Heat Riser Position

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May 15, 2007 | 01:49 PM

Tim81

Thread Starter

Burning Brakes

Joined: Aug 2006

Posts: 1,058

Likes: 27

From: Eastern North Carolina

Heat Riser Position

Hello Everyone, Can someone tell me on a 81 what is the normal position for the heat riser valve when no vacume is going to it? Mine is stuck and I'm trying to fiqure out if its stuck open or closed. The engine runs fine and idles smooth so I'm thinking its open. Thanks for any help at all.

May 15, 2007 | 02:26 PM

SIXFOOTER

Le Mans Master

Joined: Jan 2006

Posts: 9,192

Likes: 27

From: Boca Raton Florida

The vac operator pulls up on the valve lever when applies

May 15, 2007 | 03:09 PM

rihwoods

Race Director

Joined: Feb 2005

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Open...(78)...

Closed...

May 15, 2007 | 04:36 PM

Tim81

Thread Starter

Burning Brakes

Joined: Aug 2006

Posts: 1,058

Likes: 27

From: Eastern North Carolina

Thanks those pictures should help. Can you tell me what a heat riser is suppose to do?

May 15, 2007 | 08:39 PM

BarryK

Le Mans Master

Joined: Apr 2004

Posts: 7,106

Likes: 38

From: Newark DE

Quote:

Originally Posted by Tim81

Thanks those pictures should help. Can you tell me what a heat riser is suppose to do?

when the motor is cold the heat riser stays shut and therefore the warm exhaust gases are blocked off from exiting that side of the exhaust system. The exhaust gases are than routed thru the crossover passages of the intake manifold where the warm air helps to warm the intake and carb allowing it to warm up faster and the choke to come off quicker.
Once the motor warms up the heat riser valve opens and exhausr gases pass normally thru the exhaust on that side.

May 15, 2007 | 10:39 PM

Tim81

Thread Starter

Burning Brakes

Joined: Aug 2006

Posts: 1,058

Likes: 27

From: Eastern North Carolina

Thanks Barry, That was very helpful. So if the valve is stuck open it shouldn't be to big of a problem.

May 15, 2007 | 10:44 PM

big_G

Le Mans Master

Joined: Jul 2005

Posts: 5,752

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From: Austin Texas

Quote:

Originally Posted by Tim81

Thanks Barry, That was very helpful. So if the valve is stuck open it shouldn't be to big of a problem.

Not until winter hits Ohio...

May 15, 2007 | 10:51 PM

Tim81

Thread Starter

Burning Brakes

Joined: Aug 2006

Posts: 1,058

Likes: 27

From: Eastern North Carolina

Oh yeah winter:

The car stays in the garage most of the winter. But that would be a good time to repair it.

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May 16, 2007 | 04:35 AM

BarryK

Le Mans Master

Joined: Apr 2004

Posts: 7,106

Likes: 38

From: Newark DE

Tim
A heat riser valve stuck open will not cause a problem - simply that in cold conditions it takes longer for the motor to warm up.
On my '65 I replaced the heat riser valve with a spacer unit but the car only gets driven in the warmer months and is stored in the winter.

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