Testing valve spring pressure

Invectivus

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So, I bought a valve spring compression tester, and started going through my spring sets. I have a couple sets that come in at 45-50psi closed, 140/145psi open (with a couple weak outliers). I also have a third set at 70/170.

My fourth set is dual spring, with one piece retainer. The outer spring is 95/160, with the inner spring it's 120/230. That seems pretty high. They may have come with my CI head, i don't remember.

I'm assuming that with a large log, shaved but not ported, there's no reason to go above my 70/170 set, and that might even be overkill?

I also have a couple shim sets.
 
Howdy Invectvus:

I like your thinking and testing spring pressures at both open and closed position. BUt your conclusion may have to consider cam timing, cam lift and rpm range. The good thing about valve springs is that they are relatively easy to change. That's my two cents, for what it's worth.

Adios, David
 
According to the book, anything over 100lbs closed is overkill and is just wear on the cam. I used the ones the book recommended, the 1973 302 exhaust valve springs. they have a 80 lbs closed and like 200 open. As opposed to the stock 54/150
 
Is there a way to tell dual springs from a spring with a buffer?

Also, i have a set of valves that are super shiny, like stainless or chrome. are they likely to be stainless?
 
Invectivus":1v3v670c said:
Is there a way to tell dual springs from a spring with a buffer?

Also, i have a set of valves that are super shiny, like stainless or chrome. are they likely to be stainless?
Stainless valves should be shiny. I doubt there are chrome valves, especially for our engines
 
I'm not comfortable with my head assembly, and I'm not finding the measurements I should be getting.

The two 'stock' spring sets both measure a hair less than 1.800 free height rather than the 2.000 I've read on the forums and in the performance handbook. I believe the 302 springs we used came out about the same.

I wouldn't be concerned but with my one piece retainers from VI (5/16" Steel Valve Spring Retainer Spring Type:302 Spring), my installed height is 1.700 rather than 1.590. In playing around with the one piece retainers for my dual springs, the locks appear to be ~0.100 lower than the stock two piece retainers (as compared to the tops of the spring).

So assembling with the 302 retainers and 302 springs, my 70-75 pound springs had a seat pressure of 40 pounds. My shop resolved that with a spare set of inner springs they had lying around, raising the seat pressure to 80 pounds, with an expected coil bind of 1.200.

My two lingering concerns are, running an inner spring with a main spring not designed to, and also, the inner spring coils in the same direction as the main. My dual springs coil in opposite directions. I thought that was to minimize friction and prevent coils from locking together if there was slippage.

I'd appreciate opinions.
 
Use the springs recommended by your camshaft grinder.
For hi performance i either like the dual spring combo or a spring with a damper inside the spring.
Go with what your grinder says.
 
Right now, it’s a stock camshaft. I might be moving, so I can’t tear out the cam at the moment.
 
It comes down to the ramp profiles of the cam engine the rpm range the engine is used in. If you are putting new springs on the stock cam I think you're right leaning towards the 70/170# springs. They won't hurt but will keep the valves in check. Make sure the guides are replaced while the head is being done.
 
Head is a C9DE-6090-M large flat log head, new valves, Viton seals, 3 angle valve job, 30 degree back cut intake.
 
With a stock cam and the stock six valve springs (54 lbs closed / 150 lbs open) you will get valve float at 4500 RPM or less, the 289 springs will rasie this to about 5000 RPM and the 302 springs can go to 5500 RPM and sometimes more. Normally with an iron six head the 302 valve springs should be set up with a installed height of 1.680 to get 80 lb closed seat pressure (200 lb open pressure). Are these springs new or used? The springs when compressed solid should measure about 1.100. So your 1.700 installed height is near perfect a set of .030 to .060 shims or a set of spring cups should bring it into spec. Use your spring tester to see what height measurement you get when they are compressed to the 80 LB's seat pressure. The 1.200 coil bind (stacked solid will probably be ok with the stock cam. To check it measure that you have at least .050 clearance between the coils at full valve lift.

With a new stock grind cam it should have .348 total lift at the valve (a used cam might be a little less due to valve train wear) when used together with a stock spec 1.5 rocker arm. If your using some aftermarket rockers with a 1.6 ratio it's about another .035 more lift at the valve (.3712) a set of 1.65 rockers would be more yet. Check that you also have enough clearance between the bottom of the valve retainer and the top of the valve stem seal. Also since your using a stock cam you could get away using a lower installed spring height if you needed too to help get your 80 lb seat pressure of anywhere from 1.680 down to 1.600. If you later on decide to install a better aftermarket cam and because of the increased valve lift though you will then need to go back to around a 1.680 to 1.700 spring install height with recommended valve springs. Good luck on your build (y) :nod:
 
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