Hello all. Haven't been on here in a while because I haven't had a running slant vehicle. Well gas prices say that's about to change.

I plan to put the slant back in my '84 W100. A freshening up will be needed. To start, I have two slants to choose from.
1. The original '84 cast crank hydraulic cam motor.
2. A '76 steel crank solid cam motor.

The goal is to get better gas mileage and more power without killing mileage. The Aggressive Ted build is kinda the right direction I think. What do y'all think? Which motor? Any newer tricks/methods since the AT build?

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Hate to burst your bubble but a 4WD brick is not going to get good mileage even with a slant 6. They are just too heavy and not usually geared for fuel economy. That being said. A good cam for torque, bump the compression, a 2 barrel setup,and free flowing exhaust will help with power and not hurt your mileage much, if at all. And if the head is off and or apart, open up the bowl area for better flow.

Good luck

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Ted has not been on here in a WHILE. I've asked about him over the past couple of years, never did get an answer as to what he's up to now a days, I was wanting his take on my build too.

Both of your engine choices have advantages over the other but for different reasons. What gearing, how big of tires, any extra accessories like winch or cross bed tool box full of tools that you are lugging around? Do you "4 wheel" much?
You say something about putting the slant BACK Into it. What's in there now? If you 4 wheel it much, especially "off road" , I'd be inclined to go with the forged crank, for more "flywheel effect"
but the cast crank engine would be lighter if you're into shaving every unnecessary ounce" thinking it would help on efficiency carrying less weight you have that. Either one can be built to the same degree, either can take either the solid or the hydraulic cam.

I'd definitely run without lean burn either way you go, and often a bigger carb can actually make things more efficient.
Whichever way you go, I'd make sure you measure it out for things like piston depth at TDC, and combustion chambers CC and be sure what compression ratio you actually have. They will be less in that department than advertised, I guarantee you. And clean up the head as in port/polish it. Cam suggestions will be all over the board,
I suggest something along the lines of what used to be considered a "truck/RV" cam.
That said, occasionally having to adjust the valves never bothered me.
I just got the original engine out of my '85 last night, I have a '74 engine on the stand ready to drop in over the next few nights after work. But I went with a few years newer peanut plug head just to eliminate 6 potential oil leaks. I ported mine out and went with oversized valves.
Not saying that was "right" or "wrong" but definitely clean up those ports so it can breathe. Anything you can do there can only help your cause.

The worn out slant that came out of the truck got 14.5 mpg. It has a high mileage E48 (police car) 318 in it now that gets 11 mpg. I'm happy with the power just want a little more mpg.

So basic "hot rod" mods should wake it up?

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

I plan to use this truck as an overland camping truck. It will be loaded and used offroad. I'm not expecting miraculous fuel economy, just better fuel economy. Reliabilty and range are important.

I removed the lean burn for a hei. I have a choice of an A500 trans or a NP 435.

So just basic hot rod type mods should be considered? Compression bump, head work, cam, exhaust and well tuned induction system?

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Isn't that an Overdrive transmission? I don't think that was ever put behind the slant 6. But if you have an overdrive option and the gear ratio will support that. Great.

My original truck build did pretty much what you are after also. Mild cam, higher comp. Headers and a small 4 barrel. Would get @16-17mpg in mixed driving. On long trips I got as much as 22mpg with a 2.76 gear change. Normally it had 3.55 gears. Power was much improved over the stock slant and the mileage better also. But I only had a 2WD too.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

More compression and some port smoothing, with everything else adjusted to make those work (ign, cam, mixture), will get you both better MPG and better TQ/HP. Measure a piston-to-deck height at TDC and then you can design the compression by milling the block and/or head appropriate amounts. We can help with calculations if you like.

For your application, I would suggest finding a good used Carter BBD. Many of them need the throttle shaft bushed to fix air leaks there. I have found those can make very good power in a mild motor, and very good mileage. Decent ones (even rebuildable) are getting hard to find.

Lou

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Home of Slant6-powered fun machines

Great suggestions guys, keep them coming.

Any benifits to back cutting the valves on a slant?

What highway cruise rpm do most of you like?

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

I can make the a500 work and yes it's an OD.

What cruise rpm diui d yourd like to get 22mpg?

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Cruise RPM really depends on head/cam/compression. Given your heavy and tall vehicle, I cannot see you will want to cruise at lower than about 2400 RPM, but maybe you can get away with less if your motor is really torquey.

I assume you have the factory adapter plate to mate the A500 to the Slant. Truck is a good application for that combo. Note that I did not gain as much as I thought in acceleration (swapping from 904 to A500 in my Dart) because that trans is so heavy (inside and overall). MPG gain was about 10%.

It's good you are thinking through all this stuff!

Lou

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Home of Slant6-powered fun machines

I don't know what rpm we were cruising at. We ran about 375 miles from PA to a race in Wilkesboro. NC and we ran @ 70 mph the whole way down the interstate.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Huh. When I had my 81 w150 with it's 318 it surprised me in mileage. Factory thermoquad (I love those carbs on a v8) 3.21 gears, manual lockouts up front 32" tires (32x11.50-15) 727, long bed, that thing got 20 on the highway and not much under 16 in combo driving. I always thought that truck was somehow a fluke but in a good way. One that I miss.
Also had an 83 D250 with another 318/727 that I put a stock 360 cam into, EQ heads, performer intake and carb, and that really woke that engine up and mileage was better than originally. Not quite as good on the highway mpg as the w150 was, but still better than yours gets. Still around 16 in mixed driving. And better than yours gets, even with a loaded car trailer on the ball. There are times that the smaller engine doesn't win the economy race.
I've had what now, 6 Dakota's? Maybe 7. 3.9s and 318s. No 318 was worse on mileage than any of the (magnum) 3.9s
Except for my my 1st 3.9. that one wasn't a magnum, and got me 20. Best of the 3.9s I had. Other 2, 3.9s, (both magnums) struggled with 17 mpg on a good day.
My 93 club cab which was a 318 and came to me with a bad trans, I converted to a 5 speed stick. That truck was good for a consistent 20 without even trying.

I've also had /6 trucks. Including the 85 I'm currently working on.
I just pulled original slant, ready to stab in it's replacement, took alot of clues from here in the buildup of said replacement by looking thru many others' build threads.
This one I never drove enough to track mileage, less than 1 full tankful in 2 years. Bought as a project from the get go because the body is so solid on it.
I drove it enough to verify it ran, didn't overheat, knock, misfire, or anything else bad. Was partially apart, when I trailered it home. I put back together what was apart, and got it running again, and started on the replacement engine. I had thoughts of "it would be nice if I could make it get the mileage I got out of my 79 slant powered truck" but there are other differences between this one and the 79.
Mainly the 85 is long bed and 727 trans, power steering and brakes/ where that one was a 3 in the tree with manual steering and brakes and short bed. I also swapped in a 4 speed overdrive trans (833OD) on the 79. But if I can get out of the 85 with the new engine, what it would have gotten with the old (but have more ballz) it'll be good with me.

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It's good you are thinking through all this stuff!

Lou[/quote]

Yeah, that's what I'm trying to do.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Nice. The part time 4x4 shouldn't be too far behind the 2x4.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH