Hey guys,

I need some help. I just tracked my mileage for the first time since converting to the 2BBL and it came out to 11.7 over 123 miles...
Most of this was city driving and me driving like a grandma at that. No jack rabbiting or anything. I used premium gasoline as well...
The engine is entirely stock except for this conversion. The idle is set at 650-700 warm in Neutral or Park and 550ish in drive.

What can I do to make this better? I was hoping to get those high teens and low 20s that everyone else seems to get with the super six

Any and all help is appreciated,
Aspen76

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76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

Well, first off: Why using high-test gasoline? It's not better, it's not required, and all it does is drain your wallet faster. If you have to use high-test to stave off pinging, then something's the matter that needs fixed.

What carburetor did you install as a part of your conversion, and what is its history? Where did you get it? What work was done to it before you installed it?

What spark plugs are you running and how do they look? Have you pulled them and examined their firing ends?

What mileage were you getting in town before the conversion?

What other changes were made along with the 2bbl swap?

Assuming this is an automatic car, is the entire 2bbl kickdown linkage installed and correctly adjusted?

What emission control components have been removed or altered, if any?

What is your basic ignition timing?

Have you checked to make sure the vacuum advance is working and that it is hooked up correctly?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Contact Charrlie_S. Take a weekend and go to his place after you set things up, and have him give it a clean bill of health and tune up. Sometimes getting another set of eyes, especially well trained ones can help. He does it for his livelyhood, so take some bucks with you for him. He knows these engines well!

I get 11.7 out of my tow rig pulling a 24' enclosed race trailer with car, tools, camping gear and mountain passes.

I can drive the drag car at 20 mpg on a 500 cfm four barrel with no vacuum advance. Something is not right there!

CJ

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Part of Tyrde-Browne Racing

My first suspicion is a V-8 carb. Using a v-8 BBD or 2280 with the slant six choke linkage will not allow the choke to open all the way.

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Casually looking for a Clifford hyperpak intake for cheap.

I always run 93 octane gas. My thinking is that these engines were made back when gas octanes were higher so I use gas the 93 octane stuff to get closer to what they were made for.

The Carb is a Carter BBD. Dan, you told me it was a 70s 318 BBD here. According to Reed's article on Super Six conversion, the 318 BBD shouldn't be any different from the Slant BBD except for holes in the throttle blade and the choke set up.

I got it off another super six set up and rebuilt it with the rebuild kit you recommended from Daytonaparts. I was told by the guy I bought it off of that it ran but I rebuilt it to avoid any issues.

I won't be able to check the spark plugs until tomorrow or Saturday but I changed them 3 months ago. They should be champion coppers if I recall correctly.

Before this conversion with my single barrel holley I was getting 14-15 mpg when I was driving it liberally and 18-19 conservatively.

The only other changes I made during the conversion is that I sealed off the heat riser valve and the EGR valve due to some complications during the conversion. I figured I didn't need the heat to the intake since I live in Florida. I've read that the EGR valve wouldn't make any difference with power or economy. (here)

Also, the pcv valve is just sitting open because I can't find any place to hook it up on the carb.

I'm pretty sure the kickdown cable is hooked up correctly. The shifting points are definitely different but I assumed thats because more cfm = more rpms.

I'll check my timing tomorrow or Saturday when I get back to my house.

I've had the vacuum advance disconnected long before I made the change because the car was idling rough when it was connected.

Also, I don't have a choke hooked up at the moment (still waiting for an e-mail or call back from Carbsonly for their electric choke conversion that Reed recommended).

Thanks for all your guy's help,
Aspen76

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76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

This isn't true. I specifically mentioned the difference in the choke linkage between the 318 and the 225 BBD carburetors.

Did you install an aftermarket kickdown cable system? The factory Super Six setup uses a kickdown rod, not a cable.
Sounds like either or both (a) you weren't hooking the distributor advance hose up to the right port on the carb, and/or (b) the vacuum advance pod in the distributor is blown and no longer holding a vacuum, thereby creating a vacuum leak when the distributor advance hose is hooked up. Check the above diagram for where to hook up the distributor vacuum advance hose.
THe CarbsOnly kit is a great upgrade, but if you order the kit for the slant six it won't work with the v-8 carb choke linkage.

Fortunately, there is a very simple and cheap way to make the slant six thermostatic choke pulloff work with the v-8 linkage. Fab64 came up with a very ingenious solution to using a v-8 bbd or 2280 on a slant six with the slant six choke setup.









Here you can clearly see the V-8 butterfly piece hooked to the slant six choke linkage. Fab64 reports this allows the choke butterfly to operate correctly with no problems.

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Casually looking for a Clifford hyperpak intake for cheap.

Stop doing that. You're wasting money and not helping anything.
That's not correct. The rating system was different prior to 1973, is all. North America used to use the RON (Research Octane Number) rating system still used throughout most of the world, but switched to the average of the RON and the MON (Motor Octane Number). Because any given fuel's MON is always lower than its RON, the new numbers are always lower for any given fuel, but the actual antiknock performance of regular, mid-test, and high-test is the same as before. Today's 87-octane regular has a RON (old number) of 91.
There are definitely differences beyond choke hookup and throttle plate holes. A 318 carb can be successfully used on a slant-6, but they are not the same carb. Also, looking at the thread you link, this is a "who knows" pig-in-a-poke used carburetor with its ID information missing, likely already (abusively) "remanufactured" at least once, so the carb will continue to be a suspect.
Good info...
That was an error. It will cost you significant gas mileage.
This mod is not catastrophic to fuel economy.
That was an incorrect guess based on misunderstanding of what the valve is for, and it will take a chunk out of your fuel economy.
Umwhut? That'll certainly cost you gas mileage, too, since it means your idle mixture is way off -- either too rich or too lean, depending on whether the PCV port in the carburetor has been clogged off or is sitting open. It's at the rear of the carb. Refer to the BBD manual you can get here to find the PCV port.
There is no kickdown cable. It's a solid linkage. And no, carburetor CFM does not affect shift points; if it's shifting "definitely different" then either the linkage was wrong before or it's wrong now (which is more probable).
That'll be another big chunk out of fuel economy. When you hack, slash, disable, disconnect, remove, and guess at things you don't understand, it's going to cost you fuel economy, performance, and eventually safety, too. Get the three books described in this thread as quickly as you can and start reading to get up to speed. And fix the vacuum advance.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Alright, I know the kickdown is a rod, not quite sure why I keep calling it a cable, just a bad habit.
So it looks like my mechanic put the vacuum hose coming from the power booster on the pcv valve fitting and plugged the vacuum advance, Heated Air fitting and the EGR fitting on the carb. While I'm asking what goes on the bowl vent fitting?

When I had the single barrel, everything was working great for the first year I had it, then it started to idle rougher and rougher till I felt like I was on a roller coaster when I was sitting at lights. A friend at work suggested pulling the vacuum advance from the carb just to see if it helped. As soon as I pulled that sucker loose the car quieted out. Does that sound like what would happen when a vacuum advance pod goes out? I just went out and plugged it in and it got a very minor sputter at idle but nothing compared to the violence it caused with the single barrel. I took it for a drive and everything was fine driving wise.

Well with the heat riser valve being important, I guess that puts more pressure on me to get money together to buy dutra duals. Seeing how I couldnt get the bolts that hold the intake to the exhaust manifold out of the exhaust manifold after a couple hours of drilling, torching and a few "steel cutting" drill bits later...

It shifts smoothly but it shifts at a lot higher rpms then before. I never paid attention to when it used to shift with the single barrel but now it shifts from 1st to 2nd around 1900-2000 and 2nd to 3rd around 2250-2400 rpm. It just sounds like it's rev'ing more than it needs to. For the most part I try to initiate the shift by letting off the gas when it gets in that range. When I asked my mechanic if that was normal he told me that it was...but the more stuff that keeps going wrong, the more I get the feeling he doesn't know what he's doing.

Just order both books off of Amazon right now, will have to check ebay later for a factory service manual.

You guys are life savers (and more specifically for this instance, gas savers ) Thank you,
Aspen76

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76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

None of that is even close to correct. You need a new mechanic; this one doesn't qualify for that title at all.
The bowl vent hose.
Sounds like what happens when the vacuum advance isn't hooked up correctly and lots of other parameters (basic timing, throttle position at idle, etc.) are screwed up.
When does it shift at light throttle in terms of road speed?
You should not have to do anything to force or "initiate" a shift. It's an automatic transmission, but given the mess your "mechanic" made of vacuum hose hookups that are dead easy to get right for anyone with even just a little experience fixing cars of that era, it's a safe bet he screwed up the kickdown linkage and probably other adjustments as well.
He's an ignorant moron. Dump him.
Right.

Keep pluggin' along!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

This is a great thread! I need to find someone to really tune my slant. I feel I am having some of the same issues. Anyone live by the S.F Bay Area who can really tune these engines?

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1967 Dart GT Super 6

Don't feel too bad. Equipped with a Weber 32/36, I just calculated 10.7 mi/gal hauling stuff up and down mountain roads. I'm not too surprised because it is an underpowered breadbox and I had to keep my foot to the floor, but I was anticipating a little more. Hmm, I do have a good 318 w/trans but then I wouldn't feel welcome on this forum

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1985 Dodge B250 Van

I have seen 318's get the same kind of mileage when 'worked' hard, (was in a '68 Dodge P//U 3/4t) If I remember correctly it didn't get very much better when not 'worked'. I am glad I wasnt the one paying to feed it @ the time, but then again gas prices werent even above a buck a gallon then either... It was a 318 w 4sp....

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MRO....

Cheap, Fast, Reliable.... Pick 2...

Does anyone know someone good around the Tampa Bay area?

The car shifts from 1st to 2nd around 20mph and 2nd to 3rd around 40 mph.

Where can I find a full diagram of all the vacuum lines for the BBD? I've went over the service manual and watched the Chrysler video but neither seemed to cover where the lines hookup off the carb.

Thanks again for all the help,
Aspen76

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76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

Those numbers are pretty much where they should be at light-moderate throttle.
Factory service manual. Or, failing that, try this very thread, in the post by Reed.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

get in touch with charlie s here on board...great guy ,not tooo far from you and he knows his slants....when I was there I lost count of how many slants were there