exhaust question, heat riser valve connections

[spedigo]

putting a new engine in my 79 and finally got around to pulling the old one on Saturday. For the few months that I’ve had the truck it has had a pretty strong exhaust leak. Found out Saturday one of the reasons was because whoever installed it last didn’t use any manifold gaskets at all. so that along with all the other stuff, I’ve learned while working on it over the past few months, I can’t trust but what I take apart is anything close to what it should be.

so my question has to do with the manifold to crossover pipe connections, particularly the passenger side connection around the heat risers valve.

My heat riser is frozen in the open position so I’m just going to put it back in as is. What I would like to know is what exactly are the parts, donuts and gaskets, that I will need to ensure no leaks going forward?

fyi, the manifolds I am using have the integral donut shaped flange. I’ll put a picture below. Don’t know if there was a
gasket between the manifold and the heat riser when I pulled the engine. Also, what goes between the heat riser and the crossover pipe?

I know one side of the heat riser is flat and the other is shaped to fit a doughnut, but that’s about it.

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[75gmck25]

There is a flat gasket with 3 holes on the manifold side, and a donut gasket to mate with the exhaust pipe. My pipes had a slight flare on the end, but then there was an insert dropped int o the end, and it had a larger flared flange that clamped up against the bottom of the donut. It all sealed fine, but I was never sure why it had the extra flared piece.

 

[fast 99]

Earlier small blocks use a flange on the header pipe, no gasket. Not a great design. Engine movement and frame twist would sometimes loosen the joint. There is also the style with a flat manifold surface, gasket, heat riser, header pipe with flange. I don't believe style pictured will work with heat riser valve. There is yet another style with 3 springs. I may have some different manifolds and will post pictures later today. Also, some aftermarket manifolds have questionable quality. If possible use OEM.

 

[fast 99]

3 manifolds, all with different connection to heat riser or header pipe. Manifold on left of first picture is new offshore. So poorly cast I was unable to install it.

 

[spedigo]

3 manifolds, all with different connection to heat riser or header pipe. Manifold on left of first picture is new offshore. So poorly cast I was unable to install it.

so, the one with the bolts in it on top is the one like I have, with the integral flange?

The one I have is not aftermarket it’s OEM and it’s probably the original one that came with the truck. The engine was swapped previously, but I’m pretty sure those are the original manifolds since the heat riser was still there and it all was pretty much frozen together. like you said, I’m gonna do everything I can to clean these up and keep using them because I don’t want to waste time with aftermarket. Just really wanna be sure I have all the right gaskets and donuts. It didn’t originally have the spring bolt, but is it the consensus that those are better?

 

[spedigo]

Earlier small blocks use a flange on the header pipe, no gasket. Not a great design. Engine movement and frame twist would sometimes loosen the joint. There is also the style with a flat manifold surface, gasket, heat riser, header pipe with flange. I don't believe style pictured will work with heat riser valve. There is yet another style with 3 springs. I may have some different manifolds and will post pictures later today. Also, some aftermarket manifolds have questionable quality. If possible use OEM.

like you said, maybe they’re not the original manifolds and were never intended to meet up with the heat riser and that’s why I’ve had the leak?

 

[fast 99]

very possible need to match. Picture of heat riser would help.

 

[spedigo]

OK, I just found this buried on my phone. Didn’t know I had it. Looks like the flat side of the heat riser connects directly to the manifold, but on my truck there was no gasket between the riser and the manifold and I’m guessing there should be.

But not sure if there should be a doughnut on the bottom of the riser or if the way it is cast takes care of that?



then there is the sleeve that was mentioned above and then the flange

I don’t remember seeing the sleeve when I took it apart. they’re definitely was not another doughnut on the bottom.