I'm building a 460 and need to know if I should use guide plates for the pushrods. I am planning on using a set of roller rockers. I'm using '68 heads off of a 429, so I already have studs for the roller rockers. I was just curious because I have never dealt with guide plates and need to know whether to use them or not. I heard somewhere that you have to mill down the boss that the studs screw into the thickness of the plates. Do you still have to do this if you are going to use adjustable roller rockers? Thanks for the input.

 

If the table where the stud screws down is flat, you can get the regular 7/16 studs with guide plates. I think the 68's may have had a "positive stop" design on the stud which was not supposed to be adjustable. It also had a "rail' rocker arm which had rails cast into the bottom of the arm where it contacted the valve stem and kept it centered on the valve stem. You can get Comp Cams rockers for a BB Chebby (roller tip/1.72 ratio) which will work on the head with new studs and guideplates. I put those on a 76 460, except that the table for the stud and pedestal was "slotted" and required a kit from Crane Cams which included a guide plate that had a nylon insert for the pushrod to fit and did not require a hardened pushrod.

Been a while, and I dont know whats out there, so you will just have to surf a little!

 

you will have to mill the bosses on the early heads and use guide plates
there is nothing other than the guideplates to keep the rockers aligned with the valve stem

 

I am not sure you have to mill the rocker stud bosses on the 68's, but am sure it does not. I believe it is as simple as just using a new adjustable style screw in stud (7/16) with a guide plate. It the guide plate is all steel, you then need to get hardened pushrods. I used the roller tip (ball fulcrum) comp cams rocker arm---not as expensive as a full roller and fine for a street engine. Later engines used a pedestal type rocker arm and the boss had an alignment slot milled into it, which needed to be milled of for regular stud conversion. Most of the SVO catalogs show the specs for that in the back sections. The C/M/400 also used a sled type fulcrum which required milling the stud for a rocker stud.

 

If the heads were originally equiped with stud mount rockers then no machining will be necessary, but if they used any other style rocker(pedistal or rail) it will need to be worked. Stud rockers not only require guideplates but also hardened pushrods, and you'll need to measure for the correct length, it's not likely the ones you have now would be correct.

 

Yes, the heads are the screw in stud style, not the pedestal type. So the pushrod guide plates are the only thing keeping the roller rockers in line with the valves? I talked to a guy who supposedly knew his stuff on engines and he said something to the effect that I would need to mill the sides of the studs in order to keep the rocker arms from going sideways. Any truth to that? So I need longer studs for roller rockers and hardened pushrods. I was planning on buying new pushrods anyways, but why couldn't I just use stock length? I thought the only time you needed longer or shorter pushrods was when you had to have the deck of the block and/or heads shaved? I know you can buy the pushrod length checkers, but is there an easier way of doing this? I don't want to cut corners on this build, but it is kind of a budget build. Thanks for all the help.

 

Yes, guide plates are the only thing to keep rollers in place.
No, the guy doesn't know what he is talking about.
There isn't anything hard about checking for push rod length, you can do it and you will need to. There is no other way to know for sure.

 

I am going to go out on a limb here and suggest that you will not have any problems using the original length pushrods, because any new rocker arm should (yea, dangerous---I know) maintain the proper relationship between the pushrod and the valve tip---. Provided you do nothing else to disturb the height of the heads. Again, been a while, but I think someone makes (or used to) a guide plate with a nylon guide, similar to the Crane kit for the pedestal conversion (I have one of those kits along with the Comp 1411 chebby rollertips, at 1.72). May not longer be available.

Your problem with the pushrods is that without a nylon guide plate, you will need hardened pushrods and the OEM's are not. The OEM system relied upon a "rail" type rocker arm to keep it aligned. Look at the point of the rocker that contacts the valve stem and you will see on each side a cast rail that keeps it centered on the valve.

Like Mark said, it isnt that difficult to check the length and summit (and others---speed shops) have the rocker arm checkers with the adjustable pushrod to check the correct length. Look in the specs for your engine and find (or measure) the OEM length, then get an adjustable pushrod that covers that range. Chances are good you will only need the OEM length in a hardened pushrod. LOL

 

Ok, sounds good guys. Thanks for clearing that up for me.