valve spring clearance

grumpyvette · 12-05-2008, 04:49 PM

HEY GRUMPYVETTE?
How much lift can these springs handle? I've read two different things from different sources....One says they can handle .490 another says they can handle .550....What's the real deal? See links below...I appreciate any help rendered.

http://www.motorpartscentral.com/Pro...ctModelId=7726

http://www.trifive.com/forums/showth...ghlight=RV943X

you might want to keep in mind theres differances in the way max lift is being measured in some cases.
example
heres a chart and springs IVE USED

http://www.racingsprings.com/PDF/beehive.pdf

lets look at the last spring on the chart, #PAC 1520

its installed height is 1.880

coil bind is at 1.210
subtract 1.210 from 1,880 and you get .670, yet,its max lift is listed at .650, ok,
but any engine builder will tell you you really need a minimum of .050 clearance, before reaching coil bind, so the real max lift at this point is not .650 but .620 lift, AHHHH!
but thats ONLY if the valve train allows you that .620 clearance, if the valve guides,piston to valve,retainer to valve guide, or valve seals, rocker slot clearance or a dozen or more other factors are taken into account and clearances meassured, youll be lucky in the real world to see that .620 lift clearance, you might have only .590 quite easily, and require either more machine work, or differant retainers, valve keepers etc. to get even that .620 let alone the .650 listed, and yes you can get that .650 but it might require a few tweaks, machine work, and a differant installed height, etc.
I think what they are saying is , that if you just pull the old springs and install the new ones .490 is usually what youll see, do some machine work and check clearances carefully and in theory you get the larger figure.

RevXtreme 1 · 12-05-2008, 08:10 PM

Keep em comin Grump! It might be over some heads, but it is knowledge that is needed. With the LS motors we usually see the shop, or do-it-yourselfer just use the recomended push-rod length, and as this affects both the wipe patteren & the lifter pre-load (on hydraulic cams) it is rarely the best set-up. The most common result is not enough pre-load and the valve train noise "sewing machine" that the majority of the vette owners seem to accept as normal. This is NOT normal, even with the aggressive grinds on todays LS cams you should have a very quiet upper-end if setup properly. And in addition to the noise (which will cause premature wear & valvetrain instability), you are using the entire profile and are leaving power behind. This and the correct wipe pattern are what we see as the biggest build errors, with not degreeing the cam a close second. Most are fine going by the timing marks, but without degreeing it there is no way to be sure.

Our builds may cost a bit, but a customer is welcome to observe and see just what goes into their motor to see why more time is involved. Each of the steps described by Grumpy in his post, and my addittion, takes a ton more time and therefore cost. So the "lowest price" is not always the "best deal" in the long run.

grumpyvette · 12-10-2008, 11:09 AM

HEY GRUMPY?
I have some comp beehives on my bbc, part #26120
I also have a lunati voodoo hydro roller part # 60212
I have 1.72 ratio full roller rockers up top, I've cycled the engine through many times and checked clearance and have just a smidgen above .060 clearance in the middle.
This isnt a dedicated track car, just for street, and I dont plan on ever going above 5500rpm with it and have a rev limiter just to make sure, but does that amount of clearance with those parts seem safe enough to you? I don't think comp makes a stronger beehive for hydro rollers, and I dont feel like respending money, I've read many things and some people say you should have .100 clearance in the spring, and others say .060 is fine, what has been your experience?

I've called comp and they said they should be fine. However, I highly doubt they are going to reimburse me 8k in parts over their springs. I do want to protect my 8k I put in there, but at the same time dont feel like shelling out $250+ for new valve springs when the ones I have are brand new.

And I checked these clearances with no oil in the lifters whatsoever, they were completely bled down.

The people that assembled them for me http://www.m2race.com said on the install sheet that the installed height is 1.890, the installed pressure is 160lbs, and that coil bind is a .625 gross lift.

Comp says these are good to .600 lift and with the 1.72 ratio I come out to .607 lift. The tech on the phone told me it should be fine.
Would you run em?

ASSUMING your figures and info are correct,if your installed height is 1.890 and coil bind is at .625 thats 1.265 height for stacked spring coils, add .050 for minimal clearance and youll see a .575 MAX valve lift on the cam, BUT..

http://store.summitracing.com/partde...5&autoview=sku

http://store.summitracing.com/partde...2&autoview=sku

comp shows a 1.23 coil bind height, so given your lift is .607 the installed height and other clerances are critical to finding out if it will clear safely, 1.890-.607=.660-.050 for clearance =.610 so youll be ok IF the true installed height is really 1.890,
now heres what ID do,IF you want extra clearance just to be safe, ID install valve keepers/valve locks that gave me an extra .050 lift
http://www.cranecams.com/?show=brows...Number=99099-1
by seating the retainer .050 higher on the valve stem....since youve got no intention of running on the ragged edge of the rpm band, changing the installed height will lower the valve spring loads slightly but in your application thats almost a total non-issue, and yes it may require longer pushrods to get the rocker geometry correct so think thru your changes carefully.