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Double rockerarm shaft head
https://slantsix.org/forum/viewtopic.php?t=26620		 Page 5 of 9
Author:  Matt Cramer [ Fri Jan 18, 2008 12:46 pm ]
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Has anybody looked at the BMW inline 6 head? I know the bore is really close in size to the /6, but don't know much more.

Just curious.

Edit:

Looks like 100mm (3.937") and 87mm (3.4252") bore on the M3 3.2L motor. Not sure how consistent that spacing is down the displacement ladder.

Plus it would either need to be converted to a pushrod setup (custom rockers?), or a custom cam with revised lobe spacing (impossible?).

Probably not a good candidate.
I keep thinking about trying to get a BMW head from the shop next door. They do look like they have some things that could have potential.

But I wouldn't bother converting it to a pushrod setup - it seems like it would be less work to convert your slant six to overhead cams. :D
Author:  DionR [ Fri Jan 18, 2008 1:10 pm ]
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But I wouldn't bother converting it to a pushrod setup - it seems like it would be less work to convert your slant six to overhead cams. :D
But after moving the bore centers around, that would require the cam lobes to change spacing on an OHC setup. Is that possible without an unlimited budget?

Not sure a pushrod setup would work any better, though. I would bet at least one set of the pushrods would need to go through the exhaust ports.

If you've got a shop close by, grab a head gasket and see how it lays on the block. :D
Author:  zedpapa [ Fri Jan 18, 2008 5:39 pm ]
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details, please. there's no way you did that with a sawzall and a drill press. if it was that easy, everyone would have one. and what are the screws above the exhaust ports for? what about the bar along the bottom of the headers?

zedpapa
Author:  sandy in BC [ Fri Jan 18, 2008 6:03 pm ]
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what are the screws above the exhaust ports for? what about the bar along the bottom of the headers?
.... those are what you use when you have a sawzall n drillpress...but no welder.
Author:  runvs_826 [ Fri Jan 18, 2008 9:22 pm ]
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Well, I'm still a little confused how the "hemi" head has worked, but I do agree it's time to look at cutting heads to make this engine really kick it up. I know that the stock heads have been proven to flow fine, but... with time technology has improved.
Chevy guys have proven to cut 350 heads in half and weld them together and have a cool head. I'm not entirely sure how the water jackets work, or maybe their is some re-working. But we could easily do the same if we could find a head that fits well. I would love a hemi... and one day will have one in my car. However, I think their is some closer fits for the slant. From the looks of various sources for cheap heads I found these.

Ford 3.0L Bore-3.5 Spacing-4.3
Ford 4.6L Bore-3.55 Spacing-3.9

Chevy 305 Bore-3.7 Spacing-4.4

So, I think I'll get some head gaskets to see how much the 3.0L is off, I'm a little hesitant cause they are the slowest engine I've ever heard of but they should line up well. The 4.6 is DOHC so unless I want to rework the block I think I'll avoid that for right now. Last the 305 wasn't a strong motor either, but like the last 2 choices they are more plentiful than the hemi and the numbers are better on our side. I really would like to do a flow head cause it will be easier on turbo set up I'm planning. Thanks for your time.
Author:  heckshemi [ Fri Jan 18, 2008 9:44 pm ]
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Quote:
Quote:
what are the screws above the exhaust ports for? what about the bar along the bottom of the headers?
.... those are what you use when you have a sawzall n drillpress...but no welder.
You're right, this head is not welded, it's glued together!
I once read about someone who epoxied a head together so I thought I'd try it.
I'm going to start another head and I will give step by step details. Now I'm trying to get this one finished. Building the exhaust..... neighbors may not like the open headers :)
Author:  slantzilla [ Fri Jan 18, 2008 9:45 pm ]
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The stock head is not the limiting factor to Slant performance. You can make an iron head work way better than any street car can use, and with a lot less hassle than cutting up heads and reassembling them.

:shock:
Author:  Joshie225 [ Fri Jan 18, 2008 10:29 pm ]
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I have to disagree on this. The cylinder head is the single largest impediment to power production followed by bottom end strength. Because the 225 is so undersquare it's strangled by the small valves and small ports that accompany them. Even with a cam of 230° at .050" tappet rise the torque starts falling off early and so big horsepower numbers are hard to achieve. I feel it is quite easy to see how efficient an engine breathes by looking at the specific torque (ft/lbs per unit of displacement) and the engine speed for peak horsepower. The single overhead cam Dodge and Jeep 3.7L V6 is the closest modern Chrysler engine to the 225 slant. Sure its a V6 and is OHC, but it's still only 2 valves per cylinder, and doesn't have variable valve timing or an active intake manifold. The 3.7 V6 is 210hp at 5200 and 235 ft/lbs at 4000 RPM. For the sake of argument the 225 slant 6 is 145hp at 4000 and 215 ft/lbs at 2400 RPM. The 20 ft/lb torque increase isn't very impressive, but because the cylinder head and everything that goes along with it breathes so much better the torque can carries to a much higher RPM and we get 45% more horsepower. To make a slant belt out a true 210hp significant sacrifices in idle quality and low end torque must be made.
Quote:
The stock head is not the limiting factor to Slant performance. You can make an iron head work way better than any street car can use, and with a lot less hassle than cutting up heads and reassembling them.

:shock:
Author:  runvs_826 [ Fri Jan 18, 2008 11:02 pm ]
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Joshie225 have you played with v8's? Just curious cause that's what I was kinda taught on and you named exactly what I was taught as far as performance and how to make hp. Unfortunately, the slant six is a diffrent animal and slantzilla is more correct. The valves are a limitation of the bore not the head which I think you meant. Next the ports are small, but you want a small cross-sectional area to improve torque and lower rpm which is a stength of the slant. Last, the slant like many inline sixes suffers from having the flow make a horrible 360 bend to leave the head, unlike v8's or rb26det where it's a flow through design.
With the slant of the engine it isn't entirely impractical to have a flow through design, however, for me that is exactly what I want. So it will be that and aluminum instead of iron. Last, I don't expect the ports to be much bigger, but hey maybe Ford got something right.
The new 3.7's hp is taken at a higher rpm which is a key factor for horsepower, so for the slant I would think it would be the more natural long stroke stealing horsepower not the head. Maybe some more ideas will get passed around.
Author:  Joshie225 [ Sat Jan 19, 2008 1:35 am ]
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I've played with both the slant and V8s. A small port can work well if it's efficient enough, but you still need a certain cross section to keep the velocity low enough. I know everyone says keep the velocity up, but at the other end of the spectrum the velocity will only go so high before choking off flow.

The valves are limited in size by the bore and the ports are limited in size by by the valves. Making the port too large in relation to the valve curtain area only hurts torque.

The head not being cross flow isn't the big problem. It's still a wedge like a 318 or 340. The gases don't care if they enter and exit on the same side of the cylinder head. If you want real cross flow scavenging the valves have to be opposite each other like a hemi or pent roof combustion chamber. Scavenging like that can good for power, but for emissions and economy it's easy to have too much.

You bring up stroke in a little different light than me. Here's something to chew on. The Datsun L28 is the longest stroked version of the gasoline Datsun L6s. The bore is slightly larger and the stroke slightly shorter than our shortest stroke slant 6 the 2.8 liter 170. They also have marginally larger intake and exhaust valves at 1.65" and 1.38". Datsun built a free revving sports car engine. We have an over stroked, under valved truck engine.

Because of the geometry of the engine a 225 will always be handicapped, but a better cylinder head will make more power.
Author:  runvs_826 [ Sat Jan 19, 2008 10:52 am ]
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Actually that was pretty good info Joshie. I can completely agree with you on the Datsun page. My dad had a 240z that would run away from my uncle's 340 challenger like it was standing still. So the stroke can be a problem, but I defintley think there is way's of destroking it a little. A thought though, my uncle's new 440 small block has a stroke real close to mine and they spin that 7000rpm. I'm not knowlegable enough to know how, or if it's just a case of enough money into an engine will make it do anything.
The head could defintley see improvements, larger ports were some of the most fundamental lessons taught to me by the engine builder I learned off of. Besides the idea of "more fuel, makes more power" their was swirl patterns and flow and all sorts of info which lead into my second comment about the flow direction. The old chevy inliners had a special head where it was cross flow and same with the Ford guys. Now I have to agree the most major improvements will be made by the hemi design or the canted valves in particular, but there's got to be some ground covered from having the flow through design, right?
Either case it's been great swapping info, thanks for the enlightenment.
Author:  AndyZ [ Sat Jan 19, 2008 11:27 am ]
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My dad had a 240z that would run away from my uncle's 340 challenger like it was standing still. :shock:

[quote][/quote]
Author:  sandy in BC [ Sat Jan 19, 2008 11:31 am ]
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I dont care if Franks head swap makes a million HP or 145hp it is ever so cool. ....and we all know uncool hp is only half as fast as cool hp. Thats how a HyperPac manifold works.....

I once assisted in a Devcon repair on a 300PSI air cylinder supply line for the bow door on a BC Ferry.....lasted till refit. We used gauze bandages and cans of Devcon....I got to mix and spread.

Frank...you are my hero today....and that other day last week.....
Author:  AndyZ [ Sat Jan 19, 2008 12:32 pm ]
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Thats why a slant 6 that runs under 14 seconds is cooler than a V8 that can. 8)
Author:  sandy in BC [ Sat Jan 19, 2008 12:57 pm ]
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Quote:
Thats why a slant 6 that runs under 14 seconds is cooler than a V8 that can

That Chrysler Fire Power valve cover goes nicely with the Canadian "Valiant by Chrysler" tag on the trunk. ~Cool>

"Thats a Valiant , by Chrysler!"

The epoxy disclosure makes the antifreeze and oil leaks seem more important.
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