New to the site here, lot's of good reading, as well as helpful KNOWLEDGE.
I've got a well tuned solid running "bone stock" 67 S6 1bbl with auto and a 3.55 rear. Vehicle is about 3400lbs
A daily driver, used to commute, cruise, haul the family, road trips, as well as towing. I am a proponent of the Performance With Economy by David Vizard book from waaaay back. Want as much MPG as possible with as much power..(3.55 doesnt help, true, but it stays!) Looking for that reasonable happy medium on crap 87 octane with no additives. I want a gas and go vehicle at all times.
Not looking to build a strip vehicle, or do burnouts, or race up and down the roads, but want to be able to drop the hammer and get somewhere alot faster than what the bone stock combo provides. Just looking for maximum torque, maximum power in my driving range of 30-80mph, using good old fashioned engine building techniques and proven components. Vehicle has been converted to Chrysler ECU (may do the HEI conversion as I've done it on another Mopar with excellent results), and a nice home built ram air setup, and a Dynomax Super Turbo muffler w/2" pipe. A few years of tinkering and dialing it in, it runs good and yeilds about 15-16mpg. Now it is either time to do a power buildup on the slant or just swap to a 318 and build a nice stout power plant.......money willing.
Ideas/opinions on intakes, carbs, porting, valves, Erson cam kit, pistons and CR, milling, exhaust, etc....using the same trans with the stock 12" converter and 3.55 gear.....with the best bang for the buck components. No highdollar racer stuff. Looking for a top to bottom "list" of what some of you guys would assemble to reach what I'm looking for.

My '67 Valiant is a little lighter than your car. Mods include a ported head with oversize valves, head milled for a true 8.5:1 compression ratio, 390 Holley on an Offy intake and 2 1/4" exhaust off a stock manifold. I get about 20 MPG highway and run right about 17 flat in the 1/4. Car used to run mid 19s and got the same fuel economy. The power increase was noticeable. The short block is bone stock. Car has a 3-speed manual and 3.21 gears.

What's your budget?

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Joshua

Welcome on the board.
More info please. Model of vehicle? Miles on engine and on vehicle? 170 or 225 slant-6 right now?

Sounds like you need low-end torque more than you need high-RPM power, but when you write "Want as much MPG as possible with as much power..(3.55 doesnt help, true, but it stays!) I kind of wonder what you're thinking, especially since you say your cruise speed can reach 80 mph. Are you really going to base a buildup around your rear axle ratio? That's kinda backwards. Usually better results are had by planning out the goals in terms of how you intend to use the car and what you want it to do, then picking out the best configuration to achieve that goal. It's difficult to imagine 3.55s + max MPGs + easy cruise going hand in hand, unless you are planning on installing an overdrive transmission of some variety.

What size tires will you be running? What's your budget look like? For punch daily driver service with good MPG and automatic trans, off the top of my head I'd put together a shopping list that included a 2bbl carb (factory Super Six components with a new carburetor, which I'm not just saying because I have several such new carbs on the shelf ), Dutra Duals, a well-curved distributor (or a new #3874714 which already has a good advance curve from Old Car Parts Northwest if you don't want to recurve what you have) with HEI, a thoughtfully chosen and carefully degreed Erson cam, a good careful engine buildup (follow one of Doc's photo essays on here) with extra-careful head work including Engnbldr valves, stock pistons and rods, block shaved to achieve roughly 9:1 actual CR, and 2.93 or 3.23 rear axle with 205/70R14 tires. Others will chime in with their lists.

I'd also plan on spending money to make the brakes, steering/suspension, seat belts, and lights better than 1967 spec, which I'm not just saying because I might have a good headlamp or two on the shelf, too

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

SSD, No real budget...I never can afford to do anything these days...Too many toys....But I'm doing it anyways! Everything has to be the best value for my dollar. This is'nt an ideal setup I know, but am working with what I've got, and want the best mpg I can get with what I will be using.
I'm working with an 225 A100 panel. It's a 8 3/4 3.55 rear...priced a pumpkin for one of those lately? so that's one reason why the gear stays (it had a 3.91!!! before I bought it..thankfully someone swapped it out!). I will work with it. RPM's on an electronic elcheapo tach at highway speeds of 70mph (indicated on 40 year old speedo and cable!) are about 3000-3100 with 255/60-15 tires...I believe they are around 27.5" to 28"...I have'nt done the math with all the figures to find true RPM's. The gear, rear tire combo is set and won't be changed and 30-80 mph is where I operate (city, country backroads, and interstate) With this van I dont run much beyond that as I have to consider what will be left of me in a frontal!!! Not to mention I hold a CDL, so speeding on the interstate is plain stupid in my case. I can't recall the last time the gauge even showed 4000 rpm! Being a 225 I'm well aware of the nature of the beast, so low-mid is my range. But power to pass on the interstate is important...as well as pulling a grade down here in the mountains. So I need it all!!

I wouldn't consider a 318, simply because gas mileage. I mean people have short memories, and now that gas is relatively cheap they don't see the writing on the wall that it's going to change in most likely months.
I wouldn't worry about the 3.55 so much, the engine is still pretty small so torque multiplication is nice (compared to a 500ft/lb 455).
An Erson cam that enhances your torque would be a great improvements. This involves breaking down the engine somewhat, but should keep you in a budget. If you don't want to pull the engine, pull the head and put a lot of work into that. I would go ahead with the super six over a 4 in your case.

A 3.55 with those tires is roughly equivalent to a 3.23 in a A-body........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I tuned up my brother's 1983 Dodge b-150 shorty van powered by a 225 slant to get 20-21 MPG on the highway, empty, cruising at 65-70 MPH.

Read all about how I did it HERE.

I agree with you there. I'm guilty! A few short months ago I would'nt have considered a swap. I had assinine gas bills. With things today, after visiting a few Mopar shows at dragstrips, and after not having the sound of a nice v8 for sometime....well, that's all it took. I'm back to fighting reality and pipe dreams!
Would love to drop in a v8 and make it a stonkin' little hot rod (there's a side of me that wants to do an occasional pro stock burnout through an intersection and smoke the unsuspecting sucker!)....but, the reality is, this thing has to be all the things I posted initially so practicality has to win out.

Sounds like you want your cake (power) and eat (economy) it too. In my opinion, there is only one way to achieve that. COMPRESSION.

The best bang for the buck is to increase the compression by milling the head. It will increase the torque over the complete rpm range. While you have the head off, do a good valve job, with back cut valves, and some mild pocket porting (don't go crazy). You will need to measure the chamber CC's and decide what ratio you want, and cut accordingly.
On my 66 Valiant I milled the head about .100 (you don't want to go that much) and back cut the valves. No other changes to the car/engine, and picked up .3 sec, and 3 mph in the 1/4 mile. Total cost $60 for milling, $15 to cut the valves (no other work was required, good head). $12 head gasket.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Sound like your just looking for a pinch more peformance and the Slant6 should be ok for that. If you think your going to want more than a pinch then stop now and put the 318 in (with trans). I just pulled a very hot slant which got 9 mpg and put in a bone stock 318 with header and 4 barrel and I am getting 15 mpg. I havn't had time to adjust the carb at all so I think there's more mgp in it. The best part is it ran a 15.00 first time out and burns the tires 1st and half way through 2nd. Cost of upgrade was $3130. I sold the performance slant for $2000 ish so my cost for the upgrade was really $1130 which made sense for me. Unless you already have the 318 and trans, it's not likely going to make sense for you, unless you find yourself looking for more and more power.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

LWS1967, take special care with advice from Brennan, who made just about every possible expensive bad choice and wound up with a wholly unsatisfactory slant-6 buildup because he deliberately scorned the mountain of good advice he got on this board. It's a shame he chose that path, but it was his choice. It pains me to have to call him out like this, and I'm sure it's more comfortable for Brennan to remember things a little differently than they actually happened, but it's important that those who weren't on the board at that time — like yourself — be informed of what really went down.

Fortunately, there are plenty of people who have thoughtfully used common sense and taken advantage of the knowledge pool here to build slant-6 engines that very successfully meet goals very similar to your own.

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

Since you have an A100, to change to any small block you'll need the V8 frame mounts for the A100 (different than the slant ones) and you'll need a van-specific transmission (trans mounts from above). A passenger car 904 might work if you fab a trans mount that is like the later van mounts.

Your right I can't be trusted. It also pains me to ignore my halusinagenic friend who is insisting that I take my psychotropic drugs.
I think that anyone reading or rereading most of my past posts would find that there where many unclear answers. Up and down are not the same.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Yeah, now that it's clear we're talking about a van here, the 3.55 gears make more sense.

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

Well now that we know it's a van, it seems to me we might have another option. If (as is often the case with vehicles like this one) it's factory-equipped with the A-engine trans with the adaptor plate and low-mount starter, then an overdrive automatic transmission (A500, A518) could be installed without much difficulty. This would lower the 1st and 2nd gear ratios for snappier takeoff and drop the final drive ratio to a super-cruise 2.48 to rack up the miles per gallon when cruising at 80 on the highway. Combine that with a thoughtfully-built engine without need of any costly exotic parts, and the resultant vehicle would probably very closely meet the stated goals.
Or the block, or both. Milling the block has the advantage of reducing the negative deck height; you don't get that with head milling. Of course, whichever hunk of metal is shaved, it has to be done with calculator and paper/pencil in hand and brain engaged; just milling the head and/or block some arbitrary number endangers the ability to run on regular gasoline.

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