Fix or replace
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New User
Joined: Sep 2019
Posts: 14
Likes: 0
Fix or replace
I was hoping to keep the truck stock but discovered this little booger, any thoughts on fixing vs replacing, I can do the fix myself, just didn’t know if this crack location could be saved
FTE Legend
Joined: Nov 2015
Posts: 30,986
Likes: 4,137
From: Angier, NC
Someone over in the 80-86 truck area just had one fixed but his was where the manifold bolts to the intake gasket surface.
They welder heated up the manifold and brazed up the cracks but left the built up braze on the gasket area for him to file flat.
Another user the welder took the weld down in the same area to far turning the manifold to scrap.
Does the heat valve move & work? It looks like it could be leaking and why I asked.
What does a new one go for?
Dave ----
They welder heated up the manifold and brazed up the cracks but left the built up braze on the gasket area for him to file flat.
Another user the welder took the weld down in the same area to far turning the manifold to scrap.
Does the heat valve move & work? It looks like it could be leaking and why I asked.
What does a new one go for?
Dave ----
Lead Driver
Joined: Dec 2000
Posts: 6,298
Likes: 47
From: South central, Minnesota
Unless you are experienced with welding cast iron, just replace it.
But if you do try to repair it. Drill a small hole all the way thru it where the crack ends. Doing this will keep the crack from spreading when you heat it or weld it. And if you do try to repair it, preheat the manifold before the repair and then you want to control the speed at which it cools down. If it cools off too quickly it will likely crack again. I've seen people use a BBQ grille to do this or even bury it in sand. You just want to do something to help keep the heat in the cast iron and allow it to slowly cool down.
But if you do try to repair it. Drill a small hole all the way thru it where the crack ends. Doing this will keep the crack from spreading when you heat it or weld it. And if you do try to repair it, preheat the manifold before the repair and then you want to control the speed at which it cools down. If it cools off too quickly it will likely crack again. I've seen people use a BBQ grille to do this or even bury it in sand. You just want to do something to help keep the heat in the cast iron and allow it to slowly cool down.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Yup, make the best of a bad situation.
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Moderator
Joined: Aug 2002
Posts: 6,106
Likes: 385
From: Southern California
It is repairable...…. cast iron must be heated (entire area) before the welder begins welding the crack and then it must cool slowly.....meaning the welder must either heliarc it or use a oxy-acet torch..... anyone who knows how to weld using this equipment is a real welder...… and will know what and how to do it. Very commonplace with even home-welders up through the 70's
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
For the record, my exhaust manifold had a bit of a blowout at cylinder 5.
I purchased a cheap exhaust manifold from rockauto.com. It set me back about $130. It's been kicking around for about a year now. Finally got it painted yesterday with VHT's flameproof line of header paint. The last couple of days(cleaning the flash rust off and prepping for paint) have been the first time I've really looked at it. The casting quality is **** poor at best. Looks like they banged the core around for a couple of hours before putting it in the mold. The inside is full of giant lumps of extra cast. The ports look like what you imagine if I asked you to draw 6 evenly spaced rectangles with rounded corners. The bore for the flange is offset by about 3/16" in two directions. It's going to take quite a bit of burr work before I'll even imagine putting it in my truck.
Point is, be careful when buying a replacement, maybe shop around for a brand that is known for quality, and sure as heck inspect it right proper when you receive it. I wish I had pictures to show just how awful the casting is.
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
How do you feel about the HD exhaust manifolds? FORD EXHAUST MANIFOLDS
Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
I'm not a fan of them. There is no heat control valve. They have crudely shaped runner transition. The real hindrance to exhaust flow is in the head port but the right angled stubby runners into the log don't help things. I'd be surprised dyno testing would reveal any significant gains over the LD exhaust. I prefer the smoothly transitioning EFI exhausts. I've used them on several builds.
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
A toilet will flow better than an LD manifold. But that does not necessarily mean a larger outlet will translate to a performance improvement. I'd like to see the A-B-A dyno results before coming to a definitive conclusion.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
I would choose the HD manifold if I was doing a turbo build. Otherwise, I would (and did) go with EFI manifolds.
Either way, no matter what you put on, you won't have any gains until you increase the size of the exhaust as well. The stock system is pretty skinny. If I recall, my stock pipe was less than 2".
Either way, no matter what you put on, you won't have any gains until you increase the size of the exhaust as well. The stock system is pretty skinny. If I recall, my stock pipe was less than 2".
