The Stovebolt Site Forums The Shop Area Engine Shop Intake manifold

Is it possible to run a stock GM manifold with Fenton headers without heating the fuel. I understand why a stock exhaust manifold heats the fuel on a cold engine, and closes on a warm engine. I really do not want to remove the headers and stainless exhaust, but if the prevents me from having a smooth running engine I will remove it. I purchase a new stock exhaust system from Waldron's in the event I cannot run the system mentioned above. The average winter temp here in SW fl. is 75-54 degrees. and in the summer just hot.

Lookin for advice
Red

Red in my experience the originally designed scheme for heating the intake manifold is hard to beat. It was used for many years and it worked extremely well when kept in good nick.

Certainly using water to heat it is not effective and in my opinion almost a joke. I have not seen a single header design that accomplished what the stock setup did. Living in Dallas our weather isn't dramatically different from yours in Naples...actually our summers are hotter (yesterday was 103) and still I would not want to deviate from the stock design. Getting a smooth running engine (not to overlook an economically running engine) requires several things be in balance. When they are, all is well.

I'm sure some folks will appear soon with some other ideas. Good luck to you no matter what you choose.

It's possible to tap exhaust gas off the Fentons and circulate it under the intake with a heat transfer block bolted to the underside of the stock intake. That's much better than using coolant- - - -which is COLD at precisely the time it needs to be several hundred degrees. It's still not as efficient as the original equipment setup, but it's better than nothing. Send me a PM if you like and I'll get more specific about how to do the heat transfer setup.

Running Fentons and dual exhausts is a very good example of why doing race stuff on a street engine is stupid squared!
Jerry

Why can't you just use a heater exchanger like this one from Speedway? It would bolt to the bottom of your intake and feed exhaust gases from the headers.

GM L6 Manifold Heat Kit, 216/235/261 Fenton Headers

TUTS 59 -- The tubing is too small, and it's a dead end road- - - -no way to get any gas flow. That "kit" is worse than useless. It fools people into thinking they're accomplishing something.
Jerry

Ok, Stock all the way.

Red

You can wrap copper tubing around a header tube and the intake with both ends open, the heat will flow up the tube and around the intake. Not the best way but it will work. You can also heat the air using a newer air filter housing and stove pipe tubing, still better then nothing but useful. Even in 75* weather, a hot intake is needed to keep the fuel vaporized. I had a triple carb intake for awhile with no heat, it took forever to run decent, and even then it wasn't all the great.

Consider a frost plug heater in the block under the manifold. I have taken my '48 (with '61 261) to work as low as 20 below with 4 hrs of heating on a timer. When it got that cold, I would also put a magnetic heater on the oil pan all night.

You won't need to go to that extreme but mine would run great after just 4 hrs of heating.

Water heat is fine. Its not like you are driving it as a daily driver. The intake needs a little heat to help with atomization. It will take the motor a few minutes of warm up to get to 180 where the therm opens and you are all set.

The stock set up is of course the better engineered set up and it plain works, as long as the butterfly is not frozen or the spring is not broken.

Running multi carbs, there is always a little trade off. I run the water to my Clifford 2X2 and the motor, with two Holley 2300 350 cfm carbs, runs fine.

On the other hand, if you are running or want to run a single carb, then use the stock exhaust manifold. You will be much happier. If you want, you can split the stock manifold.

I have run a setup like shown on the Speedway site, though I fabricated it myself, for 20+ years. It does work reasonably well, though I've wondered about the intake getting too hot in warm weather when pulling a hill.
There is enough gas transfer back and forth due to rhythmic pressure differential to heat the intake manifold. I have an Offenhauser two single barrel manifold. It has provision for a factory-style heater for when you're running a stock exhaust manifold. I just took a quarter inch plate and drilled a couple of holes in it for the pipe fittings. I believe I used 3/8" copper tube. Works well even in Wally Montana winters, which we have where I live. On the humid coast it suffers from carburetor icing at idle until the thermostat opens. But that was a problem when it was stock. The carb(s) has a thick heat insulator under it.

Most of the wear of these engine occurs during warmup. This is due to unburned fuel washing the oil away from the cylinders until the intake warms up allowing the air/fuel to stay in suspension. The flapper in the cold engine position puts lots of exhaust heat to the underside of the intake, warming it up in a very short time.
Without that feature, you will experience more cylinder wear than normal, and crankcase contamination which will cause undue wear to bearings.
If you don't have the original intake/exhaust setup with a functioning flapper valve, you would be well advised to check for gasoline smell on your dipstick frequently and change the oil more frequently that every 3,000 miles.

I'll second Carl, you need heat to a cold intake for both drivability engine longevity.
I have been down the Fenton road with coolant heat then exhaust heat. Now I run factory set up.