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 Checking spring height/pressure
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Merrik66
Cochise

USA
373 Posts

Posted - 14 Oct 2014 :  10:31:52 PM  Show Profile  Reply with Quote
I've got a set of rebuilt heads which have sat for some time...accumulated a bit of surface rust. The guy I bought them from didn't remember what springs were used...had been over 15 years. I've dissasembled them to have them cleaned. kept track of all valve/parts/locations. My question is...how do I measure to find out what pressure at what height the springs may be? Hope that makes sense. Btw, nothing looked aftermarket as far as valvetrain goes. He had new iron guides put in. Seats look good.

cortcomp
Coyote

USA
5338 Posts

Posted - 14 Oct 2014 :  10:55:37 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Take to a machine shop, cheaper than getting a spring measurement thingymajig to use one time. Tell them your lift, and your installed height, they should be able to tell you.

Edited by - cortcomp on 14 Oct 2014 10:59:43 PM
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Merrik66
Cochise

USA
373 Posts

Posted - 15 Oct 2014 :  03:02:45 AM  Show Profile  Reply with Quote
Cort, I had thought about that. But I've got several sets of heads...various conditions. The ones in this thread are "66" and on a different thread I had some questions about some "16's". I've got a snap on grinder surfacer and a bunch of related head rebuilding tools. I thought it might be fun to learn how to set up a set of heads in its entirety including setting up proper spring height etc. The portable tool seems to run between about 80$ to 120$ and I thought might work well for just understanding the procedure. I've got a good drill press that I use a piece of 5/8 stock in the chuck to apply pressure...NOT running of course :) Understanding the relationship between the lift of a cam and what it would demand for spring pressure at certain rpms sounds kinda cool to get into. your point is good though, If I had just one engine and that was all I was going to do..yeah..for sure..just have a shop take care of it.
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Steve C.
Crazy Horse

1677 Posts

Posted - 15 Oct 2014 :  09:53:38 AM  Show Profile  Reply with Quote
The "thingymajig" thing many shops use is a Rimac machine used to measure valve spring pressure.

As suggested by cortcomp make sure you measure the installed height and have on hand the actual retainers you will be using.
The spring with it's retainer installed is compressed to the exact installed height and the resultant seat pressure is indicated.

You might find this of interest....

Commonly asked valve train questions
Page 356 here:
http://www.cranecams.com/uploads/catalog/Crane%20Cams%20Master%20Catalog.pdf

Edited by - Steve C. on 15 Oct 2014 09:55:01 AM
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Steve C.
Crazy Horse

1677 Posts

Posted - 15 Oct 2014 :  10:01:12 AM  Show Profile  Reply with Quote
Related topic.

For those who are in the process of selecting a set of valve springs, or have a new set on hand for installation.
What ever spring you choose, or have, be sure you uses a valve spring tester to varify the exact amount of pressure at the intended installed height. DO NOT ASSUME the springs will be XXX seat preassure at XXXX installed height just because the specification sheet says so. Example, I had a set of Lunati springs for a solid roller application that were rated at 200 lbs seat pressure at 1.850 installed height and when checked they ended up way above the 200 lbs. pressure at 1.850". They ended up installed at 1.920" installed height with 219-220 lbs seat pressure. This was not an isolated case for these piticular springs as we found two more sets of the same springs on the shelf that measured 230 lbs at 1.900".
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Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 15 Oct 2014 :  11:37:11 AM  Show Profile  Reply with Quote
buy new springs for your build specks, have them checked, then throw those old springs away.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 15 Oct 2014 12:12:52 PM
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Merrik66
Cochise

USA
373 Posts

Posted - 15 Oct 2014 :  6:05:28 PM  Show Profile  Reply with Quote
Thanks Steve and BP. Will use your input/advice
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