[Alpine615]

Do all stock turbo heads use the same lower intake bolt spacing, or were there differences between the inline style and the square style lowers?

[TurboRay]

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I THINK the front bolt location is different between inline and 4-square manifolds. Why do you ask? I've heard of folks drilling and tapping the "missing" hole when needed for a different manifold. If you happen to "hit water", it's no biggie....... you just need to seal the threads (RTV, Teflon paste, etc.).  <shrug>

[Alpine615]

Thank you for the response, Ray.  I ask because I bought a performance head and had it stored for 4 years, only to discover yesterday that I don't have all the required bolt holes for my TC lower...  I suppose I could drill and tap for a new hole in the head, but there's no "meat" behind where I'd have to drill...

https://imgur.com/RuCllVM
https://imgur.com/nG568yr

Alternatively, I may be able to drill a new hole in the lower intake to utilize what's available on the head, but I'm not sure if I'll be too close to the injector seal or not 

https://imgur.com/20OTUu4

What would you do?

Edit: Images shared via iCloud were only going to be available for a month, so I removed them in favor of more permanent Imgur links.

[Chuck W]

Drilling and tapping that hole in the head is perfectly fine. If you are concerned about any potential oil leaks, just add a bit of thread sealant,

[TurboRay]

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Please forgive my ignorance, BUT........ RU wanting to install a 4-square intake on a head drilled for the inline intake ~ or, vice versa? FYI ~ Marty Buth has been racing in NHRA stock class for about 2 decades with various years and styles of 2.3T-powered cars (Mustangs & TCs). He holds & has held the record(s) with both styles of manifolds ~ YET..... he's found that the (stock) inline version always has a slight performance advantage over its (stock) 4-square counterpart. <shrug>

[Dolphin1]

Even in that area there's enough material to drill and tap for a bolt

[Alpine615]

Chuck/Dolphin - thank you for the reassurance that drilling/tapping for this hole is fine.

Ray - I only have the TC intake so it's the former... I want to install the 4-square on a head seemingly drilled for the 4-inline. My question at the beginning was simply to find out if there were two different bolt patterns - I had always thought that there was no difference in the cylinder heads from 1983-1989.

I've ruled out drilling the intake because I still need to install the lifting eye, so new "hole in the head" it is.

[TurboRay]

Ray - I only have the TC intake so it's the former... I want to install the 4-square on a head seemingly drilled for the 4-inline.  

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Sooo...... 4-square it is! But, FYI, TCs came with both intake styles, depending upon the year.  <shrug>