Exhaust Heat Control Valve Question

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Oct 21, 2017 | 01:04 PM

Cavu2u

Thread Starter

Melting Slicks

Joined: Oct 2013

Posts: 2,569

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From: San Diego California

Exhaust Heat Control Valve Question

The Chevy Service Manual calls it a Heat Control Valve. You know, it fits onto the right-hand Exhaust Manifold, and the Exhaust Pipe then attaches to it by way of the extra long Manifold Studs.

Correct me if I'm wrong; After bolting (or nutting

) everything together, one should be able to grab the counterweight on the exterior of the HCV and move it up & down (open & closed). If you can't move it at all, there's a problem.

Correct?

Thanks.
Steve

Oct 21, 2017 | 01:22 PM

71VetteLover

Pro

Joined: Sep 2017

Posts: 516

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From: Modesto California

Quote:

Originally Posted by Cavu2u

Yep, if it won't move the butterfly is probably hitting the steel tubing insert that is in the pipe. The insert that centers the doughnut. Take it apart again and tap on the insert until it's all the way down.

Oct 21, 2017 | 01:51 PM

Alan 71

Team Owner

Joined: Sep 2006

Posts: 31,301

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From: Westminster Maryland

Hi Steve,
The collar would have to be REALLY distorted for the flapper to be able to hit it.
???
Is the valve installed right side up and 'clocked' properly?
Regards,
Alan

Note finger holding weight down.

Oct 21, 2017 | 02:06 PM

Cavu2u

Thread Starter

Melting Slicks

Joined: Oct 2013

Posts: 2,569

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From: San Diego California

Quote:

Originally Posted by 71VetteLover

How important IS that insert?

Here's what I think 71: I don't even want that HCV in there. This car is staying in SoCal, so why the concern for warm-up here? The muffler shop replaced the broken valve (butterfly valve missing) without my OK, cuz I liked the idea of unrestricted flow. But I let it go. I just recently r&r'd the transmission, so I had to mess with the exhaust system, evidently messing up the re-assembly. That insert tube looked homemade and beat. I attempted to make sure it seated onto the shoulder inside that valve, clearing the butterfly. Like you said, it probably isn't. Is that tube just to hold the exhaust packing ring together? Is it really necessary?

Anyway, I appreciate your time. Thanks much.

Steve

Oct 21, 2017 | 02:15 PM

Cavu2u

Thread Starter

Melting Slicks

Joined: Oct 2013

Posts: 2,569

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From: San Diego California

Quote:

Originally Posted by Alan 71

Hi Alan!

I looked at the valve rather closely, and found the word UP in one of the valve's corners, so I made sure of it's alignment anyway. The condition of that inner tube concerned me. I wonder if I could just buy a new exhaust pipe section the correct OD of that HCV's inner shoulder, then figure out the correct packing ring for it.

Thanks for the picture Alan.

Steve

Oct 21, 2017 | 02:35 PM

CanadaGrant

Safety Car

Joined: Apr 2006

Posts: 4,057

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From: BC

You can buy spacers that take the place of the valve in 2" or 2 1/2"

http://www.parts123.com/corvettecent...050g&ukey=8666

You can also just take a dremel tool or what have you and cut the butterfly out leaving just the rod so it looks original. Easy job.

Oct 21, 2017 | 03:08 PM

Cavu2u

Thread Starter

Melting Slicks

Joined: Oct 2013

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From: San Diego California

Quote:

Originally Posted by CanadaGrant

I did not know this.

Thanks much my friend.

Steve

Oct 21, 2017 | 03:15 PM

Cavu2u

Thread Starter

Melting Slicks

Joined: Oct 2013

Posts: 2,569

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From: San Diego California

Freeing up that butterfly valve was easier than I imagined.
I just backed off the 3 nuts to almost off, which of course loosened up the "stack". Loosened it up to the point of now being able to open the valve by pulling down on the counterweight. Then is was just a retightening of the nuts evenly while pulling the valve open every now and then. And when fully tightened, the valve now swings open and closed, unrestricted.

No need to freak Steve.