how critical is installed valve spring height?

[68-500]

I haven’t read 1 thing about a spring alignment shim on the bottom of the spring between the head. With out it will the spring not eat its way down into the spring pocket? Well let me slightly rephrase. It had what you called shims under the spring. But you talked about removing them to get spring height. Did you end up with something in between the spring and pocket?

 

[451Mopar]

I haven’t read 1 thing about a spring alignment shim on the bottom of the spring between the head. With out it will the spring not eat its way down into the spring pocket? Well let me slightly rephrase. It had what you called shims under the spring. But you talked about removing them to get spring height. Did you end up with something in between the spring and pocket?

I am thinking the machine shop might have put shims under the spring seat/cup locators that prevents the springs from digging into the aluminum head. Your measured install height seems really short and I think the 440 source heads ship with more install height than your measuring?
Usually the spring cup / locator us 0.060" thick, but I got some 0.030" spring locators from PAC. They look like they just machined 0.030" off the bottom of the 0.060" locators.
Are you using the Hughes valve springs or the 440 Source valve springs?

 

[Rebelrouser]

Yeah, I calculated the same change in spring pressure which worried me since Hughes likes stiffer springs. I bought the cam, lifter, spring, oil package from them for their "No flat cam guarantee" and am following their instructions, all 13 pages.

I removed the seal and the cup was shimmed. Removed the shim and remeasured - 1.875". Also checked the mic and it's good within my measuring capabilities +/- .001

View attachment 1952308

Based on this and measuring the shim, I think my original measurements are also off at least .005. I don’t think I had the gauge tight enough to put sufficient seat pressure on the valve.

I need to measure the rest of them but the guidance here is to have no less than 1.88-1.9. The only solution I have found so far, short of more machine work which I'd like to avoid, is to go with +.100 retainers and locks then shim back down.

Well, I hope their no flat cam guarantee has improved since I purchased a cam from them several years ago. I even called them before install and told them the spring pressure was way too stiff. Cam went flat in just a few hours of operation time, after installing the stiff springs, used lighter break-in springs. Basically, they did nothing for me for the flat cam. And I had a fresh engine full of metal. Even after I spent the money to ship the cam and lifters back to them and he agreed over the phone that the lobes that did not fail looked to have had proper break-in performed.