What Crankshaft to Run in High HP Turbo Slant Six

[SlumpSix]

Looking for information to start a 500+HP Turbo Slant Six build. Specifically, I'm looking for what guys are running for crankshafts and are there any aftermarket options for bore+stroke combonations etc. If sticking to the stock crank what is being done to accept the boosted power?

 

[RustyRatRod]

No aftermarket.

 

[Charrlie_S]

Several years ago, Crower made some billet slant six cranks. Most slanters just use a prepared stock crank. You should really go over to slantsix.org and inquire over there.

 

[SlumpSix]

Thanks for the info.

 

[JohnnyB]

pre-'76 slants have a forged crank and I doubt you'll break one but if you want stronger, industrial and heavy-duty trucks usually got forged shotpeened cranks.

 

[Killer6]

Look up slantracer's posts,he's the one w/the green lancer that match raced and beat
the green hellcat at MoKan. He talked about the crank twisting .030+ over the run
of a season,switched to billet I thought callies, but may have been crower.Others
in that power range have actually welded the cranks up for rigidity,so either way,
you'll probably have to have a plan of action above & beyond stock shot peened
or not. Good luck,Me likey your goal,keep us posted!!:burnout:

 

[Bill Dedman]

Look up slantracer's posts,he's the one w/the green lancer that match raced and beat the green hellcat at MoKan. He talked about the crank twisting .030+ over the run of a season,switched to billet I thought callies, but may have been Crower.
Others in that power range have actually welded the cranks up for rigidity,so either way,
you'll probably have to have a plan of action above & beyond stock shot peened
or not. Good luck,Me likey your goal,keep us posted!!:burnout:

That is an interersting question, but, I think a stock 4 1/8"-stroke, early forged crank in this application should last a long time. The reason I say that is this: Turbocharged slant sixes that run exceedingly well, like the two engines I patterened mine after (Tom Wolfe's and Ryan Peterson's,) do not run well at rpms over 5,500, making tons (500+) of horsepower without spinning lots of RPM's. That green Lancer that ran off and left the Hellcat relies heavily on lots of rpm to make its (CONSIDERABLE) naturally-aspirated power, but with a long stroke, probably generates a lot of stress on the bottom-end at those elevated revs... I don't know, but I would not count out the possibility that the stratospheric RPM that car turns five times (it has a 5-speed transmission,) on every trip down the drag strip, might contribute to crankshaft problems, but that's just a guess on my part. Add to that scenario, the high rpm launches it sees every trip, and you have SIX times that high piston-speed phenomenon occurs. Addditionally, if you factor in the "NO LOAD" aspect of the pre-launch rpm, it sounds like that engine lives a tough life...

The hot setup for the turbo cars of messers Wolfe and Peterson involve final drive ratios of 2.76:1. They both found that, after testing higher numerical ring and pinion sets, they both ran quicker and faster with the highway/touring ratios. The turbo's seem to respond well to being "held back," like a nitro motor... go figure!

This makes it possible, if you are going to street-drive your turbo car, to use a cheaper 8.25" rear end since you will have a "one-size-fits-all" ratio all the time, with no need for swapping ring and pinion ratios; one for for the hiway and one for the drag strip.


As i remember, the cast iron crank is somewhat lighter than the forged one, but the bearings are smaller on the cast crank, so the jury is still out as to whether this might be a good choice for a forced-induction application. It should be faster.... once.rayer:

To the original poster, please keep us updated on your progress in this build. There aren't nearly enough of these car being built, in my warped opinion, given their ten-second quarter-mile potemtial.. Here's mine...

 

[Bill Dedman]

Looking for information to start a 500+HP Turbo Slant Six build. Specifically, I'm looking for what guys are running for crankshafts and are there any aftermarket options for bore+stroke combonations etc. If sticking to the stock crank what is being done to accept the boosted power?

The reason there are no "stroker" cranks available for the 225's is, the stock stroke (at 4 1/8") is already too long. You can utilize increases in boost levels for more power; forget the stroker... not needed, here. :glasses7:

 

[Killer6]

Thanks Bill, I believe the weld reinforced crank was in a supercharged 10 sec. car,and
I'm not certain who else has done that.I believe the high rpm is not as much of a
factor as the high rpm launch w/a man. trans & big slicks would be as far as twisting
the crank.Impact at launch and the torsional force at peak torque(almost explosive
forces on ea. pwr. stroke w/nitro)are most likely culprits there.
Yeah,turbos like to be loaded heavy as they approach full on boost,anyone who
has driven one of them everyday notices how they like to pull a hill seemingly more
than on the flat.As far as rpm limit is concerned,for decades I have heard how turbos
just don't "rev",and in most retrofitted cases that is true.However,it isn't the turbos
fault,its your cylinder head that is the problem.NOT just us slanty fans, but nearly
all inline two valve heads,period.Turbos generate so much more torque per rpm,and
more pressure drop across the valve/bowl/seat area,that you feel when the head has
run out of flow almost abruptly.When mopar handed off the 4-valve 2.2 head task
to Lotus to design,the peak horsepower rpm jumped almost 1,200 w/the same boost
Obviously a look at the old CART champ cars,Formula 1,etc.proves this out,flow
still matters,but there is a definite limit to what we can do.Unless someone out
there would like to re-incarnate the 4-V argentinian head???Doug???

 

[Bill Dedman]

Thanks Bill, I believe the weld reinforced crank was in a supercharged 10 sec. car,and
I'm not certain who else has done that.I believe the high rpm is not as much of a
factor as the high rpm launch w/a man. trans & big slicks would be as far as twisting
the crank.Impact at launch and the torsional force at peak torque(almost explosive
forces on ea. pwr. stroke w/nitro)are most likely culprits there.
Yeah,turbos like to be loaded heavy as they approach full on boost,anyone who
has driven one of them everyday notices how they like to pull a hill seemingly more
than on the flat.As far as rpm limit is concerned,for decades I have heard how turbos
just don't "rev",and in most retrofitted cases that is true.However,it isn't the turbos
fault,its your cylinder head that is the problem.NOT just us slanty fans, but nearly
all inline two valve heads,period.Turbos generate so much more torque per rpm,and
more pressure drop across the valve/bowl/seat area,that you feel when the head has
run out of flow almost abruptly.When mopar handed off the 4-valve 2.2 head task
to Lotus to design,the peak horsepower rpm jumped almost 1,200 w/the same boost
Obviously a look at the old CART champ cars,Formula 1,etc.proves this out,flow
still matters,but there is a definite limit to what we can do.Unless someone out
there would like to re-incarnate the 4-V argentinian head???Doug???

The Argentine head I have heard of is a slightly-modified design that is much like a stock 2-valve slant six head.... mainly, a better combustion chamber and maybe bigger valves. I have only seen pictures.

I never heard of a 4-valve Argentine head. Fill me in, please.

 

[Killer6]

Posted by Polara1974 on Dec.18,2010 on .org, was the story in brief of one Mister
Augusto Cicare, and his having been commissioned to develop a racing head for
the slanty to compete in that country/region's Formula SP series.The pictures show
clearly a DOHC 24V head that had obvious signs of having been run on an engine,
w/the chambers appearing cast slightly crudely,and the valves perilously close to
the chamber edge/cyl. wall.An amazing guy in a relatively poor country,and a great
story in the history of all things mopar!
Read the thread and follow the link to the old magazine article,cool s**t!!

 

[Bill Dedman]

Posted by Polara1974 on Dec.18,2010 on .org, was the story in brief of one Mister
Augusto Cicare, and his having been commissioned to develop a racing head for
the slanty to compete in that country/region's Formula SP series.The pictures show
clearly a DOHC 24V head that had obvious signs of having been run on an engine,
w/the chambers appearing cast slightly crudely,and the valves perilously close to
the chamber edge/cyl. wall.An amazing guy in a relatively poor country,and a great
story in the history of all things mopar!
Read the thread and follow the link to the old magazine article,cool s**t!!

The search engine in slantsix.org needs information as to which forum to search. I searched the engines forum and foumd a cou[le of posts on that date, but they were not the right ones. I think I need to know which forum that post was in to actually find it. It soulds fascinating, so I hope you can direct ne to the right forum to search.

Thanks fore the info!:glasses7:

 

[Killer6]

Hmmmm,I also clicked my way to the engine forum page covering that date,and it
wasn't there,what a PITA to get there w/o a ten page"skip" option!I stumbled upon
that thread thru the google images page after typing a search for aluminum & 4-
valve slant six heads.It is in the engines forum, but not on that page for some
reason,selective editing perhaps? Anyway,type argentinean in the word box up top
and Polara1974 in the author box, and nothing else then click search and it came
up about the 3rd post down listed for the OP.Other interesting related stuff there
too, which I believe you alluded to.Some details are still a mystery,unless you can
read the mag. article in that language!Enjoy!:coffee2:

 

[Bill Dedman]

Hmmmm,I also clicked my way to the engine forum page covering that date,and it
wasn't there,what a PITA to get there w/o a ten page"skip" option!I stumbled upon
that thread thru the google images page after typing a search for aluminum & 4-
valve slant six heads.It is in the engines forum, but not on that page for some
reason,selective editing perhaps? Anyway,type argentinean in the word box up top
and Polara1974 in the author box, and nothing else then click search and it came
up about the 3rd post down listed for the OP.Other interesting related stuff there
too, which I believe you alluded to.Some details are still a mystery,unless you can
read the mag. article in that language!Enjoy!:coffee2:

Thank you for alluding to the next-to-worthless search function on that website that makes it necessary to advance one page at a time, an unnecessarily time-consuming process. All of which wouldn't be a deal-killer if the article in question were actually THERE when you arrived, but to have gone through all of that time-wasting business only to find..... nothing....., is doubly depressing.

Thamks for the information! I'll look again...:banghead: