Thread: Exhaust manifold studs

I expect that any machine shop could make them to your specs.

Not exactly exhaust manifold studs, but I replaced the two studs that hold the chain bar on the small chainsaw I have with the HT threaded bolts that come in packets at auto parts joints. Pretty sure they come in UNC.

Unscrewed the old ones that were made of cheese by screwing two nuts together on what was left of the threads, then unscrewing with a spanner.

Used the reverse method to put the new ones in after cutting the heads off.

I'd definitely use high temp anti-seize on the exposed threads if doing this for an exhaust manifold.

cheers, DL

I use studs in my 3.9. Mainly because a few of the bolts were getting really loose and had eventually pulled out the aluminium threads after a few tightenings. I used Re-coils on many, and wire type inserts like these don't like to be disturbed once fitted, so studs work well. You can use Loc-in-serts, which would be OK for bolts. Since fitting studs I haven't had any issues with loosening - I used the standard ones from Champion - the packs of one with a long nut (from Repco, parts shops, bearing shops etc), plenty of thread in my opinion. If you measure the amount of bolt that is normally embedded after going through the manifold and washer, it's about the same.

Managed to purchase a set of 3/8” UNC x 1-1/2” long studs from Nepean Boltmaster
The Champion studs only have ~3/8” thread to go into the cylinder head while the ones from Nepean Boltmaster have ~1/2” (30% more) and therefore should resist pulling out better.
7BB287B1-A43B-4B9C-BA10-53A014D34F97.jpg

Phil

These are the left side headers.
457A5AA3-B227-4D98-9D8C-E77F8BCD99F2.jpg

The tightest position that that required a stud to be fitted is the bottom fastener under the primary pipe to cylinder 5.
241A70C0-60BA-44F5-A6FB-CEF5692D2073.jpg

Its the the same situation for cylinder 6.
However, having studs makes it easy to fit the gaskets and then just slide the headers (or manifold) onto the studs and tighten the nuts up.

Phil

The headers on the 350 in my POS are similar to those........ 4 into 2 into one. Were there when I bought it in the 90's.

DL

All of the suggestions are valid but regardless, you would do well to buy a set of thread chasers. These reform the female threads rather than recut them. Also they are much easier to use than helicoils. I have used them successfully on my own alloy cylinder heads

Aussiebushman, I have a set of taps that I used to “clean” some holes (on another project) and to my astonishment they cut out material and the bolt was definitely sloppy afterwards.
I then bought a tap from Sydney Tools and it would clean the holes without removing material leaving the bolt a precise fit.
Clearly, there are taps and there are taps.
Is the same likely to happen with thread chasers.
Was just looking at these.
T117 - 971 Metric, UNC, UNF Thread Restorer Tap & Die Kit - 48 Piece | Hare & Forbes Machineryhouse

Phil