The Stovebolt Site Forums The Shop Area Engine Shop Starting heat riser work on '51's 235

I posted awhile back about my old daily driver had apparently sat too long and the butterfly valve in the heat riser is stuck. Starts, runs, but only makes it around the block and it's heat gauge is red lining. I've tried all the suggestions (oil and wiggle often, heat, soft taps with a hammer), but it's not cooperating. So, I'm gonna pull the exhaust manifold and work on it from the inside out. I figure if I can just get too it, I can get it loose. The idea of not being able to jump in it and drive is starting to get to me. Since I bought the '05 Silverado 3500 for work on our property and pulling heavy stuff, I've neglected to use the old daily driver, and this is what I get for doing that.

Anyway, since I've never pulled the exhaust/intake manifolds on this truck, I was just wanting to hear other folks suggestions, stories, problems/solutions for this. The biggest concern for me is a broken bolt, but I have no idea what other usual trouble guys have with this operation. Thanks in advance for any help on this. Lee

"heat gauge is red lining"? Are you talking about the water temperature gauge? If so, you may have a more serious problem.

Agreed. A stuck heat riser won't make the engine coolant run hot.

The first thing to take off would be the exhaust pipe ,after you do that I would not take anything else off until you sprayed your favourite penetrating oil on the inside of the manifold as you can see the inside of the heat riser .That may be enough to free it up.I also agree with the guys above might be time to check the cooling system.If you do drop the exhaust pipe and if you don’t have brass nuts on the studs it would be a good time to change them out .

If you aren’t planning to drive it in cooler weather, you could consider knocking the riser flap out and reinstall the shaft to keep exhaust fumes from accumulating under the hood. I agree with earlier assessments. You may need to flush the cooling system.

Installing brass nuts as Kevinski says for sure, they are cheap; upon reassembly, do not tighten inter manifold bolts until all head attachment bolts are tight

Ed

Thanks, guys. Strange that when I brought the heating problem up a few months ago, it was the heat riser valve that everyone agreed was the problem. It is definitely stuck closed, and it's not suppose to be. And I never had a problem with overheating before it was stuck. I'll check things out and see what comes up, but the first thing on the list right now is to get that butterfly valve unstuck. Makes no sense to me to do anything else until that's done.

And thanks for the tip on the brass nuts, K. Will do.

R- How would you knock out the valve plate without leaving openings on each end of it where it pivots? Are you saying that the whole part comes out? And if not, what will hold the valves balance weight and bi-metallic spring attachment in?

With all due respect, that seems like a horrible idea. Wouldn't that allow exhaust heat to blast the intake full time?
Now if you had suggested to leave the flap in place as long as it is stuck in the fully warmed up position, I could understand your point.
I still wouldn't do that unless ambient temperatures where I lived were around 160 degrees most of the time.
That flapper valve heats up the intake rapidly upon startup to prevent the air/fuel mixture from becoming liquid gas upon contacting an intake runner which is many degrees cooler than a fully warmed up engine would have. This leads to raw fuel falling on the top of the piston then leaking past the rings to contaminate the oil. This will happen to some degree regardless of local temperatures.

52 Carl,

I have mine apart now and finally understand the pathways.

When the flap is closed it forces the exhaust back up and over to the other side. When it is open it is free flowing, but I am sure there is some exhaust gas recirculation because nothing closes off the pathway. I assume the flow of gasses will take the path of least resistance and not backtrack if there is a open path for them to go.

K- just re-read this and I must have missed the part you mentioned about getting to the flap from the exhaust pipe connection. I was thinking the first time I read it, "you can't get to that flap from the top! The intake manifold is blocking it. Now I see what you're talking about. Thanks!

Well, it's finally done. Thank you very much Kevinski, for the go through the bottom idea. I sprayed it with some Kroil yesterday and then today went after it. I tried oiling it, heating it, beating it and talking dirty to it, but it still was not budging. So I loosened the throttle linkage, pulled the oil filter and hung it to one side (the lower hose was broke in half!! Must have dry rotted after sitting so long, so I'm glad I unhooked it from the manifold. Made it easier to get to the counter weight, too.) Pulled the exhaust pipe off the manifold and started spraying the inside bearing points. I tried tapping it, lightly prying it, putting a small vice grip on the rod, and it still didn't go. So I sprayed it some more and went back up top and put the vice grip on the weight and wiggled it, but nothing. Finally I got my ball peen and tapped the weight towards the manifold and I thought I saw some movement. At that point I just alternated tapping from both sides and within a minute or so, it started moving a hair. Then a 32nd, then a sixteenth, and finally it was moving free. I grabbed the weight with the vice grips and worked it up and down, sprayed it some more and it finally freed up enough for the weight to return to open every time. Fortunately, it was a beautiful day in the high 50's and I had a rear fender bracket on the Silverado that needed mending, so everytime I'd start to get irritated, I switched jobs. Got 'em both done.

I'm going to order a few parts before I put it back together. I'm getting some new oil lines for the filter, a new bi-metallic spring (I thing I have one, but it's in "one of those boxes in there"). Same with the gasket. I may even have new oil lines. I'm bad about buying stuff 'just in case'. Need new lock washers for the oil filter bracket and tail pipe hanger, and probably get new bolts for the exhaust connection. BTW, I won't need brass nuts, since this has threaded bushings in the exhaust manifold. The bolts came out easy and look good, but one is a little bent. The exhaust is pretty new, so that helped. Anyway, the jobs not "done", per se, but the valve is fixed, so that's good enough for me. Here are some before and after and after that pics. Thanks every body for the help and moral support. I will say I have to disagree completely with the guys who say a stuck heat riser flap won't cause the engine to overheat. Either you've never had one stuck completely closed, or you're lucky. I flushed the radiator, changed hoses, thermostat, belt (at which point I also pulled the radiator and checked it while it was out. Nothing. This stuck flap was the trouble. I would have never thought it could make the truck get hot so fast, but it does. I will forever more be checking that little spring and flap each time I open the hood. Still wasn't as bad as those king pins last summer!

While a working heat riser is a good idea, it's very unlikely to cause the coolant to overheat. Try putting a little pressure on the radiator with a hand pump and see if it goes away quickly. If you're running the original radiator don't go over 4-5 PSI or you're likely to spring a leak in the radiator or heater core. I'm going to guess the pressure won't stay there long, and you'll probably find a blown head gasket or a cracked head, or possibly nothing worse than a stuck thermostat. If the pressure stays there for 10-15 minutes or more, pull the thermostat and do a boil test on it.
Jerry

Although I finished freeing up the heat riser valve in May, I've (slowly) finished the other things up that I came across while getting it fixed. Removed the oil filter can to get to the flap rod, so I painted it and added new hoses, which entailed a new swivel fitting. Once again, I received a bad part from classic parts, which delayed finishing. I also replaced the old accelerator return spring and found the missing tab that it was suppose to be connected to. Pulled the new thermostat back off and started the truck up with it out, then checked it on the stove in a pan of hot boiling water. It opens at 180* as it should, so I put it back in.

In conclusion, after the thermostat was out, I took it around the block for a test spin, and it works fine. Put the thermostat back in, and drove it across town, and the temp is staying at 180*. I then drove it out to my diesel mechanic (I have an '04 Duramax 1 ton 4x4 I take there) to get it inspected, since it's plates expired August 2021, and brought it up to date legally. That was about a 10 mile ride and still no over heating problem. So, even though I hate to disagree with the folks who say this heat riser valve could not be the problem, I've found that it seems to be what the problem was. It didn't overheat until it stuck. Now that it's unstuck, it isn't overheating. I believe the heat riser valve was the culprit. Anyway, it seems to be running great, although I'm going to have to re-adjust to the noise level of the old bomb. After driving in the '04 for 2 years (first the bad timing gear and all the time it took to get it repaired, then the heat riser flap from sitting idle too long), I'd forgotten how loud it is to drive the '51. I'd also forgotten what it's like to drive with the windows down, the cowl vent open and the air conditioner (my vent windows open to aim the wind at me). Seems I'd forgotten how fun it was to drive, too. And the people who stop and stare when I go by. Something that NEVER happens in my '04. Thanks for ALL the help and opinions while I fought this thing. As slow as it went, and the headaches that came with it, all I have to do is think back to last summer when I changed out the king pins on this truck to realize that this was, in comparison, a piece of cake. And I didn't even split my thumb wide open like I did with that project. Twice. All is well.

Great to hear everything worked out and your back on the road!

Soak that heat riser in EvapoRust for a few days. You will be amazed. I use it on every rusty item. I get it at O'Riellys. Once you have it loose, wire it open. That is what we all do here is the South.

Hey Redbird, y'all have a lot of days where the temperature reaches 180 degrees? If so, by all means, wire that flap in the warmed up position (which is closed, BTW).

I used to have a signature line that addresses ideas like that- - - - - -
Jerry

Thanks, Redbird, but it's back together and done. I did use Kroil on it, after the PB Blaster didn't do the trick. And after putting a new bi-metallic coil on it, I'll leave it operational. Plus, here in Missouri, it gets below zero sometimes. And the truck has always fired right up, no matter how cold it gets (with a little help from the C and T knobs).