Negative cant cylinder head

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Ratu
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Negative cant cylinder head

Post by Ratu » Mon Oct 02, 2017 11:00 pm

Good afternoon everyone! Bright and sunny with a gentle fresh breeze. Spring is sprung!

I have been on holiday travelling about the show for the week. This time I was on a train and had plenty of time to read (and admire the most excellent scenes we passed through). I came across something unusual. It was in cylinder heads design.

I came across reports and commentary about Ford pro-stock cylinder-heads. There were A460, B460 types and more besides. There was even a type known as “bastard pro-stock” (I’m serious, that appears to be the real name). The development rate seems to have been high, as different variants were prepared in succession. There was even an “experimental” tunnel port version.

There are some significant alterations in the layout of the different cylinder heads. Originally the valve angles were 13 degrees by 5.2 degrees cant on the inlet valve and 9 ½ degrees by 5.2 degrees cant on the exhaust valve. Later versions had 17 degrees by 6 degrees cant on the inlet valve and 4 degrees by 3 degrees cant on the exhaust. There was a 14 degrees by 4 degrees cant inlet and 4 degrees by 3 degrees cant exhaust next. Last came the “bastard” cylinder head type and this was different. Its valve angles were 11 degrees by – 1 ½ degrees cant (a negative value!) on the inlet and 3 degrees by 4 degrees cant on the exhaust. So there was a negative cant for the inlet valve. That is very unusual.

If I understand correctly a negative cant for the inlet valve means it is moving away from the cylinder centreline (in the cant direction) and also away from the exhaust valve axis. It would seem to be slightly pointing flow towards the cylinder wall. The head was successful in competition, so it worked. What I was hoping to find was a picture of the head and also why negative cant was employed. What was the reasoning behind doing negative cant?

Comments?

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Re: Negative cant cylinder head

Post by pdq67 » Tue Oct 03, 2017 6:36 am

Sorry, donno?

pdq67

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Re: Negative cant cylinder head

Post by Carnut1 » Tue Oct 03, 2017 6:58 am

lngblkpic.jpg
Not exactly a performance application. I dug this pic up off internet. My first legal to drive, hotrod and blowup ride 1968 Scout 800 with 196 ci four. Had a reverse cant to the intake and a interesting piston dome/sump piston top. Very low profile ports. Thanks, Charlie
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mag2555
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Re: Negative cant cylinder head

Post by mag2555 » Tue Oct 03, 2017 7:05 am

There could have been many reasons for that change
It may have been called for by bigger valve size?
A change in valve spacing?
It would have for sure increased swirl which would have likely been better for burn rate.

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Re: Negative cant cylinder head

Post by peejay » Tue Oct 03, 2017 5:43 pm

Force the chamber to be concentrated to the exhaust side?

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Re: Negative cant cylinder head

Post by Carnut1 » Tue Oct 03, 2017 6:33 pm

016pspic.jpg
images.jpg
International 152,196, 304, 345, 392 chamber reverse cant and pop up/ sump head pistons. Not a high performance design but interesting. I remember as one of my first hot rodding ventures that I didn't understand the design, about 35 years later and I still don't understand it. Ports were very low and small, 3/8" stem valves sodium exhaust valves if my memory is correct. I would love some insight into this design. Thanks, Charlie
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Re: Negative cant cylinder head

Post by englertracing » Tue Oct 03, 2017 6:59 pm

I don't see the reasoning behind the negative cant but the chamber/piston on that is quite interesting.

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Re: Negative cant cylinder head

Post by Carnut1 » Tue Oct 03, 2017 10:20 pm

download (2).jpg
DCP_0097.jpg
More internet pics of same International engine family. Exhausts are ported in the head pic. Cutaway shows how flat and wide the port is intakes were also flat and wide. I remember in one of my engineering books that the lower port gave much better low lift flow. If low lift flow boosts torque up to let say 4000 rpm ( about all this engine family could muster.) the reversed cant chamber could aid in windowing the flow right past the insane ssr and directly across the intake valve face. Thanks, Charlie
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Re: Negative cant cylinder head

Post by Schurkey » Tue Oct 03, 2017 10:46 pm

Carnut1 wrote:
Tue Oct 03, 2017 6:33 pm
016pspic.jpgimages.jpg International 152,196, 304, 345, 392 chamber reverse cant and pop up/ sump head pistons. Not a high performance design but interesting. I remember as one of my first hot rodding ventures that I didn't understand the design, about 35 years later and I still don't understand it. Ports were very low and small, 3/8" stem valves sodium exhaust valves if my memory is correct. I would love some insight into this design. Thanks, Charlie
Are they canted? I thought the intake was flat, the exhaust was angled, but no cant..

Overall, I think it's very much like the Jaguar V-12 "Fireball" cylinder head done by Michael May for '81 (?) as well as the ancient Chevy inline 6.
Image

Huge amount of quench, promotes turbulent combustion directly under the exhaust valve. As I hear it, the engine can be run with high compression, and very lean--yet still make power and survive. Problem is that lean running doesn't make for an emissions-compliant vehicle.

Tiny ports and mild camshaft make for good low-speed torque, but function as a designed-in "governor" on vehicles that are known to run WFO (and probably well beyond their GVWR) from farm to elevator.

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Re: Negative cant cylinder head

Post by mag2555 » Wed Oct 04, 2017 6:51 am

I have seen a lot of those international motors in stationary power gen's and as I recall they held the load darn good even at only 2000 rpm, and talk about a air gap Intake Manifold!

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Re: Negative cant cylinder head

Post by Carnut1 » Wed Oct 04, 2017 6:58 am

Mag I tend to agree, I think the design was for lower rpm torque and that was what they did. Don't bother twisting them fast, nothing there. Think industrial durability. I remember when I sold my scout 800 I gave away an extra engine ( bought another scout to replace the weak t-90 tranny that I crunched) and the guy who bought it stated you will never wear out the original engine so why an extra? Thanks, Charlie
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