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Check the installed height on all 16 valves, and whichever has the shortest IH, shim that spring to the correct IH, then shim the rest to that same installed height. What cam, what springs, and what IH did the cam grinder recommend? If you're around the common 1.800" IH, and you're still .135" shy of CB, I think you may be on the right track shooting for .075"-.090" to CB. Again, get the cam grinders recommendations. They should know better than anyone.......
Last edited by grinder11; Nov 13, 2025 at 12:03 PM.
i am at ~1.8075 on the three I have measured. I should have gotten a better height measure tool but it works with a caliper to verify I get a range of 1.8075- 1.81.
im using comp cams 1.8 roller rockers and they suggested being within 10% of coil bind.
With the two .660 spring I come up with 30tho shims to get to .105 CB.
As they sit I’m at .135. I am tempted to put it together this way and just set redline to 6500 (will be doing a Dyno tune tho and want to know where the mechanical limits are so why not just do it right !)
It’s an Elgin USA grind. I asked about spring pressure and they just said the billet cam should be able to handle it. I’ll give them a holler and ask about install height but I’m going to guess they will say to follow spring manufactures recommendations for desired open pressures.
The cam it self is .595 at 1.7 but with rockers are 1.8 so it’s actually .630 in theory which I’m unable to measure in practice. I’m getting more like ..615 but still use the .630 for the math. Not sure if this correct.
Lifters are Howard’s 91155 and they are up to the task , BTR .080 Wall PR at 7.625 may be the weak link TBH
it’s taken me a month and I get my mind this far around it , and i know I pretty much understand what’s going on here. I do think with the .135 CB I’m getting I’ll see premature valve float. My next step is either buy a $200 pressure measuring tool or take them to a shop. I know I’ll need new seals to shim and of course shims. It all seems pretty simple and I wanna tackle it my self for the learning opportunity
I guess I’m not sure how early the valve will float at .135 vs .105 as suggested by comp.
I also am not sure if for the math equation if I should use the lift I am measuring or the theoretical lift
also before people chime in use factory stuff…yes it’s good but I’m using as cast heads with bronze guides , and I understand there’s some debate here as to whether or not you could use the factory rockers. I think you should use a roller in this case.
Thanks that’s I did see that a while ago.
Tho I think he skipped a part in the middle. He added CB+lift + .060 as a buffer but he failed to mention any additional steps such as to subtract that from the install height maybe ?
If my assumption is right to subtract and I follow that BTR method by subtracting the sum of CB, lift and a .060 as a buffer from measured install height from I’ll be at exactly 100 tho clearance before coil bind,
This is almost perfect from what comp cams said my clearances should be within 10% or scab.
however , from what I see here it looks more like I need a shim still in my case 63 tho which is too many .060 for my mind to not get wrapped around the axle about. I’m super close I know that. All that said I’m probably just gonna set it up without shims. In a few months I’ll be ready for a Dyno tune and we’ll see what happens with valve float and if it floats I’ll be shimming with the heads in PIA!
this video is super useful , hopefully others will find it here and I won’t loose it
Now when I go back to the OG thread I linked I get this statement
“The general formula for installed height is: Coil Bind + valve lift + 0.060" “
which is what BTR guy said. So it’s safe to say I subtract that value from actual install height and get the CB clearance , and in my case on 3 valve springs now I’m ~ .100 which is probably best from what comp cams says. I could tighten it up and probably spin to 8k if the bottom end was up to the task. That said , leaving it a little looser will reduce stress on the valve springs , cam and lifter. In turn I’ll get more service life. It’s a street flexer and road racing trial toy…I’m still at no need to shim. I just don’t want .160 and to float valves at 6200 RPM
Now when I go back to the OG thread I linked I get this statement
“The general formula for installed height is: Coil Bind + valve lift + 0.060" “
which is what BTR guy said. So it’s safe to say I subtract that value from actual install height and get the CB clearance , and in my case on 3 valve springs now I’m ~ .100 which is probably best from what comp cams says. I could tighten it up and probably spin to 8k if the bottom end was up to the task. That said , leaving it a little looser will reduce stress on the valve springs , cam and lifter. In turn I’ll get more service life. It’s a street flexer and road racing trial toy…I’m still at no need to shim. I just don’t want .160 and to float valves at 6200 RPM
Sounds like you're trying to make this more complicated than it actually is
I guess I’m not sure how early the valve will float at .135 vs .105 as suggested by comp.
Coil bind gap wont determine valve float. Spring rate/pressure will have more effect than anything. If youre running the ragged edge of spring pressure maybe that 0.030" makes a difference, but I doubt it.
Check them all, write them down and shim accordingly that is the correct way to do this stuff. Many people just install parts and get by, but it's not correct and won't help you catch marching errors from shops or valve/seat issues etc. I've got some heads here that have one head with sunken valves 0.060" deeper than the other head on average, that's just stupid, but you don't know till you measure it.
Check them all, write them down and shim accordingly that is the correct way to do this stuff. Many people just install parts and get by, but it's not correct and won't help you catch marching errors from shops or valve/seat issues etc. I've got some heads here that have one head with sunken valves 0.060" deeper than the other head on average, that's just stupid, but you don't know till you measure it.
i am at ~1.8075 on the three I have measured. I should have gotten a better height measure tool but it works with a caliper to verify I get a range of 1.8075- 1.81.
im using comp cams 1.8 roller rockers and they suggested being within 10% of coil bind.
With the two .660 spring I come up with 30tho shims to get to .105 CB.
As they sit I’m at .135. I am tempted to put it together this way and just set redline to 6500 (will be doing a Dyno tune tho and want to know where the mechanical limits are so why not just do it right !)
It’s an Elgin USA grind. I asked about spring pressure and they just said the billet cam should be able to handle it. I’ll give them a holler and ask about install height but I’m going to guess they will say to follow spring manufactures recommendations for desired open pressures.
The cam it self is .595 at 1.7 but with rockers are 1.8 so it’s actually .630 in theory which I’m unable to measure in practice. I’m getting more like ..615 but still use the .630 for the math. Not sure if this correct.
Lifters are Howard’s 91155 and they are up to the task , BTR .080 Wall PR at 7.625 may be the weak link TBH
it’s taken me a month and I get my mind this far around it , and i know I pretty much understand what’s going on here. I do think with the .135 CB I’m getting I’ll see premature valve float. My next step is either buy a $200 pressure measuring tool or take them to a shop. I know I’ll need new seals to shim and of course shims. It all seems pretty simple and I wanna tackle it my self for the learning opportunity
If you shim everything to the correct IH, there should be no valve float. Don't mix up CB with IH. The .135" to CB is a bit more than I'd like to see, but wont affect valve float. However, what it WILL affect is harmonics and spring surge. If most are at .135" to CB, I'd put a .050" shim in addition to the shim that's already there. Don't worry about the increased spring pressure. Another .050" shim would make-MAYBE-another 5-7lbs pressure. Nothing wrong with .085" to CB, unless you're all out racing. I do think you'd probably be fine at the .135" to CB. But if you spend a lot of time at or near redline, throw the extra .050" in there....
EDIT!! I see Comp recommends .105" from CB. IMHO, that is still more than I'd like to see. It's fine if you aren't spending a lot of time at high rpm. If you are at 6,000 rpm a lot of the time, go with .085". If I were you, buy the tool and use this as a learning experience, just like you said you want to do. The tool will pay for itself the first time you use it......
Last edited by grinder11; Nov 13, 2025 at 12:21 PM.
If you shim everything to the correct IH, there should be no valve float. Don't mix up CB with IH. The .135" to CB is a bit more than I'd like to see, but wont affect valve float. However, what it WILL affect is harmonics and spring surge. If most are at .135" to CB, I'd put a .050" shim in addition to the shim that's already there. Don't worry about the increased spring pressure. Another .050" shim would make-MAYBE-another 5-7lbs pressure. Nothing wrong with .085" to CB, unless you're all out racing. I do think you'd probably be fine at the .135" to CB. But if you spend a lot of time at or near redline, throw the extra .050" in there....
EDIT!! I see Comp recommends .105" from CB. IMHO, that is still more than I'd like to see. It's fine if you aren't spending a lot of time at high rpm. If you are at 6,000 rpm a lot of the time, go with .085". If I were you, buy the tool and use this as a learning experience, just like you said you want to do. The tool will pay for itself the first time you use it......
I am concerned with harmonics and valve control at 6-6800 I won’t live there but me I’ll be road racing and will be there often…
you
I agree with the previous idea of checking them all, writing them down, and shimming them after you have all the information. You have 16 opportunities to find a surprise.
I set up a set of heads last spring that had exhaust valves sunk deeper into the head than the exhaust valves do to a minor difference in manufacturing. The cam lift is 0.570, the valve sprins were rated at 0.600 max lift, and the suggested installed height of the spring was 1.800, with a coil bind height of 1.140. That's 0.600 of "usable" lift with that spring, PLUS 0.060 as a guard rail for coil bind height, which is perfect for spring control. Installed pressure was 130lbs, with 318lbs open.
What I found was all the exhaust valve springs installed at 1.815 or so, which gave me an open height of 1.245... Which was a full 0.105 away from actual coil bind. By my standards, "loose", which will have trouble with spring control at higher RPM. (For reference, I have always followed the rule of staying 0.060-0.100" away from coil bind total to best control spring harmonics). I added a 0.030" shim under those springs to tighten up the installed height to 1.7850. That leaves me ~0.075" to coil bind, and changes my spring rates ever-so-slightly to 134.7lbs closed, and maintains 313.3lbs open.
I know it's a lot of mental Olympics, but I've tossed together a handful of engines doing the "extra steps" of setting appropriate spring heights and have never had an issue with valve control. Blindly installing parts without checking proper clearances is a great way to be disappointed and end up doing things twice. I actually made a calculation tool a while back and it has served me really well for setting up heads without guesswork.
I agree with the previous idea of checking them all, writing them down, and shimming them after you have all the information. You have 16 opportunities to find a surprise.
I set up a set of heads last spring that had exhaust valves sunk deeper into the head than the exhaust valves do to a minor difference in manufacturing. The cam lift is 0.570, the valve sprins were rated at 0.600 max lift, and the suggested installed height of the spring was 1.800, with a coil bind height of 1.140. That's 0.600 of "usable" lift with that spring, PLUS 0.060 as a guard rail for coil bind height, which is perfect for spring control. Installed pressure was 130lbs, with 318lbs open.
What I found was all the exhaust valve springs installed at 1.815 or so, which gave me an open height of 1.245... Which was a full 0.105 away from actual coil bind. By my standards, "loose", which will have trouble with spring control at higher RPM. (For reference, I have always followed the rule of staying 0.060-0.100" away from coil bind total to best control spring harmonics). I added a 0.030" shim under those springs to tighten up the installed height to 1.7850. That leaves me ~0.075" to coil bind, and changes my spring rates ever-so-slightly to 134.7lbs closed, and maintains 313.3lbs open.
I know it's a lot of mental Olympics, but I've tossed together a handful of engines doing the "extra steps" of setting appropriate spring heights and have never had an issue with valve control. Blindly installing parts without checking proper clearances is a great way to be disappointed and end up doing things twice. I actually made a calculation tool a while back and it has served me really well for setting up heads without guesswork.
yup, I keep saying it wrong ! But clearly making the install height shorter makes the spring get more pressure , which is why I wanna use some shims with my setup
Originally Posted by grinder11
If the pressure is 160lbs@1.810", it will INCREASE spring pressure if set if@1.800, NOT decrease it.......
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To shim or not to shim? 
