The Stovebolt Site Forums The Shop Area Engine Shop Quick 235 question.

Okay on the 235
How critical is the Manifold temperature control valve spring?

When I got my truck the spring was missing (and still is), I haven't driven it a lot but when I'm in the yard it is rough warming up and it sputters, Acceleration is also hesitant at times. according to the shop manual the Manifold TCV Spring is one of the remedies.

Now I have to find one I guess I will try NAPA first.

Only problem is if the valve is stuck with exhaust directed to the intake vs. out the pipe. Many guys weld these in the open position, put a ad in parts wanted you should get tons of responce. I'd put it back stock.

the 325 is a cold blooded engine to start with, you may try soaking the valve with a penetrant oil like PB Blaster or Liquid Wrench to loosen it up. Check the spark plugs, wires, and the timing too. My 235 did the same thing when it was cold. I reset the timing to the advanced side(15 degrees) now it runs fine. I am not running a vacuum advance or the manifold heat, I have Fenton's on the engine.

The spring was missing.
I got a freebee compliments of the lady in charge at a local wrecking yard. I could have put it in my pocket, but I am an honest guy. (the spring was the freebee)

Of course she said they didn’t have one, and I could tell by the look on her face that she didn’t even know what one was. But she offered me to take a look around and there was 5

Billy,
I put a spring in on my manifold, and the engine never got hot enough to fully open teh valve-so I took it off. Here in SoCal its better to run as cool as possible, (I think its 95 degrees outside today and summer hasn't started yet).

Tlober
You just took off the spring or you took out the unit?
I saw a unit at the junk yard with two bolts in each side.

In the Shop Manuel it says if the valve is open during normal operation mode that the intake gases would expand over 3X causing insufficient combustion in the chambers. I would think in a cold climate it would be okay to have it open but in a warm climate wouldn’t you want it closed so it would only draw in cool air?

"For the sake of science" I guess I will do some experimentation with it.

This valve has nothing to do with the engine running hotter or cooler. In normal operation, the valve directs exhaust to flow in contact with the bottom of the intake chamber, thus allowing the intake chamber to come up to operating temperature quicker. As the spring warms it expands, blocking the passageway to the bottom of the intake chamber and sending the exhaust directly out the manifold exit hole.

Cletis is right on. The valve is only used for quicker warmup of the manifold. I have mine completely closed all the time. the engine always ran fine. These valves are frequently frozen in one position or another so the spring has no effect. But, if yours works and you need a new spring, everyone carries them I.E. Jim Carter, Chevy Duty, etc.

Glenn,

With a new spring I have found the valve will stay closed at an idle, even when hot. When the engine is revved up the exhaust pressure will open it up.

Billybob, I kept the valve but just removed the spring. The valve moves fine without one. My point was that in hot weather, you're not all that concerned with a cold startup so you don't need the valve closed. But if the valve is stuck closed, the exhaust is definitely more restrictive than with it open. I don't know if this makes the engine run hotter, but it sure won't help the engine breathe.