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heat riser spring replacement


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My heat riser spring on my '48 Chrysler (251 flathead) recently broke.  My question is will I have to replace it with the specific spring for that engine or are there other more accessible and common springs that will do the same job, that might be on the shelf at my local parts store?

My point being that yes Bernbaum has the spring but by the time I get it in my hands here in Canada it will cost me about $50. Who knows how long it will take to get here with the covid thing going on.

The spring has 7 1/2 revolutions to it.

 

heat riser spring.jpg

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7 minutes ago, Bloo said:

It is desirable to have the correct spring, however a cheap local spring beats the pants off of having an inoperative heat riser.

The manual specifies to coil the spring 1 1/4 turns.  No more no less,  but as long as the tab slid into the slot on the manifold thru arm and the other end hooked around the stud, and it fit inside that weighted shield, then a heat gun should determine how many turns is needed for whatever spring is used, to fully open and fully close the flapper, I would think.  But I'm sure the average parts guy is not going to want to search through their stock to find a similar spring.  I'm hoping someone has tried something that works so I'll have a make and year to narrow down the search.

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In my experience, it is less the number of turns, and more how far you have to wind the spring around before hooking it (manual generally has this). If the spring is a random one, you might have to fudge this, because god only knows which way it might point at rest. If it is really wrong, it will just open at the wrong speed.

 

Generally speaking, heat risers should have some fairly good tension cold, and not open instantly. However, when the engine is fully warm (just barely, but fully warm), and the choke is fully open and on slow idle (if automatic), the heat riser should be all the way open. I am not sure if you could really tell with a heat gun, You could tell if the spring pulls the right direction though.

 

The weight should be "helping" keep it open. On most inline engines the weight is up high cold, and falls down as the spring releases, usually toward the engine. It is pretty easy to get the spring backwards if you aren't looking close. Still better to get the right parts if you can. Hope this helps.

 

 

Edited by Bloo (see edit history)
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2 hours ago, padgett said:

Jon would know but think a Rochester M4GC used something similar.

 

GHP-Q1206-2-400w.jpg

 

 

Thanks. Yeah you're right, it sure looks the same.  So what would I use for a reference or P/N at a Napa Auto parts store to get one of those?

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5 hours ago, padgett said:

Jon would know but think a Rochester M4GC used something similar.

 

GHP-Q1206-2-400w.jpg

 

 

Don't know that a carb choke spring would be a suitable replacement for a heat riser spring operating in the direct flow of a hot exhaust gas stream.🤔 But I have been wrong, many times.😉

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1 minute ago, timecapsule said:

I guess that's your way of telling me that Andy Bernbaum is a good deal.  haha!

Bernbaum is selling them for $22.  But here in Canada through experience on an item of that size and cost you basically double it and cross your fingers that Canada Border Services don't want a share of the pie added on top of that.  But thanks for the link Graham

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