bluecab

Not sure if I should have put this in the big block section.
My 425 Toronado engine came disassembled and without much of an exhaust system.
I was getting ready to blast the manifolds and remembered that the drivers side has a flap inside it with a bi-metallic coil and counterweight on the outside.
What is this for? How does it work?
It looks like some sort of "exhaust choke" but I don't see any outlet on the engine side for the exhaust to exit when the flap is closed.
Should I take it apart and weld up the holes for the flap pivots?
I will be using the stock heads, manifold and carb when it goes back together, at least for a while.
TIA

Oldsmaniac

You are correct it is a sort of thermostat. When cold it is closed for a rapid heat condition under the carb thru the intake. As things warm the bimetallic spring is SUPPOSED to open. This is where the problem lies with these as sometimes the flap sticks closed. I usually take the flapper out and leave the pivot rod to seal the manifold where it goes thru.

bluecab

Is this feature common to all Olds of the era? or just the Toronado?
Where does the exhaust go when the flap is closed?
If I get rid of it will it cause cold start problems?
Thanks & Happy Thanksgiving

Oldsmaniac

Most GM cars used the setup mid 60's on up even the 80's Olds rocket engines. It was important even later to warm up the engine quickly so the choke would release ASAP to cut down on the rich mixture which can damage the Cat converter and also causes more emissions. There is a crossover port on the heads that matches the port on the intake manifold. Exhaust is directed across the manifold and out the other side. The flapper is not 100% so some exhaust still exits that side and also the spring is not strong enough to keep the flapper closed under higher RPM's. It was not a Toro only setup and I think some performance applications from the factory omitted this feature. The later ones used vacuum as an operator rather than the bimetallic spring.

MDchanic

I agree with Joe. Cut out the flapper, then weld up the shaft holes if the shaft isn't rusted air-tight.

These DO help get the motor running smoother and faster on sub-zero days, but most of us are unlikely to be using our cars in that sort of weather anyway.
Plus, they never work right anymore.

- Eric

bluecab

OK, I cut it out and will weld up the holes.
Is the flange ring that is pressed into the end of the manifold available?
Mine look kind of beat..

Oldsmaniac

You may want to plug the holes or tap them for plugs as cast iron is not easy to weld. At the outlet should be a gasket or just the metal ring which would be all that is left of the gasket. The new ones have the thin metal ring attached.

bluecab

I left a chunk of the shaft in the hole and mig welded it over, then ground the shaft flush on the inside and welded it, too. Looks OK, hope it lasts.
Then I looked at the Passenger side manifold and remembered that the remnants of the flange bolts were rusted in. Argh! I think my machine shop has a machine to get those out....

bluecab

Anybody know what color the exhaust manifolds should be on a '66 Toro?

MDchanic

Rust.

They were never painted.

- Eric

bluecab

Wow, That was fast....
Mine look to have been painted black under the hardened layer of grease.
Maybe I'll put some Hi-temp on them just to make myself feel good when I put the motor back together.