72 Heat riser

[Eric Fairclough]

Hello, I was under the car tonight and noticed that the heatriser pin and spring broke off. I am going to wire it but i wanted to be sure of one thing. When the counter weight is in the up position , is that open? Thanks Eric

[Duke W.]

Re: 72 Heat riser

I'd like someone to confirm this, but I'm pretty sure the valve is open when the weight is pointing down.

Another way to check is to feel the exhaust flow from both pipes. If the heat riser is closed, you can definitely detect the reduced flow on the RH side by holding your hands a few inches from the end of the tailpipes.

Duke

[Gary S.]

Re: 72 Heat riser

Yes, the valve is open when the weight is pointing down. Based on responses this board made to a post of a similar question, I had removed the heat riser. My choices were to cut the butterfly off or wire it open. I chose the latter. Fairly simple but I imagine you may skin a knuckle or two doing it on the car.
Gary

[Eric Fairclough]

Re: 72 Heat riser

Thanks guys, I am going to wire it to the down position and check the exhaust. Thanks Eric

[Jim T.]

Re: 72 Heat riser

Gary concur with you my 68 and 70's heat risers are wired in the down position. The left side muffler does last longer using this method.

[ERIC FAIRCLOUGH]

Re: 72 Heat riser

You guys were right it is open in the down position even know it feels like more exhaust is coming out in the up position. I was going to wire it then i decided to take out the butterfly inside. So i tried to get the bolts off the studs and all 3 studs broke. So tomorrow i am going to get a stud extracter for 2 of them and the 3rd broke flush so i have to drill it and get a easy out for it. I hope that will work. I think i opened a can of worms. Eric

[Patrick H.]

Re: 72 Heat riser

Eric,

Consider going to a machine shop or quality exhaust or auto repair place. They do this all the time, and for about $10 it's not worth the hassle of doing it yourself.

You CAN make it worse than what you have now.

Patrick

[Jack H.]

STRONGLY agree....

with Pat. Trying to hand drill an exhaust mani stud out of an aged flange with the mani on the car has a high probability of resulting in an off-center and/or a broken exhaust mani flange.

While it seems like 'make work' to remove the mani and hand walk it into a machine shop where it can be fixtured and worked on a drill press, that 'overhead' is peanuts compared to breaking the manifold casting or having an easy-out break off inside your stud extraction hole!

[Patrick H.]

Re: STRONGLY agree....

Of course, Jack knows this because I purchased a manifold from him because, well, I had this problem myself.

Even with the manifold off the car, using penetrant and using heat, I still broke the manifold. I actually did have it repaired and it's undetectable.

Take it away. Have it done right.

Been there, done that, swore at it.

Patrick

[Chuck S.]

Why, Doc...That's Brutal Honesty...

I thought you must levitate above those doo piles as you walked through restorations!

[Patrick H.]

Re: Why, Doc...That's Brutal Honesty...

Nah. The surprising thing is that it happened on my own car.

I've been working on my Dad's 72 for several years. NOTHING, and I mean nothing, has gone without breaking on that car, or resulting in the need to fix 3 things when I intended to break one. That's why it has been a 6 year project.

On my own 71, that essentially never happens. How Murphy struck that car I'll never know. I now have another set of spare manifolds just in case.

Patrick

[ERIC FAIRCLOUGH]

72 Heat riser studs

Well, I bought a stud remover and took out the two studs and I noticed that the threads were all rusted to nothing. The third I drill and an easy out broke inside it. So I was just going to see how well two studs would hold it and sure enough the second one striped with hardly any force since the threads were pretty much disintegrated. So the exhaust manifold is toast. I ordered a set of full-length headers and a remote starter solenoid to cure the heat soak problem it will have with the headers. I refuse to put a new exhaust manifold on the car. That design is horrible. They should have anticipated that exhaust systems will rust and made it so you can use a nut & bolt instead of the studs that go into the exhaust manifold. When the threads rust out to nothing you can't do anything with it. At least with a nut blot design you can cut off the old rusted one and put a new one in. I should mention that this is the pass side heat riser. The other one came apart with no problem. I am going to keep the old exhaust manifolds for if I ever sell it.
Eric

[Clem Z.]

Re: 72 Heat riser studs

for the stripped threads you can stainless steel heli coil.

[ERIC FAIRCLOUGH]

Re: 72 Heat riser studs

Would that be strong enough to hold the exhaust together?

[Clem Z.]

Re: 72 Heat riser studs

it will be strong enought as long as you have enought material in the manifold to install them