Cooterthief said:
I appreciate all of the help, but Im afraid you guys are preaching brain surgery to a blacksmith.
I dont know what a base circle is and I dont know what lifter preload is. But Im not sure if this is where my problem lies. ( I still would like an explanation of both).
My problem is trying to figure out if leveling the top of the pedestals will effect the length of the pushrod.
And what are guide plates and why do I need them?
From what you have described I can tell you a couple things.
1) Check your rocker arm to valve tip contact! This is very important. Many people overlook the facts of how the geometry affects performance and installation.
There is a big difference between any rocker arm made for a SBF (5.0,302,351W) and the 3.8L motor. The rocker that works for the 3.8L is the 351C/460 style rocker. Do not make the mistake of using a rocker made for a 5.0. The 93 Cobra was a 5.0 motor. These rockers are wrong.
Rockers (regardless of ratio) made for the 5.0/5.8 motors will not reach the center of the valve tip no matter how you set them. The reach is too short. You will be only barely touching the valve tip and you will ruin your guides as well as other possible problems if you use those rockers. Just because someone said they used them doesn't make it right.
On the other hand, if they are
351C rockers then that will be ok. Just wanted to clear up that little issue.
2) I'm not sure I understand what you mean saying you machined the pedestals flat. Do you mean the mounting bosses on the head or you machined the pedestals in some way? The pedestals are the "lugs" through which the bolt passes and which the rocker arm fulcrum rests on. Machining those flat would accomplish nothing good so I'm still not sure what you did.
Or did you install screw-in studs? If you installed studs of any kind then you will need to use guideplates. Guideplates are locaters for the pushrods. If/when you remove the locating bosses on the heads then there is nothing left to align the rocker arms and pushrods. Guideplates positively locate the pushrods so that the rocker arm stays in proper alignment with the valve. No one makes guideplates for these cars, you have to make your own. Some of us can do that for you if you need. I just don't follow what you did when you say you machined the pedestals flat.
3) I think it would be presumptuous for anyone to tell you what length pushrods you should use without knowing a little better what you have. When people use bolt on 351C rocker arms (no machining required) most times 7.2" pushrods solve any pre-load issues.
4) Regardless of what rocker arm setup you are using, the final decision on pushrod length is going to be up to the installer. There are many variables that can affect ultimate pushrod length. Unless you use bolt on parts you are going to have to determine the best pushrod length by doing a mock up with the new cam installed. This is how any competent engine shop would do it.
5) Regarding cam selection, you can buy a cam from any number of places but there are few places where you can get good technical information and installation assistance to go along with that purchase. When in doubt ask questions.
6) You will have to set preload on the lifters. You will have to learn what this is and how to set it or you will have to take the car to someone who does. Take a few minutes and peruse
www.cranecams.com. They have a good number of articles with pictures showing basic valvetrain setup procedures and guidelines. They are an invalueable resource.
