Is it ideal to have as little as possible ported vacuum?

That's not a yes/no answer. Highly dependent on an individual engine's configuration. Remember, some engines came with the spark port located below the closed throttle plate so the distributor saw manifold vacuum levels at idle.

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Too many people who were born on third base actually believe they've hit a triple.

So I got to checking my mpg and getting about 16-17mpg on street. Today upped the timing from 10, to 15degrees. It smoothed out some shakeyness during idle, and smoothed out a flat spot I usually have off idle. I will check for pinging on my usuall drive too and from work with hills.

The 1920 Holley Economaster that put on my 79 block shows no vacuum at the distributor port. I would assume that the throttle blade is shut. As soon as it opens I see full vacuum.
My initial is set out 10 degrees which provides a powerful and snappy take off. Mechanical is set for 20 degrees at 1800 rpm. Still getting 22 - 24 mpg for local commutes, 25+ mpg on longer drives.

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Aggressive Ted

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74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I bumped timing back to 12. It seemed to run odd. Randomly very rough at times...

Curious why I'm getting a low mpg... I was expecting your kind of #s

What carb are you running?
I see bigslant6fan has springs back in stock.

Have you replotted your timing curve yet with the new plot file I sent you?
What is the total timing at 2,500 rpm?

For reference...
My rear end gear ratio is 2.76 and the tire diameter is 26". On the back roads I may get up to 2,000 rpm. On the freeway I make it up to 2500 rpm at 60 mph. On occasion I may run it up to 2800 rpm, but that is over 70, 10 mph over the limit.

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Aggressive Ted

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74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

What ever I came up with with your chart before is what I've been running this whole time. Carter bbs 60-64 year.

2.93 rearend

2568rpm @65
1778-1975 on street.

Mileage should be a lot closer. How do the plugs look?
Is the carb running rich?

A thought on the poor mileage.....
The reason I mention this is about two weeks ago one the balls fell out out the economizer body on my carb and the mileage dropped to 16 mpg. I was wondering why it was coughing and sputtering in the morning and smelled rich once it was warmed up. It has been in the 20's for two weeks out here and didn't think too much about it until I filled up and checked the mileage. A few days later when we had a break in the weather I pulled the carb bowl and saw a ball rolling around in the base. With the ball out, it is like having your accelerator pump on all the time.....I put the spring and ball and retainer back in the body and peened the zinc body material back over so the retainer could not pop out again. The next tank was 24.5 mpg. The following fill ups have been the same. My plugs are dry and very light gray to white from all the short hops.

I am running on lean side with the #56 jet however, the engine response, spunk if very good.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Well I notice sometimes gas seems to overflow and leak out the shaft but only when car is off and happens when its a little warmer, and is rare. I know I set the float to factory specs. I can tear into it and check.

It always runs a bit rough at idle very vibratey no idea why, cannot get it to go away. Maybe its flooding itself. Other thn that drivabilty seems fine it will spin tires off line with no brake involved. Actually st stoplights on a hill in the rain here. Its hard not to break loose, got be sooooper gentle

You should probably look into making and installing a simple heat deflector to keep the carb from heat soaking and percolating the fuel. Mine isn't fancy but sure helps. The new one will look a lot nicer and be much bigger.
A new needle and seat also does wonders if you have the float set right. I found this really helps, especially on short hops shopping, etc....no stinky smells of fuel, instant starts. Of course the electric fans are nice too which help keep the carb from heat soaking. I leave them armed most of the time. The carb always stays full of fuel. I have a fuel pressure gauge mounted in line and monitor that the needle and seat are holding. It will measure from 6 pounds on up to 15 pounds after shut off on a hot day.

Have you upgraded your exhaust system? or is it still stock size pipe?

I try to drive somewhat conservatively and keep my eye on the vacuum gauge. The gauge keeps me honest most of the time.

After getting the distributor recurve dialed in a few years ago, I like the crisp throttle response. It makes driving fun.

Click on the red link below my name to view photos.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG