Slant Six Forum :: Billet Aluminum Slant 6 Head! Seriously!!

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But, suffice it to say that a ported 302 Chevy V-8 head flows in excess of 300cfm on the same displacement cylinder as a 225 /6, and that's why they run as well as they do. The Boss 302 Ford head is even better, with even larger (canted) valves and bigger ports.

Ported 302 Z/28 heads won't flow over 300cfm. They only flow 215 stock. Average ported with 2.02 valves is 250. Radical port work with 2.05+ valves will go 275, radical meaning reduced reliability and very costly.

It's hard to get 300 from a BB Mopar 906/452 head that start with bigger ports and 2.08 valves. Stock flow is around 235. Ported with a 2.14 valve is usually 290-295 is max without reliability issues but 300+ can be reached.

Boss 302 heads flow 270cfm stock, so over 300 is easy to achieve. '70 heads had 2.19 valves, same as an 427 L88 Chevy. '69 heads had 2.23, only .02 less than a 426 Hemi!

Readily available aluminum heads <drool>
200/250 Ford six has them
258/4.0 AMC has them
250 Chevy has or had them
225 Slant Six never had them <sad>

There wasn't a SBC head capable of 300 CFM until the late 1980's, and it was an aftermarket one. The Chevy inline 6 production head flows just under 160 CFM in stock trim on the intake, can be upt to 260 CFM with 1.94" valves and bolt-in lumps, and 348 CFM with brazed lumps and professional porting. Creative thinking has raised the bar for the Chevy head considerably, and shows how much farther you can go if you think outside the box.....what can be done to the stock Slant head(put your thinking caps on).

Author:	billdedman [ Sat Jan 21, 2012 3:37 pm ]
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Quote: Quote: Quote: But, suffice it to say that a ported 302 Chevy V-8 head flows in excess of 300cfm on the same displacement cylinder as a 225 /6, and that's why they run as well as they do. The Boss 302 Ford head is even better, with even larger (canted) valves and bigger ports. Ported 302 Z/28 heads won't flow over 300cfm. They only flow 215 stock. Average ported with 2.02 valves is 250. Radical port work with 2.05+ valves will go 275, radical meaning reduced reliability and very costly. It's hard to get 300 from a BB Mopar 906/452 head that start with bigger ports and 2.08 valves. Stock flow is around 235. Ported with a 2.14 valve is usually 290-295 is max without reliability issues but 300+ can be reached. Boss 302 heads flow 270cfm stock, so over 300 is easy to achieve. '70 heads had 2.19 valves, same as an 427 L88 Chevy. '69 heads had 2.23, only .02 less than a 426 Hemi! Readily available aluminum heads <drool> 200/250 Ford six has them 258/4.0 AMC has them 250 Chevy has or had them 225 Slant Six never had them <sad> There wasn't a SBC head capable of 300 CFM until the late 1980's, and it was an aftermarket one. The Chevy inline 6 production head flows just under 160 CFM in stock trim on the intake, can be upt to 260 CFM with 1.94" valves and bolt-in lumps, and 348 CFM with brazed lumps and professional porting. Creative thinking has raised the bar for the Chevy head considerably, and shows how much farther you can go if you think outside the box.....what can be done to the stock Slant head(put your thinking caps on). Well, I apologize for disseminating what was apparently erroneous information. I'll check my facts more closely next time. To the poster that said "Comparing a 4" X 3" engine and a 3.40" X 4.125" engine is ridiculous" (or, something like that) was right; there IS no comparison, because of practical valve size limitations. That was my point. Having a 170 that makes 1.5 hp/cu.in vs. a 225 that makes 1.33 hp cu.in..... Well, on the street the 225 would be the faster car, but in class racing (where they classify cars by lbs./cu.in) the 170 would prevail. You pays your money and you takes your choice....

Author:	CNC-Dude [ Sat Jan 21, 2012 4:29 pm ]
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Hey Bill, the 302 head, 186 casting # was great for its time compared to the 461 castings that everone thinks hung the moon of that same era. Just not that good.....

Author:	sandy in BC [ Sat Jan 21, 2012 4:52 pm ]
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Chevvy guys........

Author:	madmax/6 [ Sat Jan 21, 2012 5:01 pm ]
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Wrong Zilla,I built MY motor,Wyane had his built.Jefferies did my head and guided me but I built it.From my calculations its about 305 hp at the flywheel and 275ish at the rear wheels.Guzzi Mark

Author:	slantzilla [ Sat Jan 21, 2012 9:28 pm ]
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Mark, the fact remains that you and Wayne have very similar parts in your motors. No replacement for displacement unless you turn it to the sky.

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Billet Aluminum Slant 6 Head! Seriously!! https://slantsix.org/forum/viewtopic.php?t=47607	Page 5 of 18

Author:	billdedman [ Sat Jan 21, 2012 10:04 pm ]
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There may be no replacement for displacement, but a turbocharger is a pretty good "crutch." The two guys I personally know of running 225 turbos have no "heroic measures" inside their engines (no offset ground strokers or .100"+ bore jobs, roller cams, offset valve guides, or even EFI) and they both make in the neighborhood of 500 horsepower. It takes a fairly well-built small block to exceed that figure without breaking the bank. Considering all the problems associated with the breathing limitations foisted upon the 225 by that 170 head it has to deal with, forced induction would seem to make an end run around those restrictive flow problems, and be worth whatever complexity and extra expense that it brings with it (and, it DOES arrive with "baggage," believe me.) Turbocharging is just like conventional hop-up methods in this respect; you can go mild, wild, or anything in between; it all depends on how much you want to spend. I personally feel like a mild (10-pound boost) turbo setup on a nearly stock /6 engine could be the cheapest way to the 13's in fairly light A-body..... Definitely cheaper than swapping in a 360, with the necessary parts to put it into the same e.t. range. Getting a normally-aspirated /6 into the 13's requires several mods, I believe, some not cheap. Just sayin'....

Author:	Dart270 [ Sun Jan 22, 2012 6:18 am ]
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Mark, Just a comment. If you are calculating 275 RWHP (I think I get a bit higher by my calculator), I believe you are around 340 HP at the flywheel. An auto (904) loses a lot. Tilley chassis dyno'ed at about 280 HP and then engine dyno'ed and got around 345. That was with a 2800 RPM converter and yours is 4000, right? You have done some amazing work, my friend!! Lou

Author:	billdedman [ Sun Jan 22, 2012 4:01 pm ]
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"You have done some amazing work, my friend!!" I second that!!! Mark's car is SO impressive!!! Bill

Author:	Rug_Trucker [ Sun Jan 22, 2012 8:03 pm ]
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Back in '61 they were pulling 184hp from the 170's in NASCRAP with the Hyperpaks.

Author:	billdedman [ Mon Jan 23, 2012 12:58 am ]
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You can DO that with a 170; that's the size engine the head's valves and ports were designed to feed. Add 55 cubic inches (or, put another way, 33%) and it's a different story. The 225 slant six did a great job of hauling around 3,600-pound cars on the street. Trying to get it to breathe like a racing motor is an uphill battle. It can be done, to some extent, but the easy way out is forced induction. My 2-cents... Bill

Author:	slantzilla [ Mon Jan 23, 2012 3:08 am ]
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Quote: Trying to get it to breathe like a racing motor is an uphill battle. It can be done, to some extent, but the easy way out is forced induction. Most of us came to that very same conclusion about 5 years ago. Welcome to the party.

Author:	terrylittlejohn [ Mon Jan 23, 2012 4:13 am ]
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and it`s a really good party with lots of special guests

Author:	billdedman [ Mon Jan 23, 2012 4:31 am ]
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Thanks for the confirmation. That said, I think that the slant 6's REAL strengths lie in its unusually robust construction (block and head stiffness,) and the short, forged crank with 426 Hemi sized bearings. I believe that its robust block and head construction owe their existence to the fact that Ma intended it to be an aluminum engine, from the git-go, and when that didn't work out, the changes in construction that WERE implemented (in the changeover to cast iron) were cheaper to change minimally; the least amount of things possible, were modified. So, what we end up with, is a basic engine that is strong almost like a Diesel, and can withstand boost levels that would destroy my 360 Magnum in a New York minute! I go to breakfast every Saturday, with about 6 or 8 cronies... all of whom own Buicks with turbos. They tell me that using factory blocks and cranks, they dare not exceed 22-24 pounds of boost, or egregious engine damage WILL occur. They just come apart. I think a slant 6 will handle a LOT more than that, properly assembled with forged rods and pistons. Hopefully we're going to find out. Both Tom Wolfe and Ryan Peterson have taken their engines to the high 20's, boost-wise, and we're eventually going to see what comes apart after that, with our effort. At least, that's the plan... Thanks for your interest! Bill, in Conway, Arkansas

Author:	Dart270 [ Mon Jan 23, 2012 4:42 am ]
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I hope we get to see you at a Slant 6 race with this machine. Happy building, Lou

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Author:	Rug_Trucker [ Mon Jan 23, 2012 5:52 am ]
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The 184hp was being spun at 7000+? Lots of breathing going on. How much air they were pumping? I can't do the math. Bill are you Frank's friend in Little Rock?