Valve Spring Installed Height Variation

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mopowers

mopowers

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I've picked up a used set of Trick Flow 190 SB heads that I'm checking over. I'm going to have a local shop check and skim the desk surface if needed, but was hoping to lap the valves and verify installed height and spring pressures before reassembling.

What is the acceptable variation of valve spring installed height? Is .010"-.015" reasonable?
 
I try to get them as close as possible, but often times, there's not a shim with the thickness you need so sometimes you have to settle. I think the ones on my slant 6 unicorn head had a widest variance of .015".
 
And also this is my opinion......if you end up having to "settle" than you settle on the right side. In other words .010-.015 tighter than looser. Valve sprAngs loose somewhere on the order of 10% "or so" as they break in.
 
That seems doable. I did notice all of the intakes on one head were shimmed .015" and most of the springs on the other were also shimmed .015". Of course, my dumbass didn't mark the shims on that one. It'll be a fun little bench project going through it all though. I'm just hoping I can get the valves to lap in. A few of the needed to be replaced.
 
I'll be checking the installed height on the next 2 engines that I'll be working on so I'm trying to wrap my head around this.
Using nothing but common sense with no experience doing this, I'm guessing the following:
* The top of the valve stem is a fixed measurement since the valves are against their seats.
* The "Installed Height" is the height of the spring as measured from under the retainer at the top to the point where the spring sits on the head or the steel pocket it rests in.
* Any shims that are added are placed under the spring at the bottom. Cast iron heads have no spring pocket seat cups, aluminum ones do. Do the shims go between the spring and the cups or the cups and the head itself?
* As shims are added, this adds tension to the spring and increases it's rate. Correct?
 
Kern Dog said:
I'll be checking the installed height on the next 2 engines that I'll be working on so I'm trying to wrap my head around this.
Using nothing but common sense with no experience doing this, I'm guessing the following:
* As shims are added, this adds tension to the spring and increases it's rate. Correct?
Click to expand...

Pressure increases, rate stays the same within the usable range.
 
66fs said:
Pressure increases, rate stays the same within the usable range.
Click to expand...
Thank you.
I looked at it like you're preloading the spring to get the initial pressure where it needs to be with the valve closed but how does that not also affect the open pressure?
EDIT...
I am guessing that is does affect it but these springs are not progressive so for every increment that they are compressed, the increase in rate stays the same.
 
Yep. If you increase seat pressure by 15 lbs, every point through valve lift is also increased by 15 lbs. in theory. The spring rate is generally linear.
 
I don't think it's too uncommon for the intake and exhaust valves to end up at slightly different heights. It's pretty obvious when you lay a straight edge across all the stems and see light under every other stem. Comes from the valve seats being machined by different cutters in separate operations and the guy not hitting the same seat depth after the tool change for that valve and seat combo. For the springs it can be adjusted for by different shim packs for intake and exhaust. As long as it's .010-.015 it's probably nothing to worry about, but that will be variation in the pushrod geometry from one to the other. I've seen it on three sets of rebuilt iron or new aluminum heads. Just something else to rub the worry beads over.
 
How about the question that is circled in blue?

1741654565241.png


Do the shims go against the surface of the head with aluminum heads or between the spring and cup?
 
Kern Dog said:
How about the question that is circled in blue?

View attachment 1716376753

Do the shims go against the surface of the head with aluminum heads or between the spring and cup?
Click to expand...
They go between the head and the spring locator/cup. At least that's how the ones I've had were installed. It makes sense to me since the locator is probably going to be thicker than the shims used. I'd want the thicker piece against the spring.
 
I was curious about the shim placement only because of how it might wear on the aluminum.
 
You never want to have thin shims [ 010 - 0.015" ] in direct contact with the spring. They can get chewed up. If you have a shim 'package', say a 040 & a 010 together, put the 010 under the 040 & all good. Alum heads use a cup or locator for the springs. Put the shim under these. The shims will not be damaged, even if thin.
 
I'll install them however it is suggested. I don't know enough to debate it, I just thought the spring cups with their rounded edges may have been a better material to rest on the aluminum. I first thought that you didn't want to put the shims between the spring and cups because you then move the spring up and out of the cup by the thickness of the shims.....Then I figured that if I had to shim these .030, that isn't that much and should not be an issue.
I'm open to whatever is suggested. I want to learn and to do it right.
 
Kern Dog said:
I was curious about the shim placement only because of how it might wear on the aluminum.
Click to expand...
According to everything I'm seeing on the net though, the shims supposedly install under the cups. But I've torn down factory engines with cups (Toyota) where the shims were on top of the cups under the springs.
 
How did I get lucky all these years and avert destruction since I have never done this before on any engine?
Do you need to push it past 6000 rpms a lot to really risk damage?
I just find it quite curious that I've never broken anything unless the reason is that there is enough tolerance built in OR that I didn't push the engines hard enough to reveal any weaknesses.
 
Kern Dog said:
How did I get lucky all these years and avert destruction since I have never done this before on any engine?
Do you need to push it past 6000 rpms a lot to really risk damage?
I just find it quite curious that I've never broken anything unless the reason is that there is enough tolerance built in OR that I didn't push the engines hard enough to reveal any weaknesses.
Click to expand...
You probably never had anything that really needed to get that specific. The factory didn't use spring shims that I know of. I've torn down boocoos of original engines and never seen them. But then, also the factory used mild cams with mild spring pressures (for the most part), so there was really no need. Nobody said you have to do it.
 
The 360 that I'm building has a Hughes hydraulic roller that was in it when I got the engine with 2 blown head gaskets. I'll check the installed height on that one just for fun.
It is the 440/495 in the Charger that is getting a retro Hydraulic Roller from Comp Cams and with that one, I was told to set the installed height at 1.860, +/- .010. Now since the stakes are higher and now that I'm now aware of this, I can't just disregard the advice.
 
Kern Dog said:
The 360 that I'm building has a Hughes hydraulic roller that was in it when I got the engine with 2 blown head gaskets. I'll check the installed height on that one just for fun.
It is the 440/495 in the Charger that is getting a retro Hydraulic Roller from Comp Cams and with that one, I was told to set the installed height at 1.860, +/- .010. Now since the stakes are higher and now that I'm now aware of this, I can't just disregard the advice.
Click to expand...
I wouldn't disregard it either. I'd get it right.
 
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