A few Questions about GT40p heads.

[91grandmarquis]

Ok so I am picking up a set of GT40p heads, now I was told by the mustang guys over at corral that my manifolds should bolt to these, however I don't think that is true. I also need to know what Kind of Headers I need to go on these, I assume unequal length shorties? And my final question is about spark plugs, I have been informed the plugs are in a different spot slightly making them harder to get at, what plugs to I need to use on these? Just don't want to get the wrong stuff is all.

As always thank you everyone in advance.

[86VickyLX]

Ok so I am picking up a set of GT40p heads, now I was told by the mustang guys over at corral that my manifolds should bolt to these, however I don't think that is true. I also need to know what Kind of Headers I need to go on these, I assume unequal length shorties? And my final question is about spark plugs, I have been informed the plugs are in a different spot slightly making them harder to get at, what plugs to I need to use on these? Just don't want to get the wrong stuff is all.

As always thank you everyone in advance.

Stock manifolds will not work. They'll bolt up but you'll never get the spark plugs in. You need motorsport headers for your application or FRPP(?) headers shorty headers. Get the plugs rated for the vehicle you get the heads from. Can't go wrong with what the dealer recommended for those heads. You might have issues with piston to valve clearance, since the 302s with the gt40s and gt40ps had valve reliefs in the pistons.

[91grandmarquis]

Hmm I don't want to F* anything up with clearance, I thought that wouldn't be an issue? If it comes to it I suppose I could swap out the pistons for ones with reliefs, but I haven't the faintest idea of how to do it or how much work it is.

[86VickyLX]

Hmm I don't want to F* anything up with clearance, I thought that wouldn't be an issue? If it comes to it I suppose I could swap out the pistons for ones with reliefs, but I haven't the faintest idea of how to do it or how much work it is.

From what I have heard, people have had mixed success with that. Some had valves that hit the pistons, others didn't. I think it might have something to do with head gasket thickness, hough don't quote me on that... You could try a mock up, and turn the engine by hand and if you get any binding, you're gonna have problems. To swap out the pistons, you'd have to pull the oil pan off, and go through the ordeal of that in the car. Or you could pull the motor and do it that way. Or just get an explorer shortblock and go from there...?

[91grandmarquis]

Damn, Im not sure why this wasn't brought to my attention earlier if that is the case. I would much rather take the oil pan off and go that route if I need to do it, maybe somebody else will know for sure. I know I was going to have an issue with my current cam causing the same problem because of its duration, so I got an 86 HO cam. oh well such is life.

[86VickyLX]

Damn, Im not sure why this wasn't brought to my attention earlier if that is the case. I would much rather take the oil pan off and go that route if I need to do it, maybe somebody else will know for sure. I know I was going to have an issue with my current cam causing the same problem because of its duration, so I got an 86 HO cam. oh well such is life.

Scott or Thain should know for sure. The oil pan in the car, is not for the faint of heart... It involves lifting the motor up as much as it can be attached to the tranny, blindly unbolting the oil pump and pickup assembly, and jimmying the oil pan out of there. Not fun, but doable. I've done it, so has 87_Crown_Vic and a few others. I still think you should get a explorer shortblock and work with that.

You're probably gonna need a valve job for those heads too mang.

[91grandmarquis]

Yeah supposed to have had one 6k miles ago, But I am aware of this. Im hoping it doesn't come to replacing the pistons, The problem for me with getting a new block is that I would have to assemble it outside the car, using my components off the current engine and that would take a while, this is my daily driver. I was hoping that I wouldn't run into issues like this but oh well.

[86VickyLX]

My thought was, throw the gt40p heads on the exploder shortblock, get your gt40 intake and shit on there (injectors, sensors). Throw on your headers. Get everything ready, then swap all that you need from the old engine. Oil pan, oil pump pickup and probably a new oil pump, the threaded oil pump thing. Water pump and timing cover, distributor, and all accessories that aren't bound to the car, like the ac if you're keeping it. You can assemble the front end of the engine out of the car and throw it in as one unit.

[91grandmarquis]

Yeah apparently our pistons are dished, PMed scott and told him the setup with the 86 camshaft, said I shouldn't have any problems, the only reason to worry would be if I were using the 86 engine because those pistons are flat and non relieved. Its going to be much easier for me to rebuild the top half in the car as opposed to doing a swap. Although I have done a swap in 2 days, like you said, new block and heads, but nothing else.

[88grandmarq]

simple head swap will NOT cause any piston to valve interference.

installing aftermarket (high lift) camshaft with stock, non HO pistons will lead to problems if you dont calculate correctly.

GT40P heads take a autolite copper 764 or AP104 if you want a platinum plug.

Stock, iron manifold will NOT fit on P heads. tubular manifolds from a 90 5.0L town car will work as long as you use spark wires with 90 degree boots on #5 and #6 cylinders.

[91grandmarquis]

Ok Ill probably go with the tubular manifolds just until I can get the dough to fab up an x-pipe and high flow cats off of headers. My understanding is that these will bolt both to the current exhaust flange and to the heads with no problems?

[pantera77]

Ok Ill probably go with the tubular manifolds just until I can get the dough to fab up an x-pipe and high flow cats off of headers. My understanding is that these will bolt both to the current exhaust flange and to the heads with no problems?

Yep, although their not very "high flowing".

[86VickyLX]

Ok Ill probably go with the tubular manifolds just until I can get the dough to fab up an x-pipe and high flow cats off of headers. My understanding is that these will bolt both to the current exhaust flange and to the heads with no problems?

yes, they should bolt right up to the stock down pipes.

[91grandmarquis]

Excellent, only problem is they are $150 a piece, time to look for a used pair of these suckers.

[91grandmarquis]

Also, pending me needing to get a valve job on these things, They are not in my possession yet so I really don't know. Will roller rockers add any significant performance, not actually sure what they do to improve performance, maybe this question has an obvious answer, but I certainly do not know it. Also what would recommend if they are worth the $$. My understanding is they wont do much unless I completely rollerize this engine, and that means MAF if Im running a roller cam I believe, unless there is one with similar specs to an HO cam?