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Discussion Starter #1
As per the title, I need to redrill a cast Turbo manifold to run a different Turbo,

Machinist decided the new/old holes are too close apart so I need to fill in 4 first.

He suggested welding them closed and then redrilling/tapping for the new holes.

The welder suggested installing bolts in the holes and then cutting them flush.

Either method would requiring resurfacing the Turbo manifold flat afterwards.

Anyone have any experience along these lines with any input?

If welding the holes up what method or rod or filer, Nickle rod, MIG/TIG??

If cutting bolts off, use regular grade 8 or actual original Turbo studs?

What do guys use for Turbo mounting studs on cast exhaust manifolds?

Some kind of OEM or is there an aftermarket option?

Any input, recommendations, cautions and discussion are appreciated!!
 

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I guess it depends on the quality of the casting-you going from T4 to T6? You could tap the ex holes, lock tight set screws in and redrill. If welding, you could cover the holes on the mating surface with a copper backing, plug weld from the back side, might avoid having to resurface.
 

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Be careful filling holes with bolts and welding. Depending on what you use for a bolt, the material can become extremely hard, to the point that drilling and tapping will not be possible. We used to run into this when using grade 8 threaded rod to fill/weld holes in automation tooling that was made incorrectly.
 

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If you use Nickel rod be sure it is the machinable kind. The non-machinable is exactly that even with carbide tooling. A lot of people have had good luck welding v-bands etc on cast manifolds with mig using 70S-6 wire which is the most commonly used kind. I would plug weld to achieve the strongest possible repair.
 

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Discussion Starter #5
Appreciate the replys!

I should have mentioned it's an ancient Chrysler 2.2 with their oddball bolt pattern.

Spacing is odd and wide, they never used a gasket but never leaked.

I have a couple of Holsets (HE341 & HE351) I'd like to try.

The holes are blind and only 1 is real close the other 3 have a bit of meat in between.

The original metric studs are too short to accommodate the thicker Holset flange.

What do any of you guys use for studs??

Are grade 8 sufficient or is there something specific for Turbo use?

Here is a pic of a re drilled manifold I found online, not mine.

Any input is appreciated!

 

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Is that the same pattern you will be using? If so, can you rotate the turbo slightly CCW? That will improve the holes at 5 and 11 o'clock. Move 7 o'clock slightly closer to the hole, but away from the edge, and 2 o'clock will still be fine. I would bury grade 5 studs in the stock holes, with a slight chamfer at the surface, and put a VERY thin tig bead to hold them in location, BUT do not weld the 25% closest to your new tapped hole. Grind your bead flush with a fine 2" roloc. These are strictly to support your gasket. Having said all that, for all this work, is there not a header available? Sorry if you answered that and I missed it.
 
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