Exhaust manifold holes stripped

[92eagleTSI]

I've got a couple holes for the exhaust manifold stripped in the head, what size drill bit and tap should i use to retap?

 

[dave99gst]

the drill bit depends on the tap size- and that depends on how bad the holes are.
you can also have heli-coils put in the head.

 

[miklaver]

holes are going to metric size 8mm next standerd size is 21/64 witch you might get away just running that tap down it.

 

[miklaver]

go to the web site woodcraftplans.com and they have a chart showing all the fractional,metric equivalents and drill sizes.

 

[BUCK]

Tap them slightly oversize to American UNC Course Exhaust Stud - MUCH stronger than Metric Threads.

 

[92eagleTSI]

Well i did a little searching (google ) and found a chart that helped me out alot on figuring out the sizes of taps and bits. It also had some other charts that might be usefull someday. www.imperialsupplies.com is where i got them from, hopefully it will help someone else. I don't trust any of the holes because i've had the manifold off a few times and know most of the threads are pretty crappy. The manifold was warped when the previous owner welded the wastegate flange on that #1 and #4 didn't seal and the collector flange didn't seal, i believe he just tried cranking on the bolts to get it to seal which messed up the threads. This could explain the horrible spool i've got and why i haven't been able to tune it, since these leaks are all pre o2, also needed HG. Hopefully we're good now.

 

[92eagleTSI]

I almost forgot, once on the website go to charts you'll see them. Also if i get this thing fixed and tuned i'm going to the track this weekend Test and Tune for my first time and i'll have some video, unless i screw up then i won't let you see it.

 

[92eagleTSI]

Just an update. I drilled and tapped all the holes to 3/8 -16 and used 1 1/4 long bolts & lockwashers and this worked very well. I allmost felt a little woozy when i tried to tighten those babies up. Also had to remove the radiator to make room for the drill. All in all it was an easy fix.
Thanks

 

[blackrosenova40]

When you driled them and tapped them , did you also drilly the exhaust manifold holes bigger? I drilled and tapped the head to manifold stud holes on a mazda mx6 gt once and and I had to drill the exhaust manifold holes because if pidge toeing or something, cant remember what its called.

 

[92eagleTSI]

When you driled them and tapped them , did you also drilly the exhaust manifold holes bigger? I drilled and tapped the head to manifold stud holes on a mazda mx6 gt once and and I had to drill the exhaust manifold holes because if pidge toeing or something, cant remember what its called.

Sorry about that I haven't looked at this thread for a long time. I did have to drill all the exhaust manifold holes a little bigger, i think I went to 1/2" on them but i can't remember. I know the two holes on the ends were big enough (3/8") but all the others were too small so I just drilled all the holes bigger. I don't know why the 2g manifold has different size holes.