They are a good auto [no belt drives, bands, or clutches to wear out].........but the subject was getting too "off topic" so I edited my post. Unfortunately this left your comments "hanging from nowhere " ,so my apologies.
I personally didn’t spend 9k on a 65 yr old multi carb hopped up engine to put in my 89 yr old traditional hot rod with any expectations of reasonable mpg. I just tuned it for the best performance & drivability............not trying to bash the OP but; old school traditional rods aren’t typically built for maximum MPG. What’s the fun in that.
Lol,,,,,,wait a minute man,,,,,your checking your mpg with a phone ? I’ve heard it all now,,,,LoL . Tommy
With today's prices of gas, you gotta do what you need to do to prolong that ride down main street.... Without costing an arm or a leg....
If I went to Kalamazoo in September I’d put on maybe 325 miles round trip. At today’s prices it would cost me $135 @ 8.2 mpg , and only around $65 @ my 17.5 mpg. 8.2 mpg might work if you drive a Zip Code car but I would never stand for that. A performance engine can be built with a goal in mind, like to run strong yet get decent mileage. Picking the right parts and spending time on the carburetion and ignition pays dividends, no way would I drive a car that got 8-10 mpg.
I'm planning to drive to Kalamazoo in September, in this... it gets less than 8 in town, and 10 on the road. It'll probably be a 2000 mile trip there, then another 1000 or so miles on Drag Week, then another 2000 back. If I drove something that I've ever owned that got 17 mpg, it would be a really boring Drag Week. Fortunately, I played life's cards right, and the cost of gas for the trip is not a concern for me, at all.
No argument from me about your goals, but as my comment said- a performance engine can be built with a goal in mind, your’s happens to be participating in Drag Week, or whatever race event strikes your fancy. Mine was having a blown SBC that can set me back in the seat when called upon yet give decent mileage. Years ago I drove to OKC with two other rodders. One had a Model A sedan , 350/Muncie and I think 3.55 gears, a Crower hydraulic and a TR-1 with two 600’s. The other car was a ‘31 Chevy 5 window, ‘70LT-1/Muncie but he substituted a 327/350 hydraulic cam and a 600 Holley. Before the trip they were concerned that I’d be stopping for gas a lot, but we all got around 17 mpg round trip. At 15% under, two 1850 Holleys, 3.36 gears and 31” tires I was just barely into the throttle and pulling 16 inches of vacuum.
I was going to chime in with this comment earlier, but here goes................ 8.2 mpg (US) is absolutely dismal for a mild 350. Using that much fuel, it should stand up and beg like @squirrel 's does. If a mild engine is overfueling that much, you would/should be able to tell. It would be bogging down severely, and would only be happy (maybe) at full speed wide open throttle. Run your figures again over at least three tanks. Make sure your odometer is reading spot on. I think you might have made a mistake somewhere...........
Totally agree…seems it should be chugging trying to swallow all that gas. I drove it a while yesterday, so I’ll recrunch the numbers. BUT,.. no denying, I drove across town to a cruise in and the needle dropped 1/4 tank. Priorities first- coffee, coffee, coffee, then go top off and do the math.
Gas Gauges do not always read the same between the 1/4s ,This is what I would Do , Plenty of places down in Florida to do this , top off tank close to main Interstate kind of late in evening & drive 20 to 30 miles , get off Interstate top off gas tank & see how many gallons used,,, use the mile markers as a reference point of miles driven . And if you have a smart phone you can also check your MPH
Gas gauges do indeed not read evenly throughout the range of the float, and my car will go from full to almost empty in the first half of my tank! Even after bending the float arm, it's still not very accurate. But I'd rather have it read empty and still have 7 gallons, than read a half tank and be empty! You'll be glad you got the regulator, as this is a one time thing, so regardless of what fuel pump you have you'll always have the correct pressure for your carburetor. As for the car running well, and still using too much gas. It can be pretty rich and not blubber or foul enough to have rough idle. You might move the mileage up 2-3 mpg, after fixing the issue, and only notice the oil doesn't smell gassy.
Yep. Been using my smart phone to clock MPH and distance. Open country roads, minimal traffic. Now… WTF? I just topped off the tank and crunched the numbers and got 7.9 mpg. So I start it up, pop the hood, and my gauge is bouncing hard between 8-10 psi. I drive 1-1/4 miles home, pop the hood and pressure is a steady 6 psi with no fluctuations. Did God just answer my prayers? Time to drive it and see what happens now…?.
My 327 powered '51 Chev pickup gets absolutely crappy mileage, I'm sure (approx 10 mpg if my guess is accurate), but since the odometer portion of my speedo quit working, I'll never know for certain what I'm getting. Ignorance is bliss! I'm running an Edelbrock 1406 and have thought about changing it out for a Quadrajet, but how much can I improve my MPG to overcome the cost of manifold, carb and gaskets (plus whatever else I can screw up and have to replace)? Smiles per gallon is more important than miles per gallon in my book!
Poor fuel for the power of the engine is bad tuning, wastes both gas and power..Get the A\F in order...
My t-bucket with a flat top 355, 882 heads cut 30 thousands, 494 lift cam, Offy 2x4 intake with two 600cfm Carter carbs ran with one to one linkage, points distributor, th350, 4.11 gears with a 29 inch tall tire would get 15.5 mpg combined city and highway driving. The motor would spin 3,000 rpm to go 55 mph, so even though the car was light it spent a lot of time in the higher rpm band. I thought that milage was impressive for antiquated parts staying in that 3000 rpm range. It'll be interesting to see what the issue is with yours.
All ya gotta do is look at the spark plugs, if they aren't burning very clean with modern issue gasoline, the AFR is way, way off. Part of it has to do with manufacturers selling carburetors, they have no idea much less control of how or what people will do with it, or tune it, same thing with factory distributors. They don't want grenaded engines, because that means $$$ out of their pocket.
Years ago I was running a Holley 600 vacuum secondary carb on a small cubic inch v8. It ran ok, but bogged down bad under hard acceleration. It would hesitate, splutter, cough, and then go. I tried all manner of tuning, including on a dyno. Could not make it work. I swapped the Holley for a Rochester Quadrajet 780 cfm, and the whole world changed. Way better gas milage in all situations, and when I put the pedal to the floor, the response was immediate and a lot more impressive. That was the only change made, but it made all the difference.
Had an auto tech instructor years ago who had nearly all his students peering into their tailpipes as a means of checking their tuneups. Short haul driving didn't tell you much. But maybe 30 miles at highway speeds would color the inside of the tailpipe, sort of like it would color the spark plugs. Ideally, you wanted a light tan, fine, powdery coating in the tailpipe. If it looked a bit yellowish it meant the driver was probably using Shell gasoline or some other high-sulphur fuel. A black or dark gray tailpipe meant you needed to do some more work on your tuneup. As mentioned above, modern fuels no longer give you this option.
>>>Had an auto tech instructor years ago who had nearly all his students peering into their tailpipes as a means of checking their tuneups.>>> I always stuck my finger in it. If it came out looking clean, I'd sniff it too just to make sure.
There are several of us that have posted things to do / check & you can see the ones that have High Hp street driven 2-3 times your combo & much bigger cubs & getting pretty much same MPG in lighter & heaver vehicle weights . My drag car with Blown & mechanical injection would only go threw 3-41/2 gal from start up burn out stage 1/4 mile to shut down @ 0ver 1,900 hp. & I also read afew other's combos should be little better mpg , If they are happy with there mpg then Ok. I have read threw your posts , I have only seen in first post Engine details , change carburetor , then waiting for regulator, erratic fuel pressure readings , and topped off gas tank a few times . I do not recall seeing going thew sets of plug fouling or gas filled / contaminate oil change's..... Unless you are useing a MSD 44 mag So it does not add up on the 8 -9 mpg. unless you are dogging the S--- out of it constantly every time you take off. & its sounds that you fuel pressure gauge is wrong, oil filled ? Have you tried different gauges to verify the pressure you are seeing . when things do not add up in situations that I've ran across I start adding More more Gauges / etc to know what I am seeing is correct ,,, then go from there
Thanks 19Eddy30. Yes, you’re paying attention. I haven’t posted much on corrective actions, because I can’t tinker on it 24-7, and racking up miles for comparison takes a little time. Also, until there is something to report, I’ll shut up.. As I wait for the regulator to arrive, I came to the conclusion, I’ve been distracted and kind of fixated on the high pressure issue. In that light, I’m starting from scratch, hopefully with my head out of my excretion orifice. I’m thinking the gauge is crap. I’ll install a secondary gauge for verification. -Pulled a couple plugs and indeed it’s running rich. - re-tuned the new carb with a vacuum gauge but didn’t have the timing light on it. Hg was low around 10. Got it up to 13-14 with idle air adjustment before mama rang the dinner bell. I’ll try and get back on it later today. Slow and easy.. Definitely interested in installing an air/fuel gauge later. Been reading up on them…which also takes time. Oh, BTW… I would never dog the S—- out of my car.
Quick update this morning. After fully warmed up. Idle 750 rpm. Timing 12* Vacuum 11 Hg. Fuel pressure 6 psi. Throttle bogs under quick WOTs - in the garage. Haven’t verified while driving. No update on mileage.
To everyone suggesting that hot rods should get poor mileage, that's a little shortsighted. To simply: There are four major places that fuel can go (without an inherent risk of burning the vehicle down): Heat, power, out the tailpipe, or into the crankcase. Which one do you want to maximize? Performance is economy. It means that every possible drop of fuel that could be turned into power was turned into power.
Unless you have a lot of cam than 11 inches of vacuum tells alot. Try spark advance and see what it does to vacuum and milage Keep that vacuum gauge handy use a level streech of road a when you make a change if the vacuum goes up so will the milage with the same conditions.
The Jalopy Journal
