Heat Riser?
Thread Starter
Burning Brakes
Joined: Feb 2017
Posts: 870
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Heat Riser?
Putting my overhauled 66 427/425 back together. Do I really need the exhaust heat riser on this motor? I live in a mild climate. Thought i would just cut the butterfly valve out and reinstall it inline.
Team Owner
Joined: Aug 2007
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Army
I simply wire mine open with stainless steel aircraft safety wire....been doing that for decades on classics. You want the car judged or move to a colder climate ?
Cut the wire and soak things in some PB-Blaster overnight and you're back to original.
Cut the wire and soak things in some PB-Blaster overnight and you're back to original.
Last edited by Frankie the Fink; Jan 31, 2018 at 06:30 AM.
Burning Brakes
Joined: Feb 2006
Posts: 834
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From: CT
I faced similar dilemma and purchased a spacer. The incremental room gained with the spacer felt like I would get more horsepower. This of course is not true in theory but physiologically More horsepower is gained
Team Owner
Joined: Mar 2003
Posts: 26,118
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From: Greenville, Indiana
I've pulled the shaft out of several. Tapped the hole and screwed in a socket head bolt. If you save the heat riser, you'll have a rusty piece laying around for who knows how long and you may never use it.
To your question. In addition to helping vaporize fuel for cold start drive off, it also helps prevent the carburetor icing up which can happen under rare circumstances. I've only seen a carb ice once in my lifetime and that was long ago.
It gets cold here in the winter but for about 20 years, my daily driver didn't have a heat riser or a choke. No problem.
To your question. In addition to helping vaporize fuel for cold start drive off, it also helps prevent the carburetor icing up which can happen under rare circumstances. I've only seen a carb ice once in my lifetime and that was long ago.
It gets cold here in the winter but for about 20 years, my daily driver didn't have a heat riser or a choke. No problem.
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Le Mans Master
Joined: May 2000
Posts: 8,729
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From: Redmond WA
Not to be contrarian, but I'm running one. I also don't have my heat crossover blocked, and I have the heat stove and pipe in place with a running thermac.
My car starts and runs like EFI when cold. Pump twice, turn key, drive away. No two-footing.
Now you can remove all of this stuff but you'll lose driveability. If you don't mind that nonsense of driving with two feet until it's warmed up, and it doesn't bother you that the car wasn't like that from the factory, then remove all the heat management stuff. But it does serve a purpose.
Since the heat riser valve is on a spring, it should swing out of the way under load and cause no performance degradation (beyond that which the iron manifolds have already inflicted on you).
If it's 70F out all the time, less important. But cars stall when cold at 70F too for a while until they warm up. Less so with a four speed.
My car starts and runs like EFI when cold. Pump twice, turn key, drive away. No two-footing.
Now you can remove all of this stuff but you'll lose driveability. If you don't mind that nonsense of driving with two feet until it's warmed up, and it doesn't bother you that the car wasn't like that from the factory, then remove all the heat management stuff. But it does serve a purpose.
Since the heat riser valve is on a spring, it should swing out of the way under load and cause no performance degradation (beyond that which the iron manifolds have already inflicted on you).
If it's 70F out all the time, less important. But cars stall when cold at 70F too for a while until they warm up. Less so with a four speed.
Last edited by davepl; Jan 31, 2018 at 10:20 AM.
Team Owner
Joined: Mar 2003
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From: Greenville, Indiana
Matter of fact, that generation of cars got all kinds of customer complaints or rough/poor running. Not as bad as later but still many complaints.
Race Director
Joined: Jun 2006
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From: Inverness FL
St. Jude Donor '07
Not to be contrarian, but I'm running one. I also don't have my heat crossover blocked, and I have the heat stove and pipe in place with a running thermac.
My car starts and runs like EFI when cold. Pump twice, turn key, drive away. No two-footing.
Now you can remove all of this stuff but you'll lose driveability. If you don't mind that nonsense of driving with two feet until it's warmed up, and it doesn't bother you that the car wasn't like that from the factory, then remove all the heat management stuff. But it does serve a purpose.
Since the heat riser valve is on a spring, it should swing out of the way under load and cause no performance degradation (beyond that which the iron manifolds have already inflicted on you).
If it's 70F out all the time, less important. But cars stall when cold at 70F too for a while until they warm up. Less so with a four speed.
My car starts and runs like EFI when cold. Pump twice, turn key, drive away. No two-footing.
Now you can remove all of this stuff but you'll lose driveability. If you don't mind that nonsense of driving with two feet until it's warmed up, and it doesn't bother you that the car wasn't like that from the factory, then remove all the heat management stuff. But it does serve a purpose.
Since the heat riser valve is on a spring, it should swing out of the way under load and cause no performance degradation (beyond that which the iron manifolds have already inflicted on you).
If it's 70F out all the time, less important. But cars stall when cold at 70F too for a while until they warm up. Less so with a four speed.
Bill
Le Mans Master
Joined: Dec 2007
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From: Puget Sound
Now you can remove all of this stuff but you'll lose driveability. If you don't mind that nonsense of driving with two feet until it's warmed up, and it doesn't bother you that the car wasn't like that from the factory, then remove all the heat management stuff. But it does serve a purpose.
Le Mans Master
Joined: May 2000
Posts: 8,729
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From: Redmond WA
I'd reckon you just went to a better school than me and all them there GM engineers. You were able to improve on their design with fewer parts and no downside? :-)
Last edited by davepl; Jan 31, 2018 at 11:16 AM.
Le Mans Master
Joined: Dec 2007
Posts: 8,000
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From: Puget Sound
Their design was a compromise to satisfy the people that lived in North Dakota in Jan. AND those that lived in Hawaii. Here in the Pacific Northwest, our weather is so moderate that it makes a heat riser useless IMO. All my cars run/idle just fine after 30 seconds of warm up time.
Le Mans Master
Joined: May 2000
Posts: 8,729
Likes: 1,508
From: Redmond WA
Hey, I've got a K05 block heater in mine... though I've never plugged it in here in Seattle, I'm from Regina, Sask. Heat risers do plenty of good in -40 but I don't dispute you can certainly live without them here in Seattle.
Four speed cars don't even have them.
Indeed. Another example of why backing the car out of storage to "warm it up" now and then is just abusive to them...
Four speed cars don't even have them.
yep, one of its purposes is to rot out the passenger side exhaust system before the driver's side...
Last edited by davepl; Jan 31, 2018 at 11:55 AM.
Race Director
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From: Inverness FL
St. Jude Donor '07
FWIW, when I had new exhaust pipes fabricated I just eliminated the spacer altogether as my exhaust manifolds were already beveled for the packing biscuit. (I used the heavy duty truck cast iron metal biscuit rather than the soft one)
Bill
Team Owner
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From: Sitting in his Nowhere land Hanover Pa
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just note your choke will never work if you do this. but like said many times if you only driver in warmer weather it doesn't mater