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Old 01-11-2013, 04:38 PM
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Originally Posted by flyingputz View Post
I don't mean to beat a dead horse, but here's my dilemma. I thought I had this ALL figured out. I've got the #906 vortec heads, Comp 26918 springs(recommended installed height 1.80") 787 retainers and +.050 locks. This gave me my necessary height and retainer to seal clearance, with NO machining. I don't like the idea of taking away that much material from the guides and seat, especially since the guide is ALSO the spring locator. I don't even know if ANY material can be taken away from seat to increase installed height? Now my rockers are contacting on many of the retainers. If I put the standard locks in place plenty of valve tip is available, however, that takes away my retainer to seal clearance AND increases my seat pressure to approx. 144 lbs. I feel my only option is +.100 longer valves. I will take up any extra height with -.050 locks OR shims. I know I'll have to keep the geometry correct at final assembly via pushrods. BTW, cam is 222-230 dur. .509/.528 lift @ .050 with 1.5 rockers. I'll be using Comp 1.52 rollers(self aligning). Screw in studs are already in place. As stated, I already have ALL these parts. Any thoughts or suggestions greatly appreciated.
I have to admit that after 4 pages of this I'm getting lost.

So if you still have the problem let me state my understanding, or lack, of it.

I take that you have self guided roller rockers and the self guiding guides that are like washers located to either side of the roller which contacts the valve stem are themselves touching the spring retainer. Is this correct?

The other choice open to interpretation is that the body of the rocker contacts the spring retainer. Is this what's happening?

Neither situation is desirable, nor acceptable, but the causes and solutions of each are different.

Neither of these problems have much to do with the installed height of the valve, not that this can be ruled out but for the valve to be sitting deep in the seat from an exuberance of seat grinding to the head or valve, or both, would have to be very extreme to have such a huge effect on the angle of how the rocker address the valve stem as to put parts of the rocker into contact with the spring retainer or the locks. Sinking the valve seats (head and valve) forces the stem to ride higher in the guide. This moves the lock position (thus the retainer) further from the spring seat resulting in the installed length of the spring to be longer than specification which in turn relaxes the spring reducing the forces it will generate toward keeping the valve train following the cam lobe and holding the valve in the closed position. Typical flat rate shop work for this situation would be to shim the spring between the spring pocket and spring is the usual solution toward making the effective length of the spring shorter so the correct spring length is established between the bottom of the retainer and the top of the shim. The valve tip is often ground to restore the installed height of the stem to the valve spring pocket to restore the rocker angle and position to the stem tip. But this shortens the clearance distance between the lock grooves and stem tip; thus also ,where the retainer positions from the stem tip, this can get you into clearance problems between the retainer and rocker or in the case of self guided rockers the lesser distance could put the guiding bosses or washers into contact with the retainer. As an aside this is a common problem with older Ford SBs where rocker tip and stem tip wear closed the clearance till the rocker guides rubbed on the retainer, which risks pushing the retainer low enough to allow the locks to pop out dropping the valve into the cylinder.

Obviously trying to avoid shortening the Vortec's tall guide boss to provide additional lift clearance between the assemblage of the retainer, stem seal, and stem guide by sinking the valve deeper in its seat is not the way to solve this clearance problem as it gets you into the problems I describe above. When I read your comments through this; I get the feeling that this approach could be involved. Did you do this?

It is always possible that the lock angle of 10 degrees or 7 degrees does not agree with the interfacing angle of the retainer. This would cause the retainer to sit improperly as a position to the stem tip and affect spring installed length. Did you check these parts to be sure they have matching angles?

Roller rockers especially cast ones tend to be fatter than stampings; it is not unusual to have to grind a clearance into their body to clear the retainer especially where oversized springs are used.

The angle the rocker makes with respect to the retainer can also be an issue; if the studs are too short there usually isnít enough bite for the studís threads into the retaining nut which can result in thread failure. Solution is a longer stud which for sure will force a longer pushrod. Or if the pushrod is too short because the valve stem sits higher than designed then the rocker sits at a low position with a sharp angle between the push rod and stem tip that can get it into contact with the retainer. The solution is a longer push rod.

If everything is dimensionally correct and the witness marks on the stem show the roller to be properly positioned on the stem sweep but the guide washers are riding on the retainer then one can consider several possibilities are causing the stem clearance distance to be incorrect:

- This can be a result of the lock's location of the tang being other than what you expect; there are locks that move the tang up or down .050 inch being typical from the OEM position. These are often relieved for lash caps which will allow their use with roller tipped rockers. You also need to be sure the locks are the proper diameter for the valve stem. Between .310, 8mm (.3150), .3437, .375 inches there's getting to be things that are close but not necessarily correct for what you're using, so you've got the check stuff before using it.

- The distance between the lock groove and the stem tip is insufficient. Typically the SBC valves come in a .225, .250, or .290 inch clearance. Don't go by what documentation says should be there use what provides the needed clearance. Often the overall length is held at a constant and this clearance is moved by relocating the lock groove, this is done to play with spring length as a means of adjusting pressure between the weight differences of intake and exhaust valves. More engineering refinement than is probably necessary for anything short of a race engine. Use this to get the rocker correctly positioned. Keep in mind that longer valves does not mean the relationship between the lock groove and stem tip changed but is just moved further from the valve head and seat. Some heads are .1 or .2 inch taller between the seat and the spring pocket and need an overall longer stem to restore the spring length to retainer relationship. This doesnít change the groove to stem clearance aside from placing that relationship further from the valve head. This will require longer pushrods because it changes the rockerís position from the head deck (makes the engine taller is at were) but does not necessarily change the dimensions between the bottom of the spring retainer and the top of the spring pocket, I mean it can, but doesnít have to. The production Vortec head should require this kind of messing around unless youíre trying to get space for more lift without grinding down the guide. In that case you get into a lot of problems not unlike where youíre at. Did you do this?

- The guide washers are too large, given the quality issues I see almost everywhere anymore it could be that the guide washers are bigger than needed, I guess I could say grind them down, but I wouldn't do that except as a last resort after checking and adjusting everything else first.
I know itís hard to believe, but Iím out of words and will be out for the weekend. So good luck with this.

By the way, a hydraulic lifter will chase any gap that opens up in the valve train parts till the plunger runs into it retainer (bail or clip). This is what a pumped up lifter is all about. A space appears between the parts for any reason, the lifter closes it. If it was adjusted properly there's about a .020 to .030 gap between where it's running position is and its retainer. When it closes that space the next time the valve goes to close it can't, it's hanging .020 to .030 off its seat till the lifter bleeds down and returns to its normal preload clearance.

Bogie
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