Bobzilla MegaDork
Aug. 11, 2017 12:58 p.m.

New carb + working ignition system worked for a 25% (OK, technically a 24.x% jump). I might as well be driving a Prius now!

New mpg: 12.6 Where'd my smug face go?

GameboyRMH MegaDork
Aug. 11, 2017 1:07 p.m.

Should also cause reduced Visene consumption in your neighborhood

dropstep
dropstep SuperDork
Aug. 11, 2017 1:13 p.m.

Strangely enough my biggest fuel economy jump was from 12-18mpg via replacing a 2 barrel with a 750 holley on my marquis.

Bobzilla MegaDork
Aug. 11, 2017 1:16 p.m.

In reply to GameboyRMH:

I can tell you that you still don't want to follow closely for any sort of distance still. The amount of raw fuel exiting the tailpipe is down, but's its still got plenty of oil and no cats.

I did realize earlier this week that the same practices I used in my modern manual trans cars will not work on this. You know, leave in gear and let the engine slow you down with the injectors shut off until 1500rpm etc.... this still sucks fuel in even with the throttle plates shut.

1988RedT2 UltimaDork
Aug. 11, 2017 2:14 p.m.
Bobzilla wrote: New carb + working ignition system worked for a 25% (OK, technically a 24.x% jump). I might as well be driving a Prius now! New mpg: 12.6 Where'd my smug face go?

Can we get more info on old carb vs. new carb? I hear you on the Prius mpg! Nice work!

Bobzilla MegaDork
Aug. 11, 2017 2:58 p.m.

Old carb was an edelbrock 1406 600cfm electric choke. I rebuilt it because the secondaries were physically frozen. New carb is an out of the box QFT Holley 650 double pumper manual secondaries with electric choke.

BrokenYugo MegaDork
Aug. 11, 2017 3:02 p.m.

A bit of tuning with the fuel and spark and you can probably pick up another mpg or two.

Bobzilla MegaDork
Aug. 11, 2017 3:47 p.m.

In reply to BrokenYugo:

we have initial timing right around 12* BTDC, total timing (I think, that part is hazy in the memory banks we only checked once) was around 33-35-ish IIRC. We also got the carb set pulling 20" of vacuum at idle and idle speed right at 700rpm hot, 900-ish cold. Throttle response is fantastic. Revs like a monster. 5300rpms is easy peasy just blows smoke/oil out the non-baffled valve covers.

Knurled MegaDork
Aug. 11, 2017 4:37 p.m.
dropstep wrote: Strangely enough my biggest fuel economy jump was from 12-18mpg via replacing a 2 barrel with a 750 holley on my marquis.

If by 2 barrel you mean the VV carb, then that is completely believable!

Basil Exposition SuperDork
Aug. 11, 2017 9:09 p.m.

I went from 8 to 18 by unhitching the trailer.

Huckleberry MegaDork
Aug. 12, 2017 8:57 a.m.

I went from 7 to 18 mpg in the Taco just by unhooking a trailer as well.

Knurled MegaDork
Aug. 12, 2017 9:17 a.m.
Bobzilla wrote: Old carb was an edelbrock 1406 600cfm electric choke. I rebuilt it because the secondaries were physically frozen. New carb is an out of the box QFT Holley 650 double pumper manual secondaries with electric choke.

I'm convinced that Quick Fuel carbs are magic. They have atomization and transitions from one metering circuit to the next absolutely nailed. I've also never had to do any more adjustment to one than set idle speed. This accuracy allows them to be calibrated to flow the correct amount of fuel, Less well engineered carburetors just run a bit richer to cover up the glaring issues, trading off fuel efficiency for cheaper manufacture.

Sometimes you do get what you pay for!

Zomby Woof PowerDork
Aug. 12, 2017 9:34 a.m.
Bobzilla wrote: In reply to BrokenYugo: we have initial timing right around 12* BTDC, total timing (I think, that part is hazy in the memory banks we only checked once) was around 33-35-ish IIRC.

Small block? You can probably bump that up a bit more, maybe 3-5 degrees

Armitage HalfDork
Aug. 12, 2017 9:58 a.m.

I went from 11 mpg to 25 by simply removing my EZPass from the GTO and installing it in a FoST.

dropstep
dropstep SuperDork
Aug. 12, 2017 10:25 a.m.
Knurled wrote:
dropstep wrote: Strangely enough my biggest fuel economy jump was from 12-18mpg via replacing a 2 barrel with a 750 holley on my marquis.

If by 2 barrel you mean the VV carb, then that is completely believable!

Yep, that carb allowed me too buy a one owner rust free 81 marquis 2 door for 400 bucks. Performer rpm and a holley were much better then that thing!

Knurled MegaDork
Aug. 12, 2017 10:38 a.m.

In reply to dropstep:

I used to work with an guy who, by whatever black-magic means, spoke Variable Venturi, and was able to make VV equipped Fords respond and work correctly.

This is an example of an arcane Dark Art that is no longer relevant in the modern world.

Zomby Woof PowerDork
Aug. 12, 2017 10:46 a.m.

Tuning a carb - any carb is not a dark art, but the ability to apply basic troubleshooting skills. Something that will always be relevant, and the difference between a real mechanic and a shade tree, wannabe mechanic.

Knurled MegaDork
Aug. 12, 2017 10:49 a.m.

In reply to Zomby Woof:

The Dark Art is making poorly-designed 2nd-generation emissions controls interface with a rather poorly designed and cheaply made constant-depression carb. Imagine if a downdraft SU was designed by malaise-era American automakers... actually, you don't have to imagine it, that is exactly what the VV was.

mck1117 Reader
Aug. 12, 2017 3:26 p.m.

Can a jump in fuel economy be downward due to a mod? Because I have a few of those to discuss.

dean1484 MegaDork
Aug. 12, 2017 4:22 p.m.

@ the OP. It makes sense that you would see better I am betting that the vac secondary's were coming in way to soon. Now with the manual you are driving it on the primary's most of the time except when you get on it. I had the same thing happen with a camaro years back went from a Rochester (that I liked very much) to a Holley with manual secondary's.

Aug. 12, 2017 6:21 p.m.

The most dramatic change in fuel mileage I have ever seen from a single mod was when I added the front air dam to the escort and brought it down to within three inches of the ground. Of course it does nothing for City driving but, it used to knock down a solid 34 mpg highway cruising at 70 miles per hour. Now it will easily do 36 to 37 with no other changes to the car made.

G_Body_Man SuperDork
Aug. 13, 2017 11:09 a.m.

In reply to WildScotsRacing:

Air Dam seconded, mine helped me average 31 US MPG across the prairies in a Crown Vic with almost 700lbs of stuff in the back.

oldopelguy UltraDork
Aug. 13, 2017 7:10 p.m.

Dropping off a 60's cabover and the trailer for hauling it was good for almost 90% bump in fuel economy!

snailmont5oh HalfDork
Aug. 13, 2017 8:09 p.m.

My '84 T-bird added 4 MPG with he clear Motorsport headlight covers, and picked up quite a bit of top speed. I jumped from 16 to 24 mpg in my Fairmont by keeping the 600 Holley and the Performer 289 intake, and replacing the tired '79 302 (140 hp rated) with a RHO-spec 5.0 HO (270 RWHP) that my father-in-law and I built.

@ Bobzilla: If you work over the distributor a little bit, make It so you can have 15° initial, 35° total, and springs to get it in a little sooner, you might get even better mileage.

Bobzilla MegaDork
Aug. 14, 2017 8:05 a.m.

Yay, need to update this. Apparently it was a fluke. Made 4 runs after hauling the bike 70 miles. Back to 10mpg.

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