what manifolds for magnum

[cudarudy]

I installed a 5.2 magnum in a 69 cuda having problems with 340 exhaust manifolds , can't get them to seal to ehxhaust port on rear drivers side. I could use the 69 318 manifolds or manifolds from the magnum engine or will dougs headers fit the magnum heads. Really don't want to use headers . Will the magnum manifold work with power steering?

 

[Nutty runner]

Mill .020 and try again,cast manifold have any rust pits left after you blasted them?

 

[Treblig]

Did you plug the smog ports on the heads?? 340 engines (manifolds) were not designed for smog ports so if you don't plug them it might be your problem.
From every thing I've read magnum manifolds won't work with P/S. At least I couldn't get them to work. The 340 manifolds should work, I have 302 castings on my '69 Barracuda and the magnum manifold (passenger's side) works fine. The 302s have the larger machined surface at the exhaust port just like the magnum heads but no smog port. I have a set of newer 360 heads to use on my 318 and I plugged the smog ports before I did anything else.

Treblig

 

[Tom Swope]

I installed a 5.2 magnum in a 69 cuda having problems with 340 exhaust manifolds , can't get them to seal to ehxhaust port on rear drivers side. I could use the 69 318 manifolds or manifolds from the magnum engine or will dougs headers fit the magnum heads. Really don't want to use headers . Will the magnum manifold work with power steering?

Check to make sure the inside of the down section of the manifold is not being held outward from a smog boss on the magnum head. This is a common fitment issue with newer heads and when using 340 exhaust manifolds. If this is the issue then grind the smog boss down to the point that the manifold sets flat against the head ports.Surfacing the exhaust manifold will only make the issue worse.

 

[bobscuda67]

There is a port size difference between the magnum port hight and the manifold. The manifold port is longer than the head's port and causes a leak on the bottom of the manifold.

 

[Treblig]

There is a port size difference between the magnum port hight and the manifold. The manifold port is longer than the head's port and causes a leak on the bottom of the manifold.

I think he said that he had a 5.2 magnum engine in his car so it should have the larger machined surface with the smog port, but I could be wrong??? I am currently running a 340 manifold on some 302 casting that have the larger machined surface. On the passenger's side I'm running a large port magnum manifold and it seals up just fine. It's been in the car for over a year now.

I also have a pair of older (1969) 318 heads, a pair of 360 smog heads and some magnum manifolds sitting on the shelf so I can easily check if the OP really needs to know if there's a difference???

Treblig

 

[cudarudy]

Thanks for the replies , Bobscuda67 that was the problem and only made worse by what Tom Swope mentioned in his reply. I ended up using the original '69 318 manifolds but still had togrind some metal off the left side cly. head for clearance. have to wait till Wed. to get exhaust pipes re-worked for the different manifolds hopefully no leaks after that.