|11-15-2012 03:45 PM|
A stock SBC valve spring has about 80-90#'s on the seat and 240#'s open.
If you look hard enough there are springs that will give you over 200# on the seat and over 400# open and will fit into a stock package if setup correctly.
Not recommended for daily drivers but for class racing it's pretty common.
I'm not quite sure how this thread got so off topic. The reality is while it's easier to get higher pressures with bigger diameter springs, the statement you made about there being no stock diameter springs that can give you 350# open is just not factual in this day and age.
PAC-1409 Stock Eliminator Beehive Springs
|11-15-2012 03:38 PM|
Secondly a thicker wire diameter can be ran with a shorter spring or a smaller OD.
Lastly, with a different spring material you can run smaller diameter, and smaller OD and a shorter spring and still end up with more pressure and travel.
|11-15-2012 03:16 PM|
|MouseFink||That rule implies "stock valve spring pressure" because the rule makers know the best way to limit valve spring pressure is to limit the valve spring size to the stock diameter.|
|11-15-2012 02:56 PM|
|engineczar||So what do you do when the rules specify "stock valve spring diameter"?|
|11-15-2012 02:52 PM|
When I mean larger spring, I not only mean larger OD and height but I also include larger wire diameter.
In order to use a spring with a larger wire diameter, it must be a taller spring or compromise the coil bind or use a camshaft with less lift.
Well spit! A high lift camshaft was what you wanted in the first place or you would not have been trying to fit a larger and stronger valve spring. Right?
Lets go to dual springs then and keep the small wire diameter so not to compromise the coil bind height, Doggone it! You must have a larger diameter outer spring to accept the inner spring. Right?
|11-15-2012 02:10 PM|
My example is to demonstrate that you can get a stock diameter spring with 350# of open pressure.
|11-15-2012 12:56 PM|
|11-15-2012 12:47 PM|
I agree with your example.....
Larger valve spring = higher pressure.
|11-15-2012 12:41 PM|
Howards 98215, I use them all the time.
98215 Single with Damper 1.265 dia 115 @ 1.800 380 @ 1.200
@1.75 you have about 135#'s on the seat which works well for a solid flat tappet
There's also PAC1409's and Isky's 295D
All standard Stock Eliminator stuff.
At one point we were running 180# on the seat with Schubecks but we've backed off some.
|11-15-2012 12:11 PM|
IMO.........The wire diameter must be increased to increase the spring rate and must fit in a certain installed height AND diameter. If the wire diameter will not allow the spring to be fitted in a prescribed OD and height, the OD and height must be increased.
I added "IMO" just to make this self proclaimed forum cop happy.That seems to be a weed in his ***.
|11-15-2012 11:32 AM|
|cobalt327||I can't even see his posts unless someone quotes him. But to his credit he at least added 'IMO' as a qualifier instead of stating it as fact.|
|11-15-2012 11:20 AM|
Spring OD, ID, material, thickness, shape, height, coil count, etc. all go into making the spring's open and closed pressure. Increasing the OD is one of the last things they will do to increase the pressure though as it increases the mass which can lead to surge. People spend a LOT of money on spring material just to keep the OD down while supplying the required pressures.
|11-15-2012 07:57 AM|
Beehive valve spring must be fitted to the head precisely because that spring is the only one you have and if it fails, it may take the engine with it. Poor fitting valve springs will over-stress the lower coils.
The critical area for fitting beehive springs is the spring pocket. The outer edge of the spring pocket and the valve guide boss locate the valve spring on the head. The locators are very important in order to prevent the spring from oscillating around the spring pocket. That is why it is risky to use "drop in" beehive valve springs. I prefer valve spring pockets that are .010"- .020" larger OD than the valve spring and valve guide boss that is .010" - .020" smaller than the ID of the valve spring. That is difficult to achieve since the valve spring seat and guide cutters may not be available for a perfect fit, depending on which valve spring you use.
On the pair of 1995 L35, 4.3L V6 heads I am having prepared, I am using Comp Cams 26918 beehive valve springs that are 1.310" OD and the spring pockets are going to be machined to 1.350" OD for .020" clearance. Those Comp Cams valve springs are .885" ID and the valve guide boss is going to be machined to .775" OD for .055" clearance. The machinist will use a Comp Cams 4721 seat cutter and a Comp Cams 4726 guide boss cutter. Larger OD valve springs are difficult to fit because of the valve cover supports and head bolt holes. I will use ARP 12-point head bolts because a 6-point socket will not fit between the larger diameter valve springs.
IMO....larger OD valve springs provide more valve spring seat and open pressure. Economy "drop-in" valve springs should never be used with a radical roller tappet camshaft. Roller lifters are heavier than flat tappet lifters and when they are used on a camshaft with more than .480" valve lift, the valve springs should have 330 lb. - 350 lb. open pressure or the lifters may be tossed over the nose of the cam lobes at high RPM and float the valves with disastrous results. The nice thing about roller lifters is that you can safely use a high lift camshaft....providing you have adequate valve spring pressure. High valve spring pressure and hydraulic roller lifters can be a problem with eventual lifter collapse and lifter damage. It would be wise to use Comp Cams (or equal) 15850 short or 875 reduced travel roller lifters. High valve spring pressure also requires full roller rocker arms or you can burn up the rocker arm pivot balls. Full roller rocker arms MUST be used with Comp Cams short and reduced travel lifters. Full roller rockers present stud problems and valve cover clearance problems to solve especially on a 4.3L V6.
|11-14-2012 09:27 PM|
|oldworldnewtoys||I think I will give em a call. Thanks!|
|11-14-2012 08:45 PM|
Free machining! Where do you live and can i buy you a beer.
Cam seems fine. Those are pretty heavy springs i wouldnt want to cut the head too much if its weak in that area for those springs.
Might be better to get the correct springs lunati can tell you if they have a set that will work on your heads. They usally will not recommend another compaines product but maybe they know a gm part number that will work.
If they stopped making them they may have been replaced with another part number sometimes compaines will free exchange if the part number is superseeded by another one. Might want to call just to see if they have a better option or found a defect in that design.
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