The Stovebolt Site Forums The Shop Area Engine Shop Heat riser repair

I just sandblasted my manifolds and the heat riser needs to be repaired. Its rusted solid.

It looks like the plate is tack welded to the shaft.. is the the only way its held on or is there something else I need to undo?

The spring is already off, and I don't want to unpin the counterweight if I don't have to.

Personally I would try some rust removing solution like Evaporust.

Try spraying it down with some kind of lube WD40,or anything like that and take a small hammer and tap the ends one way and than the other. Let it set so the lube has a chance to get in there and work on the rust than take the hammer and tap it again,keep doing that for a few days and it will start to move back and forth.Don't hit it hard just a few lite taps and it will come loose I've done three that way and saved all of them.


Pete

did the same works great.^

I got it free... heated up the box part where the shaft went through and tapped it back and forth. I put some kroil on it and will let it sit.. its fairly loose, but still gritty when I rotate it.

Glad you got it free. Gritty means the hole in the manifold isn't all worn out. My manifold (still working on it) is severely worn. I purchase an oversized shaft from Chevs of the 40's, but the hole is still too large. Not sure how to move forward....

Bushings should fix up those loose holes. Get some with the center smaller then the shaft so you material to hone out once they are in place. Long drill bits work for this, as it doesn't need to be supper tight and accurate.

Joe

I thought about bushings, but not sure how to keep them in place other than the counter weight and spring keeping them from falling out. And, where to get an appropriate bushing. Maybe door hinge pin (shouldered) bushing would work.

Bushings can be "trapped" with some center punch marks around the circumference of the bushing. You just want to disrupt the metal that surrounds the bushing a bit. Kind of like a round peg in a now square hole sot of thing. Been done for ever on the thrust washers used in old motorcycle crank shafts. Even in the shop manual for my Harley. Where to get them? Try these folks.
http://www.dormanproducts.com/p-66649-14055.aspx
You might need to give them the size inside and out side to get what you want.

Hey guys -

Just how badly does my '54 235 need an operating heat riser?

The spring is missing from my heat riser. The damper moves freely. The weighted end of the damper keeps it open. The split in the shaft of the damper is closed together.

I live in Florida. Don't drive when it's below 40 degrees. Engine comes up to operating temp fairly quickly. 160 deg thermostat.

Any reason to install the spring? If so, where can I buy one? How hard is it to install? Seems a good chance of breaking the shaft when I spread it to install the spring.

Thanks

- Lonnie

Jim Carter and Chevs of the 40s have the spring for $18 + shipping.

I think they are more for the 50's and below when you have a risk of carb / intake icing. They are worthless for starting.

Mine was stuck midway. I have another manifold that's stuck so I will scavange a spring off that one.

Chevs of the 40s

Classic Parts

I'd try to put one on. If the split for the spring is tight, I'd be careful but still try to put one on.

The heat riser is there for a good reason and should be working for best engine efficiency.
There is a thread somewhere on this subject.

There is good scientific theory behind it. Something like , too hot a fuel charge and the engine runs lean , too cold and the fuel does not vaporize properly with subsequent puddling in the manifold and or washing of the bores etc.

I don't know, I had my truck for 25 years, before I even knew that thing even existed. When I finally did become aware of it and it's function, there was no spring. Maybe it had something to do with the engine finally wearing out after 35 years, and probably 95,000 miles, (the odometer quit about 10 years ago.) It always ran very well even in below zero weather. Although I have a feeling the aluminum intake will require some heat. I place very little stock in engineers, I have had to modify so much absolutely unacceptable equipment that had been "ENGINEERED" Think of the pinto, and the vega. Don't get me wrong, there are some very good engineers out there, and nearly all of our mechanical wonders were at least begun in some engineers head. But I have seen way more mediocre, to poor engineers, than good ones. Despite all this the scientific reasoning is sound, but in actual practice it hasn't proven to be that important in my experience.

Thanks for the education and for the real world experiences. I try to correct errors of previous owners by reverting to original configuration whenever I can. However, my ol' truck runs great like it is, although the outside of the carb does occationally frost up when first started.

I may add a spring to my next parts order.

>> Where does the "Anti-rattle" spring go?
The MPC lists two springs ... a thermostat spring(#838573) and an anti-rattle spring (#602799). Chevs of the 40s and The Filling Station sell both springs. Other suppliers list only the thermostat spring.
> MPC
> Chevs of the 40s
> Filling Station

>> How can I tell if I wound the thermostat spring too tight?
> Purpose ('54 Shop Manual)
> Installation ('54 Shop Manual)

Not looking forward to spreading the opening in the end of the shaft to insert the spring(s).

Thanks for your help,

- Lonnie

The anti rattle spring goes on after the actual heat riser spring. They are both on the shaft. Take your time spreading open the shaft, it doesn't take much to break it. When I did mine I just spread it enough to work the spring into the slot.

Lonnie, I would say you could probably get along without a heat riser. many when running headers or Fenton dual exhaust manifolds don't have any heat to the base of the carbs.
I think replacement springs are available from some of the truck part suppliers such as Jim Carter ect....
Might want to make something to keep the heat riser in the open position for sure.

John

It is better to have a functioning heat riser. It increases the fuel delivery efficency which inturn improves mpg & power.
Will the engine work without it? Sure but not as efficently...

re. engineers and failed past auto products. I wouldn't blame the engineers, (I'm not one btw, but I've had to reengineer my share for eqt), the blame falls squarely on the MBA's running the companys that have no idea what they're producing.....
I've seen them ruin good companys countless times by cheapening the products...
Dave

The exhaust stove never heats the incoming air, nor the fuel in the carb to any significant degree (remember, its not hot till the motor runs for a few minutes). It can warm the carb up... but the carb is designed to measure the weight and rate of air and meter fuel accordingly. I do agree that it will, after a while, get rid of fuel puddled in the intake (which can be easy to do by over choking the carb). But even then, on a cold motor, its useless.

The only direct mention of the hear riser I can find in the 54 Truck Service manual is page 6-57, and that's to turn off the auto-choke. Which was optional to begin with. Model BC carbs were only equipped on trucks with automatic transmissions.

ALl 3 of my 40's vehicles, 42 Ford, 43 Chevvy G506 and 43 GMC CCKW have a very thick insulating spacer to do the EXACT OPPOSITE of what you say. The insulator keeps any heat FROM the carb. That's on 3 vehicles, from 3 manufacturers. So I gotta say that heating air/fuel is not what they had in mind.

Here is the explanation of the thermostatically operated Heat Control Valve (and Manifold Heat Riser) in the 1954 Chevrolet Truck Shop Manual

Here is the Manifold Heat Valve adjustment instruction in the 1954 Chevrolet Truck Shop Manual

I wonder if you might not be able to take a hacksaw blade and open up the slot in the heat riser shaft for the spring??

John

Why would you want hot, less dense air going to the cylinders? And at the speed at which the air is traveling to the cylinders (the single barrel carb can do 300cfm) you are not putting much heat into the air.

Page 6-5 http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0605.html describes the operation of the riser.. its clearly only used at one time: startup.

I can't see how this does anything but as mentioned above... vaporize excess fuel that may pool at the bottom of the intake due to the choke or 'pumping' the gas pedal.

I've looked for a detailed explanation of why its there... haven't found one.

Since chevy is GMC's progeny I looked up what GMC has to say about it. Trucks and all that. Heat riser GMC trucks version
I find it interesting that for the big rigs a stationary setting is used...

My CCKW manual (1944) says basically the same thing: "in cold weather"... "aid in vaporization"

http://www.tm9-801.com/searchTM9/tm9_pages/261.pdf

But on that 270 the operation is entirely MANUAL. No thermostatic spring... just ON, OFF, or 'Best Guess'

http://www.tm9-801.com/searchTM9/tm9_pages/264.pdf

So I can't believe that it is a super critical item. More like 'it kinda helps more than if it weren't there' kinda deal.

Fuel injected motors (even old TBI) didn't use it.. and the fuel coming out of the injector was not a vapor, just atomized.

In case some of the information early in this post is confusing to a future reader, the page referred to in this statement in the post above is mistakenly associated with this topic:The information on the Rochester [b]BC[/b] (model [b]B[/b] with automatic [b]C[/b]hoke) does not seem to refer to the manifold heat riser or the heat control valve that I think is the topic of this discussion.

Now, I'll go back to to being amused by statements about GM putting a supposedly unnecessary (or non-critical) device on the vast majority of its 216/235/261 and 228/248/270 engines (and on many/most 302 engines). And, I'll be puzzled by why GM would spend the money on putting this device on most of those engines, if it was/is not really useful/necessary?

Natter on with unsupportable opinions and speculations . . .

The heat riser is to help keep the fuel atomized as it passes through the intake manifold.

John

Take an open top tin can and fill it with gas and hold a match to it...
It will burn just fine.
You can cook over it.
Just don't knock it over.

No s%#t Sherlock?

Where did I infer otherwise?

The point is only those molecules whether in "vapor" or "liquid" state with access to O2 molecules can react to the oxidation.

Chevrolet isn't the only engine manufacturer that determined that long exposed intake runners on carb engines were more efficient in getting the fuel/air mixture into the cylinders when they were hotter than the ambient temp.
They all do....

On the old VW opposed 4 cylinder boxer engines the long intake manifold runner(s) has exhaust heat circulating through a jacket that encloses the intake manifold where it splits directly under the carb and it's full time heat, not regulated like on these old Stovebolt inline 6's.

Should we expand the convo to discuss why many manufacturers of carb engines would preheat the incoming air on a cold engine?
Same principle.

Was surfing around some jim Handy films on youtube and found this neat film that fits right in on this thread. it talks about the heat riser at the 5:39 mark.

Great entertaining and fun film. Wish my engine looked that good (without the holes) thanks for the link.

That video has one HUGE error that we all know of.

At 6:16 it says 'speeded up in one place, slowed down in another to keep the mixture uniform SO THE SAME AMOUNT OF GAS GETS INTO EACH CYLINDER."

REALLY?????? We all know that the intake manifolds do nothing of the sort.... BUT AT THE TIME it was believed to be true.

If you believe that GM/GMC engineers had everything so perfect that every widget on the motor was perfect in design and function then you are in a fantasy land. In the 40's motors were still in their infancy and MARKETING cars was more important than the science behind them. There were no CAFE standards to meet and no safety requirements. The NHTS Agency wasn't enacted till 1965.

As my manuals state the operation of the heat riser is purely automatic... meaning you could keep it off and still run the motor fine.

I do believe that the bottom of the intake does derive a benefit of boiling off the pooled gas (as the charged incoming air makes that 90deg turn some fuel will drop out of suspension... its the same basic premise of how the oil bath air cleaners work). But its not a meter heat that can be shut off or turned on... the exhaust manifold will reach some quiescent state and that would be completely out of the risers control.

Another error in that film: 4:55

"at a speed of 800mph TO VAPORIZE THE GASOLINE".

Vaporize, No. Atomize, yes.

Its a marketing film. From the 30's.

Doesn't "being automatic" mean 'able to change from one state to another'? As in 'Adjusting to changing conditions'.
That tells me something functions better at one stage and less so at another, or why build in the "automatic" in the first place?
Or are you saying 'take it off and it will automaticly be ok'?
Why didn't THOSE advertisers think of that?

Or are we talking the semantics between a motor running "fine" and one running 'better'?


So the system works your saying?

but that it doesn't 'meter' the heat till it reaches the range for that systems operation "automatically" when the spring opens and closes?
Would "It helps regulate the heat" be acceptable?

In an attempt to keep this discussion going, when gasoline is atomized and/or vaporized, is the gasoline held in suspension (and it may later drop out of suspension)?

Atomized, vaporized, suspended (one or more), is the mixture of gaseous gasoline and air properly referred to as a gaseous mixture?

When/if the fuel drops out of suspension after turning that 90 degree angle, it that called condensing/condensation?

Just wondering.

I mistyped the that sentence (oh noes! An error that is clear to anyone NOT trying to simply be contrary!)

I posted PREVIOUSLY that the riser on the CCKW (my truck) is MANUAL, and the setting is either OFF, ON, or BEST GUESS. I even posted a link to the pages that said so.

The THEORY of how the riser should work vs the REALITY of what they do are two separate things. The Handy video clearly shows that at the time they thought two things were happening: one being the intakes on a Siamese port manufold with vastly different running lengths could somehow guarantee 'EQUAL' amounts of fuel charge to the cylinders is laughable. The other that the riser was boiling fuel into vapor. The former is wrong, the latter is somewhat correct, but not for all operating conditions.

And yes, I could see how a heat source could vaporize fuel. That HOW YOU VAPORIZE IT, by raising the temp to the boiling point. But unless you get direct contact with the metal, the air is not in the intake long enough to have any significant rise in temperature. Also, fuel pooling at the bottom of an intake box, with the choke on accelerator pedal down and VERY COLD air (like a cold star on a cold day) is a common problem. But at that time the riser is as cold as the outside air, and there is no chance of any boiling as its not warm enough to do so.

The most significant difference between atomized and vaporized fuel is the size of the fuel droplet. If you take a common hand pump like a bottle of Windex and set the tip to 'spray' you get that cloud of atomized Windex that you can clearly still see, and promptly falls to the floor. The droplets are large and heavy. Vaporized fuel is like steam from a pot of boiling water... light and small.

Of the two, which ones one would be more efficient to burn and transport through a metal tube? The steam as it will not fall out of the air, and also liquid gasoline does not burn, the vapors do. This is most noticeable with diesel fuel. You cannot light raw diesel fuel. You can drop a lit match on the stuff and it will put out the fire. But heat the diesel up till it gives off a vapor and ka-pow! Fire!!!

Take a look at this link...

http://en.wikipedia.org/wiki/Carburetor_heat

We can debate from here to eternity and second guess the engineers that designed these cars and trucks that we play with. If any of us wants to reinvent or re engineer their vehicle so be it and more power to you. The other side of the coin is to accept the way things have been designed and manufactured and enjoy them.
I enjoy hearing about both sides of the fence on an issue but in the end each of us should make the decision that her or she is happy to live with. I'm not interested in splitting hairs and being demeaned by a blowhard.
Its the holiday season....relax, enjoy and be happy. Get your Santa boots on and pull em up.

Don

[quote=pfarber]That video has one HUGE error that we all know of.

At 6:16 it says 'speeded up in one place, slowed down in another to keep the mixture uniform SO THE SAME AMOUNT OF GAS GETS INTO EACH CYLINDER."

REALLY?????? We all know that the intake manifolds do nothing of the sort.... BUT AT THE TIME it was believed to be true.

I don't think that they are as far off as you suggest. Our vision of the shape and design of the intake as a static piece of metal being asymmetric and having shared ports does not take into account the dynamic aspect of what goes on when things are in motion. When a cylinder which shares a port goes down, it draws in a volume of fuel/air equal to one which is unshared, but at a faster rate due to the smaller port. Another aspect is that cylinders which share ports do not demand fuel/air at the same moment in time. We do know that this head design is not the most efficient design ever made, but if it was as horrible as our static, linear notions would lead us to believe, they wouldn't even start, let alone run or idle.
Carl

Carb heat is not the same as what the heat riser is expected to do. When I flew (private pilot) carb heat was beat into your head as carb icing was a very real danger even on bright sunny days. Also carb heat is not intended to be a fuel economy device, but to do what it says... melt ice in the carb/venturi.

The runner length on an intake manifold can cause fuel delivery issues as the length of the runner is part of the equation that determines how much air can pass per unit of time and how much of a pressure drop. A good example of this is to put a pressure gauge on an air hose right after the regulator, it will read the same pressure that the regulator is set at. Add a 25ft hose and measure the pressure at the end and its not the same. Its less as the volume that the air has to fill is greater (length of the hose) and things like surface friction will affect how man CFM can pass. It matters even in runs of a foot or two.

Why do you think fenton double intakes give you more performance than stock? The amount of displacement of the motor has not changed, but the length of the intake to each cylinder is much smaller and more direct... improving performance.

Remember in the 40s-50s they still didn't know much about motors as there was no need to have very efficient clean cars. Today they study the heck out of every bit trying to get 1%, heck, 0.5% increase in performance.

If you do a search you can read about members having carb icing on the base plate.