The Stovebolt Site Forums The Shop Area Engine Shop Why water heat instead of exhaust on intake?

This seems to be a well debated topic here, almost to choosing sides, but as a newbie there is something that I still don't get.

I understand running exhaust heat, because it will be hot right off the bat...so helps eliminate condensation...right?

But water heat would take many minutes before it was warmed up...even longer before the hot water got to the intake and heated up the surrounding metal enough to even help.

So why water heat? Am I missing something? To me it seems that by the time the water was hot enough, the engine would already be warmed up and it wouldn't be needed.

I am asking this because I just got my recommeded shopping list from Langdons and I need to plan a few things out for when this whole intake/exhaust part of the engine needs to be updated.

Thanks

Water heat doesn't react with an alluminum manifold as much or bad as exhaust heat. Langdon worked as an engineer on several inline engines for GM. He believes it is absolutely necessary. Patrick Dykes has successfully hotrodded several of these inlines, he would argue that there are no significant gains.

Tom believes in water heat....so he sells the tapped spacer between the thermo housing, and the block. I've seen some neat arrangements where water heat was used successfully. However, the Offy intake is not water-tight and requires welding up the two holes under the manifold. The stock manifold needs to be sealed water tight! He's used it for years and is comfortable with it. And you can't beat experience!

I went with the exhaust heat! The Fentons were tapped for the compression fitting and I made my own plate for the bottom of the stock intake. Used copper tubing, compression fittings and it was an EASY install. The lines become hot almost instantly, I know the plate is getting hot because I hit it with my infared thermometer.

So which one do you use? If you're good with a tubing bender, enjoy gathering brass fittings, don't mind springing a few bucks to get your Offy intake water-tight, and trust your work with the lifeblood of your cooling system, it's the way to go. It can be a "cleaner" install. If you mess up, I could see where chasing coolant leaks, could be frustrating.

On the other hand, with the exhaust heat, you screw in 4 compression fittings, hand bend the pipe, tighten the fittings and you're in business.

I don't think you'll find anyone who has a really valid reason to use one over the other. Pressure differentials and corrosion aren't really valid under real world conditions.

So, it's your call! Have at it!!!!!

The Offy I got from Tom Langdon already had the plugs welded up tight when I got it from him. I used water heat because he recommended it. I'll see about any potential water leaks next weekend when I start the newly rebuilt engine up for the first time. I have pics of my water tubing arrangement in the engine rebuild album on webshots.

http://community.webshots.com/user/geezer

Surprisingly, most modern engines still run water heat, even the ones with multiport fuel injection where the manifold just carries air. It is still necessary once the engine is warmed up. It keeps the throttle body from icing up and controls the temperature of the manifold evenly so the mixture distributes evenly.

Don't forget that the manifold isn't the only part of the intake tract- the passages in the head stay pretty cold until the water temperature comes up anyway. Using water means the metal should expand and contract more at the same rate. The choke does the job of keeping the mixture rich enough for the engine until the metal warms up, then the water heat takes over, keeping gas droplets from sticking to the manifold.

So the heat is needed all the time? Then why is there a heat riser? Is it better that mine is broken so open all the time?

(Really I am not trying to be dense, but I seem to be missing some bit of information to make this all add up.)

The manifold can get REALLY hot and that is why I believe the heat riser and the butterfly valve are on the original exhaust manifold. It is also a cooling effect. That's why I like water. It heats but also keeps things from getting too hot. A very consistent 170 degrees. Exhaust heat from Fentons doesn't have a way to turn off the heat once things get warm. On the other hand, how much heat gets through those tubes anyway? I'd bet it gets above 170.

My choise is ex first as it is instant and hotter,,water if that is only option slower and 195,,but you need one of them for proper operation and fuel milage...doc

On my daily 235, I got an aluminum 2x1 intake with exhaust heat from fentons via the tubes.
I don't use carb spacers and never had any fuel delivery issues. Even going down the freeway for hours in August desert temperatures.

I believe only cast iron intakes require the spacers to prevent boiling of the fuel, especially when parking after a hot run.

On my current 261 project I will use the fentons that attach directly to the manifold.
Most of the heat comes from the direct connection, like with the original single intake/exhaust.
There is no heat riser baffle on these fentons, but the 2x1 aluminum intake only has a small heat chamber under the two carb's section of the log.

I think it's best to give these dual intake manifolds for street use, as much heat as possible.
What early fuel savings device patents have in common is to preheat the fuel before the carbs to improve atomization and give more efficient combustion.

High performance engines with triple or more carbs don't use additional manifold at all.

Chevrolet used exhaust heat on virtually all of the 206,216,235 and 261 engines. That is good enough for me!

The only water heated intake ever made to use water is the Edmunds brand of intakes. Virtually all of the others are set up to use exhaust heat. Fenton did offer two choices for exhaust heat, the two tubes running one from each header to the intake manifold heat plate. The other choice is the type of Fenton headers that had a heat chamber built into the back header which supplied continious heat to the intake manifold. I don't think a person could make an argument for too much heat to the intake. One thing that I do know for sure. When using the two tubes, you are mixing the two sides of your exhaust. The result is a deadening effect on the sound of the famous six cylinder exhaust. The effect is noticable and just really deadens the sound. Tom Langdon mention that to me years ago. I decided to use the two tubes, but welded two pipe nipples on the front exhaust pipe just below the flange, one pointing downward and one pointing upward. I then ran a tube from each so that the exhaust would enter the upper one which was pointing up and exit from the lower one pointing down. I installed them on the back of the exhaust pipe so they couldn't be seen from the side view of the engine. This stopped the left and right side exhaust from mixing and keep the crisp sound of the six cylinder engine. Later I found a pair of the old style Fenton headers with the rear heat chamber built in. I now run that style on my 261.

In both cases, I never encountered any heating problems. It always stays hot all of the time - continious heat, like it is supposed to be.

Joe

Ohmygawd Joe, this is the best detailed engine I ever saw!

Where did you get those spark cable dividers and the nice plate and gromets that cover the plugs?

Frank

From my days in the garage I remember some factory water heated carburetors, F**ds i think.

Joe,

Are you recommending we use one exhust input so as to not deaden the sound of the exhuast....interesting I see where this makes sense.

chev235 -

Yes, that's what I am saying.

For years I wondered why some Chevy inline sixes sounded better than others. Tom Langdon mentioned to me during a conversation several years back that mixing the exhaust of each side, or equalizing, will cause the tone to deaden. Some might say it cuts down the noise, but it's more than that, so to preserve the sound it's best to use the heat from one side of the exhaust system. It definitely gives you a distinctive, better sound. By using the method of heating I am suggesting, you keep the sharp sound alive.

Steel pack mufflers have always made inline sixes sound better than glass pack mufflers. They sharpen up the tone of the sound. They are not that easy to find, but they are still available if you look around for them.

Another thing that will almost cause a hammering sound in the exhaust is a higher compression ratio. That, of course, means the 848 head can also be a contributor to the sound. Obviously the installation of a new head is a bit more work than the first two suggestions, but two out of three isn't bad.

Joe

One of those "made you look" statements. I've got to agree, beautiful truck Joe.

Joes truck looks like a Chevy Accessory Store exploded on it...

Is it missing any Accessories available "back then"?

These are great posts. I am workling on getting a stovebolt for my truck by this spring. For what it is worth exhaust heat is quicker but one thing about water heat is that when you are parked in cold weather for say......a half hour, The choke will act like the engine is cold and starts the fast idle beacuase the manifold is cooled off. With water heat I found that the manifold stayed warmer longer and the choke did not engage or only slightly. I used to check the engine block with my hands and it was still quite warm but the choke on exaust only heat was mostly closed and had to warm the manifold and choke thermostat all over again. Just my two bits worth. Whatever works best I guess. Chevy/GMC Bolts Forever! H. Going to put a Stovebolt 292 in my 87 4X4. Evicting the 350. May go shopping today or on Monday for one in a bone yard.

Water has a much higher specific heat capacity than air. This means it takes a lot longer to warm up than air, but it also holds a lot more heat and takes much, much longer to cool down than air. It will also provide better conduction of heat to metal than air would but that doesn't really matter in this case, as I don't believe thar the conduction of the heat to the metal is a limiting factor.

what about the fuel boiling? that i've heard about. water heat would be constant. one of these days i'll get this far and will have a decision to make.