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Obtaining quench in a slant 6?
Posted By: polkat
Obtaining quench in a slant 6? - 02/18/11 08:03 AM
I've got big block experience, but this will be my first slant 6 build. It's a 225 and I can't find much info out there (slant 6 sites) on building for quench. Anyone here done it? I think the 198 rods would help, but what about pistons? Any advice will be appreciated!
Posted By: RapidRobert
Re: Obtaining quench in a slant 6? - 02/18/11 02:17 PM
maybe 2.2 turbo pistons. Go here,
www.slantsix.org EDIT missed that you have been there, I'm surprised that they dont have a ton of knowledge on this. I dont even know if those heads are open or closed ch's
Posted By: DCI
Re: Obtaining quench in a slant 6? - 02/18/11 02:33 PM
Posted By: vynn3
Re: Obtaining quench in a slant 6? - 02/18/11 02:34 PM
Quote:
I'm surprised that they dont have a ton of knowledge on this. I dont even know if those heads are open or closed ch's
No closed chamber heads for slants. A few folks have made their own...
The 2.2 pistons work on the long-rod combo to increase compression and provide a better rod ratio, but don't do anything for quench.
Quench in a slant ain't gonna happen without a LOT of work and creativity.
vm
Posted By: polkat
Re: Obtaining quench in a slant 6? - 02/18/11 08:53 PM
It's my understanding that the heads have a very thick base, and can be milled as much as .100", which will bring them very close to closed chamber. I guess what I'm thinking is to find pistons with a somewhat positive deck height to make up the difference. I realize that much measurement and mock up would be required. Maybe the 2.2 pistons would be a start.
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/18/11 11:44 PM
Just throwing this out, but if you mill the head .100" and run a positive deck height piston your compression will be well over 12-1.
With a 198 rod and 2.2 turbo pistons you will have a deck heght of -.025/.030, depending on whether your stock deck is unmolested or not. This will give you roughly 9.5-1 with a stock CC head and a Fel-Pro gasket. Stock is usually around 58cc.
The turbo pistons have a dish in them and do create somewhat of a quench effect.
Posted By: Sport440
Re: Obtaining quench in a slant 6? - 02/19/11 12:19 AM
On the sl6 combustion chamber link, arent they showing a comparison of the older vs newer sl6 head with the newer being more like a closed chamber. 68 and later.
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/19/11 12:41 AM
There is not very much difference at all in Slant chambers from beginning to end. I always use the later model heads to get away from those oil leaking spark plug tubes.
One other small point, the Slant head was designed to work with 170 cubic inches. It was never improved when they went to the 225.
Posted By: polkat
Re: Obtaining quench in a slant 6? - 02/19/11 12:50 AM
slantzilla, you said that the 198 rods and 2.2 pistons would give about 9.5:1 comp with the Fel Pros and a piswton deck of about -.025"/-.030". If the later head was milled to closed chamber, and a steel gasket (.020") was used, would this not render .045 to .050" quench, or am I missing something?
Also, excuse my ignorance, but what 2.2 pistons are we talking about here? Who sells them?
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/19/11 01:05 AM
What are you actually trying to accomplish? A good MPG street motor or a performance build?
You have to remember that you are dealing with a very small bore here. A lot of milling on the head increases compression like crazy. Cam choice will become pretty critical so you don't build too much cylider pressure.
My motor has the head milled .065" and has the 198 rods, 2.2 turbo pistons about -.020" in the hole, and a Fel-Pro gasket. I am right under 11.5-1, and it is NOT pump gas friendly. I also run a cam with 300* advertised duration and .558" gross lift.
My pistons are KB Silvolites. They have a narrow ring on them too.
There is a deal on Wiseco pistons and K-1 rods on
www.slantsix.org . When the deal started they were about the same as rebuilding a set of 198 rods and using KB pistons. Not sure how much they are now.
Posted By: RapidRobert
Re: Obtaining quench in a slant 6? - 02/19/11 01:21 AM
You'd want tighter than 45-50. I think w the long rods/2.2 turbo pistons you could mill the head/block enough to get .035-.040" but you'd have to do some valve relief milling on the pistons as said to get the CR pump gas friendly. Polkat I think your plan is solid, to get an efficient /6 (which means quench) for an economy build. Holler what you end up w
Posted By: polkat
Re: Obtaining quench in a slant 6? - 02/19/11 05:43 AM
Thanks Robert. I plan to research the **** out of it and I'll get back with what I find.
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/19/11 12:30 PM
Quote:
One other small point, the Slant head was designed to work with 170 cubic inches. It was never improved when they went to the 225.
Wow, really...??? Not that i've ever heard ov someone saying this number was better than that number, but ONE design? That blows. No offense to you slantzilla, but honestly i dont understand why anyone even bothers with these things. They are so huge and heavy, and still at best 225 cid. I can see restorations, or weird builds, but anything thats intended to run fast, or be efficient... it just seems so utterly hamstrung by the design limitations. Boost or nitrous is another matter, but N/A...???
My brother spent his new family into poverty trying to do something with his slant six in a 69 Valiant. It was neat, really neat, but even after buying the whole Clifford catalog and getting creative where that failed, it was getting beat by Neons, Conquests, Hondas, and he can definitely drive...
My Challenger definitely qualifies as a survivor... its a slant 6/3spd car, and i want to drive this thing so bad i've almost entertained the idea ov building a budget 225 for it from the numbers engine... just to save myself the swap hassles. But then i figure i wont have half the goodies he had, plus another 300lbs...
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/19/11 02:30 PM
His first mistake was buying the whole Clifford catalog. With a few exceptions, most of Clifford's stuff is useless. Building a small CI motor is not just a throw money at it and it will be fast.
Why do I do it? Because I have had tons of big and small block cars and wanted something different. I used to park my 15 second Duster next to my buddy's 10 second 383 Demon at the track, and for every person who came and looked at his car, 10 looked at mine.
I have also run
12.0@110 in a Slant street car on nitrous.
Posted By: vynn3
Re: Obtaining quench in a slant 6? - 02/19/11 10:39 PM
Quote:
but honestly i dont understand why anyone even bothers with these things.
You weren't talking to me, but I'll throw my $.02 in. To some people, old cars aren't all about going as fast as possible for the least amount of money. My mildly-modified slant goes as fast as I'll ever need it to. When/if if ever doesn't, I'll add a turbo.
Oh, and I prefer the SOUND of an inline six. V-8's sounded okay when I was a teenager, but every old pickup in TX has glasspacks and duals... <yawn>.
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/22/11 02:20 PM
Quote:
Quote:
but honestly i dont understand why anyone even bothers with these things.
You weren't talking to me, but I'll throw my $.02 in. To some people, old cars aren't all about going as fast as possible for the least amount of money. My mildly-modified slant goes as fast as I'll ever need it to. When/if if ever doesn't, I'll add a turbo.
Oh, and I prefer the SOUND of an inline six. V-8's sounded okay when I was a teenager, but every old pickup in TX has glasspacks and duals... <yawn>.
Oh i understand that just fine... we deal in (true, not trendy) rat rods here. Its not always about speed. But as much as Mopar guys want to wave the Mopar flag, the factory just did not give y'all much to work with here at all.
One ov the most memorable and just plain badass cars i've ever seen at the track was an early Maverick with a big Ford I-6 (and a 5-speed stick?) in it. This thing was scary fast, loud as all hell and just plain weird. Right out ov a Mad Max movie set. And i could not stop checking it out. But it was a BIG 6. 300cid seems to stick in my head, but i honestly dont remember. My brother's car had a neat sound, for a 6... big goofy header and a Borla... But i'm a V8 guy. A V8 at full howl sounds better than a chick saying 'yes'...
PS - its the glasspacks. Those got old when i was 18...
Posted By: patrick
Re: Obtaining quench in a slant 6? - 02/22/11 02:26 PM
FWIW, a former co worker was an engineer on that 300 CID I-6 ford had in their trucks. when they developed the EFI for it, they had to detune it, because it made more power than the optional 302 V-8.....
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/22/11 02:31 PM
Quote:
His first mistake was buying the whole Clifford catalog. With a few exceptions, most of Clifford's stuff is useless. Building a small CI motor is not just a throw money at it and it will be fast.
I was not there when he was planning this thing, i was brought into the picture when he got desperate enough to actually ask his Mopar guy brother why his hotrod was getting embarrassed by slow imports. I did port the head though, without going nuts there i can say at least that part was decent. Maybe you've gotta REALLY hog those things out...???
He also bought a Comp cam, the big solid in the catalog, which i tried to steer him away from. Not knowing anything about slant sixes then, i just thought i'd compare it to what i'd expect from a 225cid V8. It still came up short. Something in that combo was drastically wrong.
Quote:
Why do I do it? Because I have had tons of big and small block cars and wanted something different. I used to park my 15 second Duster next to my buddy's 10 second 383 Demon at the track, and for every person who came and looked at his car, 10 looked at mine.
I have also run [Email]12.0@110[/Email] in a Slant street car on nitrous.
Yup. His Valiant got the stares, and when the hood was open the crowds would form. If anything he definitely had that six looking pretty cool. Painting it bright slime green probably helped...
I'm sure my Challenger would stop traffic at a show or in the pits with its six, but i just cannot handle a slow car (or that sound i suppose).
Curious though... How much power can be made from a basic budget slant six build...??? Lets say port the head, big cam (a good cam, maybe a custom), quench, maximum pump-gas compression, well-designed header (i'll make my own) and race exhaust, a good intake and carb. No NOS or boost. Could you make 300HP N/A without getting really tricky or pricey...??? In a 2800lb car with a 4speed and gears that might not actually be embarrassing...
Posted By: 360view
Re: Obtaining quench in a slant 6? - 02/22/11 05:24 PM
If you plan to do more research,
you might consider writing a letter to
Willem Weertman
who is now retired
and seems to want to
pass on knowledge to a new generation
http://www.allpar.com/corporate/bios/weertman.htmlnotice the bit about the Slant 6 diesel engine project
sample quote
Q: The various programs to modify the Slant Six that I have read include things such as a turbo charged version and another aluminum version and a fuel-injected version, is there anything that you can tell me about those and what instigated them and why they were not pursued?
I think I mention both the diesel and turbo versions in the book. The diesel version was a pretty neat program when we were working on that one. It was quite well developed; we had a 4-cylinder version of the Slant Six engine for use, it was a turbo-charged 4-cylinder diesel version of the Slant Six engine. It was no longer slanted though. I’m sure it was upright. But the diesel version of the Slant Six was slanted.
That program died when the interest in diesel engines in the U.S. died following the unsuccessful launching of General Motors diesel version of an automotive engine. That gave the diesels a bad reputation in the field and the market dried up and with that we quit our diesel program. That cessation of our own diesel Slant Six program was a decision by Lee Iaccoca. He figured the market wasn’t there and we shouldn’t be spending any money in that direction and he was right and we just stopped working.
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/23/11 02:14 AM
300 is doable, but I'm not sure I would call it a "budget" build. 300 N/A is also getting right on the ragged edge of a streetable Slant.
More is not always better when porting a Slant head. Be careful when choosing valve sizes too. What makes for great flow on a flow bench does not necessarily work on an engine because of the small bore.
Dig around on
www.slantsix.org and you will find an engine build matrix that details many of the motors we have done.
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/24/11 11:48 AM
Quote:
300 is doable, but I'm not sure I would call it a "budget" build. 300 N/A is also getting right on the ragged edge of a streetable Slant.
More is not always better when porting a Slant head. Be careful when choosing valve sizes too. What makes for great flow on a flow bench does not necessarily work on an engine because of the small bore.
Dig around on www.slantsix.org and you will find an engine build matrix that details many of the motors we have done.
Heh... i probably shouldn't (i'm confused enough about what to do with this car...) but i will. I actually have (or had?) an account there. Made it when i was asking questions for my brothers build.
Thanks. As neat as this car is, and as much as i wanted to buy a 6 car (at the time) because it would be less structurally damaged than a V8 car, i'm now thinking i should have just got a 318 car instead.
Posted By: jbc426
Re: Obtaining quench in a slant 6? - 02/24/11 05:07 PM
To Slant...
.jpg "6493835-68Barracudasubframeconnectors008(Large).jpg")
Posted By: jbc426
Re: Obtaining quench in a slant 6? - 02/24/11 05:09 PM
Quote:
To Slant...
or not to Slant. That is the question.
PS: The slant only gets half-again the gas milage when you stay out of the throttle. When you're in the throttle, it gets about 8 times or more better.
.JPG "6493840-IMG_1137(Large).JPG")
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 02/24/11 11:34 PM
When I first put my good motor in my '66 it would get almost 24 mpg with 3.91 gears driving 60-65.
I fixed that when I starting adding more camshaft and the lift got over .525".
Even at the end it would get 16-17.
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/25/11 01:02 PM
Reading that other thread i cant believe these things weigh almost 500lbs. Thats more than a 302 Ford...
So much bad... Yet, it would be so easy to get my car on the road...
Posted By: polkat
Re: Obtaining quench in a slant 6? - 02/28/11 10:23 AM
One of the main advantages of quench is the turbulance it creates in the mixture, effectively forcing it towards the flame front, which also helps cool the chamber. As a result, you can run higher compression that will actually detonate less then a somewhat lower compression engine without quench.
However, quenching a sl6 might indeed create compression too high for present gasses. So, if one could find a piston that has enough compression height (positive deck) to reach up into the (unmilled) head, and has an offset dish of the right size to drop compression enough, I think it would work. But...does anyone make such a piston, or does one exist that could be modified with a dish?
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 02/28/11 12:59 PM
Quote:
One of the main advantages of quench is the turbulance it creates in the mixture, effectively forcing it towards the flame front, which also helps cool the chamber. As a result, you can run higher compression that will actually detonate less then a somewhat lower compression engine without quench.
However, quenching a sl6 might indeed create compression too high for present gasses. So, if one could find a piston that has enough compression height (positive deck) to reach up into the (unmilled) head, and has an offset dish of the right size to drop compression enough, I think it would work. But...does anyone make such a piston, or does one exist that could be modified with a dish?
Its been a while since i had my hands on a slant 6 head, but i'm picturing a combustion chamber more or less like a 906 BB head. I'm still not a fan ov quench pads for building open-chamber headed quench engines, and would instead try to just mill the 'step' (the flat shallow area the quench pad would fit into) completely down until the deep part ov the chamber was now essentially a closed chamber (heh heh... hope that makes sense). That done, simply get a custom piston with whatever dish you need to make your target CR. Again, i haven't looked at a /6 chamber in a while... so i might be way out there on this... But if it works it would be better than the hokey quench pad idea. Custom pistons are considerably cheaper than they used to be.
The monkeywrench here could be that the 'step' is too deep and would necessitate decking the head far enough that the deck itself would be too thin.
Just thinking out loud here...
Posted By: polkat
Re: Obtaining quench in a slant 6? - 02/28/11 09:11 PM
Yea, it would be too deep. The recessed area in the head is nearly .200" at the edges, and taking that much off the head would make the head deck a bit too thin.
I have heard about a piston, the KB268, that might work for this with the 198 rods. Will check it out.
Posted By: polkat
Re: Obtaining quench in a slant 6? - 03/01/11 02:12 AM
Also, I see no problem using a quench pad piston. KB sells a ton of them and V-8 people here talk about them all the time. The problem is finding one for s S/6 engine.
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 03/01/11 02:22 PM
Quote:
Yea, it would be too deep. The recessed area in the head is nearly .200" at the edges, and taking that much off the head would make the head deck a bit too thin.
I have heard about a piston, the KB268, that might work for this with the 198 rods. Will check it out.
I figured it might be too deep. The big block head looks doable, and some here have done it. But .200" would pooch that head i'm sure, unless the decks are 1/2" thick. Heh heh... its a slant 6, you never know, gotta be SOME good reason why a tiny 6 cyl engine can weigh 475lbs...
And last i checked (3 or more years ago?) there was no non-Mopar head that could be physically bolted onto/mated to a slant six. Apparently the slant guys have tried EVERYTHING... and i do not doubt them. But... it has been at least 3 years... and there have been a few I-6's introduced into the automotive world. If i was a slant six guy, that would be my quest... finding a modern head to bolt onto that block. Beyond the obvious benefits, making quench would be easy. But i suppose we're transcending the original question now...
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 03/01/11 11:51 PM
Quote:
But .200" would pooch that head i'm sure, unless the decks are 1/2" thick.
I know some people who have taken up to .140" off. Not sure if I'd try .200" though.
Quote:
And last i checked (3 or more years ago?) there was no non-Mopar head that could be physically bolted onto/mated to a slant six. Apparently the slant guys have tried EVERYTHING... and i do not doubt them. But... it has been at least 3 years... and there have been a few I-6's introduced into the automotive world. If i was a slant six guy, that would be my quest... finding a modern head to bolt onto that block. Beyond the obvious benefits, making quench would be easy. But i suppose we're transcending the original question now...
Correct, there is no other head that will bolt on.
There was a thread making it's way around the internet a couple years ago about a guy sectioning a couple 5.7 Hemi heads to make a SLant head. He even had a bunch of pictures of it on the motor and claimed it ran. Looked very nice.
It was bogus as hell.
I also have a buddy who posts pictures of a Slant with I believe a Toyota head bolted on to it.
It's bogus too.
Posted By: 360view
Re: Obtaining quench in a slant 6? - 03/02/11 02:11 PM
Does the Australian Hemi 6 engine
tell us what Chrysler intended to do
to improve combustion in the Slant 6?
http://en.wikipedia.org/wiki/Chrysler_Hemi-6_Engineit seems that instead of quench
they went more for 'tumble' in the intake tract
to increase burn rate through more turbulence
at lower rpms
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 03/02/11 11:30 PM
The "Hemi" 6 has nothing in common with the Slant. Nothing in common with a Hemi either.
Posted By: OzHemi
Re: Obtaining quench in a slant 6? - 03/02/11 11:42 PM
Quote:
The "Hemi" 6 has nothing in common with the Slant. Nothing in common with a Hemi either.
Yep...it's more of a poly/canted valve....Hemi sounded good though and that is what they just went with in Oz.
It's a "foot" longer than a slant too
.jpg "6506568-Picture(124).jpg")
Posted By: OzHemi
Re: Obtaining quench in a slant 6? - 03/02/11 11:45 PM
Oz on top, slant on the bottom...
.jpg "6506575-Picture(123).jpg")
Posted By: OzHemi
Re: Obtaining quench in a slant 6? - 03/02/11 11:47 PM
Exhaust port comparison.... "Hemi" is a fair amount larger in port size for intake and exhaust..
.jpg "6506580-Picture(11).jpg")
Posted By: OzHemi
Re: Obtaining quench in a slant 6? - 03/02/11 11:48 PM
And intake...
.jpg "6506586-Picture(12).jpg")
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 03/03/11 03:06 PM
[Edited by Moparts - Family Friendly Site - Keep it clean] me that beer looks good right about now... And juuuust the right temp too...
Posted By: OzHemi
Re: Obtaining quench in a slant 6? - 03/03/11 04:47 PM
Posted By: polkat
Re: Obtaining quench in a slant 6? - 03/03/11 09:41 PM
Back to the idea of quench on a slant (my original post). Here's an idea I posted over on the Slant 6 site. Got no responses so I thought I'd post it here.
Based on the factory numbers (and I have not yet specifically measured out this engine), the head chambers are recessed into the head about .200", while the piston usually sits about .140" in the hole. I'll use these numbers just for arguement.
If the 198 rods are used instead of the 225 rods, it will push the stock 225 piston roughly .147" OUT of the hole. This will give a quench (at the closest points between the head and piston) of about .073" with a .020" steel gasket. Mill the head .028" to clean it up and I'll have about .045" quench (considered good quench in most circles). But the compression will be way to high. So if I cut about a 18cc "D" type dish in the stock piston tops, I'll get roughly a 9.5:1 compression, plus have valve clearance. I've seen this done to other types of stock pistons and assume it's possible here. All of this must be measured out on my specific engine (particularly negative piston deck, since as previously mentioned, it varies between engines, as well as the 198 rod to 225 piston skirt clearance).
I suspect this will work if I can dish the pistons. I'd love to find a piston already like this. The KB268 is close, but the CH is too low. I don't mind the idea of the stock 225 piston as I don't plan to rev beyond 5K anyway.
Any opinions on any of this?
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 03/04/11 03:38 AM
You may want to measure a chamber, I'm pretty sure a +.140" deck height will be smashing the piston into the head. Most positive deck height I know of anyone getting away with was +.020", and the chambers had to be ground out for that.
With that much of the piston out of the deck you may be very close to popping the top ring out too.
Posted By: ahy
Re: Obtaining quench in a slant 6? - 03/04/11 04:13 AM
Sounds feasible. I don't know if there is enough meat in a stock piston to cut that much dish and keep enough strength though.
Here's a different twist on the same idea... calculate and measure with stock rods and work with one of the custom piston manufacturers like Ross to design a custom quench pad piston. It could be a flat top plus quench pad. CR would be dialed in to target 9.5 by letting the flat part be a little below deck. Maybe target 9.2 or so to allow for cleanup milling of the head and block without exceeding 9.5. Leave the pad a little high like KB so the piston can be fitted to the engine by milling.
Ordered for one engine it would be a bit expensive but if you find some fellow "slanters" to go in with you and order several sets at once, I bet you could get a better deal.
Posted By: polkat
Re: Obtaining quench in a slant 6? - 03/04/11 06:05 AM
ahy, interesting idea, but if 225 rods were used, it would call for a piston with a 1.921" CH, and that's just too much above the pin, for me anyway.
My understanding over at the Slant 6 site was that the combustion chamber floor sat an average of .200" above the flat face of the head (as would be seen from underneight). The floor then climbs up toward the valves and plug area. If true, then a piston top .147" out of the hole would not hit any part of the combustion chamber, particularly with a .020" head gasket between them.
Since the head simply cannot be milled enough to create a closed chamber, positive piston deck height is the only possible way to acheive real quench.
Yes, the KB 268 with 198 rods would be perfect if it had just a tad more CH. The 268's have 1.594" CH, but for usable quench with 225 rods, a piston with a CH of about 1.614" or more is needed.
Understand again that I have not measured any of this yet. I'm just speculating on how to approach it. Guess I'll do some piston research as well.
Posted By: slantzilla
Re: Obtaining quench in a slant 6? - 03/04/11 12:13 PM
The chamber is not the same diameter as the piston. Look up an empty bore with a head on and you will see the chamber overhanging. The piston will hit it.
Posted By: RapidRobert
Re: Obtaining quench in a slant 6? - 03/04/11 01:25 PM
In the old days b 4 closed chamber heads were more avail guys (w 906's) welded up the OC recess then milled it flat & no reason it couldn't b done to a slant head if there's no piston that will get r done
Posted By: Pale_Roader
Re: Obtaining quench in a slant 6? - 03/04/11 01:45 PM
Again, not sure about the six, but on a big block the piston is physically wider than the chamber on an open chamber head. Pretty sure the 225 chambers are smaller than the piston tops, so it wont fit inside... but i'm still guessing. Maybe if this is the case you could get tricky and carve out the edges ov the chambers to fit the piston inside...??? Seems like a helluva lot ov work to accomplish this quench goal though...
Or maybe i'm reading you wrong...???
Posted By: 360view
Re: Obtaining quench in a slant 6? - 03/04/11 02:13 PM
what is the rpm range
that the slant six
needs to be 'optimized' for?
it is worth remembering the basics:
Quench is best at creating turbulence
in the air and fuel mixture
near top dead center
for faster burn
and better octane tolerance
Quench works best
up to a specific RPM range
Above that RPM range
the extra horsepower to 'squirt out' that mixture can take away power, rather than add it
Quench surfaces are like a high pressure pump that the piston has to run
... the more quench area
and the tighter the quench clearance,
the greater the horsepower need to
'run the quench fire hose nozzle'
becomes as the RPM goes up
As rpm rises
just the up and down motion of the piston
begins to provide a lot of turbulence
to the air and fuel mixture
in the 1500 to 3500 rpm range
you could also get more turbulence
inside the slant six's combustion chamber
by swirling
or tumbling
the air flow in the intake port
it is relatively easy to get more swirl:
just add to the intake port
some
welded in vanes
or spirals of little dimples
or a twist-able butterfly valve
or a more "shrouded" valve seat
a dish in a piston
will 'concentrate' and increase any swirl present
just like an ice skater
will spin faster
if she pulls her arms in close to her body
tumble is more tricky
but the right intake port mods can do that too
when you see
an oval dish cut into a piston crown
rather than a perfectly circular dish
the designers are trying to
concentrate tumble motion near top dead center
as well as swirl
