Guys, just so you know, the used LT1 heads I'm porting for my winter buildup had those Crane "shim" type valve spring seats on them for about 3,000 miles of use, and when I dis-assembled the heads for porting, two(2) of the sixteen(16) seats were already cracked Not bad mouthing the Crane design or anything just wanted you to know my experience with them

 

Oh yea, Arctic_White_WS6 thanks for the part number

 

97 6Speed Z, thanks for the report. I didn't use those wimpy .015" Crane shims for mine when I put the Crane springs in. As I mentioned earlier, I had custom sized Comp seat that was .060" thick installed when I did mine.

I didn't believe Crane's tech line when I called them about those Crane shims. The guy spoke down to me like I was ignorant and said the thin Crane shims would work just fine. Obviously in the case you mentioned they did not.

 

what did they run for CC? i would be interested in some

 

I went to my local speed shop that sells Comp Cam products with the Crane springs diameters (I don't recall the inner and outer measurements off hand). Unfortunately, they did not have the exact size in stock. The set they had was just slightly to large. I didn't feel like waiting so the owner said he'd machine polish the outer diameter a few thousands of an inch to get down to about 1.50". They ended up fitting perfectly. He charged me the regular price which was about $35.

Check the outer diameter of the outside spring (1.50" will do) and the inner diameter of the inside spring (that I believe is the oem spring diameter? but can't recall) . GO to the Comp website and look on catalog page for "seat cups and locators" (p. 319 I believe) Take the Part number and go to the Summit website to place your order.

 

i have them in my 383 with a 236/242 cam
no problems through about 75 WOT runs

 

I thought that setting the correct installed height meant that the correct pressure would be had. ie - if you set the valves at the specified height, you would have the specified pressure unless the spring specs are wrong, or you have a bad/wrong spring.

Can anyone explain this?
Ryan

 

I'm no master engine builder, but once the valves are installed their height is fixed (excepting with the use of lash caps, but that's an other issue).

Spring height is adjusted by the spring seats/shims or cups and the retainer position if different locks are used (that would affect height). To achieve the recommended spring pressure one changes the spring height (i.e. lower height = more seat pressure) by adding/eliminating shims. These hardened metal shims generally come in .015"/.030" thickness. I try to get to the recommended height and have less than .010" per valve/cylinder variance.

One also should ensure that the pair of springs on each cylinder are as close as possible to each other in installed height. Minute variances in individual springs, head work, etc require checking each spring height and not assuming they are all identical.

Go to the Comp Cams website and search for their valve train tutorial and install instruction pages as they are quite informative.
Comp Cams

I hope this helps.

 

Don: I understand the shim/install height idea. However, what Cman was saying was that even though the valvesprings were installed at the correct height, his seat pressure was too high.

My question: Does the correct installed height automatically guarantee that you have achieved correct spring pressure. My understanding conflicts with Cman's post. I must be wrong, because I don't know much about this stuff .

Ryan

 

My understanding is, theoretically, all the springs in a set are identicle and all should have the same pressure at the same height. HOWEVER, in the real world, each spring is different and they will deliver different pressures at the same compressed height. Setting the spring heights is a good way to go (better than doing nothing) but the better approach is to adjust the spring heights individually to get all the spring pressures the same.

Rob
95Z28

 

Ok..this seems logical and is what my intuition told me .

thanks!
Ryan

 

l98 valve spring seats, part #10185066, have a 1.35" OD (according to a thread). So how do the crane 99893 springs with a 1.46 OD fit into these?

http://web.camaross.com/forums/showt...light=10185066

 

I was told by Lloyd Elliot to use a set of Comp 4771 locators with a little grinding to fit the heads. He said it's nothing technical, anyone can do it.

 

Ryan, I am no expert either, but the answer is basically, "no". For a stock engine using oem replacement parts the answer is generally, "yes".

It IS possible to install too stiff of spring for the particular engine valve train combo and intended use of the engine. That is why proper spring selection (as well as other valve train components is critical). Once you start modifing an engine and using different parts the equation becomes a bit more complicated. I have calculated that I have about 330lbs of pressure with the valve open, and that may be a little high for my needs. I installed the cam and springs over a year ago and so far everything is fine.

 

Agreed, while I am sure their must be a correct CC locator set to fit, I used a set of used CC locators and "polished" the OD for a perfect fit.