Plugging the Heat Riser Hole

[adam_knox]

Well I've decided to temporarily seal up the hold on the side of my exhaust manifold where the missing heat riser is supposed to mount. I don't want to weld it for the chance scenario I can come across a decently priced heat riser and live in a appropriate climate; so I've decided to seal it with a bolt, washers and nuts. Should I be concerned about using a different kind of metal for the bolt? Would hate for my cheap solution be an expensive repair should the varying cooling/heating temperatures of two different metals cause the manifold to crack! Any words of wisdom? I was hoping for a solution that doesn't involve me taking of the manifold to fix, but the pressure of the air seems too strong for a simple cork-like solution.

[turtle47]

The nut and bolt method should work but be sure to put high temp silicone all around the bolt including the threads. This should make it easier to remove later, but id be sure to find one soon, you don't want to run without one for long

[TodFitch]

The nut and bolt method should work but be sure to put high temp silicone all around the bolt including the threads. This should make it easier to remove later, but id be sure to find one soon, you don't want to run without one for long

You should be able to fine high temperature gasket stock at your local auto supply. Maybe making up some washer style gaskets would seal it without resorting to silicone sealer. (I have an aversion to silicone sealer...)

[Rusty O'Toole]

I would put a long bolt right through, with a washer on both ends. Use some anti seize compound if you want it to come out later. You shouldn't need any sealer. Do not tighten the bolt too much.

[Young Ed]

Dad and I sealed the heatriser on his 225 /6 with copper washers and a nut and bolt If you don't want to remove the manifolds I don't see why you couldn't use one long bolt and put the nut on the back side. There isn't a whole lot of room but it should fit.

[adam_knox]

For some reason there's a metal stud on the other side, so no leak over there. Ed, do you know if can I just pull that one stud out with a vice grips and then do the long bolt idea or do I have to take off the manifold to back it out from the inside? You really have me excited about the possibility of not having to take the manifold off!

[Young Ed]

Adam sorry I didn't think that through 100%. The flap is welded to the shaft that the heat risor runs on so you really will have to pull the manifolds and cut that shaft out of there. Check out my recent thread spring projects I just replaced mine. Put the manifolds back on last night. FYI a kit is about $75 if you want to fix it.

[pflaming]

you don't want to run without one for long

I have been led to believe the heat riser works in cold weather and one can run without it without any damage to the engine. Is my conclusion faulty?

[greg g]

Geez how long is "for long"? Cuz I been running for a bout 20K and 8 to 9 years with mine welded in the no heat position with no negative effects. Daily driver driven though out the year i cold climates, may be a cold running problem, light use vehicle used only in moderate weather IMHO no problem.

Is the end of the shaft still stickig out of the accessible side of the manifold? If so and you can turn it, take it all the way clockwise. Then you might see if you could find a piece of brass tubing whose ID is the same as the shafts OD. The taper the one end a bit, slide it over the shaft and then tap in into the gap between the shaft and manifold.

If the shaft is missing, a fine thread self tapping screw. a brass rivet, or a similar would work to plug the hole,

Sealing around the with some muffler goop or JB weld as well as sealing the end of the tube, might effect a repair.

Edited May 30, 2012 by greg g

[adam_knox]

Thanks for tips guys. For some reason my entire heat riser is missing, all I have are studs sticking out from the accessible side. Time and funds are short on this side, as per usual, so I'm thinking of trying the brass tapping screw method. I shall keep ya'll posted!

[JBNeal]

one of the oddities I found on that '54 Plymouth motor in my '48 1/2 ton was at the heat riser. In its place were two short bolts & nuts in the shaft holes in the exhaust manifold. The heating chamber in the intake manifold was completely full of carbon. The truck ran OK, but after reading that there was a reason for the valve, I figgered I needed it. I drilled out & scraped out the carbon, found a NOS heat riser valve kit on eBay back in '99, and eventually found a counter-weight for the shaft. Long story short, I found that I do not need this valve here in TX, as when the weather is cool enough for the need for that valve, the weather is usually wet, and I do not like to drive my truck in the rain (one too many close calls from inattentive drivers). In the summer (which lasts from May to October), I've disconnected the spring and the motor runs fine.

When it comes to sacrificial bolts, I go cheap Grade 0 variety as they are easy to cut off or drill out. One long bolt can be installed through the holes, but only snug up the nut to the manifold to keep from putting too much stress on the cast iron wall. On a similar application, I've snugged up a hex nut hand tight + 1/8 turn, then taken a punch to flatten the threads out, effectively locking the nut in place.

[TodFitch]

you don't want to run without one for long

I have been led to believe the heat riser works in cold weather and one can run without it without any damage to the engine. Is my conclusion faulty?

Somewhere I read a pretty good description of the conditions that the thermostatic heat riser deals with. I thought it was on this forum and I thought Frank McMillan posted it. But I can't find it.

Anyway, it helps most for cold start drive-ability in temperatures just above freezing to maybe the low 40s F when the humidity is high. It so happens that in what passes for winter in my part of the world, it does make a noticeable improvement. If you are the type that idles the motor for a few minutes before driving off you'll likely never notice the difference.