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Old 12-20-2011, 09:02 PM
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vortec head springs

hay guys i m getting planed out to build a vortec head swap onto my 84' sbc 350, out of and going into a k2500 gmc pick up. first off im doing a full reman and i work at a machine shop so i can do any and all work myself... lucky me! it will be atached to a sm456 (man trans) and is really not meant for anything serious, just the frequent burn out and demonic burble. at this point in time i have a block going out to +.040" on cyl's, stock d.h. (i plan on decking to 9.5-10. comp ratio) +.010" crank rods and mains, and a lunati cam 60104 (big s.o.b). i have a set of 906 vortec heads going in. im going to cut seats and replace any valves that really need it, re cut all valves and install screw in rocker studs. and here's my question. new springs or cut guide boss? i have hesitation towards cutting guide bosses due to the fact that its a daily driver not a race car i want all the guide i can get....what do you guys think about the Crane Cams spring set to increase valve lift to around .550" p.n. 10309-1
. ( http://www.summitracing.com/parts/CRN-10309-1/ ) also is it wise to continue using stock self guided rockers at that lift?. and is 9.5 to 10 about the comp i want to run this set up on pump gas?

Thanks,
Adam

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Old 12-21-2011, 04:15 PM
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The guide boss will need to be shortened to install that cam.. Springs and retainers are the owners choice.. Coil bind, retainer/seal/guide top and seat pressure will be issues.
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Old 12-21-2011, 05:46 PM
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GM designed the valve guide to also serve as the inside diameter (I.D.) locating device for the valvespring. The guide’'s large diameter acts like a sleeve that keeps the single-wire valvespring located properly. If you wish to install a performance spring that includes a flat-wound damper, measure the I.D. of the damper spring and cut the guide O.D. accordingly for clearance. Lunati recommends a 73943LUN coil spring with an I.D. of 0.883", but does not list the I.D. of the damper spring, so measure it yourself.

The Lunati 60104 isn't as big as you may think. The intake closes at 42.5 degrees ABDC @0.050" tappet lift, so your proposed 9.5-10.0 SCR should be just about right. 10.00:1 SCR computes to 8.42:1 DCR and 9.50:1 computes to 8.00:1 DCR on the KB calculator and either or anywhere in between should work fine on pump gas if you use a tight squish with it.

I would align-hone the main bearing bore and cut the block decks to square, registering off the main bearing bore and based on the dimensions of your stack. In other words, if the stack (stroke radius, rod length and compression height of the piston) is 9.003" and the block deck height is 9.025", then the piston deck height would be 0.022". Then cut the block deck height to whatever dimension you need in order to match up with the head gasket thickness to establish the squish at somewhere between 0.035" and 0.045". If you had a piston deck height of, say 0.015" and combined that with a gasket thickness of 0.028", then the squish would be 0.043" for instance.

The springs that are recommended for that cam are 73943LUN.
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Old 12-21-2011, 11:15 PM
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hay TECH thanks for the knowledge this answered some of my thoughts. I'm thinking i need to just go with the lunati springs and cut down the guide both height and O.D. it'll help me sleep better lol. I'm also wondering if their is a size/brand valve seal people like.
thanks again
Adam
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Old 12-22-2011, 12:32 AM
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According to Sallee Chevrolet the Crane p/n 10309 spring and retainer is good for 0.550" lift w/no machining required.

Quote:
The Chevrolet solution is to use Crane Cam’s 10309-1 drop-in valve spring and retainer kit which is good for .550” lift with no machining.

The installed height for this Crane Cams kit is taller and the lower part of the retainer is shorter. The “AVERAGE” clearance between the retainer and seal is .575” for this kit.
*SNIP*
As with all modifications to performance engines though, you should always measure to assure that there is proper clearance and fit.
But if you have the run of a machine shop, and if new springs are in the mix, use +0.100" valves and don't forget the backcut the factory does on the OEM valves. Take the guide boss down just enough to give you 0.060" clearance between the seal and retainer at max lift- no more. Take the guide boss OD down to match the positive type seals you'll be using.

While you're at it, why not enlarge the spring pockets to use a larger diameter spring that can control things w/o having such a high spring rate?

Use rockers w/a roller fulcrum.

HERE is a couple more things to check.

Last edited by cobalt327; 12-22-2011 at 12:44 AM.
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Old 12-22-2011, 07:04 AM
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Just use LS2 beehive springs and the correct retainers with .100" longer valves. You will have plenty of clearance and will only have to cut the guides for the type of seal you want to use. The beehives are also pretty cheap and can take a lot of abuse. Recommended installed height on those springs is 1.800" but I would shim them to be only .050" out of coil bind when you're at full lift, beehives seem to work a little better near bind and with the heavier valves you can use a little extra seat pressure.
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Old 12-22-2011, 12:44 PM
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I guess I'm old fashioned, but I insist on using the spring that the cam grinder recommends for the cam.
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Old 12-22-2011, 08:47 PM
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guys this is great info!! i like the idea of using a larger spring seat O.D. ls2 spring, and the beehives are getting very popular so i think ill pick out a brand and cut the heads seat O.D. to fit...
i guess my next question would be can i reuse my stock rocker arms and save a few bucks or am i asking for trouble and otta go to the roller fulcrum roller tip rockers? and do i go self aligning or guide plates??.
This is NOT a race engine just a toy going in an old lifted truck ill be doing 5 grand burnouts only once and a while top end is not that crucial.. but i don't want to worry about it. contradictory i know.
ant help is appreciated.
Thanks, Adam
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Old 12-22-2011, 08:51 PM
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Quote:
Originally Posted by oldworldnewtoys
guys this is great info!! i like the idea of using a larger spring seat O.D. ls2 spring, and the beehives are getting very popular so i think ill pick out a brand and cut the heads seat O.D. to fit...
The LS spring doesn't need any seat enlargement, just the correct retainer. An LS retainer will be 8mm, the one you want is the Comp p/n 787 or comparable.

Last edited by cobalt327; 12-22-2011 at 08:57 PM.
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