$ Building a Slant 6 for performance

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:wack:
Rug_Trucker said:
They now have crank kits to push a 360 to 440..............
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That makes as much sense as stroking a 225 slant 6....

The heads won't handle 360 cubic inches... how are they going to breathe at 440?

You'd have to spend a fortune on W-9 heads and/or use forced induction.
 
Rug_Trucker said:
Which heads? BTW I want to build a 262 /6 I won't be the first.
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Which heads? ANY small block heads that are not priced astronomically.

If you want a fast small block V8 that is capable of 2+ hp per cubic inch (normally-aspirated), you'd better be ready to spend a LOT of money on cylinder heads. That goes double for a 440 cubic inch, stroker small block.

The only slant six cylinder head we have to work with (except for the really hard-to-obtain "Argentina" head,) was designed for a 170 cubic inch motor. Because of the slant six's small bores, and small bore-center spacing, there's not much room in the combustion chamber for very big valves. That head is never going to breathe very well; why you'd you want to make the problem even worse, by creating a 262 cubic inch reciprocating assembly is hard to understand.

If you just want a lot of power, turbocharge a 225; there are a couple of them running that make 500+ horsepower.

Of course, you could build a 262 and turbocharge IT, but engine longivity might be a problem, then.

Just sayin'...
 
Some day maybe I'll sit down and figure out what my cubic inches are with my .105 overbore !!:D
 
6pakattack said:
Some day maybe I'll sit down and figure out what my cubic inches are with my .105 overbore !!:D
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238.8043011:cheers:

That's a 6.2-percent increase over stock.

It's like throwing two hundred pounds out the window on a 3,300-pound car...
 
6pakattack said:
So I guess that means my fat azz won't be able to drive then !!!:D
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No, it just means that it will be approximately 2 car-lengths quicker in the quarter-mile than it would have been if you'd kept the stock bore.

Two car-lengths is a lot...:cheers:

You'll also pick up 6.2-percent on your compresion ratio. If it was going to be 10:1, now (with the overbore) it will be 10.62:1.

More is better, normally-aspirated.
 
Bill Dedman said:
No, it just means that it will be approximately 2 car-lengths quicker in the quarter-mile than it would have been if you'd kept the stock bore.

Two car-lengths is a lot...:cheers:

You'll also pick up 6.2-percent on your compresion ratio. If it was going to be 10:1, now (with the overbore) it will be 10.62:1.

More is better, normally-aspirated.
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CR now is a definite 11:1 !! I think I'm going to have some fun playing when it's done !!!:D
 
Elwood67 said:
I appreciate the /6 for what it is, one of the most durable engines ever & guys on here do some really cool stuff with them. However, I've come to realize that it takes a lot of money having someone else do the machine work necessary to get a /6 much more HP. Shaving the head, if not the block too raising the compression, & putting in oversize valves. Besides your usual bolt on mods, like a 4 barrel, Offy or Clifford Header etc. Unless you Super/Turbocharge.
Not that re-sale value should be a very top priority in this hobby but it's good to realize if you decide to go V-8 after you've spent $1,000+?? or more on the /6, it's still probably not likely to fetch $200. Fewer interested buyers=lower demand= lower price. Sure, you could show some receipts, but it's still a hard sell. There is kind of a stigma attached unfortunately. For example you could start at 220 HP with a 90s Magnum 318 (for about $300 around here) and go up from there HP wise, instead of spending a ton of money on the six. However you would have to get a 318 727 trans, and 8 1/4 or expensive 8 3/4 rear end. That's probably $600-$1,000 maybe. A few trade offs. To each his own. My 198 /6 is still stock at this point, I've picked up on great info thanks to this great forum.
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Hi Ewood67
Wow you guy are very lucky being able to get parts so cheap!! Here in Australia the parts and builds are Sooo much more expensive I’d love to supercharge my slant but just not sure if I want to spend 12-15k on building and supercharging my slant, or building a snappy V8 and components to suit, and yes some people like and want a all original car to buy and others might prefer a modified car we all like and want different things.
Just wish we had all the choices and prices of in the States.
 
Turboit said:
Hi Ewood67
Wow you guy are very lucky being able to get parts so cheap!! Here in Australia the parts and builds are Sooo much more expensive I’d love to supercharge my slant but just not sure if I want to spend 12-15k on building and supercharging my slant, or building a snappy V8 and components to suit, and yes some people like and want a all original car to buy and others might prefer a modified car we all like and want different things.
Just wish we had all the choices and prices of in the States.
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Move to the U.S. as soon as possible. Now is your chance, Biden is in. Millions of illegal aliens will be given amnesty and millions more are on their way to break through the border. Come quick, Florida waits for you.
 
someone brought a 9 year old thread back from the dead..... I'll say that in the end of this most recent election season, I'm not as happy with Trump as I was before this past New Years holiday.... but I am definitely not happy we got Biden, the next 4 years (or as much of them as he shall live, he's old) I won't get into reasons..... I'm tired of the last few go rounds, where the goal winds up being to try to figure out who will be "least of 2 evils"..... and hope "your guy" wins.

but back to the thread topic...... I have read thru most of it, and bits and pieces throughout, spell out why I am building a slant for my most recent D150....
It came with one
Ive been down the "yank the slant and drop in a V8" road. More than once.
If I put a V8 in there, (and I have 5 great candidates sitting in my garage right here already) I have to buy a trans that will bolt to a V8... I already have a 727 (yes I know the difference) in the truck behind the current (original) engine.
I'll have to buy a radiator
I'll have to find V8 mounts
The money I "am not" spending on "conversion to V8" parts, is money I can put into building a much stronger, much more powerful Slant/ not only compared to what is in there now, but with only 6 pistons and rings for a 6 vs for an 8, 1 head to machine, 1 head gasket to be worried about (not 2)
and this truck is the lightest GVW of any D series trucks they ever made....
even if I put "1 ton" suspension under it, I can legally only pull the same weight of trailer as what it was originally rated for or load it to what the original intended payload it was meant for.... even if I put the 440 into it that I have here....
most of the time I won't be carrying much in this truck anyway, and it's plenty for my utility trailer or my popup as is.....
It's different from what everyone else does ( usually people put a V8 into the engine bay, scrap the slant)
The slant has always been known as a dead solid, dependable engine that will trudge on for hundreds of thousands of miles, (yeah I know so would a 318 or 360)
once this truck is finished I won't want to sell..... I don't like the newer trucks, I can put less than 1/6 the money into this one and have a super nice truck, vs pizzing it away as payments....
I just gotta figure out just how I want to build up this particular Slant engine...
I like what "my 68 Barracuda" (member here) did to his slant in his truck... main difference between his and mine, is short bed (his) vs long bed(mine).
If I don't go that way, I still have home brew, draw thru, low buck turbo bugging me in the back of my head.... biggest difference between the 2, (internal to the engine) would be "the" ideal cam to use.....
I love the D/W series trucks, been looking for a decent, solid body example for a while now..... would I have rather it came with a V8? Maybe, but I got what I got.....
 
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All that said, I'm not building a race truck by any means. But I definitely need for it to be able to get out of it's own way. Which it don't do now.
HP wise, I hope to get at least in between what a stock for 1985 318 and a stock for 1985 360 out of my slant, so that would put it at 140-150 hp. At a minimum. A high (for a slant) revving version wouldn't be very suited to a truck that was built with a front end that resembles a brick wall.
My basis for my build is a 74 forged crank bottom end and an early (as peanut heads are concerned) peanut head, without all of the extra holes for the AIR pump.
 
Hi Bill

Mate is there anyway I could possibly have the build information of Tom Wolfe and Ryan Peterson or of yours and Freddy’s Please??.
I’m wanting to build the 225 slant engine with some grunt behind it, I’d personally be happy with somewhere around the 250rwhp!.
So Bill is it possible to have a just over mild lumpy cam in it with a turbo? I still haven’t completely decided if I’m going turbo or supercharger I’m guessing this decision will also come down to what HP can actually be made with a supercharger and any information on others that have used one! I’m only a virgin to a slant engine so I no nothing about them apart from what I’m now reading, so any help you could throw my way would be Greatly Appreciated.
Thanks again mate

Bill Dedman said:
If you can stay awake for all this, here is a comparison I wrote awhile back for a ball-park cost-analyis for going with a turbo225 and a small block of equal power.

YMMV...



Comparison of turbo Slant Six 500 HP build vs. 500 HP 318/340/360 small block build





The following is written in reference to the 225 motor. The 170 is a different kettle of fish.


It would seem that slant 6 motors (remember, this is a 225 thread) were built (though, not intentionally,) to be force-fed air and fuel.
Whether it's done with a supercharger, nitrous oxide, or a turbo, it once-and-for-all, makes an end run around the built-in breathing problem that slant sixes suffer from birth. Because of their small bores, they can never have the kind of breathing that will deliver horsepower in the 1.75 hp-per-cubic-inch range. Not with that original, cast-iron, 2-valve head, at least.

The engine is rpm limited because of the long (4-1/8") stroke, so it's never going to deliver the goods at 8,000 rpm. That's the rpm where most small-block Chevys that are really "built" seem to make big power. I'm talking the small-displacement, short stroke models.

RPM? Forget it.

Because of the fact that the original plans for the slant 6 included an aluminum block (and, the fact tht that aluminum isn't as strong as cast iron,) the basic specifications for the slant 6 block were robust, to say the least; they had to be... aluminum needs more mass and are to be as strong as it needs to be for reliability, than cast iron. Well, the engine that went on to live in Mopars of various descriptions for many years, turned out to be cast iron.

But, the changes in the cast iron version, from the aluminum parameters, were minimal.

That meant that the resulting engine was an unusually strong critter, not unlike a Diesel, in basic construction.

A forged steel crank with mains the size of a 426 Hemi’s made for an equally-strong bottom end.

Along the way, someone a whole lot smarter than I am, realized that what this all meant was, you could boost the s**t out of this little motor without hurting it. Boost = performance increases!

Tom Wolfe and Ryan Peterson built the prototypes for the engine that is in the '64 Valiant that Freddie and I plan to run. We bald-facedly copied their lead, and we are HOPEFULLY going to run within a second of their cars. There are only minimal differences in their "recipe" from ours. But, they did it first; we're just copy-cats.


In this diatribe, I am going to try to justify why anyone would want to go this route, ($$$$$$$$$$$,) and perhaps point out a few reasons why it might not be such a good idea, after all...


There are (at least) two kinds of people out there; those who just want to go fast, and those who want to go fast and prove something in the process.

Anybody can stick a big engine into a light car with easily predictable results: It's gonna be F-A-S-T!!! Those 440+ cubic inch A Bodies are hard to outrun... and, with good reason! Ma made it pretty easy to drop an RB engine into an A-Body, and beyond getting it to hook, the problems in getting it to go fast are not actually what you'd call "insurmountable." Whoever said, "There's no substitute for cubic inches," said a mouthful!

Senor' Schumacher has made the task of installing a big engine into a Dart or Duster a lot easier, with his motor mounts and custom-fit big-engine-in-a-in small car headers. The appeal is almost overwhelming, if you love "speed."

Some folks, though, look at that operation and say, "Ho Hum... It SHOULD be fast; big block in a small car.... so what?"

Some of those detractors want to produce a fun car with a smaller engine, but not TOO small.. There are the 318/340/360 guys who don't want the hassles that go with the installation of a third-member-breaking big block, but would still like to trim a few Corvettes.

To them, a small-block is the answer; they don't want to mess with a slant six, because 1. They don't like the way they sound, and 2. it's hard to build one that will outrun most Corvettes. They probably have never SEEN an 11-second slant six car. Or, a 12-second one; thirteen second slant six cars are not even that plentiful.... so, they know that they can stick a set of headers on a 340, raise the compression to 11.5:1, go with any one of a hundred different solid lifter cams, and presto," a low 12-second car that will embarrass most street driven anything, Corvettes, included.

Enter the slant 6 turbo, the type of engine that most regular-guy Mopar enthusiasts think is an oddball, weird combination that yeah, may be pretty fast, but has to be expensive!!! Right? I mean, you don't get 2+ horsepower per cubic inch out of a slant six without a ton of costly, cutting-edge technology!

Well, that's just not true.

Let me point out what ~I~ have found out about this turbo six business that has made me wonder whether it might not be actually CHEAPER than building an equal-power small block. Especially, if you already HAVE the /6, but will have to buy a V8.


Here are a few ways that the turbo slant six can be a cheaper alternative to an equally-powerful small block.

For purposes of comparison, let's compare two 500 horsepower engines; one normally-aspirated 360, with time-honored, normal hop-up mods to produce 500 flywheel HP and a turbocharged slant six with equal power.


Lets start with acquiring a rebuildable engine "core."

People give away slant 6's all the time. The one we are attempting to build was, in fact, given to us. It was on its way to the dump, if we didn’t want it. “Free” is always good…

That scenario is also possible with small blocks, but not as easy... and virtually impossible to find a "free" rebuildable 340. But, you don't HAVE to start with a 340; it can even be a 318... but that won’t be as easy. A 500-horsepower 318 is not hard to imagine, but probably would need some pretty good heads, and 12-1 compression. It would also need to be rpm capable, to a large degree. (7,000?)

Not so hard with a 360, but they are not as much in abundance for free, I think. Could be wrong about that. More like $150 for a rebuildable "core."

Advantage, slant 6.

There is more of everything to buy for 8 cylinders compared with 6. Pistons, valves, bearings, rings, valve springs... retainers, keepers...

Advantage, slant 6

The driveability of a turbo slant 6 is not much different from a stocker, in that the main thing(s) that destroy driveability, are radical cams with a fast, ragged idle, and big ports that allow the fuel to fall out of suspension (at low rpm) in the ports, due to low velocities brought on by the size of the ports. The turbo slant six cams don't have much more duration than a stock one, and the ports, even in ported heads, aren't very big.

Advantage, slant 6.

The slant six's that have been turbocharged with high-boost (over 20 pounds,) don't seem to like rpm's and don't NEED rpm's to deliver the goods. Tom Wolfe and Ryan Peterson, the two examples I am citing here, both contend that their engines have a de-facto red line of about 5,500 rpm. With such a low red line, the reciprocating stresses, even with a 1-and-an-eithth-inch, stroke, are low enough that these engines will never fail due to bearing loads brought on by excessive piston speed, That is MY opinion; nothing more. Making 500 horsepower from a normally-aspirated small block is going to require that you spin it, probably fast enough to put engine life in jeopardy, if you do it very often.

Advantage, slant six (my opinion)

Because of the relatively low rpm operation of the turbo slant six, the valve train can remain, with stock pushrods and rocker arms, due to the low valve spring pressures required. The money you DON'T have to spend on needle bearing, rollerized rockers, special, heavy-duty pushrods and roller lifters is money saved.

Advantage, slant six.

The rear axle ratios in the two quickest A Body turbo slant six cars that I have seen evidence of, are 2.76:1 for the strip AND for the street. The turbo motors are weird, in that the car slows down with normally-"steep" rear gears, such as the 4.56:1 units often found in small-block cars. The turbo motor seems to make more power (not unlike a "fuel" motor) when it is "held back" and not allowed to increase rpm quickly. The significance if this is, the turbo motors also can use the same ratio for highway driving AND drag strip action. The small block "built" motor wouldn't think much of a 2.76:1 rear end on the drag strip, nor would it perform up to its potential, with a 4.56:1 on the highway. So, if you build a small block and it does double duty, you really need two sets of gears; one for the drag strip and one of the highway. No problem; you can change third members in a couple of hours (or, less.) But, they don't give away 8.75" A-Body housings these days, and neither is it cheap to buy and maintain two sets of third members, with different ratios; one for racing, blah, blah, blah...

The turbo slant six car can easily make do with a "one-ratio-fits-all" rear end. A late model, A Body 8.25" rear end from a junk yard will be lots cheaper (or, one out of an Aspen/Volare car) and will come with highway (and drag strip) gears already in it.... and is plenty strong for this application. More money saved.

Advantage, slant six

Because a high-stall converter is neither desirable nor necessary, turbo slant six converters are going to be cheaper than a 4,000-5,000-rpm unit that would be probably necessary for a wildly-cammed small block. Once again, the street driveability issue comes to light. The tighter slant six converter would not create as much heat as a high-stall, small block unit would, in daily driving.

Advantage, slant six

I BELIEVE that a turbocharged slant six motor is about 80-100 pounds
lighter than an iron small block. Can't prove that, but I'd bet on it.

Advantage slant six

The "bling" factor at shows might be of interest to some. A nice-looking small block has a LOT of competition at car shows and usually needs to have something really special, in cosmetic appeal, to win an award, just because there are so many... But, a slant six with a turbo on it is such a rarity, judges HAVE to pay attention.

Advantage, slant six

Then, there are the negative factors... and, there are some!

You can always put a turbo on a small block and go much faster than you could EVER hope to go with a slant six


Advantage, small block

No roller cams are available for slant six engine (no available roller-tappet cores) so, the ZDDP issue is always a problem.

Advantage, small block

You REALLY need both an intercooler AND a chemical intercooler (alcohol injector) for a hi-boost turbo slant six, and they don't give these away. None is needed on a normally-aspirated small block,

Advantage, small block

I don't think that a turbocharged slant six is a very good bracket car for drag racing, because of problems with turbo-spool on takeoff, and consistency. We are not building our car to run brackets; if we wanted to win bracket races, we'd build something else.

Advantage; small block

Detonation under boost will destroy a turbocharged motor on boost, quicker than you can say "turbo." So, fuel of sufficient octane is always going to be a problem. E-85 would be the perfect hi-octane fuel, but the quality of it at the pump is so iffy, you just can't trust it when it comes to boosted motors. The normally-aspirated small block, with high-compression pistons is choosy when it comes to octane, too, but the results from normally-aspirated detonation are usually not as "catastrophic" as when it happens with, say, 25 pounds of boost. So, I have to say that the turbo slant six is a problem child in that area. Bear in mind that I originally said a "500-horsepower" turbo slant six. That's what we are talking about, here, But to be realistic, the great bulk of whatever turbocharged slant six motors come to pass, MOST will never see boost levels that high, and the picture changes greatly at 7-10 pounds of boost. But, that wasn't the argument, here. Soooooo...

Advantage, small block

The sound of a well-tuned, high-revving small block at full song, is music to almost everyone's ears. Slant sixes with turbos are quiet: the turbo impeller sort of homoginizes the sound waves...

Advantage small block



Due to the very-limited rpm range (less than 5,500rpm, tops, usually) the slant six turbo motor doesn't need a high rpm ignition system like a high-winding, 500 HP, normally-aspirated small block. A stock distributor will work fine, with no worries about effective spark at 7,000 rpm... 'cause, that boosted slant 6 is never gonna see even 6,000 rpm, much less 7,000...

Advantage, slant six

There are no aftermarket (aluminum, or otherwise) cylinder heads for the slant six, so the best you can do is to port the original head, and add some cheap 1/75"/1.5" valves (some folks have used 318 valves.) And, there's only ONE head to deal with, so there's just no place to spend money (of the quantity the V8 car can absorb) on the head. A complete ported head for a slant 6, ready to run, will be cheaper than a pair of aftermarket V8 heads that will support 500 horsepower, I believe.

Advantage, slant six



I hope that after reading all this meandering post, I have made a case for it being actually cheaper to build a 500 HP turbo slant 6 than it is to make the same amount of power with a normally-aspirated, small block V8.
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Turboit said:
Hi Bill

Mate is there anyway I could possibly have the build information of Tom Wolfe and Ryan Peterson or of yours and Freddy’s Please??.
I’m wanting to build the 225 slant engine with some grunt behind it, I’d personally be happy with somewhere around the 250rwhp!.
So Bill is it possible to have a just over mild lumpy cam in it with a turbo? I still haven’t completely decided if I’m going turbo or supercharger I’m guessing this decision will also come down to what HP can actually be made with a supercharger and any information on others that have used one! I’m only a virgin to a slant engine so I no nothing about them apart from what I’m now reading, so any help you could throw my way would be Greatly Appreciated.
Thanks again mate
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I'm sorry to say Bill Dedman passed a few years ago. If you do a search of this site, he posted a lot of info about his car/engine.
 
I too am new to building a slant 6 to a higher level than a stock rebuild. Of which I've done a couple over the past 30 or so years, nowhere near as many as some of you guys here.
Truth be told, I joined the slant 6 forum some years ago, like many who join a forum, whether it be for a certain car engine or garden tractors or whatever, to sell the original engine out of a car that I had then, figuring that I would have the best chance to do so in a forum with a bunch of people who keep them going and modify them.join, sell, and split.
Slant zilla ended up buying that engine and using it in a dedicated race car. He may still have it.

But, I hung around for the "other topics" that aren't engine specific. Well now a year ago, I tripped upon my present truck that I had assumed from seeing it sit-in the PO's yard that it had a v8 in it, was surprised to see that it doesn't. I came back to the/6 site for help finding the missing parts I would need to see if that engine would run. I got it going. And undid some past owner neglect and wiring harness butchery, once I knew I had a running truck.
That car that I wanted to sell the engine from is still here, I had grand plans to build a hot street small block for it, like everyone else. The car still sits in the corner. Still don't have the V8 in it yet either. But I definitely plan to get there.
I have had a couple of trucks with a slant 6 in them, one I wasn't able to keep very long due to life (I had wrecked my 87 dodge van and no money to fix, I made a deal with the body shop to fix the van straight up for my 69 D100) . Not a proud moment.
Working on newer crap at my job, I realized how bad I missed the durability, simplicity and looks of an 80s D/W series of truck/ of which I've had a few. I watched this 85 sit, and sit, and sit some more. I had been wanting to stop and ask about it for a few years, but every time I went by, it seemed like there was no life around the house where it sat.
One day, I was going thru that town on my way somewhere else, and now there was a for sale sign in front of it. And now it's mine. I think that the fact that my son bought an 80 D150 with a slant 6 in it a few months before I got my 85, that he had asked me to help him with in gettin' running as best as I could, helped me decide to leave this 85 a slant.
I've swapped a 318 into a 79 D100 before, and I remember having to find a truck pan, truck mounts, truck bell housing, truck radiator for that 318.
After hanging around several mopar sites, and reading about what some of you guys have actually done with your slant 6's and that they still hold together as well as they did in stock form (except for the most extremely wild builds) plus the V8s of the time really weren't all that powerful anyway, that I could build a slant that would at least match the HP of the V8s of the time that my truck could have had. Plus less weight, plus not having to find all those V8 conversion parts (or another truck to sit around as I robbed it of the parts I'd need to convert this one) would leave me more $$$ left that could be put back into another slant 6 to build it better than the ones I just did a stock rebuild on 20-30 years ago. I didn't have to be in a hurry, as this time the truck wouldn't be competing for garage time vs having to be back together for work the next day, meant I could take time and pluck deals as they popped up, not having to pay prevailing prices for the parts I would pick to go into it.
I have 1 problem though at this point. Too much info. I am stuck between 2 ideas for my build.
For lack of a better way to describe it, I figured that the best way to build my engine would be to follow the Covalt's and Dad truck's truck engine builds, and model mine after their trials and results. Dad truck is a member here under a different name, I don't know if the Covalt's are here but they are people who I know from the /6 site just like Charlie. But parts of me are wanting to build it as a home brew, junkyard sourced draw thru turbo setup with some parts made right here at home like mounts, flanges and such.
But I also know that the best parts combo for each one aren't the best parts combo for the other idea that I have. I know that I want to keep it carbureted for simplicity, and I want to drive this truck daily once done in seasons that don't involve snow, ice and salt. Also to use to load up with camping and fishing gear, hook my popup to the ball and haul it to my yearly August campout in ohio and the covered bridge festival 2-1/2 hours away in October. Mean time it's hurry up and wait for the block and crank to get out of machine shop jail, finish porting the head while hoping not to draw water into the chamber before I hand the head off for finishing.
 
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I just got my stock original cam shipped off to Oregon to be transformed into teh cam that seems to be a favorite among those with slant engines built similarly to what I am trying to achieve from mine.... JEEZ!!!!!! post office screwed me. $42 (and it was "cheapest option" they had next one was $52 choice 3 was "only" $110) just to ship it THERE!!! I was thinking it "might" cost that much, ($40-ish) "both ways".
 
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