The Ford Barn

Craig CT · 01-19-2020, 09:56 AM

000

JWL · 01-19-2020, 11:03 AM

The valve stem does not influence ramp speed or duration. Those changes must be imparted at the cam lobe.

Ol' Ron · 01-19-2020, 04:52 PM

Using a split guid ans early valves in an 8BA engine cam be done. However this lwould lead to more oil seeping into the combustion chamber thru the valve stem. Bad Idea.

Pete · 01-19-2020, 06:18 PM

Quote:

Originally Posted by Craig CT

The mushroom valves have less diameter and split guides. Has anyone used them on an 8BA performance cam to affect ramp speed, duration or anything else. Thanks in advance, Craig.

I have never done it that way but you definitely could do it to increase port flow
only. In the olden days 1.625 head diameter mushroom stem valves were available. They came with the head undercut, the port exposed part of stem reduced diameter and polished for lighter weight and improved flow.

Bored&Stroked · 01-19-2020, 08:05 PM

I'm not a big fan of the split guides - due to the larger opportunity for movement/slop in the guide bore and around the stem - as well as side-to-side misalignment on the stems, etc.. I used to run custom 5/16 valves in my race flatheads (with split guides) - and they well Hell on the stems.

But, if one is looking for optimal port flow, one could just sleeve the late 49-53 guides for 5/16 or 8mm stems - such that you can run valves with smaller stems. Of course you'd probably also have other "features" on your custom valves - to provide less restriction in the port and deliver better flow (especially at low lift).

But that whole discussion heads down the path of high-end race modifications . . . which we could ponder until the cows come home! LOL

Craig CT · 01-19-2020, 11:12 PM

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Quote:

Originally Posted by Craig CT

The mushroom valves have less diameter and split guides. Has anyone used them on an 8BA performance cam to affect ramp speed, duration or anything else. Thanks in advance, Craig.

Hello again; I cited the lesser diameter stem and split guides as the known weak points. It's the much wider stem base that will be affected differently by the ramp and will keep the valve open longer
at the top of the lobe than the 8BA valve.

Pete · 01-19-2020, 11:21 PM

The cam does not ride on the valve tip, as noted above by JWL.

40 Deluxe · 01-19-2020, 11:25 PM

Quote:

Originally Posted by Craig CT

Hello again; I cited the lesser diameter stem and split guides as the known weak points. It's the much wider stem base that will be affected differently by the ramp and will keep the valve open longer
at the top of the lobe than the 8BA valve.

Actually, no! Valve stem width has nothing to with the cam lobe ramps. It is the bottom of the lifter (Ford called them "pushrods") that contacts the cam lobe. All flathead lifters have the same dimensions, whether mushroom valve stems or not!

Ol' Ron · 01-19-2020, 11:48 PM

Know Craig, I think he was talking about a stock engine. However, I usually cut the stems down on SbC valves when I undercut the bottoms

01-19-2020, 09:56 AM	#1
Craig CT Senior Member Join Date: May 2010 Location: Sherman, CT Posts: 336	valve question 000 __________________ " When I was a boy of fourteen, my father was so ignorant I could hardly stand to have the old man around. But when I got to be twenty-one, I was astonished at how much he had learned " Mark Twain. Last edited by Craig CT; 01-20-2020 at 09:09 AM.

01-19-2020, 11:03 AM	#2
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: valve question The valve stem does not influence ramp speed or duration. Those changes must be imparted at the cam lobe.

01-19-2020, 04:52 PM	#3
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: valve question Using a split guid ans early valves in an 8BA engine cam be done. However this lwould lead to more oil seeping into the combustion chamber thru the valve stem. Bad Idea.

01-19-2020, 08:05 PM	#5
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,906	Re: valve question I'm not a big fan of the split guides - due to the larger opportunity for movement/slop in the guide bore and around the stem - as well as side-to-side misalignment on the stems, etc.. I used to run custom 5/16 valves in my race flatheads (with split guides) - and they well Hell on the stems. But, if one is looking for optimal port flow, one could just sleeve the late 49-53 guides for 5/16 or 8mm stems - such that you can run valves with smaller stems. Of course you'd probably also have other "features" on your custom valves - to provide less restriction in the port and deliver better flow (especially at low lift). But that whole discussion heads down the path of high-end race modifications . . . which we could ponder until the cows come home! LOL

01-19-2020, 11:21 PM	#7
Pete BANNED Join Date: May 2010 Location: Wa. Posts: 5,423	Re: valve question The cam does not ride on the valve tip, as noted above by JWL.

01-19-2020, 11:48 PM	#9
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: valve question Know Craig, I think he was talking about a stock engine. However, I usually cut the stems down on SbC valves when I undercut the bottoms