Cracked Head: It’s Complicated

[Ishiftem]

Ok so short story. While porting this exhaust port years ago I put a small hole in it next to the guide. So I bring it to a guy who used to be really good with an O/A outfit and an iron filler rod. Well unfortunately age had gotten the best of him and I was too nice to say anything. He made a mess of it. He chased the puddle all around the bowl and up around the seat. One simple hole turned into a bunch of small ones. So to fix this mess a put the head over two bags of charcoal got it hot and brazed of the porous areas. It has been good for years but finally cracked in the bowl and into the seat. So the way I see it I have two options:
1: cut for a new seat less maybe .010. Grind out the crack and braze it. Then finish cutting for the new seat and install seat. The problem is hitting water cutting for the seat. There isn’t much material there and I don’t want to try a shallow seat and risk it falling out.
2: Use something like muggy 77 rod and tig the crack at the seat and then braze the portion of the crack that is in the bowl area. I can’t weld in the bowl area because the existing braze will contaminate the weld. I’m not sure the seat can be cut without leaving a low or high spot due to the difference in hardness between the iron and filler material. Afraid it might burn out there. Or maybe I weld the entire seat so it all cuts the same.

I just can’t decide the best way to go because I’ll likely only get one shot at this.

[1980RS]

Me, I would grind that out and tig weld it with Muggy weld. I welded my 1 ft. long water jacket cracks in a std. bore 409 block and had nothing to lose. It turned out great and held 35psi. on both sides for over an hour. One thing I noticed that my new AHP would arc weld so much better that the Lincoln welder I used. I have a set of Vortec heads that I need to put some weld in a chamber area to get the intake head flow stop stalling over the .550 lift range. Filling it in with muggy weld will get that job done. for me, I trust the stuff.

[mag2555]

It may be time to put that head to rest!

[BillK]

It may be time to put that head to rest!

Basically what I was going to say.

[Ishiftem]

Quitters!

[mag2555]

I learned to quit the second time a coolant leak bent a rod and cracked a main cap due to hydro locking!

[Ishiftem]

Well that wouldn’t be good!

[racear2865]

I have successfully repaired a few heads that I had little other choice as there were no replacement. I drill a hole (in the valve cover area) right above the hole I want to repair. I then bead blast totally clean thru that hole. I weld a pass thru using muggy and tig. Then use a small paint brush and coat as much of the area thru the hole you have drilled with Seal-Lock Fluid Weld. Which is good for over 2000*. Let completely dry and then coat with JB Weld Extreme Heat metallic paste which is good for 2400* continuance , then recoat with Fluid Weld then coat with a water proof coating. Then tap that hole for pipe tap and seal.. When you fire it. Only let run for a couple minutes. Ive done this with 4 motors on my dyno. Ive run all above 6000 rpm and had no leakers. I taken the sealed plug out and looked at all and had no cracking of the sealer.. Just an opinion.
reed

[Ishiftem]

I ordered some muggy 77 and I’m going to tig the seat area and either braze or tig in the bowl area. I like the pipe plug idea. Hopefully I can get in there and bead blast the back side to clean it. The things you do when you have more time than money! Or sense! Now to find an old gas grill to heat this thing up.

[SupStk]

I want to offer a word of advise. Since the head has been braised on, you need to get all the brass out or else you will have nothing but trouble laying in the iron.

[mag2555]

What motor is this a head for?

[Ishiftem]

I want to offer a word of advise. Since the head has been braised on, you need to get all the brass out or else you will have nothing but trouble laying in the iron.

Yeah, that’s one of the reasons it’s complicated. There is no way to get rid of all the braze so that’s why I figure I can weld the seat and braze the bowl.

[Ishiftem]

What motor is this a head for?

Hi perf 409. It’s tough to find just one head. Plus the machining a stock head will need and a ton of porting.

[mag2555]

Well as posted your going to have to heat/ melt out all of that braze that you can, and even grind it out if need be, then V out the crack in small sections.

Then fill that V in with muggy weld just enough to close it up but not fill it in all the way and then continue on bit by bit.
Lastly over fill the Length of the whole V in one shot, and in fact over fill it so you can grind it back.
As you know this should be done with the head toasty hot.

Not to be a Asshole here, but just for future reference anytime I have ground thru a casting around the valve guide area it has always been in the area where you did.
Then once I got my flow bench I found out that it’s added flow wise worth that chance of grinding thru.

Those areas of heads are where the normal .160” to .180” of port wall thickness goes to hell and many times especially with factors of core shift that area is left with only .060” of meat left even in a brand new casting!

[Ishiftem]

The funny (or not so funny) thing is a ground through because I was watching the side of the burr next to the guide and didn’t notice I ground through the wall. So I found another pair of heads. Did the exact same thing to the new one!! Brazed that up too, finished the porting and it’s still going strong. The best lessons are the expensive ones.