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Old 01-20-2011, 01:39 PM
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Help with Head / Valve Spring selection

I need help too pick put the right valves ,springs ,and pushrods for my setup. I am using an older gm block, 3970010 bored .030 ,have a retrofit comp cam part#12-600-8 VALVE LIFT @ 1.5:1 .511"in .497"ex ,retroroller lifters. The heads i want too use are the 305 416 castings, only because they have been ported allready but that is all that was done. Pistons are silvolite .030 with 4 valve relief. If anyone can help with part numbers i need that would be great, alos i am looking at roller tip 1.6 rockers from comp cams. So figure them as well...Thanks in Advance..

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Old 01-20-2011, 01:44 PM
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call comp about the springs when you get the valves figured out
800-999-0853
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Old 01-20-2011, 01:48 PM
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CompCams shows what to buy too match the cam ,but they do not tell you the head that it is to be installed on, and the prices are overkill, i see a great selection on ebay from big names, but need part numbers and specs..
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Old 01-20-2011, 01:51 PM
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Most people i emailed at speed shops, tell me to go with a .200 longer pushrod for roller cam, some said .100..some list thier springs to handle up to .550 lift..but only recommend them for flat tappets and not roller..so i am very confused..
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Old 01-20-2011, 02:00 PM
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i believe you need to get your heads built and then measure for pushrods
but im sure someone else here knows more than me about it
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Old 01-20-2011, 02:03 PM
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Quote:
Originally Posted by matts37chev
i believe you need to get your heads built and then measure for pushrods
but im sure someone else here knows more than me about it
Good advice Matt. http://www.google.com/#q=pushrod+len...73bcec2e6e3c54 .


Cole
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Old 01-20-2011, 02:05 PM
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Originally Posted by eloc431962
link no workie
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Old 01-20-2011, 02:13 PM
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The head casting number itself isn't important. What diameter springs are the heads setup for? Stock is usually 1.250 in diameter but often they are cut for larger diameter springs. ie 1.44, or 1.55, or 1.625 diameter. You're also going to have to know the height from the spring seat to the underside of the retainer as this determines your spring setup height. On a stock SBC the height is generally around 1.800.

That cam calls for 125# on the seat with a rate of 372#/in

If we know what diameter the head is machined for and the spring setup height then we can spec out a matching spring.

As far as pushrods go you really should wait until it's all assembled then order the correct length. But if you decide not to the stock length for a retro roller is 7.200 long
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Old 01-20-2011, 02:35 PM
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ok so if i take my caliper and measure around the outside of the spring that will give me the thickness, and then i measure the seat on the head across to find the width of that , but for spring height..dont i need the proper valves first..as i am changing them as well?
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Old 01-21-2011, 07:14 AM
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If you have no valves then yes you need them to get the height. When they ported did they also change the size of the seats or did they leave the stock size? If still stock do you have the old valves?

For most applications on stock SBC heads there's only two different lengths. Stock or +.100 for your application the stock length would be fine.

If they left the seats stock and you still have the stock valves then you can use them to get the approximate installed spring height. At least close enough to know which springs to order.
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Old 01-21-2011, 07:21 AM
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the heads were left stock, and all parts are still installed, the guy who owned them before me , just had them rebuilt and ported, and put about 5000km on them and then took them off when he got rid of his car due to an accident. I was thinking of leaving the stock 1.5" exhaust valves and just putting in new 1.94" intake valves..will that work or do i need to replace the exhaust valves with performance ones...thanks
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Old 01-21-2011, 08:27 AM
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Tough call. While the heads have only 5000km since the rebuild the valves themselves have ???? miles? You can get 1 piece stainless valves from places like Competition products for fairly short money. In this case $6 a piece.

http://www.competitionproducts.com/S...uctinfo/E2809/
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Old 01-21-2011, 08:51 AM
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Since you're planning to upgrade the Intakes and you need Springs etc..
It will be cheaper to get a matched kit.
Examples:
16= 8-1.94" Intake / 8-1.50" Exhaust
http://www.competitionproducts.com/S...ductinfo/8430/

Valves/Springs/Retainers/Locks/Seals
http://www.competitionproducts.com/H...ctinfo/851395/

Last edited by SSedan64; 01-21-2011 at 08:54 AM. Reason: spelling
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Old 01-21-2011, 09:06 AM
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Stock Pushrod length for Retrofit Roller Lifters is 7.300", for OEM Roller Lifters it's 7.200"
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Old 01-21-2011, 09:40 AM
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What does it say on the cam card for installed/seat and open spring pressure?
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