1998 4.3L V6 exhaust flange studs

[ASJT3]

My latest acquisition is a 98 Chevy K1500 with the 4.3L V6 Vortec. I'm going to have to replace/rebuild the trans soon so trying to get exhaust y-pipe removal out of the way.

I started using a torch to help remove the rusty y-pipe flange nuts but looks like they ate up the stud threads on the way out. All of the replacement sets I find (e.g., Dorman 03133) include plain replacement studs (with a small unthreaded shank portion near the middle). However, looks like the studs currently on the truck have a hex feature on the top that can be used to torque the stud.

I'll use a stud extractor and a torch to remove the old studs, but how to install these new plain studs with nothing to grab onto? Is the idea just to thread them in by hand with some hi-temp anti-seize and then just tighten the nut down on top until it's snug?

Thanks,
Alex

[Schurkey]

The studs can be double-nutted and screwed into place...however I don't think anything beyond finger-tight is needed if the female threads in the manifold are in good condition.

Anti-seize is probably a good idea.

[ASJT3]

Originally Posted by Schurkey

The studs can be double-nutted and screwed into place...however I don't think anything beyond finger-tight is needed if the female threads in the manifold are in good condition.

Anti-seize is probably a good idea.

Thanks! Will run a tap thru the threads to ensure they're in good condition. I bought both the stainless and regular steel kits. Never used stainless but seems like a good idea, don't think galvanic corrosion is a big concern here.

-Alex

[Schurkey]

Ideally, a thread-restoring tap, not a thread-cutting tap.

I have this set--very recommended. Sometimes sold under the "Lang" brand name. "Lang" and "Kastar" are different branches of the same company. BEWARE OF KNOCKOFFS FROM CHINA.
https://www.amazon.com/Kastar-971-Me...s%2C184&sr=8-3

[Blue Bowtie]

a.k.a., roll-form taps versus a cut tap. it takes a little more power to drive one into crusty cast material, and all the lubricant you can supply is fair game.

[ASJT3]

Thanks for the replies...heating the flange red-hot and using the stud extractor to remove the old studs did not go as planned. They were all extremely recalcitrant and did not want to come out, and I sure did not want to put too much torque and break them.

My problem is the threads on the studs are completely stripped for the last ½ inch where they engage with the nuts, but otherwise studs are in good condition...Has anyone ever tried a weld buildup on the degraded threads and then cutting new threads on the weld material (ground-down to match the shank diameter, of course)?

[Schurkey]

Originally Posted by ASJT3

heating the flange red-hot and using the stud extractor to remove the old studs did not go as planned. They were all extremely recalcitrant and did not want to come out, and I sure did not want to put too much torque and break them.

Don't heat the manifold. Heat the studs. They need to glow orange or red, so a plain ol' propane torch is not likely hot enough.

AFTER they cool, they may thread out easily. Don't put torque on them while they're hot.

Originally Posted by ASJT3

My problem is the threads on the studs are completely stripped for the last ½ inch where they engage with the nuts, but otherwise studs are in good condition...Has anyone ever tried a weld buildup on the degraded threads and then cutting new threads on the weld material (ground-down to match the shank diameter, of course)?

Nearly impossible to "grind down" the shanks so that they're round again. And the welding will essentially heat-treat the metal. And then, you have to get the tap started so that when you've cut the threads on the welded section, you're aligned with the already-threaded part.

No, that's extremely unlikely to work out.

[ASJT3]

Originally Posted by Schurkey

Don't heat the manifold. Heat the studs. They need to glow orange or red, so a plain ol' propane torch is not likely hot enough.

AFTER they cool, they may thread out easily. Don't put torque on them while they're hot.


Nearly impossible to "grind down" the shanks so that they're round again. And the welding will essentially heat-treat the metal. And then, you have to get the tap started so that when you've cut the threads on the welded section, you're aligned with the already-threaded part.

No, that's extremely unlikely to work out.

Darn, wish I had checked back for a reply before I started! I heated the manifolds flange red hot and ended up shearing 2 of 3 studs….took 3 hours of my Saturday night to drill & tap out the studs I’ll chalk it up to “character building.”

Thanks for the advice Shurkey, I’ll remember this for next time! Truck is all back together now. Just need a new tranny…