how critical is installed valve spring height?

[copper67sat]

I bought a new pair of 440 Source Stealth aluminum heads for my 383 build - 9.5:1 street build with HUG SEH1620BL-12 flat tappet hydraulic cam (specs below). Based on things I have read in this forum and elsewhere, I sent the heads to the machine shop to be checked and they reported that some of the seats were not installed correctly. Supposedly they corrected the seats and blended the chambers, performed a valve job then set the valve stem heights and spring heights to "Competition Specs", whatever that means. 440 Source specs their springs at 1.875" installed height - I wish that I had checked these before they went to the machine shop. I bought the Hughes springs (HUG 1106H) that are recommended for the cam which call for 1.880" installed height. That seemed close enough to the 440 Source spec that I didn't think I'd have to make any adjustments but thought I'd check anyway.

I measured anywhere from 1.825" to 1.844" using a Proform valve spring height micrometer. I verified the measurements more than once, especially for the min and max outliers, and the differences are far larger than my measurement error. First, the variation from valve to valve bothers me, but perhaps more importantly won't the shorter than spec installed heights lead to higher spring loads?

I started down the path of using +0.100 retainers from Hughes along with the appropriate shims to bring the spring heights into spec. However, the machine shop installed metal clad viton valve stem seals which do not appear to be easy to remove and reinstall and the shims won't fit over them. Am I overthinking this or should I try to get the machine shop correct them?

If I can't get the machine shop to step up or do the work on a timely basis, can the valve seals be removed and reused? If so, how? Also, are there any issues with using multiple shims? The shims come in .015, .020, .030 and .050. I mapped out the combinations of shims needed bring each valve into spec and some valves need as many as 3.

Thanks in advance for any guidance from the experts.

 

[PRHeads]

Did the heads get reassembled with different retainers/locks than they were delivered with?
The reason I ask is, the IH on them is usually pretty close to 1.875, and should actually have increased slightly after the seat work.

Have you verified the height mic is correct?
Just set it to 1.875 and measure it with a caliper.

If the IH is actually as short as you say, there’s likely shims under the spring cups.

Carefully prying the seals from two sides will usually get them off.
Take the little springs off before working the seal up over the keeper groove.

If you’re going to use that Hughes spring I def wouldn’t be running the IH any shorter than 1.88”, and if 1.90” was available that’s what I’d shoot for.

 

[copper67sat]

Did the heads get reassembled with different retainers/locks than they were delivered with?
The reason I ask is, the IH on them is usually pretty close to 1.875, and should actually have increased slightly after the seat work.

Have you verified the height mic is correct?
Just set it to 1.875 and measure it with a caliper.

If the IH is actually as short as you say, there’s likely shims under the spring cups.

Carefully prying the seals from two sides will usually get them off.
Take the little springs off before working the seal up over the keeper groove.

If you’re going to use that Hughes spring I def wouldn’t be running the IH any shorter than 1.88”, and if 1.90” was available that’s what I’d shoot for.

Thanks for the advice. I did not provide the shop any different retainers or locks so presumably they were reassembled using the same ones delivered by 440 Source - they certainly look what came on them. I wish I had taken baseline measurements before any work was performed so I'd know how things changed after the machine work. As you stated, I also expected the heights to increase after the machine work which makes me wonder if they were way out to start with. I am also finding that the chamber volumes vary from 82.2 to 83.6 cc which is more than I expected and larger than 440 Source states (80 cc) but I'm not sure that will make much difference in the big scheme.

I will definitely check the micrometer. It is brand new but who knows what quality control they have.

 

[PRHeads]

I’ve checked several stealths for chamber volume…….and 82-83 is what I often see after cutting the seats.

If there are no shims under the cups, and the mic is correct, that’s pretty far from spec imo, and I’d address it……somehow.

 

[PRHeads]

Looking at the posted specs, the Hughes springs have a rate of 336lbs/in.
If they’re 150lbs at 1.880, that would put them at 166lbs at 1.830.
Imo, that’s asking for a problem.