With a carb [ versus EFI ], aiming for the 'correct' A/F ratio or slightly leaner to get best economy might not yield the best economy. The quality of the air/fuel mixing, droplet size, distribution differences within a manifold will have an affect on efficiency. A slightly richer mixture than stoic might produce the best economy.
Gas Mileage query Holley 318
- Thread starter Jason Maitland
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Yes it's called the federal government butting their noses in where it doesn't belong.
Rat Bastid
Dunamis Metron
Exactly. You have to prepare the fuel BEFORE it hits the chamber. Most of it anyway.
You can get some surprising results if you work at it a bit.
If a 360 with an xe 268H and 750DP carb can get close to 20 mpg with 3.23 gear, you are a bit off on the tune up.
Holley carbs are notoriously rich EVERYWHERE in the curve.
Get an AFR meter and go to work tuning the brass in that carb. It takes more than swapping out jets alone.
Holley carbs are notoriously rich EVERYWHERE in the curve.
Get an AFR meter and go to work tuning the brass in that carb. It takes more than swapping out jets alone.
As long as they allow us to keep running carbs on the old stuff I'm happy. One day I will try EFI on a classic but not with with the current build.
just did 1100km's last weekend in ve valiant....up to SA riverland......390ci...lunati roller cam...231/[email protected] 750 mech...904...3.23's.....tuned air bleeds to give 14.2-1 at cruise....seen 6km's/litre cruising at 2800rpm...14.5mpg....really happy how it runs....too old too push it....so i just keep putting in fuel......$2 15/litre.....
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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If I told you that back in 2004, on a certain all-day roadtrip, my [email protected] equipped, alloy headed, 11.1Scr 367, with a manual trans and a final drive of 1.97 (Double-overdrive) made 32mpgUSG, with a massaged and hiway-dedicated Holley 600; in a 68 Barracuda at 4000pounds cruising weight; would you believe me?
With this combo; 65=1600rpm/75=1840/85=2100 .......
Well nobody else does either.
This engine, today, has well over 100,000 miles on it, now with a similar cam to yours (230/237/110).
The point is as I said before; once you give the engine the Ignition timing it craves, you just lean it out, lean it out, lean it out, until it complains and then give it a tiny bit back. I don't even have an AFR gauge. What I did have, was an adjustable throttle stop, that I tuned with beforehand. The throttle stop was set to achieve about 65 mph. then I added advance until the mph peaked. Then I reset the Stop to again achieve 65 mph. Then step by step I leaned it out until I lost speed, then went a hair richer. How simple is that!
Next, I reset the stop to achieve 75mph, and repeated the testing/adjusting. and so on. Then some days later, we (my 20yo son and I) hit the Road, for to attend the 2004 CarCraft Nationals in Shakope Mn (or however it is spelled), and had just a super great time. Yes, we bought the commemorative T-shirts, and some other memorabilia as well.
BTW, that combo went [email protected],(best of ONE run lol) with no trackside tuning, 3.55s, and spinning the street 245s most of the way, lol. I mean what can a guy tune with the tires on fire, and is there any sense in running a second time?.....I didn't think so......
No.
If I can get 14-15 mpg with this set up on a 340 in a 70 Dart with 3.23 gears, yes I think that you can do better. 
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