. The problem with too high a CFM rating for the rest of the engine is that it wastes fuel - the engine cannot make efficient use of the added fuel/air mixture. Thus the fuel mileage is worse than it needs to be. If you have the model number of the carburetor that is on your car, I may be able to look up the CFM rating for you, and compare it with the original for which the engine was designed.
If you put 19 gallons in it, and it ran totally out of gas and came to a stop by the side of the road at 140 miles, that is indeed only 7.4 MPG.
I can't explain that other than to urge you to get the engine to a good tune-up shop (not one of the chain operations - they are not mechanics - they are simply parts sellers and changers and don't really have the equipment to diagnose an engine). Find an old time mechanic who has an engine analyzer and ask him to check the car out thoroughly. There is an excellent shop here in Temecula, but that is 120 miles from you. I'm sure there is one in your area. A good mechanic can probably adjust the jet sizes and metering rods to improve your mileage by at least 10 to 20% with the existing carburetor.
Welcome to LA - it must be an enormous change for you. I came here from New Jersey in 1960, and it was for me! The locals couldn't understand my accent- it took me a few years go get used to theirs. I might as well have come from Jersey (the island)!
Dick
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QUESTION: the carb I have on there is an Edelbrock 1406 600cfm.Spoke to a tech at Edelbrock,told me that is the best carb they make for this car.Told me changing the jets would make no difference in mpg,told me to check fuel pressure and float level.What do you think/Cheers
AnswerWell, I disagree with him slightly about the 600 CFM. I suppose that is the lowest one they supply, but 600 isn't outrageous, so I don't think changing the carburetor is going to make much difference. I was thinking it might have a 750 or 850 CFM carb on it, so let's get off of that issue for now.
His suggestion about checking the fuel pressure and float levels is a good one, but this requires a bit of knowledge that you may or may not have. One thing you can do without opening the carburetor is to buy and install a fuel pressure regulator in the fuel line from the fuel pump to the carburetor - then you can set it to 3.5 PSI and be sure that your fuel pressure isn't too high. Or, of course, you could buy a fuel pressure gauge and test it - just open the fuel line and insert the gauge in the line, then start the engine. It will idle for a few minutes without the fuel line being connected to the carburetor, giving you time to read the pressure. It should read between 3.5 and 5 PSI, with lower being better in my opinion.
One question I didn't ask yet is regarding the air filter and the choke settings. If you take the car to someone with an engine analyzer, he will check those things, but you can make some checks yourself. With the engine fully warmed up and idling, remove the air cleaner assembly and look at the top of the carburetor. Is the choke flap all the way open, or is it partly closed? Also, inspect the air cleaner element. You should be able to see sunlight through it if you hold it up against the sun - if not, replace it. I hope this is the original air cleaner, or at least the same size or larger than the original. Another thing you can do is to inspect the tail pipe after a good long run on the freeway. You should see a light gray coating inside the end of the tailpipe - if you do, your carburetor is set right.
I'd still like to have to have the intake manifold vacuum measured - and since you live in LA (at sea level), I'd want to see at least 20 In. Hg., and preferably 21. If the vacuum is lower than that, the car needs to be seen by a professional tune-up mechanic with the right tools. He should check the timing settings (idle, centrifugal and vacuum advance) the compression, and the point dwell angle 30 +/- 2 degrees. If all of that checks out good, he should check the valve timing and timing chain wear.
By the way, if you buy a vacuum gauge, you can also use that same instrument to measure the fuel pressure (they work both ways).
The float level was set in the carburetor when it was new - if no one has fiddled with it, it should still be right, but if you suspect someone has played with it, you could open the carburetor and see where it is set, but you should have a rebuilding kit for the carburetor to do that, as it will have the right dimensions and the measuring tools and instructions for doing that. There are also instructions for setting the metering rods - it is possible they have been fiddled with, causing the car to run too rich - but if so, your tailpipe will show black soot, not the light gray coating.
The Edlebrock 1406 is a very good carburetor, most folks have absolutely NO problems with them - so I continue to wonder about all the the other variables we've discussed.
You could consider a smaller car for daily driving - and keep this beautiful collector car for weekend jaunts up the coast! (Just kidding.)
Dick
