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Posted by: bkrantz May 24 2021, 07:37 PM

As I showed in my rebuild thread, I found one of my cylinder heads with an insert for one exhaust stud, but installed at an angle. The other head has one oversize stud hole (9mm?).

My first thoughts: remove the insert and inspect the hole. I may attempt to drill a larger hole at the proper angle and install a bigger insert. If I do that, I may do the same for the other head, which will be the same hole position.

Comments?


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Posted by: infraredcalvin May 24 2021, 09:57 PM

Look to have plenty of meat, you definitely need straight studs otherwise you won’t get headers/heat exchangers on.

Posted by: JamesM May 25 2021, 12:24 AM

How much money you looking to spend?

Quite a few ways you could go but that all depends on your goals here.

The safest bet, get brand new heads, but that obviously isnt an option for everyone.

Frugal approach? Assuming you are not looking to have any other work done on the heads, and assuming the insert is the solid style and not a heli-coil, screw a stud and test fit your heat exchangers on the bench. If the stud is still angled well enough to let the heat exchangers slide on properly then I would say that may be the best you could hope for with that head.

If you have the proper setup to do so you could attempt to re-drill it straighter and run an oversized insert, but that could be a gamble as well, especially if the current insert is actually functional as is.


Personal opinion here, but anything beyond that requiring welding on the head I would just get new (as in brand new) heads. Exhaust stud issues may be my least favorite thing to deal with on 914s

Posted by: 930cabman May 25 2021, 04:36 AM

Agreed with the available meat, but location, location, ..... If you know a friendly machinist I would have him look it over. Given the correct setup, this is simple stuff, given a cordless drill and a bench vise, it's another story

Posted by: stownsen914 May 25 2021, 05:57 AM

Ugh, what quality. Should be correctable though. Probably best to have a machinist do it and use a timesert.

Posted by: ClayPerrine May 25 2021, 09:37 AM

The absolute best way is to have someone remove the insert, and TIG up the hole. Then re-face the surface around the hole, re-drill the hole straight with a 6.8mm drill, and re-tap it. To do it absolutely right requires a vertical milling machine.

Clay

Posted by: pilothyer May 25 2021, 10:10 AM

This would be the best way to address this problem.

Posted by: 914_teener May 25 2021, 11:31 AM

You are halfway to a new head given this fix.

If I were rebuilding a TIV I'd just get new castings and spend the bucks. Just not worth it

Posted by: Front yard mechanic May 25 2021, 06:59 PM

Bolt it up and run it

Posted by: bkrantz May 28 2021, 04:08 PM

I found a machine shop owner that is willing to try removing the insert, welding the hole, and re-drilling for the stud. But he needs an exhaust to be sure the stud position is correct.

Can this be done with the short 75-76 exhaust pipe section? Any difference in exhaust ports or stud locations on the 75-76 heads?

Posted by: Shivers May 28 2021, 04:22 PM

Should be the same

Posted by: DRPHIL914 May 28 2021, 04:56 PM

@http://www.914world.com/bbs2/index.php?showuser=23343
is this a new casting??

Posted by: JamesM May 28 2021, 05:38 PM

If this isnt a machine shop that regularly works on type4 heads you might want to rethink that approach. Given the location of that particular stud and its proximity to the combustion chamber and valve seat they may wind up doing more harm than good.

Posted by: bkrantz May 28 2021, 10:06 PM

No, the original head on my 2.0 (I think). But I was dumb and did not recognize the issue before I paid for valve work.

Posted by: ClayPerrine May 28 2021, 10:15 PM

When I repair them on the car, I use the short cast section cut off of a 71 914 heat exchanger. I bolt it up with the other stud, and use it as a guide to re-drill the hole.

Posted by: bkrantz May 29 2021, 10:15 PM

@http://www.914world.com/bbs2/index.php?showuser=1143 do you have that section handy, and can I rent/borrow it?

Posted by: ClayPerrine May 29 2021, 10:49 PM

Yes. It is in my tool box. PM me your address and I will send it.

Clay

Posted by: 914werke May 30 2021, 09:08 AM

Keen minds think alike. I did the same but I also drilled it up to accept an actual hardened drill guide. Then got 2-3 guides of varing ID size so I could driil-out the broken stud & preserve the head whenever possible.

Posted by: bkrantz May 30 2021, 08:33 PM

Thanks. PM sent.