Welding Aluminum Car Block

Date 12-14-2009 20:20

The block is cast aluminum. I have no experience welding to cast aluminum, but welding to cast iron is tricky. Do your homework before welding.

You may be money ahead getting a new block versus patching this one up and then replacing everything when the repair fails.

By RonG

Date 12-14-2009 21:17 Edited 12-14-2009 21:21

Correction, it will cost considerably more to find out it won’t work than just the cost of the block, like time (is money) and possibly non re usable parts to assembly and test it plus another failure could do greater damage.

Just my opinion but I think a new block would put your mind at ease and cost less. As far as welding on the block, you can still do that and make a pretty good determination by NDE of the quality of the repair.

Bare in mind the heat sink qualities of Aluminum and the effect it may have on all the very high precision configuration of the block.

By Tommyjoking (****)

Date 12-14-2009 22:48

Leon Cast Al can be tough to weld out properly...especially cast that has been exposed to oil, gas, antifreeze. Considering its a block it will be made from a good grade of materials. Your first problem is that typically any repairs to aluminum heads and or blocks are pretty much exclusively done via TIG welding. I would not waste my time trying to weld it out via MIG considering you are trying to repair cast. I would definitely want to magnaflux the damaged area to check for cracks that may be unseen. Once over that hurdle then you will have to clean the material to be welded very well ..(it will not want to clean up to a weldable condition).....lots of shops that do this for a living have acid etch tanks to truly clean up the pores of that material. You could attempt to clean it by hand with solvents and finally an alcohol wipedown around the weld area and use carbide rotary files to dress the area up before welding. For patching material I would consider a T6061 material and 4043 filler rod....you will need to design you patch in such a way that you get 100" penetration all the way round the joint and you may fill any buildup necessary with filler rod after the initial patch has cooled down. To get a good weld depending on the thickness where the patch goes it will more then likely require heating that area to at least 400F before a weld attempt. All the while insuring that you are not causing a mechanical distortion in the block so as to make it unusable. So that is just a quick once over if what you need to accomplish.....what would a reputable machine shop in your area charge for the repair....$300..$500?? That is very reasonable considering what would have to be done to do it correctly.

Unless you really have the tools necessary at hand to properly fixture the block, heat it and weld it ....I would just start looking for another block to rebuild or take it to a very good machine shop.

Tommy

By low_hydrogen (**)

Date 12-15-2009 01:05

Question?

I'm no aluminum expert but I have welded tons of cast aluminum with my tig machine. Salvage yard here in town brought me a busted bell housing just the other night. I agree with everything you said. I clean, clean, and clean some more I put a 5" inch cardide tip skill saw blade backwards on my 4" grinder. Use a stainless steel wire wheel brush. I usaully grind to the bottom of the crack with cardide tip blade, clean some more than 4043 filler and weld it out bottom to top than weld a bead on the inside.

I'm pretty much self taught on the tig I was curious what the preheat was for? are you drawing moisture and oil out of the pours or does it have something to do with keeping distortion to a minimum, cracking etc.

I've never had a bell housing crack back out on me but have never welded a aluminum block? just curious to learn more about tig and aluminum

Never tried preheat cause I have some experience in anealing (sp?) aluminum and was cautious about using a torch on a bell housing since I haven't had a failure yet? havn't had a need to change how I been doing it getting it, clean is the biggest problem.

Salavge yard tried to weld it their selves and failed they cleaned it with something so I called them to make sure it wasn't brake cleaner etc! they use "oven bake off" lol they said it's cheaper to degrease with that than carb choke cleaner and cuts throught tuff baked on grease lol there was still a film on it when I got it and the were using stick rod and a brazing torch said they had done it this way a hundred times! lol

By FixaLinc (****)

Date 12-15-2009 18:00

That oven cleaner will take paint and grease off cheap enough but will start a oxidizing process on aluminum turning it dark like you saw.

By Tommyjoking (****)

Date 12-17-2009 07:13 Edited 12-17-2009 07:16

low_hydrogen

The preheat is just in the case of a rather thick part......if you get into 1/2 inch and up (on aluminum) it can be difficult to get the puddle started and weld with enough travel speed to keep porosity out.   If you have a thick section and especially if you are welding thin to thick, preheat makes it all go much better. And you are correct that a good preheat will make sure its all good and dry as well.    This technique can also help with "shock" type distortions and help minimize them as well as preventing creating a stressed area in the part and possibly causing more damage. Keeping track of interpass temp, carefully applying the "right" amount of deposit per pass, and annealing are all things that can be factors when doing thick welds on aluminum.

On thinner cast structures (like bellhousings) preheat usually is not necessary as you have discovered.   You are right when it comes to repairs like that getting it cleaned up to an acceptable level is the toughest part most of the time.

Tommy

By DaveBoyer (*****)

Date 12-15-2009 03:00

Before You think about welding up the block get the crankshaft checked out thoroughly and be sure it is still repairable. How does the cylinder look?

After welding, the block may need to be line bored. This could be a rather expensive repair depending on what all is damaged.

By jwright650 (*****)

Date 12-15-2009 15:25

Here is a guy who is selling off some of his LSX parts.....might be able to work a deal with him?

http://www.pro-touring.com/forum/showpost.php?p=606906&postcount=1

By FixaLinc (****)

Date 12-15-2009 18:11

What conditiion the rest is in for more cracks, cylinder condition, needing line bored for crank or all good yet before spending time and money on it. I'm sure it can be patched up and used but is it all good still ? We have welded, tapped and bolted patches, and even JB welded holes in blocks and heads for irrigation engines that ran for years yet but those were cast iron too.

http://www.sdpc2000.com/details/gm-performance-parts/12621769

http://www.sdpc2000.com/