Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 02-12-2021, 04:53 PM   #1
Seabees
Senior Member
 
Join Date: Jul 2017
Location: Eastern Oregon
Posts: 202
Default valve spring tension

Howdy boys, I have a question for you "Experts"! In Les' book, he states valve spring tension should be 60lbs (+/-3) at 2.5" compression. At 2.75" compression it should be 36lbs. After speaking with Joe at Snyders, wondering why the new sets I bought tested at 40lbs at 2.5", he informed me that the original Ford specs calls for 40lbs. I called my good buddy Jim Brierley, who has built more engines than I ever hope to, and asked him what he thought. His figures say at 2.375", the compression pressure should be 38-40lbs. So, what is Les referring to when he is stating the spring tension at 2.5" compression should be 60lbs? I did try to call Les, but no answer. I left a message. I'm sure he's a very busy guy, which I understand. Thought I'd put the question to you guys. OK engine builders, what say you?
Seabees is offline   Reply With Quote
Old 02-12-2021, 05:54 PM   #2
d.j. moordigian
Senior Member
 
d.j. moordigian's Avatar
 
Join Date: May 2010
Location: Fresno, Ca.
Posts: 3,636
Default Re: valve spring tension

To do it correctly, you need a spring checker..!

1. New springs will loose about 10# in just running them for the first time..
2. Install the valve with the retainer (NO spring) and measure too a 1/64"..
3. Then check the spring in the checker and shim too that height, what ever pressure that
you need / want..

I've used this method for OVER 55 years...it works every time. Remember this,..the
lifter and valve NEEDS to follow the cam lobe, too run properly..
d.j. moordigian is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 02-12-2021, 11:04 PM   #3
Seabees
Senior Member
 
Join Date: Jul 2017
Location: Eastern Oregon
Posts: 202
Default Re: valve spring tension

Thanks D.J. No. 2 in your answer is a bit confusing to me. What am I measuring? I do have a "spring checker". That's why I know the springs I have are 40lbs at 2.5" compression. Again, my question is, what compression pressure should they be at 2.5" compression? 60? 40? Thanks.
Seabees is offline   Reply With Quote
Old 02-12-2021, 11:08 PM   #4
700rpm
Senior Member
 
700rpm's Avatar
 
Join Date: May 2010
Location: Portland, Oregon
Posts: 5,892
Default Re: valve spring tension

Boy, you guys put a lot more thought and worry into this stuff than I do. If my engine is otherwise majorly rebuilt by respected people and sources, (new babbit, rings, pistons, valves, seats and guides, etc.,) I buy new springs from Snyder’s or Bratton’s, install ‘em, set clearances, and go. That’s been my Modus Operandi for over fifty years with no problems involving spring pressure. The spring’s job is to return the valve to the cam. If it doesn’t do that, it’s more likely to be a sticky valve due to bad guide, a bent valve (very rare), or a broken spring, or something else, but not spring pressure. 60#? 40#? I don’t know and don’t care and never have. Sometimes too much information creates unnecessary problems, and sometimes ignorance is bliss.
__________________
Ray Horton, Portland, OR


As you go through life, keep your eye on the donut, not the hole.

Last edited by 700rpm; 02-12-2021 at 11:17 PM.
700rpm is offline   Reply With Quote
Old 02-12-2021, 11:37 PM   #5
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 2,332
Default Re: valve spring tension

This came up once before in this thread. They didn't really get to a conclusion, but they did establish that 40 lbs @ 2.375" was quite common among springs that were tested. No one was sure where Les got those numbers. Something that tends to muddy the waters further is that the standard one-piece replacement valve guides lack a shoulder, which alters the installed length of the springs and thus their operating pressure. Some folks compensate by adding shims/spacers, while others compensate by changing to stiffer springs.
alexiskai is offline   Reply With Quote
Old 02-13-2021, 12:09 PM   #6
katy
Senior Member
 
katy's Avatar
 
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,011
Default Re: valve spring tension

Sponsored Links (Register now to hide all advertisements)
[QUOTE=d.j. moordigian;1984857]To do it correctly, you need a spring checker..!

A drill press and a bathroom scale will suffice.
__________________
If you don't hear a rumor by 10 AM, start one!.
Got my education out behind the barn!
katy is offline   Reply With Quote
Old 02-13-2021, 08:15 PM   #7
Jim Brierley
Senior Member
 
Join Date: Jun 2010
Location: Temecula, CA
Posts: 4,066
Default Re: valve spring tension

Katy, Amen!
Jim Brierley is offline   Reply With Quote
Old 02-13-2021, 11:28 PM   #8
Seabees
Senior Member
 
Join Date: Jul 2017
Location: Eastern Oregon
Posts: 202
Default Re: valve spring tension

Jim, She'd never let me use it!
Seabees is offline   Reply With Quote
Old 02-14-2021, 12:49 AM   #9
johnneilson
Senior Member
 
Join Date: Jun 2010
Location: 34.22 N 118.36 W
Posts: 1,044
Default Re: valve spring tension

Tell her you are checking the calibration

J
__________________
As Carroll Smith wrote; All Failures are Human in Origin.
johnneilson is offline   Reply With Quote
Old 02-15-2021, 03:49 PM   #10
d.j. moordigian
Senior Member
 
d.j. moordigian's Avatar
 
Join Date: May 2010
Location: Fresno, Ca.
Posts: 3,636
Default Re: valve spring tension

Quote:
Originally Posted by Seabees View Post
Thanks D.J. No. 2 in your answer is a bit confusing to me. What am I measuring? I do have a "spring checker". That's why I know the springs I have are 40lbs at 2.5" compression. Again, my question is, what compression pressure should they be at 2.5" compression? 60? 40? Thanks.
You are measuring the "installed height" of the valve stem and the retainer.
With that figure you measure the spring, in your spring checker, and that will
give you the spring pressure with the valve closed. This is done with the valve
in the block / head...make sense now...?
d.j. moordigian is offline   Reply With Quote
Old 02-15-2021, 04:02 PM   #11
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 2,332
Default Re: valve spring tension

To add more context to D.J.'s reply, the central idea with the spring pressure is that the spring needs to clamp the valve face to the seat when the valve is fully closed – both to keep it from leaking and to facilitate the sinking of heat from the valve into the block. There's a certain target pressure needed to do that.

You need to make sure your spring will deliver that target pressure at a certain length. That length is the "installed height," the total distance between the ends of the spring when it's installed in the valve chamber. It'll be pressing against the retainer at the bottom, and against either the shoulder of the valve guide or the block itself, depending on the type of valve guides you have. This variability is why you should take the length to be tested from your actual engine instead of from a book.
alexiskai is offline   Reply With Quote
Old 02-15-2021, 04:51 PM   #12
johnneilson
Senior Member
 
Join Date: Jun 2010
Location: 34.22 N 118.36 W
Posts: 1,044
Default Re: valve spring tension

Spring rate and installed spring height are two different things.

Seabee' is asking why he has two different spring rates and specs.

Les' specification is more than likely for the "V8" spring, which is a common performance upgrade to the Model "A" springs.

J
__________________
As Carroll Smith wrote; All Failures are Human in Origin.
johnneilson is offline   Reply With Quote
Old 02-15-2021, 05:47 PM   #13
old31
Senior Member
 
Join Date: Jan 2016
Posts: 2,088
Default Re: valve spring tension

I am 100% on board with 700's post#4. I have never given thought to spring tension. Buy the spring and install. But, I am sure checking tension is the correct way.

Now you guys want me to buy a bathroom scale and a drill press. Next thing you will ask me to check MY weight.. GEEEEZ.
old31 is offline   Reply With Quote
Old 02-15-2021, 07:28 PM   #14
Seabees
Senior Member
 
Join Date: Jul 2017
Location: Eastern Oregon
Posts: 202
Default Re: valve spring tension

Ok guys, now we're getting somewhere. Thank you Mr. Nelson! It looks to me that, 40# on my spring checker, at 2.5 inches, is where I want to be. And thanks to you also, D. J. and Alexiskai, I will check the installed height and see what I get. My biggest concern with all of this is of course, I don't want to have to pull the damn apart again! Although, each time I do, it's a new learning experience! Thanks guys, I appreciate the help. I'll let you know how it turns out. It appears this engine has gotten hot at some point in it's long life, and the springs are what I feel are the problems with it running correctly. Yeah, I've check the carb and dist, numerous times. It ain't that! Timing gear is fine also. I'll keep you posted.
Seabees is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 02:55 AM.