Shooting myself in the foot - Heads are apparently not interchangeable.

[Xylene]

After all the pain of rebuilding this 302 5.0l engine, I was in the process of installing the alternator accessory mounts and found out that on these heads 3 of the 4 sides contain 3 accessory bolt holes, but one only had 2. Of course the side with only 2 bolt holes requires 3.

So my question is this. Are the heads not really interchangeable? If they are could it be that one of the accessory holes was not drilled out? You can see in the photo that it appears there is a place where the hole should be but it is roughly filled in.

Is drilling this hole a viable option or do I just suck it up and undo everything and reverse the heads? If I do that can the gaskets be reused on the intake manifold, valve covers and the heads (the engine has not be started yet) or do I need to replace them all again?

Thanks

 

[crunchie_frog]

Heads changed year 97.5 to GT40P heads, is that what heads you put on or do you know? I am pretty sure their are markings that designate but you would have to google to find out what they are. Can you use the heads you have, if it were me, I would go ahead and try your idea of drilling and tapping the holes you need. There may or may not be any difference in the factory tune if you do not have the GT40P heads, I think there might be though but it might not make that much of a difference.

 

[Xylene]

Heads changed year 97.5 to GT40P heads, is that what heads you put on or do you know? I am pretty sure their are markings that designate but you would have to google to find out what they are. Can you use the heads you have, if it were me, I would go ahead and try your idea of drilling and tapping the holes you need. There may or may not be any difference in the factory tune if you do not have the GT40P heads, I think there might be though but it might not make that much of a difference.

Mine are marked as GTP (there might have been other markings that I cannot see now). The only other marking is 11 and 12. I am pretty sure they are meant to be interchangeable except for that accessory hole.

If I decide to pull the heads again, do I need to replace all the gaskets? I know I would need new head bolts.

 

[Xylene]

I decided to attempt to drill it out. I templated the holes and began to drill to find out that the hole was plugged up with some plastic, perhaps a plastic plug.

Any ideas as to why there would be a plastic plug in this hole? Do I need to worry about anything if I choose to use it now?

 

[BKennedy]

If the hole is already threaded, its meant to be a accessory mount. Maybe there are threaded and plugged holes on both sides so the heads are truly interchangeable?
You might be overthinking this, I do it all the time.

 

[Xylene]

I drilled out the plastic and hooked up the accessory mount. Hope all is well

 

[Pete Deering]

A head manufacturer, told me, it is high temperature silicone. They use that, so they can tell if the engine overheated if go to return them.

 

[donalds]

A head manufacturer, told me, it is high temperature silicone. They use that, so they can tell if the engine overheated if go to return them.

^^^ cool

 

[Xylene]

A head manufacturer, told me, it is high temperature silicone. They use that, so they can tell if the engine overheated if go to return them.

Thats good to know