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Don’t understand why trick flow heads are offered in different installed valve heights????
So you can get the correct spring for the correct lobes. All the valves are the same length so they change the installed height per the spring and application.
The baseline heads have the 1.90” installed height using standard retainers, spring locators and shims (mine have one .015” shim) under the locators to yield that installed height. The other more costly versions utilize retainers with +.050” and “likely” +.100” for the 1.950” and 2.00” installed heights respectively. (They may cut the spring seats for the 2.00” installed version, I’m not sure) The valves and spring locators are the same pieces for all those heads.
And just a word of caution...I know everyone says they'll get their heads checked, and I know TF are some of the nicest OOTB quality-wise...but their spring specs as-tested do not match the paperwork specs. At least on the BB heads. So if you are buying check (or have your shop check) specifically the pressures and installed spring heights on every valve. It's more time for sure, and I guess it all depends on how nitpicky you are with this stuff but I found them all slightly different and they will need correcting. Not valve stem height but spring height which = pressure. Okay so this thread was a month old...dammit!
So what kind of variation in pressure did you measure?? There’s variation in everything it’s just a matter of how much
20-25 lb/in difference on the seat2s. The springs specs say 420 lb/in rate but they checked at just over 430. Tested seat pressures ranged from 160-180ish on springs that the paperwork says are 138 @ 1.95 installed height.
You can always get the bare heads without springs/retainers/locks and have a competent machine shop finish them off and install the appropriate springs for your cam. I ended up doing this with my TF heads - my machinist was really impressed with the castings and overall quality - he just touched up the valve seats to verify them, added springs and now they are on my engine.