Comp cams Valve spring help

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Comp cams Valve spring help

Post  HorsinAround on August 17th 2012, 10:21 pm

I have a set of Comp Cams 928 valve springs that I am planning to install on a set of early scj aluminum heads. I went to comp's web site to find the recommended installed height and I think I am seeing conflicting information, but would like someone more knowledgeable than I to look at it and clue me in.
First in their valve spring chart, it says the 928 installed height is 1.850
http://www.compcams.com/Base/pdf/ValveSpringChart.pdf

In the product info for the spring they list the seat load at 1.880

So do I shim to set the installed height at 1.850 or 1.880?
http://www.compperformancegroupstores.com/store/merchant.mvc?Store_Code=CC&Screen=PROD&Product_Code=928-16&Category_Code=
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Re: Comp cams Valve spring help

Post  rmcomprandy on August 17th 2012, 11:59 pm

HorsinAround wrote:I have a set of Comp Cams 928 valve springs that I am planning to install on a set of early scj aluminum heads. I went to comp's web site to find the recommended installed height and I think I am seeing conflicting information, but would like someone more knowledgeable than I to look at it and clue me in.
First in their valve spring chart, it says the 928 installed height is 1.850
http://www.compcams.com/Base/pdf/ValveSpringChart.pdf

In the product info for the spring they list the seat load at 1.880

So do I shim to set the installed height at 1.850 or 1.880?
http://www.compperformancegroupstores.com/store/merchant.mvc?Store_Code=CC&Screen=PROD&Product_Code=928-16&Category_Code=

They can be installed at ANY height which will give the correct recommended amounts of force and allow the correct amount of valve lift.

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Re: Comp cams Valve spring help

Post  DanH on August 18th 2012, 2:07 am

read the cam card and set to required spring spec

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RE Cam card

Post  HorsinAround on August 18th 2012, 1:17 pm

Ok, I am looking at the cam card and the only thing it says about the springs is "recommended CC valve spring 928. Valve spring specs furnished with springs."

Since I got the cam, lifters and springs from a friend of mine and he didn't have any paperwork with the springs, so I am trying to go off the website.
Also, the alum. Cobra jet heads came off a 530 pulling motor that had a .8 lift roller cam, so I believe the valves are longer than stock. (with the 928 springs, I am having to shim .090 on the intakes and .150 on the exhaust) The cam I am going to use is comp. p/n 34-653-5 and the specs are as follows
Grind FF 310B-8

Valve adjustment .030 intake and exhaust
Gross valve lift Intake .656, exhaust .641
Duration @.020 Intake 310 exhaust 314
Timing @.020 47BTDC and 49ATDC
Installed at a 108 c/l

Duration at .050 Intake 270 exhaust 276
Lobe lift intake .3750 exhaust .371
Lobe seperation 108

Since it appears the valves are longer, I was looking at comp's valve spring chart and they list a 930 spring that has the same spring loads/rates throughout the lift range and is also set up for an installed height of 1.900 which means I won't have to use no where near the shims I have used on the first 3 chambers. Any thoughts?
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Re: Comp cams Valve spring help

Post  rmcomprandy on August 18th 2012, 2:46 pm

Use whatever spring at whatever installed height you want which will give you the correct amounts of force and allow the required valve lift; (hopefully .090" before coil bind in a race type situation).

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Re: Comp cams Valve spring help

Post  HorsinAround on August 21st 2012, 7:41 am

Been messing with this over the weekend and after talking with Comp Cams yesterday, ordered a set of CC double springs that will give me the recommended seat pressure and open pressure with a 1.900 installed height for the intakes. However I was still not satisfied with the situation on the exhaust side and after measuring it appears that the pockets have been cut deeper which explains why I'm seeing a 2.00 installed height with stock length valves. So last night I happened to glance over at a set of Manley Nextec doubles I had on the shelf that are +.100 and took the inside spring out then measured the force of the outer spring and damper and at a 2.00 installed height, the open and seat pressures are perfect. So is there any reason why I couldn't use outer's of the Manley set I have?
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