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Heat riser valve coil spring, 55 tbird 292

Posted By 55charliebird 5 Years Ago
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2721955meteor
Posted 5 Years Ago
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the heat riser  is needed hear in vancouver aria, i have duel exhaust withe 4v crb,elect chokewarms up quickly,no stumbles. have in the past  used different mufflers,stock type on 1 bank,low restricted other bank.like preveous moments you need the heat under the carb,along with electric choke
KULTULZ
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Either Ontario or upstate NY, you not only have the ambient air temp to tend with but also higher humidity (lake effect) that can lead to icing. You need to heat that carb plenum as quickly as possible (again, IMO).



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Tedster
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KULTULZ (10/19/2019)
Either Ontario or upstate NY, you not only have the ambient air temp to tend with but also higher humidity (lake effect) that can lead to icing..




I've read carb icing is really the main purpose of the valve & crossover. I don't know how true that is. Temperature differential between ambient air and carb venturi can be up to around 70 degrees, so icing is a factor well into moderate "nice" weather.

I went to dual exhaust ramshorn manifolds on my Y, so there is no valve installed.

I'm a little unclear what, if anything further is needed to be done, and what condition exists without one. Exhaust gasses are free to mingle under the carburetor without a valve?

Did the engines that were OEM equipped with ramshorn manifolds have a valve?

Should the crossover ports be blocked off completely if the valve isn't used? Sacrifice a little cold-bloodedness for a better summertime highway use? See where I'm goin' with that?
charliemccraney
Posted 5 Years Ago
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The only time I've experienced a  cold weather issue is when I used a 1" aluminum spacer on a B intake,  After the initial start and on days that were 40s or below, It would run progressively worse, until it just wouldn't run.  After heat soaking for a bit it would start and run fine.  Switching to a shorter non metallic spacer fixed that.

Over the past 10 years or so, with the Blue Thunder intake, several carburetors and non metallic spacers of varying height, I have not had an issue.  I haven't tried an aluminum spacer for a long period of time, yet.  The crossover passages are restricted with a gasket, and no heat riser valve was used in any case.  I am in Georgia but it does get below freezing, sometimes to single digits and I drive it all year round.

Since upgrading the ignition about 10 years ago, cold weather driving just hasn't been an issue.  I don't even use the choke, even on the coldest days.  So a really good ignition might help a lot in colder climates but probably something more than a simple drop in points upgrade.


Lawrenceville, GA
KULTULZ
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Should the crossover ports be blocked off completely if the valve isn't used? Sacrifice a little cold-bloodedness for a better summertime highway use? See where I'm goin' with that?


The only practical reason for the elimination of the riser valve is to allow the carb plenum to remain cool so as to allow passage of a denser fuel charge to the cylinders.  One would have to live with it while cold on the street or at competition, the charge will less likely separate @ high RPM.   

Like Charlie stated, a hot IGN SYS is going to help tremendously (less plug fouling from puddled fuel and long accel pump shots). If a street engine is used mostly as a driver, the valve is important (IMO)

This all changed with heated air cleaner inlets and electronic fuel injection.   

And how many times have you looked down and the choke cable was still pulled?

FORGOT -

If you have a hot or somewhat hot street engine, yes, you want to block the crossover as exhaust pulses will cross over.

FORGOT AGAIN -

Unless you actually remove the valve or disable it (wiring it open), do not block the crossover. It was part of a service back then to check and lubricate the valve.

(All of the above is IMO as your results and mileage may vary)





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Tedster
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Carburetor icing doesn't really have anything to do at all with freezing temperatures. That's what made it such a hazard in the carburetor-only days of aviation. Not as much of a big deal when we can just pull over to the side of the road.

So if I'm thinking this through correctly (always in some doubt ..) I'd want to maybe install some thin shim stock to block the crossover ports in the summertime before a long drive. Or is the intake plenty warm enough year round, once normal operating temperature is reached?
KULTULZ
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I'd want to maybe install some thin shim stock to block the crossover ports in the summertime before a long drive. Or is the intake plenty warm enough year round, once normal operating temperature is reached?


Is the engine bone-stock or pumped up? What you are describing was popular back in carb days as it did increase performance somewhat. But the valve has to be removed/disabled to prevent shut-off if the valve suddenly closed and remained closed. One bank of cylinders would have no exhaust outlet.

Yes, venturi icing is a combination of outside ambient air temp and humidity. I have never experienced it myself.



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It is basically bare-bone stock Y-block, with the exception of ramshorn exhaust manifold. I'm not concerned about performance aspect as just running it as intended. Did the engines with dual exhaust or ramshorn manifolds have a heat riser?
2721955meteor
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Tedster (10/20/2019)
It is basically bare-bone stock Y-block, with the exception of ramshorn exhaust manifold. I'm not concerned about performance aspect as just running it as intended. Did the engines with dual exhaust or ramshorn manifolds have a heat riser?

factory duals had heat riser valves. rams horn  manifolds wher only used on trucks and industrial applications.not sure but would think they hada heat riser on 1side. i would sujest  diferent mufflers, restriction higher  on 1 would give some help.
my application  is rams horn on pasenger side,driver side has a heat riser  valve.in 1949 merc  m47
use the driver side single stock manifold, as it makes a smother exit that misses the steering boxes useing the manifold  backwerds give a nice turn down the front
57RancheroJim
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I think it's all relevent to what you are using the engine for and where you live. I use the BEST intake gaskets that only partially block the cross over. On my street engine daily driver I want some heat to the plenum so the fuel vaporizes rather then dumping raw fuel into the cylinders JMHO.


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