Removing old heat riser

[AZJeepNut]

I'm replacing an old heat riser. Searched for posts about this and found a brief mention and some pics in a topic in the Your Stock Jeep Project area (Too rusty to save?) by 1955CJ-5. Mentioned there that he welded the flapper to the shaft. Is that the common method of attachment? If so, what is the usual, or easiest, way to remove the old shaft and flapper from the manifold? Or is it OK/better to leave the old shaft and flapper and just replace the other parts? Thanks in advance for your usual great advice!

[athawk11]

AZ,
Yes, the correct approach is to weld the shaft to the flapper.� Frankly, I'm not sure it could be done any other way.

The shaft rides in bushings that are pressed into the manifold. If the bushings or shaft are worn out, you will have a lot of play on the shaft/flapper, which may equal a small exhaust leak.� Note: It is normal to have some 'in...out' movement on the shaft, as the flapper is not super tight to the walls inside the manifold.
�
If your shaft is tight and smooth as it rides in the bushings, I would not take it apart.

If you do need to take it apart, you can use a small cut wheel to remove the shaft from the flapper.

Tim� �

[AZJeepNut]

Thanks! I checked the play on the shaft/flapper and compared it to the play with a new shaft and bushings held to a bench top. Seemed about the same, maybe a little more in the old shaft. I'm leaning toward just replacing the external parts, but I'l sleep on it a bit.

[1955CJ-5]

Hi AZ....

I cut mine out with a hack saw....but I only did it because the end of the shaft where the spring and counterweight go had been broken off...

The shafts both fit pretty well and my new shaft was no tighter than the old, but I did not replace the bushings..as much trouble as I had finding a usable manifold i was not interested in risking a crack..

And be sure to take a few pics or somehow remember the relationship between the flapper and the spring groove in the shaft....

[AZJeepNut]

1955 . . . Good stuff. I hadn't thought about the potential damage to the manifold from removing the bushings. I probably won't replace the flapper and bushings. I did buy a rebuild kit but it did not include a flapper and I haven't found any that do, nor have I found any replacement flappers for sale. In case I have a senior moment and crazily decide to go ahead with a complete replacement, where did you find a new flapper (or did you)?

[1955CJ-5]

I found a (mostly) NOS replacement here:

https://www.armyjeepparts.net/

It may have been listed as an M-38 or GPW part. It included the shaft, flapper, spring, washer, counterweight and the spring retainer that bolts to the manifold. Most of the parts were still in cosmoline...but I think the spring and retainer were new...

Once you get the old flapper out, if you decide to try, I'm pretty sure you could separate it from the shaft and re-use it...

[1955CJ-5]

I see they have just the flap....the heat riser  kit is under MB and GPW exhaust parts..

https://www.armyjeepparts.net/p-328-heat-control-valve-flap.aspx

[AZJeepNut]

Thanks! AJP also has the flapper as a separate item so I'm tempted to buy one now . . . just in case. But I'd be really torqued if I did the complete rebuild and ended up busting the manifold so no decision yet. Maybe I should find a replacement exhaust manifold to have on hand ;-)

[1955CJ-5]

I think if you were careful you could get the old bushings out, but I wouldn't be going at it with a big hammer! Id maybe find the right size drill and go from there, but if you egg the hole in the manifold...maybe some serious penetrating oil, a little heat and the right sized drift punch....and lots of gentle tapping...

I went through seven manifolds before I found one that was usable, including the one that came with the jeep, one repro and the rest were used....but that doesn't necessarily mean that the next one you buy won't work..!

[AZJeepNut]

Looks like a classic risk/reward situation. If good manifolds were cheap and plentiful (and apparently they're not!) I'd cut that flapper out and convince the bushings to retire. The odds seem to favor leaving the old flapper, shaft, and bushings in place, however, and going with the partial rebuild. Thanks all for helping me make the smart decision!

[Ryan_M]

I replaced the flapper and bushings in my original manifold. I discovered a crack in the manifold during the process and had it repaired. Got the whole thing back together and had a significant leak around one of the new bushings, which eventually blew out entirely. I tried stuffing it back in place a couple time before throwing in the towel and ordering a complete manifold with heat riser assembly from Walcks.

[AZJeepNut]

That's kind of depressing. Do you think the replacement bushings were a bit undersized? I bought a rebuild kit that included everything but the flapper. The bearings are brass or bronze and have small spines around the circumference running parallel to the shaft. I assume that the spines are meant to compress as the bearing is driven into the manifold and thus ensure that the bushing is held tightly.

I can see that getting to the point where a replacement manifold complete with flapper installed would be the best way to avoid any more nasty surprises. I'm going to have to inspect the manifolds again to be sure that I'm not already at that point. I appreciate hearing about your experience. It's valuable information to pass along whether it was a good experience or not so good.

[F Bill]

I replaced the flapper and bushings in my original manifold. I discovered a crack in the manifold during the process and had it repaired. Got the whole thing back together and had a significant leak around one of the new bushings, which eventually blew out entirely. I tried stuffing it back in place a couple time before throwing in the towel and ordering a complete manifold with heat riser assembly from Walcks.

It sounds like your bushing hole was oversize and a custom bushing made up on a lathe would have also been a solution, if the manifold is worth the time to repair.

[Ryan_M]

I replaced the flapper and bushings in my original manifold. I discovered a crack in the manifold during the process and had it repaired. Got the whole thing back together and had a significant leak around one of the new bushings, which eventually blew out entirely. I tried stuffing it back in place a couple time before throwing in the towel and ordering a complete manifold with heat riser assembly from Walcks.

It sounds like your bushing hole was oversize and a custom bushing made up on a lathe would have also been a solution, if the manifold is worth the time to repair.

You're probably right about a custom bushing being a viable answer - I was just sick of dealing with it. Since I had so many other problems I chose to cut my losses, get the new one, and be done with it. I haven't had to mess with it since.

[1955CJ-5]

I wonder if the bushings weren't meant to be pushed in from the inside...perhaps the hole or even the bushing is slightly tapered? If they were inserted from the inside they couldn't go anywhere once the shaft/flapper was installed...

When rebuilding the fuel pump the means of securing the valves and the shaft were by peening the rims of the holes..perhaps that would have secured the bushing?

Just speculation of course....