delete heat riser

[52concord]

so i got my manifold split and it looks exactly like this one, i want to completely block if off from exhaust air going to the intake manifold, should i cut a piece sheet metal and put it between the intake and exhaust manifold?

Edited December 25, 2013 by 52concord

[Don Coatney]

Yes

[greg g]

I found a thin piece of stainless steel, cut it to fit It was about the same thickness as the gasket.  I counter sunk the holes a little bit and ground down the heads a bit so it would fit in under the casting in my intake manifold. I did not bolt my manifolds together.

[52concord]

you guys have any trouble with exhaust leaks or blowing the heat riser gasket?

[greg g]

I have a slight tick but that is after 11 years.

[james curl]

I did the same thing and after 20,000 or so miles it started to leak so I pulled the exhaust manifold and installed a baffle in the other opening so that no exhaust gases get into the chamber.  Now I have no more leakage between the aluminum intake and the cast iron exhaust manifold.

Edited December 26, 2013 by james curl

[blucarsdn]

There has always been two schools of thought regarding retaining/omitting a heat riser in a split maniforld exhaust..On an inline engine, the majority of which have the intake/exhaust manifolds hanging on the side of the engine, the retention of the heat riser is a must if the vehicle is operated in cold climates..

Many years ago I ran a performance exhaust/muffler shop, all of the factory built split manifolds that we sold, such as Douglas, Belond, etc., all had a 1/2" hole in the blocking plate.with the heat riser "valve" left in place..Any custom fabrications that we did, the heat riser was left in place.

The application of headers on an inline engine usually required the use of a hot water heat riser.. Many of the aftermarket intake manifold manufactures provided a water jacket in their manifolds...

Of course a V type engine is a completely different application, the carb sits right on top of the engine...

Cold raw fuel dumped right into an engine will make it run rich, improper air/fuel mixture.. If a person takes the time to completely read the instructions that apply to aftermarket exhaust/intakes, you will note a foot note about heat risers being needed.. Bill

[Don Coatney]

A heat riser has two functions. To assist with startups in cold climates, and to prevent/avoid carburetor icing that can occur well above freezing temperatures.

 

Something I have not been able to wrap my thought process around is a water powered intake manifold heat riser to assist in cold startups. A heat riser needs to supply instant heat for cold startups. The exhaust gases supply that instant heat. Engine coolant fluid trickling through an intake manifold supplies heat only after the engine has come up to operating temperature and does nothing to assist in a cold start situation.

 

Carburetor icing is a whole different animal than cold startups. I have experienced carburetor icing when conditions are such that a very slight elevation change drops the dew point and manifold vacuum alters the freezing point of water. There is a small percentage of water in all gasoline. The carburetor icing happens at the throttle butterfly area inside the carburetor and reduces the flow effectively choking the engine. I believe an intake manifold that is water heated would have prevented the carburetor icing that I experienced.

[blucarsdn]

One additional item that I failed to mention in my earlier comments, is the noise factor..Split manifolds that have the heat riser removed and a solid blocking plate between the two sections of the manifold, tend to make more noise than systems that retain the heat riser. Of course to some people the added noise is what they want...

During the period that I ran a muffler shop, I built many systems that would "rattle the windows" under full throttle..I had a girl friend that lived on the edge of town on a country road, she had to be home by 10:00 on week days. I'd take her home then go crusing around town looking for a drag race, etc.. On my way home I'd go by Kathy's house, under full throttle, then back off, this was sure to rattle the windows in Kathy's house.. My way of saying good night.. Of course her dad did not like the noise as he was trying to get to sleep.

The flat head V8 people like to block the heat risers under the intake with pennies or thin shim stock.. Really makes a louder exhaust, however, it also makes the engine run rich and be very cold hearted..

Of course many people equate egine power with the sound of the exhaust.. I once had an exhaust shop owner tell me that in many instances after market exhaust systems that claim to improve fuel mileage actually don't, because the drive keeps his foot stuck into the engine so he can hear the noise... "Hay look at me"... Bill

[Don Coatney]

The picture in the first posting to this thread is a picture of my manifold. I do have a true split with no crossover. The noise is music to my ears. This is the only sound clip I have.

 

[hkestes41]

The picture in the first posting to this thread is a picture of my manifold. I do have a true split with no crossover. The noise is music to my ears. This is the only sound clip I have.

 

 

Sounds good Don. I have the Langdon cast iron Fenton repop headers on mine. I think it sounds good too here is a video right after installing my 218 http://www.youtube.com/watch?v=AxfKQ4KMM9s I have moved all the "Speed Parts" to my 230 and added an Edgy head but have not done a video of the 230 but the exhaust sounds pretty much the same.