Author Topic: Why not use 5/16" valve stems in performance builds?  (Read 1198 times)

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dozz302

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Why not use 5/16" valve stems in performance builds?
« on: September 25, 2022, 10:22:47 PM »
Hello, I was reading some of the FE builds and they were using 11/32" valve stems. Why not go down to a 5/16" stem like the Hemi's?

jayb

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #1 on: September 25, 2022, 10:54:28 PM »
No reason not to.  My heads use 5/16" stem valves.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

TomP

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #2 on: September 26, 2022, 12:18:58 AM »
I used 5/16 stems in my TunnelPort heads back in the 80's. SI brand stainless 426 Hemi sized 2.25" intakes and BB Chev .100" extra long 1.88" exhausts which had to be cut down in diameter to 1.80". I can't find my book where I wrote the weights down but as I recall they were close to the stock hollow stems for weight.

blykins

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #3 on: September 26, 2022, 04:35:39 AM »
We do. 

Doing a Tunnel Port with 5/16" valves right now. 

I also do quite a few builds with 7mm stuff.

There's not a tremendous amount of flow difference with the small stem stuff, but on a build with longer, heavier valves (like Jay's heads), or a high rpm engine, the weight savings helps quite a bit.
« Last Edit: September 26, 2022, 04:39:42 AM by blykins »
Brent Lykins
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Barry_R

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #4 on: September 26, 2022, 07:16:26 AM »
No reason at all.  The only reason I use 11/32 is market acceptance.  It's hard enough talking "old school" guys out of 3/8 stems.

MeanGene

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #5 on: September 26, 2022, 07:47:21 AM »
We put 426 Hemi valves in when I built my buddy's 70 Boss 302 in '79- work done by Hannan's in Hayward

Joe-JDC

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #6 on: September 26, 2022, 10:01:59 AM »
I use 5/16" valves whenever possible, but I have run into an issue that has me stumped with them.  As some of you know, I entered a Y Block in the EMC competition a couple of times, and on the iron headed engine, I tried three different sets of heads with different valves and spring combinations.  On one set with the lightweight 5/16" valves that were +.200" SBC, the lash would go away on a dyno pull with the oil temperature at peak, water temperature high.  When the engine cooled off, the lash returned.  The stems were growing enough to take all the lash out with heat.  No tuliping, no seat erosion, no guide wear, no measurable loss of horsepower unless I did a back to back pull.  Tried everything with adjustment, changed heads, problem went away.  Still don't understand why that set of valves did that.  Inferior metal or not heat treated properly was our guess.  Joe-JDC 
Joe-JDC '70GT-500

pbf777

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #7 on: September 26, 2022, 01:30:01 PM »
No reason at all. 

The stems were growing enough to take all the lash out with heat.    Still don't understand why that set of valves did that. 


     Note that with the reduction in diameter so goes the circumference surface area, and at some point in the adoption of smaller stem diameters this isn't going to prove adequate to support the valve in the guide leading to higher specific loading, this causing displacement of oil film thickness and the corresponding expected excessive wear rates; and although we might find this an acceptable tradeoff remember in comparison to O.E.M. production intended applications, in this field we don't generally rack-up the mileage.  And also don't forget that some of the heat acquired by the valve is intended to be transferred to the engine cooling system thru the stem to guide relationship, and with loss of this surface area here and it's interaction in this function one might expect the valve to run hotter in operation!   ;)

     Scott.

Dr Mabuse

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #8 on: October 31, 2022, 08:44:48 PM »


The stems were growing enough to take all the lash out with heat.    Still don't understand why that set of valves did that. 


     Note that with the reduction in diameter so goes the circumference surface area, and at some point in the adoption of smaller stem diameters this isn't going to prove adequate to support the valve in the guide leading to higher specific loading, this causing displacement of oil film thickness and the corresponding expected excessive wear rates; and although we might find this an acceptable tradeoff remember in comparison to O.E.M. production intended applications, in this field we don't generally rack-up the mileage.  And also don't forget that some of the heat acquired by the valve is intended to be transferred to the engine cooling system thru the stem to guide relationship, and with loss of this surface area here and it's interaction in this function one might expect the valve to run hotter in operation!   ;)

     Scott.
[/quote]

I was wondering why guide wear and heat transfer was not mentioned in prior posts.

It reminded me of a time I took some FE parts to an aviation instructor friend's classroom, to have them checked for cracks - the students were amazed at how thin the 3/8" valve stems were. I was surprised at how thick the 1/2" Lycoming engine valve stems were in comparison!

Those 1/2" stems could certainly transfer more heat through their guides. Mandatory aviation engine rebuilds probably come way before engine wear beomes critical.

machoneman

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #9 on: November 01, 2022, 09:16:58 AM »
And many a radial aircraft engine had sodium filled exhaust valves to aid in heat transfer. Regular replacement was the order of the day when a mandatory teardown was performed. Ford had the right idea when FE valves with sodium were brand new. Yet most here know that as they aged, the sodium weakened the stems and literally broke.

Btw, I never read, saw, heard that GM nor Chrysler ever used OEM sodium valves. Anyone know?
« Last Edit: November 01, 2022, 11:19:50 AM by machoneman »
Bob Maag

GerryP

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #10 on: November 01, 2022, 11:35:21 AM »
...

Btw, I never read, saw, heard that GM nor Chrysler ever used OEM sodium valves. Anyone know?

Not from "back in the day" when Ford was using them.  But more modern engines used sodium filled exhausts.  The GM LS7, and the GM LNF (2.0 turbo Saturn and Pontiac Solstice).  I'm sure there are probably other examples but those two come to mind.

machoneman

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #11 on: November 01, 2022, 05:16:19 PM »
Thanks. I thought correctly in days of yore only Ford used sodium valves.

I wonder then as noted how any modern engine overcomes sodium etching inside the stems and eventually fails. Is it the SS construction? Or some kind of coating before the steel pads are welded to the valve tips?

Bob Maag

winr1

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #12 on: November 02, 2022, 10:54:11 PM »
Any weigh the difference of weight between the different valves, larger stems to smaller ??

................

"Posted by: blykins
« on: September 26, 2022, 04:35:39 AM »Insert Quote
We do.

Doing a Tunnel Port with 5/16" valves right now.

I also do quite a few builds with 7mm stuff.

There's not a tremendous amount of flow difference with the small stem stuff, but on a build with longer, heavier valves (like Jay's heads), or a high rpm engine, the weight savings helps quite a bit.
...............

Brent, what about a street FE that does an occasional blast ....can ya correlate valve weight, cam specs/rpm to spring pressure ??



Ricky.


blykins

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Re: Why not use 5/16" valve stems in performance builds?
« Reply #13 on: November 03, 2022, 05:00:00 AM »
Any weigh the difference of weight between the different valves, larger stems to smaller ??

................

"Posted by: blykins
« on: September 26, 2022, 04:35:39 AM »Insert Quote
We do.

Doing a Tunnel Port with 5/16" valves right now.

I also do quite a few builds with 7mm stuff.

There's not a tremendous amount of flow difference with the small stem stuff, but on a build with longer, heavier valves (like Jay's heads), or a high rpm engine, the weight savings helps quite a bit.
...............

Brent, what about a street FE that does an occasional blast ....can ya correlate valve weight, cam specs/rpm to spring pressure ??



Ricky.

Absolutely. 

This is why guys were hitting 5500 rpm walls with hydraulic rollers 15 years ago.   They were porting heads, using 3/8" stem valves that were now 2.150"/2.190"/2.250", and using the same cam lobes that the SBF/SBC guys were using.  "My FE won't rev over 5500!  Hydraulic rollers are junk!"  Then they would add spring pressure to try and make it work, then overcome the hydraulic function inside the lifter and make things worse.  FE's have some of the heaviest valves out there, including the BBC.  The length, coupled with a thick stem, coupled with a big head diameter is just a big no-no. 

Any time you can reduce valvetrain weight, you are doing yourself a big favor.  You can use a more aggressive cam lobe and you can do it with lower spring loads.   Ten years ago, Cup guys were using 6mm-7mm hollow stem titanium valves with non-adjustable rocker arms on solid roller camshafts.  They were turning 9800 rpm with just 400-450 lbs over the nose.   Not saying everyone needs to run 6 and 7mm titanium valves, but the relativity is there. 
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
Instagram:  brentlykinsmotorsports
YouTube:  Lykins Motorsports