I would make aluminum plugs and weld them in

That sounds good...how thick/deep would these plugs ideally be? Friction fitted then welded?

1/4-3/8 thick enough to tap them in. tight enough so they don't fall out when you start to weld

thank you

No epoxy will hold.

Welding is the way to go, and the closer the weld or other is to the top surface, the more likely you will need some resurfacing.

Tell me if this would work, 5/16" aluminum all-thread or rod, create a "shelf" with a step bit and recess the rod for the welder...trueing up the surface is no problem if needed. The passages are about .3" wide by 1.5" & 2" long with .5" depth to play with.

I would make a piece of flat 1/4 to 3/8" aluminum cut to fit in the opening. Clean all of the surfaces that are going to be welded so you dont have to oay for them to seobd a bunch of time on that. Then tap the center of all plugs so they can be held up with a small bolt. Send it to a good welder and let them weld the plugs in. They can then take the bolt out and weld that hole shut. If you do all of that little prep work it won't cost as much for the welder. He will just have to weld them in. You get them back and true up the surface and your good.

Dropped em off at the welder yesterday...my spare time lately is worth the $95 per hour & he's gonna do it all, including resurface.

That is the way to do it

Finally got these manifolds ready...but tell me if this a problem...I took all 4 pieces to the welder to fill the passages (the studs were still in the manifolds). When I took them to another machinist to clean up the surfaces they said the aluminum threads stripped out & needed timeserts, then a resurface...They look real good, but I've never used thread inserts before.

So tell me if this is a problem or not...I don't know if the original studs actually reached into the water jackets of the manifold (I did not pull them). Tonight I threaded the new stainless studs into the timeserts & they pretty much insert to varying depths...some penetrating too deep to get a washer & nut on. Are the studs SUPPOSED to loosely screw in at the proper (equal) depth and then rely totally on a thread sealer (ARP?) to keep the water out of the very same joint I just welded up? What's the proper method for studs, timeserts, and thread sealer?