Rally68

After re-assembling my exhaust I have a pretty noticeable leak where the heat riser is on the passenger side. I didn't disassemble that joint but was moving the exhaust around a bit, taking it apart and putting it back together. I'm clueless about this part.

What does the valve do?

Does it need lube/maintenance?

I've seen where vendors sell spacers to replace the valve; is this a good or bad idea?

Lastly, will I ruin anything (gasket, etc.) if I try tightening this joint?

Thanks!

7T1vette

That valve is meant to [partially] close off the exhaust flow on the right bank to force heated exhaust up into and across the intake manifold for heating the carb choke. That valve has a bi-metallic spring on it which unwinds as it heats, so that it will open the valve completely once the engine is warmed up. To keep the valve from locking up, it needs to be lubed...but it has to be very hi temp lube or graphite product [dry lube]. The shaft is all that needs to be lubed. To test, just move that counterweight up and down to be certain there is freedom of operation. If the heat riser is leaking exhaust, someone didn't install the 'donut' gasket to it.

69Vett

they make a spacer to eliminate the heat riser completely,
I suggest that if you live in a warm climate, with min. cold weather. 69VETT

Alan 71

Hi R68,
There's a packing 'donut' and a sheet metal extension 'sleeve' that fit in the connection between the heat riser, and the head pipe. Did they get moved around a little so they're not giving the seal you had before disassembly?
Regards,
Alan

7t3shark

You can also easily wire it open. First thing I did after picking up and never had any cold weather driveability problems. Later when had intake manifold off, blocked off the crossover passage to keep carb cooler after engine was warmed up.

Rally68

That's what I'm thinking. I hope it's that simple. I'll get to the bottom of it this weekend.

Until then, I'm disturbing the peace

TimAT

If you want to lube it, there's a product called "Mouse Milk" Works great in Hi-Temp applications. Used on small turbocharged aircraft to lube the turbo wastegate.

7t3shark

Not sure if still available but in late '60s, GM sold a aerosol heat riser lube that worked well.