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Evolving the Side valve flat head design idea

Engine tech, for those engines, products, and technologies of yesteryear.

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Pete1
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Re: Evolving the Side valve flat head design idea

Post by Pete1 » Fri Jul 31, 2020 10:36 pm

I often wonder why H-D when they had an almost unlimited development budget, didn't think about bigger ports and valves.
While bigger is sometimes slower flow with N/A, on a flathead Ford it means more hp if the volume goes up. We did flow testing back in the late 50's with
ports enlarged by welding steel tubing in machined out blocks and the bigger we went the bigger the dyno numbers.
Ron Main found this in later years by going over 300 with a flathead.

Truckedup
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Re: Evolving the Side valve flat head design idea

Post by Truckedup » Sat Aug 01, 2020 5:57 am

Big HP numbers at the expense of a wider power band might not be the best for dirt flat racing done in one gear...

jed
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Re: Evolving the Side valve flat head design idea

Post by jed » Sun Aug 02, 2020 5:21 pm

I was thinking the same thing. Large intake ports and valves would work good at Bonneville but not so well on a short
track engine.

Pete1
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Re: Evolving the Side valve flat head design idea

Post by Pete1 » Sun Aug 02, 2020 7:03 pm

jed wrote:
Sun Aug 02, 2020 5:21 pm
I was thinking the same thing. Large intake ports and valves would work good at Bonneville but not so well on a short
track engine.
I would agree normally but I only have data on large flatheads, 315 ci or more. Nowdays 321. It works.

jed
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Re: Evolving the Side valve flat head design idea

Post by jed » Sun Aug 02, 2020 9:08 pm

Are these engines NA??? From the data you have you give us a us intake valve size, the throat size, where is the choke point,
the adverage CSA, how big in cc's are the intake block ports, the length of the intake port from intake seat to the plenum
or the end if the injector stack, are the valve seats sunk or raised, a 45' seat angle, gas or alcohol, compression.
what about exhaust valves, ports ECT. Are the Pistons dome and what shape.
I know lots of questions just thought I would ask. lol

frnkeore
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Re: Evolving the Side valve flat head design idea

Post by frnkeore » Tue Aug 04, 2020 3:12 am

I've got a question about the FH Ford engines:

Knowing that the flow is blocked to the rear of the valve and that to keep compression up, that you need to have no more than .040, from the top of the valve, to the top of the cyl head, the valve curtain won't have much more than a 180 deg, effective area, because of the contour of the rear part of the head, that wraps around the valve.

It's common to put 1.6 in & ex valves, in these engines BUT, the intake ports are very hard to increase flow. The ports are only 1.312, in diameter and very hard to open up, in the middle area. The bottom of the bowl, is only about 1" in diameter but it an be opened a little.

The actual question is, if you install 1.72 SBC valves on the intake side and open the bowl, as much as is practical, will the larger diameter of the curtain, make up for some of the lack of flow, around the back side of the valve. Will it make a noticeable increase in flow, just because it has more curtain area?

I know that it won't increase the CSA of the port, itself but, would it allow the port to flow more of it's potential with it's wider curtain?

1.72 valves, have been put into these engine but, I have never seen or heard of HP or flow improvements with their use. I had always though of it as useless, because of the CSA of the port but, now I wonder if the curtain improvement, by itself will help flow.

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