OK, got some power pack heads back from the machine shop. They look nice. I've got some Comp Cam Magnum Roller Tip rockers. These are not full rollers, they just have the roller tips. The slots in the heads where the push rods go look good, no one has machined them or opened them up or anything. My machinist says that I don't have to put screw in studs or guide plates on the heads to run the roller tip rockers, but I open the Comp Cam's package and the instructions say I do need guide plates. WTF!?! I call the guy and he says, I'll be fine with out guide plates. What do ya'll think? OK to go without guide plates. I mean other than the roller tips the rockers are more or less like the stock rockers.
Guide plates should be used. You'd be better off with the stock type of rocker, disadvantage being the roller tip doesn't allow constant rotation of the valve, helping to keep it cleaned of deposits.
On a stock small block head the pushrod slot is machined for a relatively precise fit to the pushrod...and it takes the place of the guideplate. I don't think the type of rocker matters. The need for guideplates arises when you open up that hole for a thicker pushrod, or because your high-lift cam is causing a binding problem. Once you open up that hole you need to provide some other means of aligning your valvetrain hardware...hence the guideplates. Screw-in studs are usually needed once you start monkeying around with the higher spring pressures needed to control a bigger cam, and/or because you need to install...you guessed it...guideplates. Bigger springs can pull the pressed in studs out of the hole. The machine shop will tap the holes and machine the tops of the stud bosses flat so that the guieplates will fit right. Hope that helps. -Scott
Pinstriper, I see from your profile that you own a speed shop. I'm afraid that if you give advice to your cusomers like you just gave you won't be in business long. The valves in a SBC do NOT rotate (exception being the smog motor exhausts which are equiped with rotator retainers. The roller tip rockers keep the tip of the pushrod from forcing the end of the valve back and forth thus promoting wear on the guide. They are BETTER than stock rockers in that regard but are not necessary as evidenced by the millions of SBC's that have the conventional tips. The roller tip rockers refered to in the post will not require the guide slots to be enlarged thus negating the need for screw in studs and guide plates. However if the spring pressure is such that the press in studs start to pull then a screw in stud should be employed or the studs pinned. Frank
Frank, all I go on is by the testing, engine tear downs, and inspection of components and wear patterns. Only advice I can offer is the findings that were made.
Fab32, Thanks for your adivce. I believe I will put the heads on as is, but check the studs after a few miles to see if they are pulling out. If they are, I'll worry about it then. The springs i'm running are the ones that came with this cam kit. I have not put on the cam and timing set yet, but plan to. http://store.summitracing.com/partdetail.asp?part=CCA-K12-210-2&N=115&autoview=sku
Um.... actually, the valves DO rotate.... If you ever look at your rockers when they are set up properly, you will notice that they will hit just off to one side of the end of the valve.... This causes them to twist a fraction every time they are opened.... This is true of just about all motors....The rotating retainers were added to make them twist more, to help get an even better seat. I can't remember right now, but I think they were also used with double springs, which is why the assistance was needed......... Most roller rockers, when properly set up, will also spin the valves, just not as much as a standard rocker... If you still aren't sure, pull a head off of just about any motor, and mark the valve location... Run the motor for a while, and take the head off again... I bet the lines will not match up..
Big Olaf, Ssorry but it just ain't so. Tear down any small block that has lots of miles on it. look at the end of the valve stem end rocker. It will have awear pattern on it the matches a wear pattrn that's on the end of the valve. If thje valve rotated the wear pattern would be round and smoothe, it's not. Also the tip of the valve stem would be square and flat, it's not. Now, what I'm sure your refering to is the lifters and the cam lobes. The lifters have a very slight crown to them when new, the lobe is ground with a slight taper and the lifter runs off center to the centerline of the lobe. This causes the lifter to spin in operation and mate together. This is why you always place a used lifter on EXACTLY the same lobe it was broken in on if you remove the cam and place it in another engine. Been doing this for over 40 years and a SBC was my first rebuild. A '55 265 2 bbl that had solid lifters and poly locks stock. Did you know that? Frank
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