10 mpg

[brianw]

That's all I got the first time I put gas in my '69 Calais. It has a .060
over 425 with mt-3 cam, aluminum 368 intake, and a custom 2 1//4 into
3" y-pipe. I am using the original Q-jet since I wasn't quite ready to drop
the $350 for a Jet Performance one. It has a large cap HEI with curve kit
and adjustable vac advance. I've pumped the (bias ply 9.50x15)tires up
to 32 psi and dialed the trans modulator back to shift a little sooner. I will
probably try a little more initial timing (It has 10-12 degrees already)
Maybe it would like manifold (not ported) vacuum to the dist too. My question is
weather all this stuff will get me anywhere or am I just stuck with a 5000
gas hog. I have heard of guys getting 18+ mpg with a 500 and even the
66 Chrysler I once owned (4950 lb curb weight) got 13/17. Maybe I've
shot myself in the foot with that 368 manifold?

[pageboy]

You should be able to get better than that. What is the range of mechanical advance in the distributor, and where is the mechanical advance topping out? The top of the mechanical curve is more important than the initial timing. Manifold vacuum on the advance unit will definitely help in town mileage. How much advance is the vacuum unit adding? The 368 manifold will be a little restrictive and may be hard on the power level, but it shouldn't be killing gas mileage like this.

[dave_brode]

Brian,

They are almost worthless for heavy throttle AFR monitoring, but a $30-$40 narrow band 02 meter would allow you to monitor your cruise AFR.
Fwiw, I like to see light throttle cruise AFR in the 14.2 to 14.4-1 range.
The narrow band meter would also allow you to see how quickly your carb goes from near stoich to rich of stoich, when the power piston raises. You *might* need a lighter spring, if the cam has much more duration that stock. That's assuming that your primary jets and metering rods are giving you a decent light throttle afr. I'd tweak those first, then the power piston.
Dave





w"]That's all I got the first time I put gas in my '69 Calais. It has a .060
over 425 with mt-3 cam, aluminum 368 intake, and a custom 2 1//4 into
3" y-pipe. I am using the original Q-jet since I wasn't quite ready to drop
the $350 for a Jet Performance one. It has a large cap HEI with curve kit
and adjustable vac advance. I've pumped the (bias ply 9.50x15)tires up
to 32 psi and dialed the trans modulator back to shift a little sooner. I will
probably try a little more initial timing (It has 10-12 degrees already)
Maybe it would like manifold (not ported) vacuum to the dist too. My question is
weather all this stuff will get me anywhere or am I just stuck with a 5000
gas hog. I have heard of guys getting 18+ mpg with a 500 and even the
66 Chrysler I once owned (4950 lb curb weight) got 13/17. Maybe I've
shot myself in the foot with that 368 manifold?[/quote]

[panel63]

How did you redo you tranny speedo gears for the large tires?how accurate is your speedometer or are you guessing?

[dave_brode]

panel63,

Drive 10 miles on interstate, and see how far your odometer is off. Say you went 10 miles, and odometer went 8 & 1/2 tenths. So, you're 15% slow. Theoretically, you need a driven gear with 15% less teeth. Or, a drive gear with 15% more teeth.

Note that the housing where the driven gear fits will be marked with
the driven gears that it works with. There are several different housings.
You may need a different one of those too, if you can't swap in the needed driven gear. However, you sometimes can grind off the tabs where the retainer clip seats and rotate the housing around to allow it to work with the needed driven gear.

There are several different drive gears as well, so worst case, you might need to swap all three.

Iirc, Richmond gear stocks many different drive/driven gears and housings.
Dave


"]How did you redo you tranny speedo gears for the large tires?how accurate is your speedometer or are you guessing?[/quote]

[STDog]

How did you redo you tranny speedo gears for the large tires?how accurate is your speedometer or are you guessing?

what large tires? Stock on the 69 was 9.00 x15. Now he claims 9.50 x 15 (not sure where to get those.) but they are wider, but not really bigger in O.D.

[SMITH29]

That's all I got the first time I put gas in my '69 Calais. It has a .060
over 425 with mt-3 cam, aluminum 368 intake, and a custom 2 1//4 into
3" y-pipe. I am using the original Q-jet since I wasn't quite ready to drop
the $350 for a Jet Performance one. It has a large cap HEI with curve kit
and adjustable vac advance. I've pumped the (bias ply 9.50x15)tires up

to 32 psi and dialed the trans modulator back to shift a little sooner. I will
probably try a little more initial timing (It has 10-12 degrees already)
Maybe it would like manifold (not ported) vacuum to the dist too. My question is
weather all this stuff will get me anywhere or am I just stuck with a 5000
gas hog. I have heard of guys getting 18+ mpg with a 500 and even the
66 Chrysler I once owned (4950 lb curb weight) got 13/17. Maybe I've
shot myself in the foot with that 368 manifold?
xxxx
By all means put the vac. advance on manifold vacuum and readjust carb idle and mixture screws. That will save fuel by itself and engine will run cooler on hot days in the city driving.

Make sure mechanical advance is working by verifying with a timing light with vac. advance disconnected. You should max at around 34 degrees @ about 3000 rpm.

An inexpensive Air Fuel Ratio meter will be of great help in setting the carb for the best mixture. You need an inexpensive single wire oxy sensor and a bung welded into the exhaust preferably at the " y" pipe or 2 oxy sensors with a switch. I have experience with them and they take the guess work out of dialing in a carb and you can monitor all the time.
Ask Al if he has AFR gages., 02 sensors and bungs.
I'm using the SUNPRO by Actron and they are accurate if you put a 1.2 meg load resistor from the sensor line to ground when using a GM single wire 02 sensor.

Add a vacuum gage to the dash and use it to educate your foot when going for economy.. It also tells you if the engine has the proper vacuum at idle and the general condition of the cylinders by needle wiggle.


Make sure engine is operating at 190 degrees.

Empty the trunk.

[dave_brode]

Brian,

More: NAPA has weld in "bungs". I bought a box of 10 pretty cheap, but they are just jam nuts. Same thread as an 18mm spark plug, iirc. You might find a jam nut at hardware store, or you could cut a normal nut thinner, do allow sensor to protrude into exh pipe proper amount. I can send you one for $3, if you get into a "jam" and can't find one [pun intended]. The cheap meters are common on ebay. Summit, Jegs etc, too. The one wire 02 sensors are cheap too.

You can buy plugs for the hole, or use an 18mm spark plug if you don't want to leave the sensor in the exhaust system when not monitoring.
Dave




They are almost worthless for heavy throttle AFR monitoring, but a $30-$40 narrow band 02 meter would allow you to monitor your cruise AFR.
Fwiw, I like to see light throttle cruise AFR in the 14.2 to 14.4-1 range.
The narrow band meter would also allow you to see how quickly your carb goes from near stoich to rich of stoich, when the power piston raises. You *might* need a lighter spring, if the cam has much more duration that stock. That's assuming that your primary jets and metering rods are giving you a decent light throttle afr. I'd tweak those first, then the power piston.
Dave





w"]That's all I got the first time I put gas in my '69 Calais. It has a .060
over 425 with mt-3 cam, aluminum 368 intake, and a custom 2 1//4 into
3" y-pipe. I am using the original Q-jet since I wasn't quite ready to drop
the $350 for a Jet Performance one. It has a large cap HEI with curve kit
and adjustable vac advance. I've pumped the (bias ply 9.50x15)tires up
to 32 psi and dialed the trans modulator back to shift a little sooner. I will
probably try a little more initial timing (It has 10-12 degrees already)
Maybe it would like manifold (not ported) vacuum to the dist too. My question is
weather all this stuff will get me anywhere or am I just stuck with a 5000
gas hog. I have heard of guys getting 18+ mpg with a 500 and even the
66 Chrysler I once owned (4950 lb curb weight) got 13/17. Maybe I've
shot myself in the foot with that 368 manifold?[/quote][/quote]

[MilesO]

Smith29 & Dave,

Thanks for the bung/sensor comments. When I replace my exh sys next month I will add those on each side to aid in tuning after engine install. The vac guage is an item I installed for years in all my cars to good advantage as suggested. The empty trunk idea could be expanded to the top of the dash for some folks..

Miles

[cadillac512]

I've seen customers' cars with 5 lbs hanging from the mirror and key rings.......drives me crazy! :evil:
Terry

[brianw]

Thanks guys for all the helpful suggestions. (my tires are 9.0x15 by btw)
I'll be busy for a while with this stuff. I've about got my vac advance and
modulator settings dialed in but this hasn't helped much except to make it
run better. I need to figure out how to make my transmission kickdown
switch work since carb and manifold are from different years.
I suspect the carb is rich due to the fumes I smell in spite of a fresh engine and the fact that its a 425 which are known to be lean from the factory. I have used a vac guage in the past but not for many years. I still need to hook up water temp, oil pres, and voltmeter ; guess I'll have to make my gage panel bigger.
Also, anyone know what rpm an old externally regulated alternator starts to put out decent current? Mine doesn't seem to do much at idle and battery is not staying fully charged.

[dave_brode]

brian,

I'd start with a new float in the carb, if it's a phenolic, and more than a few years old.
Dave


< I suspect the carb is rich due to the fumes I smell in spite of a fresh engine and the fact that its a 425 which are known to be lean from the factory.