Cmon Guys I Need Your Help On This One

Been there, etc.

You need to figure out which GT40's you have. I have a set of SVO Gt40s and a set from a Lightning truck. The SVO set did not have valve rotators, and was easy to set up. The 351 Lightning production heads had valve rotators and the keeper groove is at a different height on the intake and exhaust. (cant remember which is which right now)

This should not be a problem if you got new valves, but if they were direct replacements you need to check. However... there are several length valvestems for small block Fords, so you need to check and measure. 289s and some 302's had shorter valves. Rail rocker types have longer stems, etc.

Then you have to make sure you have the correct pushrod length. It takes more planning than I ever imagined to get these right.

On my Lightning set, I just changed springs to a Comp Cams set with their retainers and keepers. One set of keepers is .050 offset so the valvespring height is correct. I just used a patched together set of old stock bolt on rockers and they work fine. I have stock 78 length pushrods with 94 heads, and 79 rockers. No adjustment, I tried shims, but did not need them. Runs to 6000 rpm easily.

On the SVO set, I have Comp retrofit studs and Comp roller tip rockers, with stock 79 length pushrods. It is adjustable, and it works just fine.

I bought a set of Crane springs, but their tech people were not at all helpful. I have always had spot on advise from Comp Cams.

However, I do not remember if the Lightning heads had valve lash caps, but if they did, you have to use them. Otherwise the pushrods will be loose, you will get little valve lift, no power, and it will destroy the valve stem quickly.

You probably need to shim the rockers. I gather that you are still using a pedastal type rocker. Also, I usually give them 18ft lbs. Go to the speed shop and get at least .010 shims. These "shims" go under the pedastals. Really you need to measure and figure out what thickness shims and which rockers actually need them but I have found over time that the .010's pretty much always do the trick. Good luck.

Valve lash what?

Valve Lash

A small clearance must be left in the valve train to allow for this expansion as the engine warms up. This clearance is called valve lash.

If there is too much lash, the engine becomes noisy as the rocker arm slams down on the tip of the valve. If there is too little lash, the valve doesn't seat properly, and burns out, or compression is lost. Lash must be adjusted from time to time. This is measured with a feeler gauge, and the lash is adjusted until there is a slight drag on the blade of the feeler gauge. Lash can be adjusted either hot, or cold, depending on the manufacturer, so check the service manual. The exhaust valve will usually have more lash than the intake valve, because it gets hotter.