aftermarket block,...
remove the top two threads and tap the blind holes deeper

the issue is, is that most of the "book" listings for studs will then be too short or not have enough block thread length.. so, you have to measure and call arp factory to obtain the proper length in order to have enough top fine thread length to use the hard washer and the full nut....
but we do this on every block.

 

You're right!

I ordered some undercut studs, and lo and behold... they didn't screw down in the block far enough to engage the small bulbous area before the undercut . I shined a flashlight down in the hole, and there is room to tap them down a couple more threads or so... but then I'm afraid they will be too short.

They're going back. I've never had a problem with the standard studs, so I'm going to avoid the hassle and use the standard units.

I don't know why ARP even sells these things if you have to modify the block to make them work, then order longer ones. I guess you could just screw them in until they bottom out, and have a couple of the coarse threads sticking out???? The head seems to bolt on, but it sure doesn't feel right.

Going to have to call them in the morning...

Thanks, OB.

 

full diameter is stiffer and do not stretch as much

we have had no problems in power adder setups with undercut studs.. but as said, adding to the thread length is necessary.

 

the reason to remove the first thread and a half out of the deck of the block is to help the deck itself from distorting upwards around the threads and raising the material ..thus making the gasket not seal as good everywhere else..
most every MAIN CAP threads in the block are done this way for the same reason..
it keeps the top thread from pulling or raising up when torque is applied..

and as said, the threads that are supp;ied on the studs are not as long as I wished that they were.. so, as said, you have to call them with your specific length needs.. they will usually send a longer thread than what is needed and you shorten as needed ..
as said, you have to tap the block deeper...!!!

 

Great...

I called ARP, and they said that the bulbous area was just there to keep the stud from screwing down too far into the block... as it could just keep going if the threads were too deep... and that it was fine if it stuck up above the deck. Okay... AWESOME!

Then, I asked him about the undercut studs in general. He said that they stretched more consistently than the standard units. I asked him about applications... and he said that engines that don't have excessive cylinder pressure are what these are recommended for, and that the regular studs were safer for engines with large amounts of boost or nitrous.

My 363 will make close to 600hp n/a, and will have a 200hp nitrous plate... so it looks like I'm safer with the less expensive standard studs. I saved some money getting these drop shipped by a company on Ebay, so I'm probably stuck with them. They are brand new, hardened washers and 12pt nuts are still unopened in their sealed packages. I only hand tightened 2 long and 2 short bolts into the block to see how the heads fit. Part # 254-4703. $215 at Summit. I'll sell them for $170 shipped.