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Valve spring question
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clay
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1972 Chevrolet Nova

PostPosted: Mon Mar 07, 2011 10:14 pm    Post subject: Valve spring question Reply with quote

I'm getting started on the cam swap on my cousins Vortec 350. I go the retainer to seal clearance I needed but it wasn't quite as simple as I thought. Anyway my question is on springs. I want to add some pressure as it only has 80# seat and 180# over the nose. I am looking at going to about 115# seat and 300# over the nose. This is a hydraulic roller setup. My question is how much pressure can I get away with using the press in studs? I'm thinking 300 is up there for press in studs but maybe o.k. but I don't really have experience with this. What does everybody think? Thanks, Clay.
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af2
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1933 Willys Coupe

PostPosted: Tue Mar 08, 2011 1:38 pm    Post subject: Reply with quote

Clay, you will pull studs at that #.
My son put a lt4 cam in his Vortec and ran springs at 260# and couldn't figure out why the valve adjustment would last a couple days. About the 3rd adjustment 2 studs with rocker were laying on the head.
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Paul P
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PostPosted: Tue Mar 08, 2011 3:55 pm    Post subject: Reply with quote

Stud girdle might take care of it.
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PostPosted: Tue Mar 08, 2011 6:26 pm    Post subject: Reply with quote

I had the studs pull out on my factory heads. I forget the spring pressures but they were mild. My vote is to swap them for screw in studs that way you don't have to worry about it.
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Skunkworkx
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PostPosted: Tue Mar 08, 2011 9:16 pm    Post subject: Reply with quote

Either pin what you have or go screw-in....I'd vote screw-in.

Press-in ain't gonna cut it.

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clay
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PostPosted: Tue Mar 08, 2011 10:32 pm    Post subject: Reply with quote

Well everybody is telling me what I didn't want to hear - but I'm glad to be hearing it. It was sort of my gut feeling but thanks to everybody for their input. I hate not to add some spring pressure (factory springs are weakish for even a flat tappet hydraulic) so it sounds like screw in studs get added to the bill. Thanks guys, Clay.
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coppergmc
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PostPosted: Wed Mar 09, 2011 3:32 am    Post subject: Reply with quote

If you ever tried pulling a stud out, you would swear that they could take some serious spring pressure. Even though some studs are easier to pull out than others, they are all a pain in the neck to pull and tap.

I've used pressed in studs with double springs for some hydraulic rollers cams with .525 lift. I am not sure how much spring pressure I had at max lift but it was probably in the 250lb range. It's been a long time since I've messed with many springs. Springs like these http://www.competitionproducts.com/CP-Street_Strip-Valve-Spring-Package-1250-Diameter/productinfo/VSA4/ might be okay for what you are trying to do as long as you aren't getting anywhere near max lift. I don't think the spring rate is all that much. Might have to buy the cutter for the guides though.
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Big Dave
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PostPosted: Wed Mar 09, 2011 9:59 am    Post subject: Reply with quote

There is a whole bunch of vibration being added to the pull of the spring not to mention the heat cycling that causes a pressed in stud to pull out. PAC sells a spring that doesn't require any cutting to fit your stock pockets with the seat and open pressure you want (PAC-1200). It has a max lift of only 0.550 inch though and goes into coil bind at 1.1 compression.

You do realize that 350 pounds is the absolute maximum a hydraulic roller lifter can support without collapsing so if you have an aggressive ramp with these springs you will be encouraging pump up rather than controlling it (not to mention promoting accelerated wear on the cam if cast).

Big Dave
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af2
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PostPosted: Wed Mar 09, 2011 10:28 pm    Post subject: Reply with quote

coppergmc wrote:
If you ever tried pulling a stud out, you would swear that they could take some serious spring pressure. Even though some studs are easier to pull out than others, they are all a pain in the neck to pull and tap.



Think of a manual (spring) impact working on the studs 500 blows per minute on an engine idling at 1000 rpm.
Think what a pneumatic impact does at much less BPM.
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clay
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PostPosted: Thu Mar 10, 2011 12:04 am    Post subject: Reply with quote

Quote:
You do realize that 350 pounds is the absolute maximum a hydraulic roller lifter can support without collapsing so if you have an aggressive ramp with these springs you will be encouraging pump up rather than controlling it (not to mention promoting accelerated wear on the cam if cast).


I'm stopping at 300#'s. That should be plenty of this motor. I didn't think I needed to go crazy but 80 seat and 180 open just sounded really weak for any sort of performance setup to me - all stock it's obviously fine and will run forever. Cam will not be cast - it's a billet hydraulic roller. Now if everybody thinks the 80 and 180 will work, I'll stay with that. Duration is in the mid 220's intake and right at 230 exhaust at 0.050. Lift is right at 0.500" with a 1.5 rocker which I'm sticking with. I'm thinking maximum usable rpm will be 5000 - 5500. What are everybodies thoughts on this? Clay

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af2
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PostPosted: Fri Mar 11, 2011 3:22 am    Post subject: Reply with quote

You will be way ahead staying with those #'s. Very Happy
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clay
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PostPosted: Sat Mar 12, 2011 12:27 pm    Post subject: Reply with quote

That sounds fantastic. This is a case of I don't know. It just sounded really low for spring pressure. What I might do is pin the studs while I have the engine out then if the weaker springs become a problem later I can easily swap to stronger springs when it's in the truck. Thanks guys. Clay
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coppergmc
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PostPosted: Sun Mar 13, 2011 2:20 am    Post subject: Reply with quote

Sounds like a 6pj?
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clay
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PostPosted: Sun Mar 13, 2011 11:50 am    Post subject: Reply with quote

Quote:
Sounds like a 6pj?


Huh?

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disturbthepeace1
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PostPosted: Tue Mar 15, 2011 1:12 am    Post subject: Reply with quote

Pining the studs is well worth the effort. I have done a couple and it's pretty easy and will hold the stud just fine. I still think those spring pressures are low for that cam and a heavy roller lifter. Your prob leaving hp on the table if you run it up to 5500 for any sustained amount of time.

Jmo
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