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I've got a million questions about slant sixes...
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Author:  65CrewCabPW [ Sun Jun 15, 2008 12:51 pm ]
Post subject:  I've got a million questions about slant sixes...
Ok, that was a white lie. I have less than that, but not a lot less... :)

Let me explain...I have a project truck - a crew cab Power Wagon, and I have two options for a motor.. The existing 318 (poly) or a slant six. I have both motors. The 318 is in and runs great, the slant is a core engine in my garage. I believe the bellhousing is a dual pattern in the truck, but I'm not sure. Either way, I think I can come up with the parts.

Next, I'm looking to use the least fuel... and tow an travel trailer. And, I want to run it on propane.

Here's the targets: The 318 I estimate that once stroked and bored (402 CID) and all that jazz, can reach about 275 HP in the setup I envision. That includes closed loop propane fuel system, Megasquirt operated ignition (including knock sensor, etc) with careful timing curves, and so on. It would have gawdawful torque, but I think fuel efficiency would suffer due to friction and pumping losses being very high (mild cam 11.5:1 CR with 4" stroke).

The slant six would need to be able to reach 210-220 HP @3800 and about 350 ft/lbs torque at 2400. I figure this would require turbocharging. Remember, this is on propane - good octane fuel.

So, this brings me to some questions that I haven't found the answers to in the last couple years of reading (here and elsewhere).

My engine is, I believe: a 68-72 engine, already 30 over, needing rebuild after some amateur hack messed it up.

1. How do I find a clutch to handle the torque? The stock 318 clutch won't, much less the wimpier SL6 clutch setup.

2. At that horsepower level and sustained long duration loading, is cooling an issue? do I need a better water pump? Any other improvements to be made there? (I plan on a large engine oil cooler)

3. What size of valves can I upgrade to without seriously compromising the head?

4. Is there a rollercam/lifter combo that can be used? Modern oils are slowly moving away from the additives that make our flat tappet cams survive. If not, there's always diesel oil and synthetics.

5. Does anyone have suggested timing curves for this kind of engine? Remember, it's propane, and probably need around 5-7 PSI boost to reach the HP and torque required.

I'm looking at using 2 of the little mitsubishi turbos that chrysler uses on the 2.5, that are so horribly undersized on the 2.5, running in parallel. One turbo for the front 3, one for the back three. This is so I can have water cooled turbos and lots of wastegate opening. Exhaust restriction minimalized as much as possible.

6. Camshaft... I'm t hinking something with about a 112 to 116 centerline, about 248 - 258 duration, 430 lift. Will I need better valve springs? Remember, I don't want to run this thing past 4200 or so, absolute max. My understanding to now says a split duration camshaft is not optimal with a turbo, nor do I want any large overlap. Also, timing should be close to straight up or slightly ahead?

7. I'd like to start about 9:1 compression ratio for this. Again, using megasquirt for ignition, including vac advance and boost retard, mech advance, and knock sensing. Is knock sensing an issue with the solid lifters?

8. Should I use full groove mains for better rod oiling? What can I do to improve oiling reliability. No, I'm not looking to run a high pressure pump... I suspect stock has enough flow, I just want to ensure good distribution.

Now, you ask, where did I come up with the targets and why? Well, I used the "scientific method" where I used an estimator to calculate the approximate road horsepower required for wind drag and grade horsepower to move the truck and trailer on appropriate grades along with the horsepower needed to do this. I then plugged in the numbers and calculated rpm vs mph for 3rd and 4th gears for the NP435 and for an NV4500 (including 5th) and tried to put the engine in the "sweet spot" of 2000 to 2500 for towing on the flat and slight grades. By calculating the horsepower needed, I can then figure the torque needed @2100, 2500, and 2800, and then work backward. I figured various loads and grades and the speed you want to maintain - adjusting the axle ratio to let you get the motor in the right rpm for that. I ended up choosing 3.73's and it now has 4.10's, which I figured to change anyway. The 318 would get 3.55's. This gearset lets you get into 3rd gear clear up at 50 mph @3800 rpm and will easily pull a 6+ percent grade w/3000lb rv in tow.

I know you can make an easy 20% improvement on "stock" with just cam, intake, cab, compression ratio, etc, and going with "stock" of about 200 ft/lbs torque and 145 HP. I figure I need to gain 55-60% torque and 50% horsepower, roughly, while not raising the rpm significantly, as in, 4000 for max HP and 2400 for max torque. Or, at least 340 ft/lbs @2400 regardless of where the peak might be. This doesn't seem to be unreachable nor unreasonable. Let me know if you think otherwise.

I'll eventually discuss fuel issues with Frank Raso about what carb or carbs to use, so I can control the Air/Fuel ratio for max economy with a closed loop setup. (propane gets cooler if you go lean... how's that for a nice arrangment?)
Author:  SlantSixDan [ Sun Jun 15, 2008 1:50 pm ]
Post subject:  Re: I've got a million questions about slant sixes...
Quote:
Ok, that was a white lie. I have less than that, but not a lot less... :)
Welcome on the board. We've got a million answers about slant-6s.
Quote:
I'm looking to use the least fuel...and tow an travel trailer. And, I want to run it on propane.
How much time and money are you prepared to spend to save the maximum amount of fuel?
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The slant six would need to be able to reach 210-220 HP @3800 and about 350 ft/lbs torque at 2400.
That's diesel-engine territory. Tough target.
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I figure this would require turbocharging.
Yup!
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1. How do I find a clutch to handle the torque? The stock 318 clutch won't, much less the wimpier SL6 clutch setup.
Clutch options behind the slant-6 ranged up to 11", and there are XHD components available for the 11" clutch. Shouldn't be a problem.
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2. At that horsepower level and sustained long duration loading, is cooling an issue? do I need a better water pump?
There is no better water pump. The stock item is rather good. See here (and previous thread linked therefrom) for some interesting info — my experiment with this stuff in my 318 truck is working out extremely well so far.
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4. Is there a rollercam/lifter combo that can be used? Modern oils are slowly moving away from the additives that make our flat tappet cams survive.
You can do the custom work and get the custom parts to fit a roller cam if you gotta-just-gotta, but you needn't. A flat-tappet cam will survive just fine. The worry over the reduction in ZDDP — which I helped to perpetuate, on this board and elsewhere — appears to be largely overblown, even more than the worry over the elimination of lead in gasoline was.
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5. Does anyone have suggested timing curves for this kind of engine?
Completely custom, starting from scratch.
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I'm looking at using 2 of the little mitsubishi turbos that chrysler uses on the 2.5, that are so horribly undersized on the 2.5, running in parallel. One turbo for the front 3, one for the back three. This is so I can have water cooled turbos and lots of wastegate opening. Exhaust restriction minimalized as much as possible.
Interesting idea. Those turbos, by the way, are not "horribly undersized" on the 2.5, unless what you're trying to do is make 400 hp in a K-car.
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6. Camshaft
see here.
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7. I'd like to start about 9:1 compression ratio for this. Again, using megasquirt for ignition, including vac advance and boost retard, mech advance, and knock sensing. Is knock sensing an issue with the solid lifters?
Solid lifters confuse knock sensors.
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8. Should I use full groove mains for better rod oiling?
Surely. Not a bad idea.
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What can I do to improve oiling reliability.
See here

Additional Slant buildup threads worth seeing:

This one and
this one .
Author:  Matt Cramer [ Sun Jun 15, 2008 4:16 pm ]
Post subject: 
I kind of like your idea on two of the 2.5 liter turbos. If you're running a free flowing exhaust and intake, a single one can start building boost at 1,000 RPM, hit 10 psi by 1,500, and be way out of its operating efficiency by the time you hit 3,000. Two of the little beasties would be about right.

On the issue of a timing curve, there's quite a few injected slant sixes out there, a couple propane burning slants, and I've worked with people who have used Megasquirt with propane - but I haven't seen any propane injected slant sixes with electronic timing control. I'm planning to dyno tune my own turbocharged and Megasquirted slant six, but it's running 93 octane gas, not propane. To get the most power - and more importantly, the most mileage - out of this engine, you're going to need to spend a couple hours getting your timing curve dialed in on a steady state dyno. You might be able to use a gasoline curve as a starting point, but you're going to need to make one that's right for your engine.

A good tune can also reduce the need for knock sensing. We've got a Miata in our shop that's putting over 250 hp to the wheels from 98 cubic inchesl, it's running on pump gas, and it doesn't use a knock sensor. Instead, Jerry made sure the tune didn't knock by fastening a microphone to the block while on the dyno and listening through a set of stereo headphones. The human ear isn't as easily fooled by lifter noise.
Author:  Royceflo [ Sun Jun 15, 2008 7:41 pm ]
Post subject: 
Just as a Side note. The 318 poly would make a great turbo motor, I have no clue about propane injection, however, I have a twin-turbo Poly.

A few things to consider when choosing between the two is that the 318 poly is a pretty expensive motor to build in general. For one, any piston that you choose to use, other than stock is going to be a costum job, nobody makes forged, or hypereutictic or anything for the poly.

Also, unless the propane system could work with a dual barrel carb (I don't know propane flow requirements) the intake will cost at least 400-500 for used 4 barrel. Nobody makes new ones any more.

The only way to go with a 402 poly is a 4 inch stroke and plus .090 on the bore. Mopar makes and sells the crank. You can go with a 360 ci poly and turn down the journals on a 360 crank as well. Save some money. Either way the pistons have WAY different valve cuts.

The whole rotating assembly is the same as an LA 318. A few variations, but all is interchangable. The heads, with the cantered valves take to turbocharging very well. Also, the bottom-end is grenade proof.

I think though, after building one of my own, that the poly is a better engine the the LA 318. However, costs way to much to build. If you are considering a v8 vs the /6. Use an LA 360 and stroke that as opposed to the poly. There is almost no info about the poly out there, and it could end up costing 10x as much and twice as along.
Author:  SlantSixDan [ Sun Jun 15, 2008 7:47 pm ]
Post subject: 
Quote:
any piston that you choose to use, other than stock is going to be a costum job
It might've started out as a typing error, but it came out as a terrific new word I'm going to use: "Costum". It perfectly describes special parts that you have to have made to spec and invariably cost a lot! :lol:
Author:  Royceflo [ Sun Jun 15, 2008 7:50 pm ]
Post subject: 
Ha, well I'll just have to go and act like it was intentional!
Author:  65CrewCabPW [ Sun Jun 15, 2008 8:57 pm ]
Post subject:  Re: I've got a million questions about slant sixes...
Quote:
Welcome on the board. We've got a million answers about slant-6s.

How much time and money are you prepared to spend to save the maximum amount of fuel?
This isn't about spending money to save fuel. This is a project to build a dream rig. The "saving fuel" is about... "As long as I'm spending too much money, why not burn the least fuel?" :)


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The slant six would need to be able to reach 210-220 HP @3800 and about 350 ft/lbs torque at 2400.
That's diesel-engine territory. Tough target.
350 is 63% higher than stock specs. If I could get 320, which is under 50% increase in torque, it would be acceptable. The specification I worked from required 285 to be "workable", which is 33% increase, which I don't think should be difficult at all. Anything over 310 is "nice".

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I figure this would require turbocharging.
Yup!
I had considered running the 318 near stock... sleeving back to standard bore, and running about 8:1 compression ratio and turbocharging it instead. I eventually decided that was just a way to waste fuel. Too short of stroke for earth rotating torque, and turbocharging creates a loss in efficiency.
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1. How do I find a clutch to handle the torque? The stock 318 clutch won't, much less the wimpier SL6 clutch setup.
Clutch options behind the slant-6 ranged up to 11", and there are XHD components available for the 11" clutch. Shouldn't be a problem.
Ahh, ok. I didn't realize there was an 11 inch clutch. What applications used it and where would I look for the flywheel?

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5. Does anyone have suggested timing curves for this kind of engine?
Completely custom, starting from scratch.
Does anyone have the "original" good curves? It would be nice to have something to work against. I've found information on conversion to propane
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I'm looking at using 2 of the little mitsubishi turbos that chrysler uses on the 2.5, that are so horribly undersized on the 2.5, running in parallel. One turbo for the front 3, one for the back three. This is so I can have water cooled turbos and lots of wastegate opening. Exhaust restriction minimalized as much as possible.
Interesting idea. Those turbos, by the way, are not "horribly undersized" on the 2.5, unless what you're trying to do is make 400 hp in a K-car.
I own a turbo 2.5/5speed Caravan, and IMHO, the turbo is seriously undersized, even at stock HP levels. It will spool wildly at 1400 rpm on a starved for flow 2.5 Turbo 1.

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7. I'd like to start about 9:1 compression ratio for this. Again, using megasquirt for ignition, including vac advance and boost retard, mech advance, and knock sensing. Is knock sensing an issue with the solid lifters?
Solid lifters confuse knock sensors.
I've heard some slants that had no audible valve train clatter. Mine was total thrash for noise... what's involved in going to hydraulic? I understand it's fed through the pushrods?

Thanks for the quick answers...
Author:  kipamore [ Sun Jun 15, 2008 10:55 pm ]
Post subject: 
I love this kind of stuff!

What are the weights involved here? Power wagon weight? Trailer weight? What kind of grades are we talking about? Are we driving in the artic or the tropics? Will this battleship be on truck tires, car tires or what? Do you want air conditioning? You didn't mention, but are we talking 4x4 or 4x2?

Just trying to get the picture. Also...is cost NO object or is cost SOME object here? Have you considered a drugged up diesel (meth, propane, water injection)?

Kip-on-Truckin'
Author:  65CrewCabPW [ Mon Jun 16, 2008 12:23 am ]
Post subject: 
Ok, my Power Wagon weighs in about mid 4K. Actually, a little less, but i expect it to weigh a little more when I'm done.

The trailer I want to tow is about 3K and probably a 5th wheel - a "lite" or otherwise easy-towing version.

This calculator makes some rough estimates of power needed:
http://chillaxnet.com/tools/hpcalc.shtml

This calculator shows you the rpm in gear vs speed.

http://www.car-videos.net/tools/speedrpm.asp

This is what I work from, using an NP435:

6.61 1st
3.34 2nd
1.67 3rd
1.00 4th

285/70/16 tires
3.73 axle ratio

You have to ignore 5th gear. The calculator insists on adding it.

I'd like to use an NV4500, but I'm not THAT rich. It costs a lot, and 5th gear would not be used much, due to lack of really low end torque.

This does a nice conversion from horsepower to torque:
http://www.ajdesigner.com/phphorsepower ... torque.php

I want the tow rig to maintain 55 mph on a 4% grade in top gear. I want to be able to pull 6+ percent while maintaining at least 40 MPH.

Further, I want ot keep the engine between 2000 and 2600 for "normal" driving while towing. This means that I should be able to hit 70 mph without exceeding my "good" rpm range.

Now, how did I arrive at all this?

Well, a LOT of hours researching internal combustion, spark ignited engines and how load, throttle percentage, aspiration type, etc, effects BSFC - Brake Specific Fuel Consumption. In other words, smaller engines tend to get more MPG, because they operate at a higher percentage of their maximum power. What I learned is that the BSFC always follows a bell curve... with middle RPM doing best, and lower and upper ranges falling off. So, I wanted a motor that naturally aspirated was running at least 50% but preferrable well more of its rated power while running 1% grade and 10 mph headwind. Too slow of rpm, and thermal efficiency falls, too fast, and pumping, friction losses go up dramatically.

So, I set about figuring out how much HP I needed to move the truck with the trailer in tow... Then gearing to get that rpm range. Then, figuring out how much power is needed to do the job.

So, I estimated the horsepower for flat running on the highway - at the speed I want to cruise - 65, and the slant six was running at over 80% of it's rated power at the rpm chosen. Even more interesting, was that rpm and max torque on a s tock engine matched.

IN this case, the NV4500 would be nice, but it'll barely move on the flat over 55 mph with the /6 in overdrive. It's just an economy cruise gear when not towing at highway speeds.

Shortening the gears to 3.91's has the effect of moving the rpm range a bit high and the "shift" point too low of MPH. What you want to calculate the most important, is the 3rd gear speed / horsepower requirements. With 3.73's, hard grades can be pulled at 40-50mph while keeping the engine in the mid 3k rpm, where your horsepower is and torque has fallen. 4.10's would drop that speed all the way to around 35, so you end up crawling at a small throttle opening at 3800 for miles. I've experienced that with the 318 and my BIG trailer (stock 2bbl poly towing 5300 lbs). I've actually just stood on it and wound that poly to over 4K just because I was so tired of going slow. I walked off and left a 5.4 Triton pulling a smaller trailer... But my God it sounded bad... I was going 45 - 50 mph in third. Calc says I was running 4000 - 4100 (speedo isn't accurate, reads kinda slow).

I spent quite some time working the 3.55 gears, and unless I can find a close ratio 5 speed, it's not workable. Beter yet would be a 6 speed, with 4th of 1.3 and 3rd of 2.3 and 2nd of 3.2 and 1st of 5, or close approximation of that. The 3.91 wasn't too far off, but would start to hurt if you wanted to run on the interstate at interstate speeds.

As for budget... I have a budget for the project, of about 15K total. Quite a bit of that will be soaked up with bodywork / paint / insulation / small rust repair / comfy seats and air conditioning. This is my "new" truck. And our intended use is to take a 5 month long trip around the US, visiting around 43 states w/trailer in tow to see our wonderful country. Somewhere really great, we're going to be celebrating 25 years married, on May 3rd 2011... I have a couple years to finish this.
Author:  SlantSixDan [ Mon Jun 16, 2008 6:59 am ]
Post subject: 
Original timing curves are all over the place, dependent on what distributor's being run (year, model, etc). Not trying to be evasive, but what kind of info are you looking for out of an original curve?

11" clutches were used in HD truck/van applications and the heaviest-duty taxi/fleet cars. Have to use the direct-drive starter; the gear-reduction type won't fit unless you have one specially built. Finding the parts will likely be a challenge, but maybe not impossible. Start beating the bushes!

The '81+ hydraulic lifter setup is indeed top-fed. You can without too much difficulty retrofit to an earlier block. Make sure the custom cam you get has a fully-grooved #4 journal; that's the oil supply to the top end. Install the '81+ rocker shaft, rocker shaft bolts, rockers, pushrods, and lifters.

Frank Raso's definitely the Propane go-to guy around here. I've not played with it, but every time I tank up my ('89 318) truck, my mind used to wander to this … until just now when I went to fetch that link to post it here, and now my mind is wandering to the same company's new ESIP systems...h'mmmm!

(Don't wanna shanghai the SL6 truck buildup thread, but I have driven 2.5T1 cars with the Mitsu turbo that've had puh-lenty of skedaddle with minimal lag. Seems to me it's dependent on the overall configuration of engine and vehicle. I'd definitely want a larger turbo to haul around a minivan.)
Author:  kipamore [ Mon Jun 16, 2008 8:07 am ]
Post subject: 
I'm going to play devil's advocate, not because I want to discourage you but because I'm sure you've already thought through all this and I want to hear your conclusions.

1. LPG isn't sold everywhere. How will this affect your tour? Also, how does LPG stack up against gasoline in terms of mileage and range more importantly?

2. Conventional wisdom states that for this app you'd want a big inch motor loafing along at 1800-2000. It also states that you'd want as many gears as you can get so you can pull all hills optimally and cruise unloaded better. Conventional wisdom also states that you'd want an automatic for towing (stop 'n go, wife friendly). The same wisdom would dictate a 4x2 dually as best suited to the 5th wheel.

3. This kind of rig doing this kind of job is a very known quantity. Dodge has made trucks with 318's and 5.2s for decades that do exactly this job all day (so have GM and Ford). In terms of building to a goal, how well would a newer truck perform at this same job? How would either of your combinations stack up against them?

4. The engine that absolutly leaps to mind for this job is a mechanical Cummins (pre-99). I'd guess 25mpg are not out of reach. How come no Cummins?

I'm hoping the answer to all the above questions is "because it's way cooler to do it with a slant six!".

Kip-on-Truckin'
Author:  65CrewCabPW [ Mon Jun 16, 2008 11:31 am ]
Post subject: 
Quote:
I'm going to play devil's advocate, not because I want to discourage you but because I'm sure you've already thought through all this and I want to hear your conclusions.

1. LPG isn't sold everywhere. How will this affect your tour? Also, how does LPG stack up against gasoline in terms of mileage and range more importantly?
No, it's not sold everywhere like gasoline is. But I'm looking for enough tank capacity to make that not an issue... let's say... 70 -90 gallons. The best way to buy propane is NOT at flying J or gas stations, but to find propane dealers with fueling stations. They have up to a $1 a gallon less fuel, and if you're out of state, often they don't charge you tax. RV use, you know :)

Propane should achieve about 65% of the fuel economy of a diesel that's also optimal. At this moment, locally, propane is 47% the cost of diesel and the gap widens weekly.
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2. Conventional wisdom states that for this app you'd want a big inch motor loafing along at 1800-2000. It also states that you'd want as many gears as you can get so you can pull all hills optimally and cruise unloaded better. Conventional wisdom also states that you'd want an automatic for towing (stop 'n go, wife friendly). The same wisdom would dictate a 4x2 dually as best suited to the 5th wheel.
Conventional wisdom has "some" truth to it. My alternative to the SL6 was to build a 402 CID poly engine, modded to the 9's for torque. I think both approaches are workable, and would probably achieve relatively similar goals. For economy, the big engine would require an overdrive, or the tallest gears I could get. Remember, fuel consumption per horsepower produced in a gas engine (throttled) requires you use a large percentage of available power. That can be achieved by chugging down the road at 1300 rpm, too, but thre are inherent inefficiencies, mostly thermal, involved in running that slow.
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3. This kind of rig doing this kind of job is a very known quantity. Dodge has made trucks with 318's and 5.2s for decades that do exactly this job all day (so have GM and Ford). In terms of building to a goal, how well would a newer truck perform at this same job? How would either of your combinations stack up against them?
Newer truck, same thinking, same mod types to achieve same goal = same results. I have this truck, like it, and it's unusual. Crew Cab 60's trucks are darn rare anymore.
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4. The engine that absolutly leaps to mind for this job is a mechanical Cummins (pre-99). I'd guess 25mpg are not out of reach. How come no Cummins?
You mean, like I have in this truck? Modded Cummins (180% of stock HP), pulls like a freight train, gets decent milage, even towing...

Image

Quote:
I'm hoping the answer to all the above questions is "because it's way cooler to do it with a slant six!".

Kip-on-Truckin'
That's kinda the answer. The answer is really...

"I am going to spend the money once in my life to get a "new" truck. This truck will be unique to me, will last until I am no longer fit to drive it and will let me enjoy it's uniqueness and it's character..." Oh, and I'm a Mopar nut from the word "Go" and even the Cummins powered truck isn't Mopar powered...

Everyone else is doing the "ordinary". I don't want to achieve their results, so why duplicate their efforts?

And yeah, I suspect that the turbo slanter will be the topic of a lot of campground, forum, and other conversations for many moons to come.

[/img]
Author:  65CrewCabPW [ Mon Jun 16, 2008 11:35 am ]
Post subject: 
Ok, I lied. I wasn't done with the questions...

How much can I safely bore this thing out?

I'm seriously considering sleeving it back to stock bore size, so I can have the absolute best metal and strongest wall thickness because of the immense strain I plan on putting it through.

Anyone sleeved an engine? If so, where'd you get the sleeves, etc?
Author:  Joshie225 [ Mon Jun 16, 2008 12:07 pm ]
Post subject: 
Folks regularly bore slant .100" oversize. It's best if you read the block article. http://www.slantsix.org/articles/dutra- ... blocks.htm
Author:  sandy in BC [ Mon Jun 16, 2008 3:42 pm ]
Post subject: 
Ill bite.....

I used to run a Chev Suburban 1 ton 4x4 with a 4 speed and 250 inline 6. The 6 was mildly modified.

I had to constantly wind the piss out of it to maintain highway speeds with a load.

In the end the mileage was poorer than the Vortec EFI 350 I replaced it with. .....and thats without pulling a trailer.

If you run a six at 80% of capacity you end up running in the enrichment mode all the time. Durability goes out the window with economy.

sorry........
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