Tapping Thread

[GRace]

After almost having my new motor together I noticed that the center exhaust manifold bolt hole is stripped out. It's the one with the oil passage behind it so I have to fix it. I bought a metric tap set but the M8-1.25 tap is wider than one of the exhaust stud nuts.

Should I be able to thread a nut of the same thread onto the tap? Should I just take it all apart and have the machine shop stud every one of them? I want this to be extremely reliable without any risk of a stupid oil leak messing up many hours of work.

 

[Bchiles]

I had a similar problem with mine I believe that is the correct tap size. If you cant re tap the the whole then you may need to drill it out and helli coil the whole I had the head off when I did mine. It made the job way easier for an at home job.

 

[Junkyardspecial]

I had to turbo an engine once, and ended up tapping the block. I just remember the tap will have an inner diameter and outer diameter. the outer is obviously going to be bigger but not by much. It is quite easy to do, but if you have any doubt at all, bring it to a shop, if you mess it up, you could do irreversible damage to the soft metal.

 

[BogusSVO]

if the hole is stripped, then you need a heli-coil, you can not "Retap" threads from the air.

the exhaust studs are 8 x 1.25, except on some years 4g that have a 10mm lower coroner studs.

after the heli-coil, you will need to put sone type of high temp thread sealent on the stud to prevent the oil leak. This is best done when the hole is clean and dry.

http://www.dsmtuners.com/forums/maintenance-repairs/361131-how-install-heil-coil.html

 

[GRace]

I called the machine shop and they want $10 per hole that is helicoiled. Is that a decent price? I would imagine that I don't have to helicoil the other holes that are fine. I am going to have them replace all of the studs with stainless.

 

[BogusSVO]

GRace, $10 a hole sounds fair enough, that is about the going rate around here too.

I would advise against the stainless steel studs tho, they may be pretty, they may be stronger, but the downside of them is, if you ever break one and have to have it removed, It is a true PITA.
a regular grade 8.8 mild steel stud will be just fine.

It is not so much the shear strengh that you need as clamp force.

 

[99gst_racer]

Though, the good thing about stainless studs is that they will do a much better job at resisting corrosion. And that alone will prevent a seized stud and/or nut. I've have several issues with the stock studs (whatever material they are made of), but I've never had one single issue with the stainless studs and I've put them on every 4G63 that I've rebuilt.

$10 per hole is reasonable. The Helicoil kit itself usually runs $40-50 and that will do 10 holes.

 

[GRace]

I'll check the price difference between stainless and OEM studs. If they are close I'll just get the stainless. I want all new studs and bolts that will not cause me any problem initally.


I now know why DSMs get their reputation for being unreliable, stupid people halfass everything and wonder why it breaks or leaks oil/coolant. This block had a 7 bolt tensioner pulley arm, I wonder why the valves got messed up. Must have been bad keepers...That's my rant for the week.

 

[99gst_racer]

These are the ones I've always used: www.ssstuds.com