I'm seriously considering swapping some gt-40p heads onto my '76 302. I have a bunch of questions though. One of the biggest questions I have is whether headers exist that fit these heads. I've seen that some Dynomax headers might fit, but I'm not positive about it. Anyone know of other solutions to this problem? I'm also wondering if I buy these used on ebay or at a boneyard (if I can find them), what do you guys think should be done to freshen them up? I'm trying to keep things as cheap as possible, but this can't be a crap job and has to be reliable. Could I use the stock rockers? Are all of the bolt holes and water passages the same as the stock 302 heads? Would I have to do any drilling and grinding to make it work? And finally, I'm also planning on doing a cam change to go along with my Performer intake and 600 Holley 4 barrel carb. When I do the cam change, how would I check the valve to piston clearance? Would I have to have the pushrods shortened and if so, how would I figure out how much to have them shortened? Thanks in advance. -Neil
I would look at shorty headers of some type. I know that factory 5.0 headers from a '87 Mustang GT sit out too far for our shock towers, I have a set in a box that I tried. Maybe the aftermarket has a tighter hugging set. As for freshening heads up, valve seals at a minimum. I would have a machine shop look them over to ensure that you don't have any burned or bent valves. If you are going to change the cam, you may need to change the valve springs to match. Carefully check the rocker arms, unless you are converting to roller tip rockers. They can often have excessive wear or cracks. Even if you are not changing to a higher lift cam, valve springs may be worn. Hope that helps. Seth
The gt40p heads use rocker arms that are pedistal mount and if you want adjustable rocker arms they will need to be machined for screw in studs either way you will need a new set of rockers can't use the ones from your 76. Also you will need to drill 1/4" holes in block because the head steam ports do not match up to the block (could probably drill the heads instead I don't know if anyone tried it that way) below is what world Products tells you to do installing their windsor heads on a early 302, it would be the same for the gt40p head on a early block. Drilling Water Holes for 289 Engines and Early 302 Engines: In 289 and early 302 applications, using a 302 – 351 W head gasket as a template, with a ¼ drill bit, drill a steam hole to the left of each of the three center head bolts in the upper row.
Crane markets a kit to put screw-in studs and guideplates on pedestal mount type heads without machining. I've used it twice (on F3ZE GT40's & GT40P's) revved 5.0 to 6500 without issue. Check centralcoastmustang.net they have a listing for early model Mustangs that might work on a Maverick. get a pushrod length checker from Summit or Jeg's and follow instructions that come with it to determine the correct length pushrod. You might be able to use stock rockers but will still need to check for correct length of pushrods.
