I am hoping to make a long drive to attend the final race of this season in my 1980 Aspen. I expect to spend 16 to 18 hours on the highway in 3 days time and gas isn't cheap. The motor is a 225 with a super six and large exhaust. All of the pollution equipment is gone because I got the car as a rolling body. With only a few hours to spare, I need to try and improve the highway fuel economy for this trip. This will be the last time the car is used in it's current form, because I am building a new motor and trans combo, but couldn't possibly finish in time. I don't care what the changes will do to my 1/4 mile et because the car is only running in the 18 as it is. I'll worry about being fast next year

These are the best hopes I have for improving the gas mileage. I would like to do them all but don't have time. I'm looking for informed opinions about which would be a best use of my time . The car got 13 mpg on the last highway trip to the Columbus race. I know that 16 mpg isn't unreasonable for a slant six powered car.

1. Re-enable the lockup feature of the 904 transmission to reduce highway rpm (I think this would take about 2 hours. I just need to drop the pan and valve body to put the light spring back into the lockup valve)

2. Change the rear end ratio from 3.23 to 2.94 ( I have the gears and have done this swap before. This is an 8 1/4 rear end and I expect it to take about 3 hours considering my crude methods)

3. Pull the rad and front timing cover to degree the cam back to something a little more sane. I retarded the cam as an experiment and the result was lots of low end grunt, but an early drop in power. I hope that moving from a few degrees retarded to a few degrees of advance, the peak will move considerably up the rpm band and result in improved fuel economy on the highway. ( I estimate this will take about the same amount of time as changing the rear end ratio about 3-4 hours)

4. There is no egr system on the motor, but I might be able to work one up out of some old parts. Not exactly sure how to make it work or how much improvement I could gain

I don't know what will help the most and I have very little free time to invest in 'fun' right now.

Looking at the numbers, I fear it may be worth just buying the extra gas.

800 miles/13 mpg= 61.5 gallon
800 miles/16 mpg= 50 gallon
11.5 * $2.75 = $31.63

Thanks for any advice.

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1980 Aspen 225 super six

I would re activate the lockup....

Stay with the cam timing ....its now prolly best for mileage.

think about the gear change...are taller tires available?

I think your time and all fluid costs ie: trans fluid, 90w , might come to a lot more than $31.

Your cheapest bestest combo is to leave it alone and drive slow.

next cheapest taller tires

Cheapest of all ....no ales ...no pizza

My last trip to StL....OKCity...and home cost bang on $800....over 4000 miles at 75-95 mph.

24 of red ale and 2 pizzas $70

Day pass at Gatewayraceway $20

Having Possum Parker sneak ya in the Georgia way.....worth $40

Time spent with old slant farts who cant remember Where anything happened....or When...but have no trouble with What happened....priceless

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Yeah....Im the one who destroyed this rare, vintage automobile.....

EGR does not improve your mileage.

TC lockup will give you about 5% on the highway.

Not sure the switch from 3.23 to 2.94 is worth the effort, but if it's not much effort for you, go for it.

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

Paul,

I wouldn't bother with gears. No big changes between those you mentioned MPG-wise. Cam timing would make some difference, but an unknown amount - leave it.

Make absolutely sure your vac advance works, and set it for at least 45 deg total advance (mech + vac). This could gain you as much as 15-20%.

Lockup - definite yes. Well spent time if you can get it to work.

Make sure valves are not too tight. This can cost you huge MPG, as I have found. When in doubt, set to 0.012"/0.022" hot. This will not damage anything.

If you have another carb laying around (1920?) that might help, but unknown.

Vac advance, lockup, and valves are my 3 recommendations. We'll look at it in Bristol too...

Lou

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Home of Slant6-powered fun machines since 1988

I am not doing too bad with a 1920 Holley. I had the 1945 and set it aside on Doctor Dodges recommendation. In fact I got several to try and found a 1920 Economaster which gives me 22.5 if I drive crazy and 24.5 if I drive nice. Haven't taken it on a trip yet, it may do better. I have been fine tuning the distributor by recurving it and running a 11R vacuum advance. Stock soft spring and a really long looped end one out of a big bock dist. That really helps. You can see my set up below. I drive 120 miles a day, town stop and go and freeway, about a 50/50 split.

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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

Something is wrong with your cam setup. Retarding the cam moves the RPM range up, not down.

Advancing it gives more low end, but it runs out of wind up top.

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Official Cookie and Mater Tormentor.

Thanks for all the replies. They are very helpful.

Reactivate the lockup sounds like the resounding winner, and it shouldn't be too bad. The fluid is new and gasket is rubber (not cork), so it should cost nothing but my time. I don't know if I need to drop the valve body or if there is room to work while it is installed, but either way it's a doable project. Just wish I hadn't fooled with it in the first place. Live and learn.

As for the cam, I don't think I want to tear into this motor. Based on your input, I know it will be the most work and it doesn't sound like anyone thinks it will give me big gains. To better explain the cam situation, I was experimenting and drilled out the alignment hole on the cam gear to shim the cam to a retarded position. This is inaccurate and I did no tests to confirm the real degree of the cam. The result is an engine with lots of grunt and an early end to the power band. Other factors surely play a role and I will continue learning as tools and experience come my way.

As for EGR while I know it's primary purpose is to reduce emissions, I also thought that filling some of the combution area with burnt gas would reduce the amount of fuel/air mixture used. I have heard before that this theory doesn't stack up, so it does not suprise me now that no one suggests I put time into it. I doubt I'll have time anyway.

I am not going to change the rear end ratio. It wouldn't be very hard since I've done it several times now, but I will want it the way it is when I put the new motor in, so it seems like double work for very little gain.

As for the carb, it's a super six, so switching to a smaller carb isn't an option. I don't have single barrel carbs around anymore. This is a v-8 version of the BBD and I'm pretty sure the jetting is far too rich based on the engines power and the golden brown spark plugs. Maybe I'll tear it open and put slant six jets and rods in? I've been meaning to do it for a while and I plan on staying super six with the new motor. I've alway suspected/known that the poor mileage was due in part to the jetting, but had never done much more than drop the metering rods way down for long trips. That low rod position seemed to create a very lean spot at light trottle and often forced me to put my foot into it to get enough power to hold cruise speed. I don't know why I don't feel like messing with the carb, but it's a very good suggestion and I would be foolish not to try.

Thanks again, it's very helpful to have feedback and it's not like I'm gonna get much response from my wife.

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1980 Aspen 225 super six

EGR when combined with additional spark does increase mileage - but this is really only marginal. In your case, it most likely will not be worth your effort.

Mitch

I will reiterate - check your timing and vac advance.

As Dennis said, your cam is undoubtedly advanced, but no need to change that now. This is an easy mistake to make if you are not actually reading degrees with wheel and dial indicator.

Carb could have a big effect - good place to spend time.

Lou

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Home of Slant6-powered fun machines since 1988

I will check, but don't expect to need to make any changes as this car had it's timing worked out last year. I will make some marks on the damper and be sure that I've got the 45 deg at part throttle, but again it should be very close to that now.

I dug out another old BBD carb and pulled the jets and rods to compare to the current carb. The parts carb had 2228 rods and (don't have them with me,but I think) 356 jets. The current carb had 2231 rods and 359 jets. I could remember these numbers wrong and I will check again if anyone cares to know, but I am sure about the last numeral of the jet and rods. I'm planning on leaving the larger rods and using the smaller jets. This looks like it will make very little difference when comparing the clearances, but I don't know how much change will be necessary to result in improved mileage. It's already apart, so here goes nothing.

I've got the trans drained and the lockup will be back in business before the day is over.

Just hoping this isn't all for not if I have to be at work at 7am on Monday.

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1980 Aspen 225 super six

How is your carb tuned(bbd)? I was getting no better than 15.2 with my bbd untill I adjusted the carb my self and now I'm 18.5 to 19.5 and thats going 65 to 80 mph all freeway with some inner city. I dont know about the holley 1920 but the 1945 I took off for the bbd was putting out 21.5 at the same speeds. I did increase the jet size up and it worked really good on it. Check your advance, thats sound advice. I'm around 45-48 all wound up at 3000 rpm.

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it's like a vw, sounds like a million miles an hour but goes really slow. (for now)

Well, the lockup doesn't seem to have worked? Don't know why, but doubt I'll have time to drain the tranny again. It was worth a try, but I have no idea if the lockup ever worked in the first place, as I disabled the lockup by replacing the spring with a spacer before I ever installed it when I first got the trans. Maybe I missed the lockup kicking in, but I don't think so. The converter seems very loose, maybe it's a cheap quality replacement.

I still think this carb is not lean enough. I've got excellent throttle response and it revs right up to faster than I want to be going on local roads. Too much fuel in the mix still I guess, but I don't have any more ideas on how to get a leaner mix from this carb. The rods are down and I actually think it runs even better with the smaller jets! I might be able to squeeze a little more adjustment with a different plastic control arm to the metering rods, if I can just find it in the shop. I guess I can also use that little allen head adjustment screw, but I don't think that gives much more adjustment.

I shouldn't be complaining, for 3 years I've done everything I could to make it go faster without thought of fuel use. I hardly drive it 2000 mile per year.

I checked the timing and everything is tight to how I've been trained. Initial timing is 12 BTDC and 30 total mechanical advance seems to drop in pretty quick. With the vac attached, I get 45 to 48 deg before it stops adding advance and this also comes in at what sounds to be plenty early for highway rpms at part throttle. Don't have a tach to tune, so it's all by ear.

I might have another hour to tune this week, but it's really getting time to move on to other projects. Thanks to everyone, and I'll get back to you all about the mileage I get after the trip.

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1980 Aspen 225 super six

Couldn't find the other plastic control arm (I could swear I had seen an article that explained the difference between the slant six and v-8 versions and showed the special arm) I used the allen screw to drop the metering rods as much as possible and was able to squeeze a tiny bit more adjustment out of the arm. This seems to be getting closer, as I can finally feel a hint of progression through the throttle. Before, it was all or nothing as the engine took off at the slightest crack of the throttle. I'm sure there is still more that could be done with jetting and rod selection, but I have never found a source for BBD parts other than random ebay purchases of core carbs. I also have several holley 2280 carbs and a couple of much older carter 2 barrel carbs, but they have all proven to be jetted rich for a six. If anyone has sources for jets for any of those models, I would be very helpful. It seems like the best reason to go to a 4bbl setup is so you can find a tuning kit.

I feel like this will get better mileage now, but time will tell how much better. I am very happy with the results based on local driving. The car has much better manners and even seems to idle a little smoother.

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1980 Aspen 225 super six

I am happy to say that it was well worth my time to tinker on the car before this long trip. After adjusting the kickdown, the lockup converter finally took action the first time I hit 45mph and worked most of the trip as I could feel the notable 'hum' of the road though the drivetrain.

The total travel was around 950 miles by my odometer. Most of the miles past at around 70mph and nothing over 80 mph. At 65 MPH, those little "your speed is" signs on the highway confirmed that my speedo is working pretty damn good, so I'm going to trust this mileage even though google maps says 810 miles round trip.

Looks like 18-20 mpg depending on exactly what's left in the tank and who's mileage you trust. Better than I expected and saved me a couple of stops along the way. The car is very lean for driving around town, and I don't think I would keep it this way for daily driving. I also raised the metering rods and adjusted the kickdown for better times at the track and put some around town miles on the car in that tune, so I am sure that 18 is repeatable for highway trips. This car is heavy, so almost any A-body should be able to perform as well or better.

Thanks for the suggestions and hope that helps others.

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1980 Aspen 225 super six

Almost, with all the 'extras' thrown into the 1973-1976 year, those guys although roomy and easy to work on due to beancounter cut backs/standardization of parts, still toll in at a very heavy weight compared to the pre-73 era...

18-20 is reasonable, but I'm sure there's a little bit more in there someplace...

-D.Idiot