Exhaust manifold temps

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Dana67Dart

Dana67Dart

The parts you don't add don't cause you no trouble
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Recently someone posted about their exhaust manifold temps asking if they were normal.

IIRC his were reverse of mine, his rear cylinders were colder than his front.

I was doing some testing and my dart was just idleing outside in the driveway (32 deg outside air temp)

Car started from shut off for several days.

Idleing till the engine was about 170 deg (about 30 minutes maybe)
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I recently did the same with my 74 D200, 360 la with Magnum heads.
I got the same kind of results as you did.
Old truck still runs pretty good, I think it has to do with surface of exh manifolds.
 
The center readings will almost always be higher because you have two cylinders dumping right next to each other into the same area of the manifold. Not sure about that back one on that one side.
 
cudamike13 said:
I recently did the same with my 74 D200, 360 la with Magnum heads.
I got the same kind of results as you did.
Old truck still runs pretty good, I think it has to do with surface of exh manifolds.
Click to expand...
Mostly.
Theres always variances in mix per runner but you're spot on.
 
Treblig said:
The center readings will almost always be higher because you have two cylinders dumping right next to each other into the same area of the manifold
Click to expand...
That makes sense, and I always wondered what Chrysler was thinking by doing that. but the two front cylinders being 50 degrees cooler doesn't make all that much sense.
 
Dana67Dart said:
That makes sense, and I always wondered what Chrysler was thinking by doing that. but the two front cylinders being 50 degrees cooler doesn't make all that much sense.
Click to expand...
Combustion temp is more important.
Things saturate when crowded, so it's not anything to worry about.
There's also that small element of mixture variation from intake runner to run her and unless you know that they're all exactly the same you can't really attribute it solely to siamese ports.
 
The driver's front is cool also because it's unblocked from the fan.
 
Not to worry. You need to remove the manifolds and measure the thickness to make sure that's not throwing your readings off. :lol:
 
Look at your firing order as far as which cylinders each side of the carb feed. 2 center cylinders on one side and 2 outside on the other side. Lean cylinders up to the point of misfire wil run hotter.
 
BTW, I'm not worried about anything I just found it interesting and the other poster with the same question seemed to have the opposite issue IIRC
 
Dana67Dart said:
That makes sense, and I always wondered what Chrysler was thinking by doing that. but the two front cylinders being 50 degrees cooler doesn't make all that much sense.
Click to expand...
Not only Chrysler. Nearly every older V8 G.M. engine too. I recall reading that they did that so that the intake manifold runners could more approximate equal lengths. The intake runners are all "paired", making a more compact manifold with shorter runners. Also the design makes it easy to route a lot of exhaust thru the crossover in the intake manifold, aiding faster warm-up.
 
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