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Heat riser valve on the manifold ?


JOhan_Sweden

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Hi,

 

My valve is missing the thermostat spring (or everything that are supposed to be inside) and I was thinking to do a quickfix and just lock it in possition.

The question is: -Which possision is best? max clockwise or max anticlockwise?

Stock P15, 1948

Just driving in summer...

Can this affect the problems I have with the car being difficult to start if the motor is hot and I park for a while? It´s smells gasolin and I need to crank longer than normal.

Or do I need a thicker bakelite gasket or/and a heat shield betwen the manifold and the carburator?

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If the valve flap is still inside, it is probably better (for your you in Sweden) to lock it in the closed position. An open valve would always heat the fuel too much, which leads to the symptom you describe.

Some people remove the whole valve system and install a sheet metal plate between the intake and exhaust manifold, which leads to an always closed pre-heating condition.

For European climate conditions I would yet recommend a functioning solution. Sometimes I can use it, also in summer (on cooler days)

 

Enclosed a link to the solution, which I installed at my motor. Works very satisfactorily.

http://p15-d24.com/topic/40386-heat-riser-valve-do-it-yourself-solution/?tab=comments#comment-428539

 

Also a link to the tech section, where the heat riser system is explained.

http://p15-d24.com/page/p15d24/tech/heat_riser_adviser.html

 

 

 

Edited by PT81Jan
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The heat riser in an  inline engine is probably one of the most misunderstood items in an engine. In colder climates like Sweden, and those parts of other countries that have mild to cold temps, the carb hanging on the side of the engine requires that the fuel be pre-heated for proper vaporization.

Correctly fixing a faulty hear riser is not an easy matter, in all probability you will have to find a exhaust manifold that has a working heat riser.

Blocking the heat riser into the closed position is not a good solution, the plate has to open under accelleration. Blocking plate into the open position would be better, however the engine will run rich in cool/cold weather.

People that put headers and/or split manifolds on inline engines experience a lot of problems with the engine running rich because they eliminate the heat riser. The general solution to this problem is to put a hot water fixture on the base of the intake manifold.

I have encountered a lot of problems in my life with hear riser issues, I was raised in East Idaho where the temps get down to -30 in the winter. As a teenager i constantly messed with cars trying to make them run better, which usually resulted in huge problems in the winter. When I moved to southern Nevada in 1954 subzero temps were not a problem, 100 + degrees were. I moved to southern California in 1956 which changed the whole climate issue. Quite cool on the coast, 100 + degrees ten miles inland. 

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When will you do the bulk of your driving?  If it is a summer only vehicle, chances are pretty good the heat riser will not be an issue.  Mine has the flap removed the pivot hols welded shut and a stainless steel separator between the manifolds.  I usually drive my car into late November, and bring it out as soon as all the winter salt gets washed off the roads. As such it has operated in temps below freezing without issue, other than needing partial choke for a bit longer.  I do have the heater return line zip tied to my intake manifold so it picks up some heat when the heater is operating.  So if the bulk of your driving will be above 0 c I would fix it in the fully clockwise position and see how it behaves.

 

If you are going to be operating year around then a correct fix is probably the best choice especially if your cold season is also high humidity.

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