Heat Riser Removal

[Lunchbox]

What’s the best way to remove the heat riser from an 340 exhaust manifold? Currently it is seized closed can wiggle it slightly.

 

[Katfish]

Soak with PB Blaster and heat cycle it with a torch.
I cut mine out and tapped it for a bolts.
Not for the original guys, but my car is just a driver.

 

[Lunchbox]

Soak with PB Blaster and heat cycle it with a torch.
I cut mine out and tapped it for a bolts.
Not for the original guys, but my car is just a driver.

Worked like a charm! Had a hose clamp I put around the large diameter counterweight, allowed me to get a larger channel lock on it without messing it up. PB, heat, work it, repeat. Moves freely now.

Looking at the butterfly it appears to be welded to the shaft on the inside of the manifold. Thus the reason to cut it to remove it.

Is it safe to assume this isn’t needed for fair weather cars? Would like to remove the butterfly but still make it look stock on the outside.

 

[Katfish]

Yeah, that's probably what I should have done.
With a little patience, you should be able to cut away the butterfly and leave the shaft intact.

 

[Former owner]

Worked like a charm! Had a hose clamp I put around the large diameter counterweight, allowed me to get a larger channel lock on it without messing it up. PB, heat, work it, repeat. Moves freely now.

Looking at the butterfly it appears to be welded to the shaft on the inside of the manifold. Thus the reason to cut it to remove it.

Is it safe to assume this isn’t needed for fair weather cars? Would like to remove the butterfly but still make it look stock on the outside.

You really want to have it in good operating order. It is used to heat the choke. When the exhaust crossover stops, you will get an accumulation of crud, first in the heads, and then up into the manifold. Mine was rattling, so I just wired it open to stop the noise. Mine was a 71 Cuda 340 with manual transmission. Once the heat riser was disabled and the aforementioned buildup began, the choke remained partially closed after warmup. When the engine was shut off, I began to experience dieseling (after running) because the idle was set to spec (900 RPM). This was in sunny CA, BTW. So after pulling the heads and cleaning out the caked carbon from the passageways (and the mating passages on the intake manifold), I secured a heat riser repair kit manufactured by Everco, and fixed the heat riser. Everything returned to normal after that. Not sure if any of those kits are still out there, but I would absolutely try to fix that.

 

[Chryco Psycho]

Cut the plate out & leave the shaft