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Username Post: '60 manifold heat riser ?        (Topic#358082)
Posts: 334
Loc: San Diego
Reg: 04-17-19
09-16-19 03:27 PM - Post#2775662    

Hey ya'll what does the manifold heat riser do? Why is it there and how does it operate?


Frequent Contributor
Posts: 1244

Loc: Tennessee
Reg: 12-06-10
09-16-19 04:05 PM - Post#2775663    
    In response to Eth727

The heat riser valve on the bottom of the right exhaust manifold is for quick warm-ups during cold starts, especially in cold climates. It has a bimetal spring that closes the valve when cold and opens as it warms up.

When close the valve forces hot exhaust gasses (to the left exhaust manifold) through the cross over passage in the intake manifold to heat up the intake manifold plenum and runners to help warm the cold intake air and atomize the fuel. Once the engine warms and heats the bimetal spring it opens so exhaust gasses are no longer forced through the intake cross over passage and can go out the right exhaust pipe. But some hot exhaust gasses will still go through the intake cross over passage heating the intake and intake fuel air charge.

Most street rodders block open the heat riser valve or remove it and block the intake passage openings on both sides of the intake manifold with new gaskets with blocking plates to avoid the excessive heat from the exhaust gasses.

Mel Foye 
*VIP* Original Founding Member Group
Posts: 4972
Mel Foye
Reg: 09-29-00
09-16-19 04:11 PM - Post#2775665    
    In response to Eth727

Per Smokey when atomized fuel comes out the base of a carburetor it is just above freezing so that makes the droplets want to join together.
Per a face to face with Jim McFarland the smaller the droplets the better as the total surface area is greater than with bigger drops.
The heat riser is a spring loaded butterfly valve that directs exhaust up to the area just under where the fuel comes from the carb base to help the droplets remain small.
Since the exhaust flow impacts the size of the opening of the riser as rpms go up it opens more.
I don't remember if heat causes the spring to relax some.
A lot of folks say remove or tie it open based on where you live but to me I think the atomized mist temp would remain close to the same.
Unless we are running headers we use the heat riser.

Posts: 334
Loc: San Diego
Reg: 04-17-19
09-16-19 04:34 PM - Post#2775668    
    In response to Mel Foye

Yeah mine is rusted stuck about 3/4 of the way. I'm in San Diego. I'm putting a stock 2" dual exhaust. I'm going to spray some wd40 to loosen it up so it can work properly.

"10th Year" Gold Supporting Member
Posts: 1788
Age: 76
Loc: Las Cruces, NM
Reg: 01-20-11
09-19-19 04:53 PM - Post#2775913    
    In response to Eth727

There is a graphite based spray lubricant made specifically for heat risers. That would be a better choice than WD-40.

Good luck with yours!

Mike Ahlmann
Las Cruces, NM
'50 Tin Woodies (two) Ramon and Willard
'58 Impala Sport Coupe
'69 El Camino SS-396
'07 Ford F150 to haul parts for above
'16 Ford Explorer 3.5 EcoBoost - Red Rocket

Silver Supporting Member
Posts: 7402
Loc: Nova Scotia, Canada
Reg: 08-21-01
09-21-19 04:14 AM - Post#2776033    
    In response to mahlmann

I would recommend you free it up and fasten it open to keep the heat from being pushed through under the carb. Today’s fuels are much more volatile than they were back in 1960 and the heat under the carb causes them to gas off. I am in the cold north and have never used the heat riser or a choke for that matter, unless it was electric. Never a problem on cold starts.

63 Pontiac Parisienne Sport Coupe(CDN Chev mechanically (409, 4 speed),62 Bel Air SC (sold), 59 El Camino (sold), 62 Bel Air SC(sold), 63 SWC Vette (sold),
Member #2194


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