I Need Hollow Exhaust Manifold Bolts

It's not the hole that makes them an interference fit - as far as drilling goes. You ca drill 'em all but that alone won't solve them coming loose IF that's your problem. 

6PakBee wrote: billd wrote: ...I have a set of used bolts that have been re-plated - if I can find them I can post photos. I could also post the service bulletin as well. (If I have't already as I've posted a few over the years) I would appreciate that.  I'd only be going for a cosmetic look, not necessarily functional.  I'm kind of anal that way.

The bolts are not drilled all the way thru, so once installed you can't tell the difference. Other than having the correct marking on the head. Someone with more expertise will have to tell us what the correct head marking is.

The original bolts were made by Rockford and have Special head markings, Grade 5, Zinc Plated and "waxed", 3/8-16, Class 3 thread, drilled thread end.  I have drilled many Grade 5 of these bolts for installs, when I ran out of NOS ones.  I use the extra thick washers. ...as george w states above, I have never had one come loose, even with Class 2 threads.  Lock washers don't work, for the temp of the exhaust will take the temper out of the lock washers. I had constant problems years ago with the two rear bolts on the right side of my 69 AMX with 343 and the bolts coming loose.  I made up a set of drilled shank bolts and it never loosed again in 50K miles I drove it before I sold it.  I can say I do not use any gaskets on exhaust manifolds to heads, I have a manifold decking machine and I run every exhaust manifold across it, before it goes for Jet Hot Coating or what ever coating the customer wants...no problem with leaks.  I check the heads for flatness and correct the head on the Bridgeport as needed.

If you don't have the superior anti-seize type exhaust manifold bolts that were used on '66-'91 AMV8s to bolt the manifold to the head, just use some type of anti-seize compound on the threads of a common substitute fastener.

(grade 3 should do fine*)

*Loctite's anti-seize PDF pages shows using grease on the threads is second best solution, oil on the threads is better than nothing (page 3):

http://www.loctite.co.uk/uke/content_data/364645_AG13053_RW_BR_AntiSeize_UK_WEB.pdf

If it's for a concourse restoration, the special bolts can always be located and installed at a later date. (time permitting)

Just be glad you don't have to deal with cross threaded or seized spark plugs in an aluminum head!