There was a big problem with 20R heat shields causing the exhaust manifold to crack between #2&3 exhaust ports. I’d remove it. It serves no useful purpose.

 

Fred is always good at giving me extra homework. I'll pull that ugly fker off tonight. Need to do the oil as well anyway.

 

Well I got my block plate and figured I would get started by pulling off the heat shield. As always more suprises. Little JB weld and I should be good to go eh?
Seriously though what are my options?

 

Shouldve left the heat shield on lol

 

Rofl no kidding right. So I realized I need blockoff plates for the air injection on the manifold, I only have the "carb" plates from LCE. So my options are buy the plates and get a new manifold or repair this one OR buy headers in which case I shouldn't need the air injection block plates right?

 

That’s what I was talking about. Maybe someone can stick weld it or try to find a used manifold with no cracks. This was very common with the 20R.

 

No lie, seeing that picture made me go take a look at my manifold

 

How bad are the 20r ebay headers?

 

Your manifold can be repaired using a stick welder with nickel rod. MIG will also work but the weld won’t be as strong.
Due to the high carbon content of cast iron, high heat has a tendency to crack the cast (tell us something new ).
If you decide to weld leave the manifold attached to the head. This way all the studs should line up when you have to remove it. Don’t know anything about headers. Maybe another member will have more information.

 

Yeah so I can weld or braze the manifold from what I've seen. I should be able to preheat the manifold and weld it while still on the truck. In theory that should be the cheapest option IF I can find someone with a welder/torch. If I start renting equipment it makes sense to buy headers for 130 bucks.

 

Not sure I would try brazing. That puts a lot of localized heat in one area.
Talk to a weld shop. They will know what will work best. You could have them seal the air injection ports at the same time. That would save buying the block off plates. Or do like I did and tap and plug.

 

I've seen a few people talk about welding exhaust manifold cracks like that - they recommended to pre-heat it in the oven at max temp/500F for at least an hour to warm it through before attempting the weld. I wanna say they used an arc welder too

 

I found a 2nd crack making repair even less likely. I'm just gonna dole out the 130 for a set a cheap ebay headers and report back.

 

Your exhaust manifold is held on by a combination of bolts and nuts(studs). I replaced all bolts with studs and nuts. This allows you to use maximum torque without the danger of stripping the threads in the aluminum head. It’s usually not a bad idea to replace all studs with the manifold off.
The best penetration oil that I’ve found is a 50/50 mix of acetone and atf fluid. Put into and old spray bottle, shake well and apply to all the exposed nuts. You can also use a paint brush to apply. This mix is great, and better than any commercial product I’ve used. And it’s cheap to make.

 

Ok good sounds like a plan. Do you know what thread/pitch of studs I need?

 

I think it’s M8x1.25. Could be M10x1.25.
It’s been so long I’m not sure. The pitch is definitely 1.25