Remove Heat Riser, Yes or No?
Thread Starter
Burning Brakes
Joined: Oct 2009
Posts: 1,066
Likes: 57
Remove Heat Riser, Yes or No?
'71 w/350. My heat riser is presently wired open. I have no complaints, other than a slight exhaust leak where the manifold meets the heat riser and exhaust pipe.
I'm going to fix the leak, but while I'm there, should I replace the heat riser with a spacer?
I live in New England and drive the car until Thanksgiving, when it's ~40-45* outside. So far, outside temperature hasn't been a problem with the riser wired open.
Thanks
I'm going to fix the leak, but while I'm there, should I replace the heat riser with a spacer?
I live in New England and drive the car until Thanksgiving, when it's ~40-45* outside. So far, outside temperature hasn't been a problem with the riser wired open.
Thanks
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
All it does is raise the temperature of the intake so the fuel atomizes better. If you're not having any problems, it's not going to hurt you to remove it. After all, it's wired open anyway. There's a gasket between the riser and the manifold, and a donut and sleeve to the pipe.
Le Mans Master
Joined: Aug 2006
Posts: 7,426
Likes: 1,559
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Heat riser headache!
Within the last week I noticed that my heat riser did not open at all, after a few days of applying some penetrating oil it now opens about 3/4 of the way. I'll give it a few more blasts of PB and if it fails to work properly I plan to replace it with a new donut, gasket and a spacer. We both have divorced chokes and I'm not a mechanic but I figure the worst that can happen it that the choke will take a few minutes longer to get hot and fully open without the butterfly in there.
I have stock cast iron manifolds and if the PB does not work I'll just wire it open as I'm sure that I'll break a stud off and have more of a problem than I have now. PG.
I have stock cast iron manifolds and if the PB does not work I'll just wire it open as I'm sure that I'll break a stud off and have more of a problem than I have now. PG.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
It just helps the carb warm-up faster and shut off the choke sooner. If that doesn't bother you, pull it out. Or, if you want it to look original from the outside, just use a Dremel or die grinder and grind the rivets off the shaft to remove the butterfly valve inside the heat riser. Then it will always be open, but you don't have to buy a spacer and it will still look 'stock'.
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
Why don't ya just fix it so you get better cold motor driveability like it was intended for. Putting a new one in is relatively cheap and ez and something you can do yourself. My .02.
afterthought - now if you've never had the exhaust manifold bolts off (and replaced with brass and the studs replaced with SS ones, the manifold will have to come off for that. What happens is the studs get worn down (sorta looks like a skinny wasted girl) and you can never really tighten the bolts.
afterthought - now if you've never had the exhaust manifold bolts off (and replaced with brass and the studs replaced with SS ones, the manifold will have to come off for that. What happens is the studs get worn down (sorta looks like a skinny wasted girl) and you can never really tighten the bolts.
Last edited by TWINRAY; Nov 3, 2009 at 10:03 AM.
Le Mans Master
Joined: Oct 2006
Posts: 7,565
Likes: 103
From: North Carolina "life is good"
2025 c3 ('68-'73) of the Year Finalist - Unmodified
It just helps the carb warm-up faster and shut off the choke sooner. If that doesn't bother you, pull it out. Or, if you want it to look original from the outside, just use a Dremel or die grinder and grind the rivets off the shaft to remove the butterfly valve inside the heat riser. Then it will always be open, but you don't have to buy a spacer and it will still look 'stock'.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
It's only as hard as it is to remove those retaining nuts on the three studs out of the exhaust manifold. [this is where the mad phantom lets go of that wicked, haunting laugh in the background] 
I've never seen one that came off easy. Most of the time one of the studs breaks off...or one or two screw out of the manifold. Actually, if the studs do come out, it makes the exchange easier.
I've never seen one that came off easy. Most of the time one of the studs breaks off...or one or two screw out of the manifold. Actually, if the studs do come out, it makes the exchange easier.
Intermediate
Joined: Dec 2009
Posts: 41
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Lots of penetrating oil (PB Blaster for example) well in advance and you still need to prepare to pull the manifold when the studs start snapping off. Those guys get pretty slim from rusting and it takes very little to get them to break.
Racer
Joined: Jan 2010
Posts: 348
Likes: 2
From: Lowell MA
1969 L46. Shouldn't the riser fully open and stay open once the engine reaches operating temperature? My riser is nice and free and snaps up nicely when the engine is cold. When the engine fully heats up, the riser will move down slightly. I can easily push it fully down but it returns to about only 1/8 to 1/4 open. If I rev the engine up, it only opens slightly more. Had the engine reworked last spring and it now has an 180 degree thermostat. Runs at about 170. When the car was brand new, it used to run at 210. Think that has something to do with it? I can definately hear a difference in the exhaust tone when I manually push it fully open.
Race Director
Joined: Jul 2004
Posts: 12,703
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From: Scottsdale Arizona
It's only as hard as it is to remove those retaining nuts on the three studs out of the exhaust manifold. [this is where the mad phantom lets go of that wicked, haunting laugh in the background]
I've never seen one that came off easy. Most of the time one of the studs breaks off...or one or two screw out of the manifold. Actually, if the studs do come out, it makes the exchange easier.
I've never seen one that came off easy. Most of the time one of the studs breaks off...or one or two screw out of the manifold. Actually, if the studs do come out, it makes the exchange easier.
It never hurts to try penetrating oil to start but I don't think I've ever seen more than 1 of the 3 come out this way. Inevitably they'll snap. I usually file it flat, drill it out and put in a helicoil. Faster and easier than struggling with it. You do have to remove the manifold to do this properly though.
