The Stovebolt Site Forums The Shop Area Engine Shop Is heat needed on the intake manifold?

My 235 has the stock intake with Fenton headers. Some say that without the heat riser from the stock exhaust manifold the gas will not completely vaporize. The fuel air mixture from the carb. tends to cool the intake manifold and causes the fuel to unvaporize and leave unburned fuel , hurting low rpm throttle response and fuel economy. I've never noticed hesitation with my setup. My fuel economy could definitely stand improvement. BUT, would a inlet manifold heat plate like the one sold by Langdon's Stovebolt really help much?

The heat riser only comes into play when the engine is completely cold. Once the engine has warmed and the heat riser opens, it stays open. What kind of fuel mileage are you getting. Your expectations might be too high for 55 year old engineering.

To tell the truth I don't know what my mileage is. When I put new stick on numbers on the odometer, and put it in , it only worked for about 1/10 of a mile and since the new electric wiper motor and linkage block the removal of the speedo, it hasn't been touched. It just seems like I'm getting less than 15mpg.The carb has never been rebuilt and kind of oozes a little gas around the base,maybe that should be my next project

If your truck stays in Seattle, you probably won't need a heat riser. The riser in my 235 is stuck open, and I've had no problems getting it started this winter. The temperature here is similar to Seattle - ooccasional frost but rarely below 20F.

As for your gas mileage, 15 mpg is about average for these old engines. You might get a few more or less mpgs depending on how well the engine is tuned.

The carb has never been rebuilt and kind of oozes a little gas around the base,maybe that should be my next project
This sounds like a worthwhile project.

It just seems like I'm getting less than 15mpg.
As stated above, 15 mpg it not bad. However, besides your mpg being a guess, mpg is dependent upon many factors (types of roads and how fast you accelerate and drive).

I've never noticed hesitation with my setup.
It is ain't broke, don't look for reasons to fix it.

All that being said, your set-up (a non-heated intake manifold) is ((as you very nicely described) not at all like an original set-up with an exhaust manifold physically attached to the intake manifold (with or without a working heat-riser). In the "natural" set-up, heated exhaust gases are deflected to warm the intake for a reason. And, that extra heat is not needed after warm-up BUT there is still a significant amount of heat being transferred to the intake manifold, even after the heat-riser is closed.

Tim is right, just because the heat riser valve closes, doesn't mean the heat is shut off. Heat is needed unless you are racing or live in Texas, it helps the fuel stay vaporize in all drive conditions. You can get away with out it as many have done, but it will run better with it. Chevrolet and GMC new what they were doing in this area.

Joe

Well then, maybe the $35 manifold heat plate from Langdon's stovebolt is a good investment. It uses the heater hose passing thru a plate bolted to the original intake manifold where the old heat riser went.

If its just a plate and a few threaded holes, why not make one yourself? It might be a good winter project, and if its as cold there as it is here ( 11*) they you should have time!

Joe

Not a bad idea, I'll have to study on that idea

Maybe thats the problem with mine,its never had heat to the manifold and will have to look into one.