How to check installed height?

[granitestategn]

First, my apologies. I know this has probably been asked before but my search didn't reveal the info I was looking for. I plan on changing my valve springs to Comp Cams 980's. What is the correct installed height for these springs and how do I check it? I own a dial caliper. Is it possible to use it to check installed height? I have access to mic's and depth gauges if I need them. What kind of tolerance are we talking about? I'm thinking not too close since they're springs. Is 0.005" close enough on installed height? I plan on installing them w/o the stock cups (which are under the retainer, right?) but with the dampers (inner spring) supplied by Comp Cams. Forgive me, I've never had my valve covers off! Also, is there an inverted cup (oil deflector) between the spring and the head? If there is, should I feed it to the dog or leave it in there? I just wanna make sure I get this right. Any help would be appreciated! Just kidding about the dog.

 

[Intercooler]

A lower spring cup but no upper. Throw them out and get shims to make the installed height at the desired spring pressure closed. If you want 90 lbs. on the seat it may be a .030" shim. Maybe more or less all depending. A ballpark is 1.7"- 1.725".

 

[granitestategn]

Thanks Intercooler!

Thanks for the info on installed height. Any suggestions on what tool to use to measure. I also have a machinist rule that is incremented to 0.01". It might be tough to read when in position, though. Anybody ever use a dial caliper? Thanks again.

 

[Intercooler]

Have your springs pull tested to figure out what height is needed for seat pressure by a machine shop. Install.

 

[granitestategn]

OOPS!

After reading my last post I think I didn't phrase it very well. What I was asking was how to measure the installed height of the spring after you put the retainer and split lock on. Can you get the depth gauge end of a caliper (the back end, opposite end from the jaws) in there to measure the height? I am assuming you have to install the spring, retainer and split locks. Then you measure the installed height. Then you determine what you need for shims to obtain the desired installed height. Then take it back apart, install required shims and put the retainer and split locks back on. Re-check installed height, and voila, you're done. Is that the correct procedure? Sorry to take you guys back to Valvetrain 101. I've always just pulled the heads and taken them to the machine shop and said "Three-angle valve job, new springs, new valve guides and seals, make 'em flat." Then I walk away.

 

[ijames]

I couldn't see a way to do it with the spring installed, and I didn't have a small diameter check spring, so I just put the retainer on with the locks and pulled on it hard to seat it so the measurement didn't change with extra pulls. Then I used a snap gauge between retainer underside and spring seat on the head while keeping tension on the valve, and measured that with calipers. Trying to do it with a depth measurement from the top of the retainer to the head then subtracting the retainer thickness didn't work because the spring covered the entire seat.

 

[granitestategn]

Thanks Carl

That's the info I was fishing for. Does a machine shop use a small diameter spring to check the measurement? I wonder what the "textbook" way to do it is? BTW, I looked at the CC980 box and it says 91# @1.700". I was thinking they were a little lower. Does anyone know if that box information is actual test data for the actual springs inside the box or is that just a "nominal" number for that catalog number?

 

[JDEstill]

I did it similar to the way Carl did. No spring, just retainer and locks, and pulled the assembly up while I measured. I bought this "telescoping gauge set" http://www.ntxtools.com/Merchant/me...e=01&Product_Code=CHB-50215&Category_Code=351 which I used in conjunction with my calipers to find the height between retainer and head. Then figured up how many shims I'd need to get the desired installed height.

John

 

[tom h]

I have a box of CC980s I haven't yet installed ... all this talk of carefully checking "installed height" ... I was going to have the springs tested & verified before install, but I hadn't planned on checking the "installed height" (until maybe now!).

Isn't the installed height fixed & defined only by the machining accuracy of the spring pocket in the cyl head, and by the retainer/keeper/valve assembly?

How much variation will there be on a stock setup, and how critical is it ?

In late 2001 I received some very thorough Actual spring data from Bob Kolhouse (don't know screen name).

For CC980's, NO cup used, 16 springs were measured.
ONE Spring was slightly off, here's data on 15 springs.
1st number is average, 2nd number is Std Deviation.

(To interpret Std Dev, if you measured a large number of randomly chosen springs (say, 100), 84% of the springs would be within +/- 1 Std Dev of the Average. 95% of the springs would be within +/- 2 Std Dev of the Average. And, over 99% of the springs would be within +/- 3 Std Dev of the Average.)

free length (inches): 2.030 , 0.006
Load (lbs) @ 1.700" : 75.5 , 0.74
Load (lbs) @ 1.250" : 196.7 , 1.58

From this, it works out approx 4 lbs for a 0.015" shim.
(std Comp Cams shims come in .015, .030, .060").

The oddball CC980 spring was 80 lbs @ 1.70", maybe a good reason to buy a 16 spring set & keep the best (which I didn't think to do). The springs themselves seem very uniform.

For some reason the "claimed" specs on springs always seem higher than "real" ... eg, the CC980 "spec" is 90 lbs @ 1.70". All the other spring data from Bob (stock, LT1, and CC979) showed the same trend.

So the $64 question is, how much height variation does a "typical" set of stock heads & valves have ... and should I worry about it ??

 

[salvageV6]

I just dropped mine in two cars with the stock cam and pushrods and valvetrain.

I did test them first as well.

 

[87LtdT]

Hello Tom H....Bob Kolhouse here.

Your quoting my data from 2 years ago gives me a nice warm fuzzy feeling I get so much info/help from others on this site that it makes me feel good that I occasionally help others??

Good job on explaining the data too...Bob

 

[granitestategn]

Thanks guys!

Thanks for all the responses and great info. I guess if the valve spring shims only come in 0.015", 0.030" and 0.060" I don't have to worry about being off by 0.005" (or more). You probably don't need to do anything unless you're off by 0.010"-0.015". I'll probably see if I can check the height without standing on my head. Possibly borrow a set of snap gauges from work. I'm wondering if it's even worth checking on a bone stock engine with original heads and valves when doing the job "heads on engine in car". I think it would be much more critical if:

1) The heads are being rebuilt w/ new valves
2) You've done a valve grind w/ original valves

Also, with the heads on the engine I would think you may have trouble with carbon in the valve seat. Without having the heads off and clean, how can you be sure? I'm starting to think I got myself all wound up over something kinda minor.

Last question: Has anybody changed their factory original valve springs and found a variety of different size shims under the springs? That may be the telling tale. If nobody has, the factory machining tolerances were probably close enough to at least make them all equal.

Thanks again for the great responses!

 

[JDEstill]

tom, granite -

I'm sure the factory intended all the valves to be at exactly the same height

On my car, which has had the heads worked on a couple of times at least, I found that the retainer to spring pocket was around 1.73"ish for the most part, but there was some variation. Got notes around here somewhere... when I was trying to install a set of springs at 1.700", I needed 0.030" of shim on most of them, but a few only needed 0.015", and a couple did need 0.045".

If you go to the bother of finding out that your new springs are 90# at 1.700", and that's what you want, then why skip the next step? Make sure they actually get installed at the height you want, so you get the pressure you want! If you know they are at X psi at 1.70", but you don't know that they are actually installed at 1.70", I guess you are a little better off than not knowing anything, but you could be doing a lot better.

John

 

[granitestategn]

John

Thanks for the reply! Definitely food for thought. What tool/method did you use to determine the installed height? Did you use snap gauges or inside mic's? Did you do the job in the car or on the bench?

 

[tom h]

Originally posted by JDEstill
If you go to the bother of finding out that your new springs are 90# at 1.700", and that's what you want, then why skip the next step? Make sure they actually get installed at the height you want, so you get the pressure you want! John

Yeah, after thinking this over I agree with you ... it such an effort to do the valve springs, may as well do it "right". 4 lbs per .015 shim is quite a bit, don't want to leave it to guesswork. I'm ordering a "telescoping" guage for the job!

 

[JDEstill]

Re: John

Originally posted by granitestategn
Thanks for the reply! Definitely food for thought. What tool/method did you use to determine the installed height? Did you use snap gauges or inside mic's? Did you do the job in the car or on the bench?

Gregg - I used the "telescoping gauge set", see my post above, combined with my calipers. I've done it twice, both on the car. It's pretty easy once you have the right tools. I did try to do this once with a friends inside mic and I didn't have enough room to get in there and measure anything. That's when I bought the telescoping gauge set.

John

 

[granitestategn]

OOPS!

My bad. I guess I should read the whole thread before opening my pie hole. I've got access to those tools at work. Guess I'll have to borrow them when I do the job.