The Venerable Slant 6 vs Our Beloved Flathead 6s

[Tim Keith]

There is a rumor that Ram and Jeep will have a 3.0 liter gasoline inline six option.   The motor would be turbocharged and replace the 5.7 Hemi in Ram trucks and SUVs.  With Trump in office the fuel economy regulations have been temporarily slacked up, otherwise the V8 would have been gone from the options after 2018.   Since 2011 a turbocharged version of the "Pentastar" V6 has been in development, but with the popularity of the Ford Ecoboost V6,  the engineers want a motor that is better than Ford offers.   An inline six might have more usable torque for a light truck than the V6, and hopefully better fuel economy.  Some reports say that the 3.5 Ecoboost is impressive in power output, but not so great in fuel economy - the reason for its adoption in the first place.    Like it or not, the tricks that can keep gasoline V8s viable as per government regulations could be ending.    The inline six would be very compact in dimensions - smaller than the slant six.  The old flathead was pretty compact, this new inline six would only be used in rear drive vehicles.

 

I hope there is a new inline six in the Ram/Jeep future.   I'm not sure about the complexity of a 400 horsepower inline six in a truck, but it ought to be as reliable as the Cummins inline six - if the rumors are at all true.   The inline six project goes by the name of "Tornado".   The costs of the turbo 400 hp V6 is pretty high, ( the Hemi was relatively low cost to produce).  An inline six is hoped to be more economical to manufacture.    Currently the death of the popular Hemi V8 is postponed for a couple years.   2019 Chevy trucks have a new inline 3.0 six diesel option.

 

I just got a 1966 slant six this week, along with a 904 automatic.   I like these motors.    The stock compression ratio is only about 7.0:1, not much better than most L-heads.  The published CR numbers were optimistic.    There is a lot of potential in the slant six if you can raise the compression and rework the cylinder head.  A slant six with 180 honest horsepower feels pretty strong.   The late model 225 was rated at about 90 hp, but there isn't much difference from the 1965 motor - actually the late camshaft is better.  With timing changes, better exhaust and it should run as strong as those from the early years.  Add 50 horsepower to a 225 and its almost like a 318 .

 

 

Edited January 31, 2018 by Tim Keith
new content

[Tim Keith]

 

While not a Mopar L-head,  the LF-39 is a large bore/short stroke aircraft flathead six that is currently in production - its very light too.

 

https://en.wikipedia.org/wiki/D-Motor_LF39

[Andydodge]

Keithb7.............just read your engine rebuild story, made me smile......I especially like the photo............reminds me of me 45yrs ago removing the V8 from the donor car that I installed in the 40 Dodge...........brings back some happy memories.............regards, Andy Douglas 

[55 Fargo]

9 hours ago, Tim Keith said:

There is a rumor that Ram and Jeep will have a 3.0 liter gasoline inline six option.   The motor would be turbocharged and replace the 5.7 Hemi in Ram trucks and SUVs.  With Trump in office the fuel economy regulations have been temporarily slacked up, otherwise the V8 would have been gone from the options after 2018.   Since 2011 a turbocharged version of the "Pentastar" V6 has been in development, but with the popularity of the Ford Ecoboost V6,  the engineers want a motor that is better than Ford offers.   An inline six might have more usable torque for a light truck than the V6, and hopefully better fuel economy.  Some reports say that the 3.5 Ecoboost is impressive in power output, but not so great in fuel economy - the reason for its adoption in the first place.    Like it or not, the tricks that can keep gasoline V8s viable as per government regulations could be ending.    The inline six would be very compact in dimensions - smaller than the slant six.  The old flathead was pretty compact, this new inline six would only be used in rear drive vehicles.

 

I hope there is a new inline six in the Ram/Jeep future.   I'm not sure about the complexity of a 400 horsepower inline six in a truck, but it ought to be as reliable as the Cummins inline six - if the rumors are at all true.   The inline six project goes by the name of "Tornado".   The costs of the turbo 400 hp V6 is pretty high, ( the Hemi was relatively low cost to produce).  An inline six is hoped to be more economical to manufacture.    Currently the death of the popular Hemi V8 is postponed for a couple years.   2019 Chevy trucks have a new inline 3.0 six diesel option.

 

I just got a 1966 slant six this week, along with a 904 automatic.   I like these motors.    The stock compression ratio is only about 7.0:1, not much better than most L-heads.  The published CR numbers were optimistic.    There is a lot of potential in the slant six if you can raise the compression and rework the cylinder head.  A slant six with 180 honest horsepower feels pretty strong.   The late model 225 was rated at about 90 hp, but there isn't much difference from the 1965 motor - actually the late camshaft is better.  With timing changes, better exhaust and it should run as strong as those from the early years.  Add 50 horsepower to a 225 and its almost like a 318 .

 

 

All interesting stuff Tim thanx.

On Compression ratio and HP ratings

Ive never come across a 7 to 1 rating for any 225

Where did you get that info or determine those numbers?

On HP always rated at 145 hp then detuned to 110 hp numbers.

Again where is the 90 hp info from that seems like the 170 slant HP numbers?

7 to 1 on compression ratio with the modern OHV head seems low.

Please post info on this to give us clarity on what Ma Mopar was doing for marketing specs..

Here some info Tim i stand corrected on the varying HP ratings and why.

http://slantsix.org/forum/viewtopic.php?f=19&p=153796

Edited January 31, 2018 by 55 Fargo Spitfire

[55 Fargo]

https://www.allpar.com/ed/fauxpar/hemi-dead.html

Here is a report from All Par on the demise of the Hemi reports.

This is veering off topic but will of course be of interest to Mopar enthusiasts..

Edited January 31, 2018 by 55 Fargo Spitfire

[55 Fargo]

10 hours ago, keithb7 said:

When I was about 16, in Grade 10 I bought a 1976 Dodge Dart. If I recall it had a 225 slant 6 engine in it. My Father was dead set against me buying any "P.O.S. import" he called them. North American built or nothing at all, I remember him saying. I spent what seemed like forever trying to find a car that Dad approved of. Finally I settled on the Dodge Dart. He gave it his blessing after going over the car with me. Within a few days I noticed it was hard to start when it was hot. It would crank fast but never start until it cooled down again. Dad was no mechanic. He had no idea what to do. I was new to cars but my brother who was 18 at the time in Grade 12, was totally a gear head. He was planning to be a heavy duty mechanic. 

 

Bro and I spent a couple of days troubleshooting together. We had few specialized tools. Finally we begged and borrowed a compression tester. Yup low compression across all 6. We quickly made a decision to pull the engine and rebuild it. Ourselves. In the back yard. No garage. We borrowed an engine hoist and by day's end the next Saturday, we had the engine out on the ground. Pulled the head. Found a tired engine with a considerable ridge at the cylinder top. Flipped it over on a piece of plywood and pulled the oil pan. I removed mains and rod bearing and lifted out the crank. Then out came all the pistons.  Bay day's end Sunday I was staring at a pile of parts and starting to add up the bills. I was in high school and working part time as a dishwasher in a restaurant. If I recall I had about $300 in savings and I got paid again soon. I ordered an engine rebuild kit. I bought a reman exchange crank. Block and head was brought to a local car wash pressure washer where I blasted it as clean as I could. Next trip was to drop the block and head off at a local machine shop.

 

I worked every Friday night after school and all day Sat and Sunday for weeks to pay for the needed parts and machining. Timing chain, carb kit etc. Dad convinced me to pull the torque and have it checked over too. I was tired of school and working, but I wanted my car bad. I had a sweet girlfriend and wanted to take her on dates. With no car, we could not meet very often. She was patient as I worked my butt off to buy everything I needed. She even came and hung out with me sometimes while I was re-assembling the engine. She was an angel.

 

Finally after probably a month we were re-installing the slant 6 engine in my Dart. There was no way we could line it up to the 747 auto transmission bell housing. Finally we determined that the exchange crank I installed was for a different transmission. Drat! More delays. We pulled the torque again and had it machined to fit the crank. All went together well finally. The car started! I was excited. It was idling a little rough but I had no money left for new spark plugs, cap, rotor and wires. My brother took it to his Grade 12 shop class on Monday and hooked up to a scope. Hmm.. Spark looked off. He pulled all the plugs again. I had installed them. Several had zero gap as they had been dropped and kicked about for the past month. I had  little experience and overlooked the plugs. He cleaned and gapped my plugs. Set timing and adjusted carb. He was my hero. The car was running in top shape now. I could not have done the engine rebuild without my brother. I had a ton of respect for him for helping me.

 

Next came the courting again! Dates and ice cream often with my slant 6 Dart. Good memories with my girl. She's still with me today. It was just our 25th wedding anniversary in early January. I was a young dumb 16 year old. I drove the Dart for about 6 months and sold it for something faster. That was a huge mistake. I bought another car that I soon had to rebuild it's engine as well. I repeated the whole process again. I learned the hard way. This time big Bro was in trade school. I was on my own and rebuilt the V6 engine myself. Lots of frustration but what does not kill us makes us stronger. 

 

Below is a pic from 1987.  Here we all are man handling the slant 6 engine. I'm in the blue coveralls. Big bro in the white T-shirt. Dad pulling the hoist. Good memories.

 

 

How does all this relate to the flat head six? Well today I own a '53 Chrysler with a 265 L6 flat head. The story is a little similar. I bought my '53 last May and drove it home. Within a month I had the head off and did a full valve grind and all new valves. I'm a little smarter today with more experience. Today I can afford to order parts as needed. Today my best girl is home with me every night. No stress as I have other vehicles! LOL.  My '53 is not my only car. My old Dart was.

 

I believe the 225 slant 6 was rated at 94 HP. My flat head is rated at 119 HP. I am unsure of the actual torque of each. I would say that my flat head '53 has considerably more torque. It lugs down nicely and pull hills smooth. It was over 30 years ago that I owned the slant 6. The performance details are a little blurry. I do recall street racing my Dart against a 1974 Ford Pinto 4 cylinder, standard 4 speed tranny. It beat me off the line. Today I'd say I prefer the flat 6. I love how it sounds. It idles so quietly. It runs so smooth. It seems easy to maintain. I like it!

Great Story Keith.

Hope more follow up with their stories too.

Now see your HP rating of 97 hp 225.

Ive not come across an hp rating that low.

Hope to uncover this and see whats what and post my info in a more accurate manner.

Thanx again.

 

[keithb7]

Seems the HP varied during the 70’s oil crisis. I found this:

 

“225 Cubic Inch Version

The 225 cubic inch Slant 6 enjoyed the longest production run of all, being manufactured between 1960 and 1983. The 225 engine produced 145 horsepower, which was increased when the Hyper-Pak was introduced in late 1960 but decreased again when the focus of the Slant 6 shifted from high-power to fuel economy and reliability. The 225 had the 3.40-inch bore of the 170 and the 198, but its stroke length was longer still at 4.12 inches. Until 1974, the 225 shared the same cylinder block as the 198, before changing to a new block with the part No. 3462605. The crank of the 225 would fit in the engine of the 198 and shared its crankshaft specs.”

[55 Fargo]

Hey Thanx all for sharing info on the Slant 6.

Ive owned a few and they were not fireballs for sure but did okay and were tough.

100 hp net hp is most likely where a 225 is at with a 1 bbl carb.

Now the engine in my 55 Fargo is a 228 and rated at around 102 hp.

Mine in a tired well worn state is most likely 72 hp to the rear wheels.

Im hoping my fresh mild built 265 is a good improvement.

 

[Kevinb71]

Growing up (late 70's) my Dad had a 63 Dodge 1/2 ton with a slant six three speed work truck. I did my best to kill that truck, but it just kept coming back for more. I had alot of respect for that engine and truck for that matter. A good friend's Dad bought a '76 Dodge 4 wheel drive new. They farmed and used it to pull the gravity box's of grain to town. It always seemed to have enough torque to do the job. They did seem to burn intake valves fairly often. I always wondered why that engine did that and not other /6's that I knew of. My guess was that being a '76 the factory had leaned it out too much for the job it was doing. I now there was quite a bit of changing going on in the induction department in the mid 70's. They put 200k miles on that truck and the older two boys loved the truck. I think they still own it. I know the 251 in my 49 Chrysler is as smooth and seems strong, but the Clunk a matic and the Fluid Drive negate any comparison performance wise. My intention is to put in a three speed OD that i picked up this summer. Maybe then I can compare.

[knuckleharley]

I sold a 48 Dodge pu with a 218 in it to a local friend a few years back. This guy owns a commercial garage,and collects cars he likes. One is a early 60's half-ton Dodge stepside his grandfather bought new. He restored it several years ago and keeps it inside. I am pretty sure he told me it had a 225 slant 6 in it,not the 196.

 

I remember him telling me when he first put the 48 on the road he was shocked at home much more torque it had than the more modern slant 6. There is an arched bridge not far from his shop that he has to drive over,and he said the power increase of the 48 over the newer one was really noticeable pulling that grade in high gear at highway speed.

 

BTW,the 218 is bone stock,too.

[55 Fargo]

34 minutes ago, knuckleharley said:

I sold a 48 Dodge pu with a 218 in it to a local friend a few years back. This guy owns a commercial garage,and collects cars he likes. One is a early 60's half-ton Dodge stepside his grandfather bought new. He restored it several years ago and keeps it inside. I am pretty sure he told me it had a 225 slant 6 in it,not the 196.

 

I remember him telling me when he first put the 48 on the road he was shocked at home much more torque it had than the more modern slant 6. There is an arched bridge not far from his shop that he has to drive over,and he said the power increase of the 48 over the newer one was really noticeable pulling that grade in high gear at highway speed.

 

BTW,the 218 is bone stock,too.

Hey Knuck,

Very interesting story.

Trucks weight difference and rear gearing differences?

The slant 6 has its torque band at a higher RPM too compared to the 218.

Now here is a statement you will widely find on the web. 

The slant 6 was introduced to replace the woefully inefficient L head 6s. That i have trouble wrapping my head around...lol

Dont get me wrong as the Slant 6 rated 6th out of 10 in the worlds best engines of all time

 But the Legendary L head 6 is woefully inefficient. 

How about the L head is too tall, too heavy, and costs more to build going into the 1960s. 

I dunno a flathead might look kool in a Dart Swinger....lol

[knuckleharley]

6 minutes ago, 55 Fargo Spitfire said:

Hey Knuck,

Very interesting story.

Trucks weight difference and rear gearing differences?

The slant 6 has its torque band at a higher RPM too compared to the 218.

Now here is a statement you will widely find on the web. 

The slant 6 was introduced to replace the woefully inefficient L head 6s. That i have trouble wrapping my head around...lol

Dont get me wrong as the Slant 6 rated 6th out of 10 in the worlds best engines of all time

 But the Legendary L head 6 is woefully inefficient. 

How about the L head is too tall, too heavy, and costs more to build going into the 1960s. 

I dunno a flathead might look kool in a Dart Swinger....lol

I don't know because I don't own either truck,but I am guessing the early 60's pu is heavier.

The odd thing is IRRC,my friend told me his grandfather ordered the truck with something like 4:30 gears in the rear because he liked to idle up his produce rows,and because the truck was so heavy when he loaded it down to take to the market to sell produce off the back of it.

[classiccarjack]

@Tim Kieth,

 

If this new inline engine is produced, it sure would be nice if they carry over the same bell housing as the Hemi/Magnum/LA/A engines!  That way if I buy one, I can put a transmission behind it that doesn't require a computer to operate it....

[Tim Keith]

16 hours ago, 55 Fargo Spitfire said:

All interesting stuff Tim thanx.

On Compression ratio and HP ratings

Ive never come across a 7 to 1 rating for any 225

Where did you get that info or determine those numbers?

On HP always rated at 145 hp then detuned to 110 hp numbers.

Again where is the 90 hp info from that seems like the 170 slant HP numbers?

7 to 1 on compression ratio with the modern OHV head seems low.

Please post info on this to give us clarity on what Ma Mopar was doing for marketing specs..

Here some info Tim i stand corrected on the varying HP ratings and why.

http://slantsix.org/forum/viewtopic.php?f=19&p=153796

 

The best source for slant six information is slantsix.org.    The Lean-burn era 225 wasn't the best times for the slant six.  I have heard these have from 80 to 95 hp, but most '80s slants sixes have been converted to regular carburetors and standard electronic ignition - so there isn't any real difference in actual output.   The '71 and earlier motors was rated at SAE gross hp, and the later motors were rated at SAE net.   I don't see that the water pump and alternator account for the difference between 145 hp for the older 225 and 110 hp after 1971, but there aren't any major differences in the design of the motors, other than that later '70s motors used cast iron crankshafts and then a few years after that,  they also adopted hydraulic valve lifters.

 

The 225 pistons and cylinder heads are shared with the 170 and 198, which mandates that the piston crown of the 225 be  .140 - inch to .170 - inch and greater below the block deck.  This precludes any meaningful "quench".  The L-heads can actually do better than the stock 225 in quench.  It is somewhat popular to use 7-inch 198 connecting rods in the 225 to move the piston up in the cylinder bore.    Popular pistons choices with the 7-inch rods are the dished 2.2 turbo pistons.  I have heard that the GM 3.1 V6 pistons through 2004 are also a low cost choice with the 7-inch rods - if you are willing to overbore to 3.50 - inch.   If you can use 91 octane pump gas  a compression increase beyond 9.0:1 is worth the risk.   Typically a camshaft profile is chosen that provides a "dynamic" CR that enables higher static compression ratio beyond what would have been practical in the era of classic hot rod motors.  There is information on the slantsix.org site on choosing a streetable camshaft that might seem too radical.

 

The 170 is a "zero deck" motor, the piston crown is very near the top of the cylinder.  The 170 is a sweet running motor, would have been better if Dodge had built a lighter version of the A-body.

 

From the 1958 design to the last 1987 225 used in the US, most  slant six changes were pretty minor.  There was a lot of room for improvement, but with cheap V8s management didn't see a reason to improve the motor.   A bit of trivia - the BMW S54 used in the E46 M3 is a 198 cubic inch inline six with the same bore (within .030-inch bore) and stroke as the Mopar 198, but the normally aspirated BMW motor makes 334 horsepower.   If the slant six had pushed the casting to the same limits as the BMW the cylinder bore might have been near 3.75-inch.

 

The L-heads were great motors for their time, probably the best considering how poor gasoline quality was before the second world war.   If we had cheap propane, the L-head would especially like that fuel, should run quite a bit more miles before an overhaul is needed.

 

[maok]

In the the late '60s Chrysler Australia had a high performance version of the /6  160hp

[Andydodge]

Maok.....I forgot that one........just checked the Valo shop manual I have, yep the 1969 VF Pacer had 9.2:1 Compression with 160 hp @ 4500rpm and 220ft/lb torgue @ 2500rpm, used the 2 barrel Carter BBD on a specific intake manifold........I thought that the VF pacer also had a twin outlet exhaust manifold but can't find any listing in the manual..............andyd.

[maok]

17 minutes ago, Andydodge said:

Maok.....I forgot that one........just checked the Valo shop manual I have, yep the 1969 VF Pacer had 9.2:1 Compression with 160 hp @ 4500rpm and 220ft/lb torgue @ 2500rpm, used the 2 barrel Carter BBD on a specific intake manifold........I thought that the VF pacer also had a twin outlet exhaust manifold but can't find any listing in the manual..............andyd.

 

Andy, I don't think the VF Pacer /6 had more power, just more bling.  I wish I had a Pacer now...:(

[Tim Keith]

Actual Power Ratings For Stock Slants

http://www.slantsix.org/forum/viewtopic.php?f=19&t=61743

 

The good news is they respond well to simple mods.

[55 Fargo]

17 minutes ago, Tim Keith said:

Actual Power Ratings For Stock Slants

http://www.slantsix.org/forum/viewtopic.php?f=19&t=61743

 

The good news is they respond well to simple mods.

General Motors testing Slant 6s.

Sounds a bit dubious in my opinion Tim

Not that it cant be accurate but either Chyrsler or a 3rd party independent analysis would have more credence with Me.

Now i have lurked on Slant6.org.

Great site tons of knowledge and interesting stuff.

I did not completely read this link yet, but when I read GM testing of Mopar engines my Spidey senses begin to tingle....lol

The Dude on the Mustang Chassis dyno rating were interesting Ford guy, gets into.the act of testing the Slant 6

At any rate, thanx for your input on this.

Now what would a 218, 230 or a 250 from say 1950 rate at.

I think im glad i have a 265 for my truck.

Greg Gs 230 mild build 1956 head milled, dual carbs, stock cam 127 hp to the wheels at approximately 3100 rpm? So very good...

Bet my tired 228 has about 70 hp to the wheels.....lol

Edited February 2, 2018 by 55 Fargo Spitfire

[Flatie46]

Tim your right about the L-heads liking propane.  The Yale forklifts we use to have at our plant did very well on this. The engine in my '46 coupe was a Jasper re-man engine that was suppose to go in a fork lift but they signed a rental agreement on a new fleet before it was used.  ( It was actually set in a forklift but never put into service, long story, anyway I got a new engine for free )  Propane  burns much cleaner in the combustion process and promotes longevity.   I saved the propane set up and tank in case I ever wanted to run it like that again. 

[Tim Keith]

I don't think GM's testing was done for public release, not back then anyway.  They probably wanted to release  output specs for the their 230 six that were in the ballpark.  I don't care about the numbers  too much, but I would like to have better pulling power in my D150.   They say that if you want better seat in the pants kick, then lose some weight   That goes for myself.  GM's six was good from the block down, they never saw a need to improve the  cylinder head.  Mopar advertised its 12 port head back in the 1960s as a great feature, and it was.  Imagine if an "LS" type head were installed on the Chevy six     The 1/2 ton 2019 Chevy  will have an option of a new  3.0 inline six diesel six.  Jeep buyers keep asking for an inline six to replace their beloved 4.0.

 

The P15-D24 forum is more active on daily basis,  slant six .org comes alive on the weekend!  There is a lot of racing activity in the /6 world.   I still own 3 Mopar flathead sixes.

[55 Fargo]

18 minutes ago, Tim Keith said:

I don't think GM's testing was done for public release, not back then anyway.  They probably wanted to release  output specs for the their 230 six that were in the ballpark.  I don't care about the numbers  too much, but I would like to have better pulling power in my D150.   They say that if you want better seat in the pants kick, then lose some weight   That goes for myself.  GM's six was good from the block down, they never saw a need to improve the  cylinder head.  Mopar advertised its 12 port head back in the 1960s as a great feature, and it was.  Imagine if an "LS" type head were installed on the Chevy six     The 1/2 ton 2019 Chevy  will have an option of a new  3.0 inline six diesel six.  Jeep buyers keep asking for an inline six to replace their beloved 4.0.

 

The P15-D24 forum is more active on daily basis,  slant six .org comes alive on the weekend!  There is a lot of racing activity in the /6 world.   I still own 3 Mopar flathead sixes.

I had a 64 chevy truck short box, 292 4spd that truck was no slouch.

360 for your D150 or hopped up Slant 6 time.

There is no doubt that Slant 6s can be made to go.

Dont think too many Chrysler flathead 6s could perform like this slant 6.

I love this video...

..

Edited February 2, 2018 by 55 Fargo Spitfire

[Young Ed]

1 hour ago, Tim Keith said:

 

http://www.slantsix.org/forum/viewtopic.php?f=19&t=61743

 

The good news is they respond well to simple mods.

 

Back a few years Dad had a 63 valiant convert. He upgraded to it from his 63 Falcon vert. I can tell you even though the Falcon had a 4spd it was junk compared to the valiant(actually it was mostly because of the poor trans). Anyway the engine in the valiant was super tired  and a buddy of a buddy said he had an excellent running one that was pulled out of an A100 for a v8. Got it for $40. After hunting down the proper oil pan we put it in and it just wouldn't idle. We tried everything-had the manifolds planned for flatness tune up etc etc. Even pulled the head to check on the valves. Finally I ran into the guy who got it for us and he said it had a cam in it. IDK what the specs were of that thing but if you stomped it hard it would sure launch you! I drove that car from our place in MN to the Peoria IL plymouth club national with the roof down the entire time. Pretty good windburn but it was so fun!

[Silverdome]

55 FARGO, that video of  /6 versus Hellcat was taken just down the road from me. Do you know who the participants are and where they're from?

[55 Fargo]

15 minutes ago, Silverdome said:

55 FARGO, that video of  /6 versus Hellcat was taken just down the road from me. Do you know who the participants are and where they're from?

No I dont is it in Missouri  i take it.

Ill see what i can dig up.

That friggin 61 slant 6 is some powerful beast.

Its Mark Goodman or Wes Allenbachs Carthage Mo....

Edited February 2, 2018 by 55 Fargo Spitfire