removing exhaust heat riser valve
Thread Starter
Racer
Joined: Sep 2002
Posts: 389
Likes: 0
From: san diego ca
removing exhaust heat riser valve
I've read a bunch of old posts about what this is, how it works, and whether or not it is needed. I've decided it's not for So.Cal, and mine is pretty rusty and not so smooth in opening/closing. So I'm thinking of removing it.
Here's my questions:
1) do I really need to buy a pricy ($30-50) spacer to put in it's place?
2) can't I just bolt up the passenger side the same as the driver's side?
There seems to be enough slop in my tired old exhaust pipes (engine is currently out) that would make up for the 1" lost by removing the heat riser.
Or would removing it tweak the angle of manifold/donut meeting up with exhaust pipe that would not get a good seal?
'nuther options is gutting the riser and plugging the axle holes, but I like K.I.S.S.
Thanks,
John.
Here's my questions:
1) do I really need to buy a pricy ($30-50) spacer to put in it's place?
2) can't I just bolt up the passenger side the same as the driver's side?
There seems to be enough slop in my tired old exhaust pipes (engine is currently out) that would make up for the 1" lost by removing the heat riser.
Or would removing it tweak the angle of manifold/donut meeting up with exhaust pipe that would not get a good seal?
'nuther options is gutting the riser and plugging the axle holes, but I like K.I.S.S.
Thanks,
John.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
The spring always rusts and breaks. We use to take them off and knock or cut the pin out to remove the flap. Then weld the holes on both side.
They were designed to help the car warm up faster.
They were designed to help the car warm up faster.
Racer
Joined: Feb 2013
Posts: 364
Likes: 39
From: Sebastian FL
spacer
I've read a bunch of old posts about what this is, how it works, and whether or not it is needed. I've decided it's not for So.Cal, and mine is pretty rusty and not so smooth in opening/closing. So I'm thinking of removing it.
Here's my questions:
1) do I really need to buy a pricy ($30-50) spacer to put in it's place?
2) can't I just bolt up the passenger side the same as the driver's side?
There seems to be enough slop in my tired old exhaust pipes (engine is currently out) that would make up for the 1" lost by removing the heat riser.
Or would removing it tweak the angle of manifold/donut meeting up with exhaust pipe that would not get a good seal?
'nuther options is gutting the riser and plugging the axle holes, but I like K.I.S.S.
Thanks,
John.
Here's my questions:
1) do I really need to buy a pricy ($30-50) spacer to put in it's place?
2) can't I just bolt up the passenger side the same as the driver's side?
There seems to be enough slop in my tired old exhaust pipes (engine is currently out) that would make up for the 1" lost by removing the heat riser.
Or would removing it tweak the angle of manifold/donut meeting up with exhaust pipe that would not get a good seal?
'nuther options is gutting the riser and plugging the axle holes, but I like K.I.S.S.
Thanks,
John.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Thread Starter
Racer
Joined: Sep 2002
Posts: 389
Likes: 0
From: san diego ca
Aha, good to know, thanks everybody.
I don't weld, but was thinking I could try to find a local shop.
I don't have a tap set, so even that option was looking costly to buy the tools.
I hadn't even thought about muffler cement; I'll do some googling...
Favorite brand? I guess I'll also go down the path of a local weld shop.
I don't weld, but was thinking I could try to find a local shop.
I don't have a tap set, so even that option was looking costly to buy the tools.
I hadn't even thought about muffler cement; I'll do some googling...
Favorite brand? I guess I'll also go down the path of a local weld shop.
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Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
dont try and run without the spacer, pulling the pipe up by the bolts will stress the ex. manifold outlet and it will crack!.... i know. i have mine installed but its gutted and a muffler shop welded the holes up for me...$10
Racer
Joined: Aug 2005
Posts: 355
Likes: 18
From: Corona Ca
Dunno about Corvette ramshorn manifolds but many Chevy manifolds used with the riser are not machined to accept an exhaust donut, so can't be sealed as well. Another issue besides the stressing of the pipe/manifold...
The flapper can be removed from the assembly with the shaft left intact (done that) or the flapper and shaft can be removed and the appropriate sized hammer-in plugs (like small freeze plugs) or dowel pins can be pressed or hammered in (done that too). These may require a correctly sized drilled hole, but easier than welding or tapping for some.
Good luck
Tom
The flapper can be removed from the assembly with the shaft left intact (done that) or the flapper and shaft can be removed and the appropriate sized hammer-in plugs (like small freeze plugs) or dowel pins can be pressed or hammered in (done that too). These may require a correctly sized drilled hole, but easier than welding or tapping for some.
Good luck
Tom
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Thread Starter
Racer
Joined: Sep 2002
Posts: 389
Likes: 0
From: san diego ca
The flapper can be removed from the assembly with the shaft left intact (done that) or the flapper and shaft can be removed and the appropriate sized hammer-in plugs (like small freeze plugs) or dowel pins can be pressed or hammered in (done that too). These may require a correctly sized drilled hole, but easier than welding or tapping for some.
Good luck
Tom
Drifting
Joined: Apr 2008
Posts: 1,305
Likes: 2
From: Lewisburg WV
thegazman
Interesting, Tom and 7T1vette both mention leaving the shaft intact. Clearly this would be better than what I have now, but what about the shaft itself impacting airflow. Is zero obstruction of air-flow worth it to take the shaft out? More work to plug/weld/putty the holes (bummer), but better airflow with less turbulence (bonus). It would be good to do this only once...just over-thinking my options.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
Every 'stock' C3 ever built has a heat riser valve [and shaft] in it which presents some blockage to exhaust flow. If you need to improve exhaust flow, install larger headers WITHOUT the heat riser in it. Otherwise, the stock stuff was designed to provide adequate exhaust flow under all NORMAL operating conditions...even wide-open-throttle.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Or you could just give the shaft end a few squirts of WD40 when it's cold and loosen it up so that it works nicely. Then close the hood and just drive it.
Seriously, if you have a cast iron manifold and a "divorced" choke, (with the bimetal spring bolted to the manifold), I wouldn't do more than that. Because otherwise it will take about forever for the choke to come off after a cold start.
If you have an aluminum manifold, you could probably get away with removing the heat riser. Or if your car has an electric choke.
Remember what Boss Kettering said, "Parts left out cost nothing and pose no service problems."
If Chevrolet thought it was necessary to have some sort of manifold heat, I'd leave it be.
Seriously, if you have a cast iron manifold and a "divorced" choke, (with the bimetal spring bolted to the manifold), I wouldn't do more than that. Because otherwise it will take about forever for the choke to come off after a cold start.
If you have an aluminum manifold, you could probably get away with removing the heat riser. Or if your car has an electric choke.
Remember what Boss Kettering said, "Parts left out cost nothing and pose no service problems."
If Chevrolet thought it was necessary to have some sort of manifold heat, I'd leave it be.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
I've seen/owned a lot of old cars with heat riser valves. Nearly all of them have had the riser valve stick at some time or other. I have never been successful at lubricating a stuck valve to free it for more than a few days. Once they get corroded enough to stick, they appear to be "doomed". I think the valve would have to be removed completely, cleaned and the shaft polished, to have any shot at it being viable for very long. If GM really wanted these things to last very long, the shaft should have been made of stainless and the manifold should have had stainless bushings for the shaft.
But then, GM designed the car for about a 5-10 year [first] life span.
But then, GM designed the car for about a 5-10 year [first] life span.