I know that the 727 big block tranny cases from the early 70's and the A518 tranny cases from the mid 1990's are both cast aluminum, but does anyone know what type of cast aluminum alloy each of these are? I've got to do some serious welding on each and was wondering what TIG filler rod to use on each for the best results?

Otherwise I'll just start experimenting with 4043 and go from there.

Thanks!!!

Mark

No idea, but I'm intrigued as to why you have to do serious welding on them? I'm guessing it's not because they're broken (easier to get another case), some sort of Frankenstein 727/518 mash up?

Very likely the alloy is 356 which is a common alloy for these type of thin wall castings. I've welded cracks and tabs back on using 4043.

Sounds like he's going to weld a B/RB bellhousing onto a 518.

Yes, I'm going to do the pain in the ass that everyone is telling me not to do. No great reward without great risk right?



You're going to like this one feets. The aluminum KB 572 will be going into my 1973 Imperial coupe backed by this transmission. I'm concerned the torque of the 572 will rip up the bell housing that I weld up -- so I'll take any suggestions that anyone has to make sure this doesn't happen. I'm not going the Ultrabell route either. I really don't trust all of the torque being held by the tranny pump bolts -- that's not going to work for me at all. The plan is to clean up the cases in a Tornado parts washer, do the proper cutting of the bell housings to the cases, and then take the pieces that will get welded together and get them alkaline dipped to clean up the aluminum as best that we can before TIG welding. Would there be a better acid dip that I should consider? I just want to make sure I get as much oil and impurities out of these pieces before welding and would take any suggestions on what works the best. I plan on doing lots of practice getting this just right. I know what a PITA this is going to be to be able to get the big block bell onto the 46RH and 46RE transmission cases -- but I think I've got more time than brains, so, why not? Besides, I really like how the 73 Imperial rolls down the road, and that's what it's all about, right? With that huge torquey motor and a nice OD tranny, it will be damn near nirvana.

I'm going to use a CNC to cut off each bell housing and then use a precision jig to get the proper orientation and indexing to the big block bell on the 46RH transmission case. I'm really interested in the 46RE transmission controller too, so I can go that route too if that project gets completed and works well. I'll probably end up making one of each so I can go either way. Seems like it's a lot easier to find 46RE trannys than 46RH. I've got a couple of 46RH trannys right now as well as a 46RE. I've got to round up some big block trannys too, that shouldn't be too hard though. I've just got to make sure the threads aren't all screwed up on the bell, and that the right ear is on the driver's side of the big block bell for the 73 tranny linkage.

Wish me luck, I think I'm going to need it....................

Here's a couple pictures I found on the Internet where someone had done a similar bellhousing swap. In this case a BB 727 bell onto a SB 518. I'd give credit to the original poster of these but I have no idea who that might be as I saved these a number of years ago.

Yes, I have seen these photos before -- I actually purchased the jigs from the guy that did this. I'm going to be making new ones that are a lot tighter on the tolerances.

Do you guys think that this weld shown will hold on a 750 foot pound torque motor, or will it have no chance? I know the main deal with welding aluminum is knowing what alloy you have so you have the correct filler rod, and then the next big deal is cleanliness, cleanliness, cleanliness............or you'll have absolutely no chance.

butch brooks was doing similar with an amc bell to a 727---he ran a 4 wheel drive jeep dragster--gained some notoriety and amc sent 2 engineers out to look at the unit---they ordered up 2 test mules which he built----the rest is history---amc ordered the 727 from chrysler after that---i dont think he ever had a failure---butch is one of the more storied transmission builders in the west....

Would it be possible to just weld the BB flange lip(from the 727) onto the 518? Puts more weld into it (bigger diameter) and less torque into the welds.

You've got to cut the bell somewhere, and if you cut it farther towards the block, the bells don't match up at all, and you'd have to add a huge step in that area because of the difference in the size at that area. Also, if you did that the starter wouldn't match very well for the big block setup either.

I was wondering if I could program the CNC to cut the bell more of a zig zag rather than straight towards the pump like the photo above. I know the CNC could get it right, but how is that going to be to weld that aluminum? Will that be an impossible thing to accomplish because of the fluid nature of welding aluminum?

Quite nice!
I like the project.

My Imperial was originally destined to get turbos, efi, and OD but it has taken a back seat to the other project I've been lusting after for years.

You musta been listening to E-Booger. Lots of Clutchflites were subjected to insane torque and I never heard of the pump bolts failing.

Let's see, shear strength of six 5/16" bolts..............

I'm listening to John Cope of Cope Racing Transmissions. Those bolts were never designed to handle continued hammering of 700 foot pounds of torque in a street car. John has seen what these Ultrabells look like in the application that I am talking about, so I trust what he says on this subject, so that's the route I'm going. John said I'll have a tough time with getting the bells done correctly, so this will not be a two week project by any stretch of the imagination. This is going to be a car that will be driven thousands of miles too -- so I just want to do the best job that I can. This will not be a race car that puts on a quarter mile at a time (so no trailer backup deal for me). I've finally figured out what I want in a car -- if I gotta put this car in a trailer to get it around, I don't want it. This bad boy will be driven, so for reliability's sake, this KB engine is getting Stage V heads and valve gear, as well as FAST EFI with a crank trigger and coil on plug spark. I want reliability -- plus it's gotta be cool.

If I wanted to go a cheaper route I'd do this to a 1968 Coupe deVille with a GM LS9 and a built GM 200R4 tranny...........................but I'm not that guy. I like Mopar gear, even if it has a price premium associated with it.

is it possible to make a adapter plate like the GM Chev to Buick/Olds???

Yes, I looked into that too. I would need to grind on a brand new aluminum KB block, because the starter is not in the correct location indexed to the block (small block vs. big block starter location).

Unless someone else has better information on this deal -- that is my understanding of what would need to be done.

Why not use an Ultrabell and add some spot welds to the connecting seam? That should give an added measure of security and if it needs to come apart in the future, you could just cut the welds and unbolt it.

As well as heli-coiling the pump bolt holes or some sort of nutsert.

Don't know about the welding but... you should use a 46RE case to build the 46RH and use the adapter sleeve in the plug in hole so when you decide to convert to a 46RE you do not have to re-do the trans with another case. If you use the RH case you will have to bore the hole bigger for the RE plug or make another case.

Why worry about building another transmission? Build this one right and don't worrry about it.

I like your thinkin feels!!!!!!!!!!!!