installed spring height question

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Aug 17, 2011 | 03:50 PM

3rdCoastPowerSports

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From: Loony Bin

installed spring height question

i have a tsp233/239 cam that requires 150lbs of seat pressure. I have a set of slightly used PRC dual springs (.650). i put the retainer on the springs and put the spring in the valve spring tester. @ 1.800 i get 125lbs seat pressure, @1.75 i get 150lbs of seat pressure. so obviously i want the spring installed height to be 1.75 so i get 150lbs of seat pressure (fyi @ 1.75 installed height i have a 60 thousandths tollorance before coil bind, is that ok?). MY question is when setting up the spring installed height do i measure from the inside of the seat to the inside of the retainer or do i measure to the top of the retainer since the 1.75 installed height measurment was acceived with the retainer on? or do i just minus the outer spring retainer thickness? my brain is turrning and turning

,,, thanks

Aug 17, 2011 | 03:55 PM

Sales2@Texas-speed

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From: Texas!

You have to take into account the .050" retainer thickness AND have the retainer on the spring when measuring pressure on the duals springs. The 233/239 doesn't "require" 150#, and I believe we spoke about this on the phone earlier this afternoon. When measured properly with the retainer in place, you will have about 145#@1.800". That is plenty for that cam, and we've tested and confirmed this on both our engine and chassis dyno many times.

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Aug 17, 2011 | 04:16 PM

3rdCoastPowerSports

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From: Loony Bin

Quote:

Originally Posted by Matt@Texas-Speed

yep we spoke this morning on the phone,,,, i thought you said 150lbs of seat pressure was the requirement for the cam, my mistake.... i undersand that setting a brand new prc dual (.650) spring at 1.800 will get me about 145lbs of seat pressure but as i stated these springs are used,,,, maybe 5,000 miles on them or so, from testing them they seem to have lost 15lbs or so of seat pressure from brand new (when i set it up at 1.800 i only got 125lbs or so of seat pressure and yes i tested with the retainer in place) thats why i was saying to install at 1.75 so i get a higher seat pressure since the springs have lost some tenision.....

is my thinking correct on installing them at 1.75 (since they are not new and have lost some tenison)? if i install at 1.800 that would only get me 125lbs and that doesnt seem like enough.

Aug 17, 2011 | 04:46 PM

Sales2@Texas-speed

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From: Texas!

So with the retainer on, and the top of the retainer at 1.850" you're only seeing 125lbs?? You could also use a dial caliper between the top and bottom pad on the pressure tester, with retainer in place, and see what the pressure is when the caliper shows 1.800". It will not be quite as accurate on height as the micrometer is, but it will get us pretty close!

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Aug 18, 2011 | 01:33 AM

3rdCoastPowerSports

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From: Loony Bin

ok i re-checked the springs. at a spring height of 1.800 (1.850 if measuring from base of spring to top of retainer) i get roughly 141 LBS of seat pressure. if i install them at a height of 1.780 (just measuring the spring not the spring and retainer) i get 145lbs of seat pressure..... sounds good to go to me... What do you think matt? thanks for the help by the way

Aug 18, 2011 | 04:26 AM

vettenuts

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From: Little Rhody

In a nutshell, the spring installed height is measured from top to bottom of the spring itself. So the measurement is taken from the top of the seat to the bottom of the retainer. A spring height micrometer is a good investment when taking these measurements. I usually set up a spreadsheet and record the installed height then compute installed force, open force, clearance to coil bind, clearance between the retainer and seal, etc. I have also found that stock heads usually set up less than 1.800" and typically come in at approximtately 1.765".

Aug 18, 2011 | 10:43 AM

3rdCoastPowerSports

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From: Loony Bin

Quote:

Originally Posted by vettenuts

I usually set up a spreadsheet and record the installed height then compute installed force, open force, clearance to coil bind, clearance between the retainer and seal, etc. I have also found that stock heads usually set up less than 1.800" and typically come in at approximtately 1.765".

you do all that without a spring tester (big vice looking unit)? if so please send me the formulas and your method so i can do the same. A buddy who owns a machine shop let me use his big spring tester machine. out of the 16 springs 2 of them checked a little weaker (roughly 5 lbs lighter) so i am going to use a .030 shim on those 2 so they are exactly equal to the rest.