346 caddy engine

[cadillac60]

Can anyone tell me the length of the exhaust manifold bolts?

Regards

B Watson

[harry s]

Bruce, Are talking about the studs that hold the manifolds in place or the bolts that connect the exhaust pipe?   Harry

[cadillac60]

Harry,  I am talking about the bolts that hold the exhaust pipes down using the wing style clamps I think there are 4 on each side.

[harvey b]

Bruce, on my 37 they are studs,they stick out of the block 4 inches,they are 3/8 with fine thread on the top and coarse thread on the bottom,mine have brass nuts on the top,not sure how far they thread into the block,possibly about 1/2 inch to 3/4 inches?.Hope this is some help.  Harvey Bowness

[cadillac60]

Harry,   Thanks for the reply.  Mine is a 38 caddy > I do have studs at each end of the exhaust Manifold but on the inside of manifold I have 4   9/16" Bolts on (each side of the engine) that go thru a large wing style hold down.

Regards

Bruce W

[harvey b]

Bruce, i dont know what you mean?,on my car the studs,8 of them are all in a row,4 per side,possibly some thing has been changed on your motor?.All that holds the intake and exhaust is the 8 studs.can you explain some more,I might be able to get you a better  picture of my car.i will try and attach one i have. thanks Harvey

[rismt]

Bruce ... I believe someone modified your motor and removed two of the studs on each side and replaced them with bolts. Attached (I hope ... was having trouble uploading these pictures) are 3 photos of a 38 motor showing a total of eight studs for the manifolds. I am traveling and do not have access to some extra studs I kept so I can't give you measurements right now. I will be home next week so let me know if you need measurements and I am happy to send them to you.

Good Luck,
Bob Schwartz

[Steve Passmore]

Bruce, your not confusing to exhaust studs with the 4 bolts that hold your inlet manifold down are you?  As the other posters have rightly stated, there are 8 long studs for the exhaust, no bolts.  They will be the same size as the 4 you already have.

[harry s]

Bruce, I think you are talking about the four bolts  (2 on each side) that go through the heating flanges on the intake manifold.  They are 3/8" NC. I'm not sure about the length but they need to be at least 1/2" to 3/4" longer than the depth of the holes in the manifold. The holes in the flanges in the block go all the way through. Hope this clears it up.     Harry

[cadillac60]

Bob & Harry,

I stand corrected, I think Bob is correct. A closer look shows two studs on each side & two bolts on each side. My guess is when the engine was rebuilt the original studs broke off & replaced the 2 back ones on either side with 9/16 bolts. So the only way I can find out the length I guess is to take one of the other bolts out>

Regards

Bruce

[markl]

Bruce,
Just checked my "spare" block (39?) which has one of the rear studs removed.  Can run a 3/8" X 20 tap down the hole and chase the threads to a depth of 7/8".  This is a standard taper tap, not a gun tap.  BTW, this is not a blind hole, it appears to communicate w/ the water passage.  The stud above the block measures 4", the upper 3/4" of which is threaded, 3/8" NF.  So the proper replacement stud should be 4-3/4 or 4-7/8" in length.

The thing you keep mentioning that is a little odd is that you are calling the bolts 9/16".  If that is truly the case, the best you could hope for is to insert a Heli-coil to get it back to 3/8" X 20.  Since I believe this is a water passage at the bottom of the hole, everything will have to be well sealed when all is said and done.  You might want to bring an experienced machinist into the fray if you have not used these (or similar) thread inserts before.

Mark Lowery, CLC #25216

[rismt]

Bruce ... not sure if needed, but, attached is a picture of the intake & exhaust manifolds fully installed that depict both the 4 intake manifold bolts as well as the 8 studs.

Bob Schwartz

[cadillac60]

Markl,

That's what I was looking for even though a few of mine have been changed to bolts over the years I wanted to make sure of the correct size,


Thank you

and thank all of you that were so good to give your input.

Bruce W

[markl]

Bruce,
Just a quick correction: It was a 3/8" X 16 tap I used to chase the threads in the block, the standard thread for the NC series bolts, studs etc.  So if some of your holes for the manifold studs have been tapped out to a larger size, it will be a 3/8 X 16 female threaded Heli-coil that you should be looking for.

Took a quick look in my McMaster-Carr Catalog (#107) and they don't list a stud that would be directly applicable.  So you might want to check around with places such as Egge, Terrill Machine etc.  If they can't be had off-the-shelf, McMaster-Carr does list a single-end stud in 3/8"-16 that is 6" long.   These studs come w/ the threaded end at 1-1/2" length, class 2A fit.  I would cut some of the excess threaded length off such that when the stud is threaded into the block, all the threads are engaged w/ the block, none exposed.  Then the stud could be cut off to yield just 4" standing above the block.  This end could have the 3/8"-24, NF threads cut into it.
I would dress the upper end on a lathe or at the very least in a drill press to give the original rounded  appearance like you'll notice on your other studs.

Mark Lowery, CLC#25216

[markl]

Bruce,
I was hoping to read a post from you saying you found a commercial source for the studs.  Have you found a place to buy them off-the -shelf or are you having to resort to fabricating them yourself?  My inquiry is far from selfless as my 37 block has been surfaced and therefore these studs were removed.  I still have them (somewhere!), but the more I think about it, just as with head bolts, I'd like to install new ones, particularly if they can be had from a supplier.

Mark Lowery, CLC #25216