This is a subject that I assume most people just do what seems right using guesswork to arrive at a solution.. I'm talking about running exhaust systems near items such as steering boxes, transmissions, master cylinders, etc. I am in the proccess of building an exhaust system where the primaries need to run VERY close to the water pump (not hot rod related) and my Dad will be running the exhaust system under his '40 Ford very soon. Dad's exhaust system will be running very close to both the steering box and the master cylinder. The point of the question is how do you determine how close you can run an exhaust component next to a heat sensative object? I know that there are heat sheilds, exhaust wraps and thermal coatings that can help but even so, there must be some rule of thumb when it comes to these things. Is there a rule of thumb? How close is too close to a water pump? Or a master cylinder? I realize that there are many factors involved in "How close is too close?". Even so, I would like to hear how you have determined how close is too close and I would also like to hear about people running their exhaust too close to something and the issue's they have had with it as well as how it was resolved.
I too am curious about the experiences people have had with exhaust heat problems. I just finished installing a vega box very close...like 1/2' away from my headers on the flathead of the 34 pickup. I understand the temps at the exhaust piping isn't nearly as intense as header temps. I've used heat wrap on headers before to shield a smallblock starter but what about steering boxes??
I look at it as the fluids like antifreeze, oil, and brake fluid all have temps that they run the best at. Antifreeze below 240 degrees, brake fluid (check fluid manufacturer for operating temp) and engine oil at normal engine temp anything above these and the system operation will be affected. The temp near header pipes is the worst so if your close you need to shield the heat from these items. You need a infrared heat gun to check temps at the component your concerned about. On my 40 ford I had to run the exhaust under the motor from driver side to passenger side and run both pipes down the right side to avoid the power brake booster and master cylinder using exhaust wrap on the pipes near my oil pan, oil filter, and trans cooling lines. In the auto industry we used 9 inches from a heat source as a standard. If you were less than 9 inches you had to change material or add heat shielding to with stand the higher temps. Hope this helps some.
You could always add a single layer heat shield on the pipes, like many crusier style motorcycles use. You'd be amased how much difference a 1/4" air gap and a bit of sheetmetal can make. You could also have the pipes ceramic coated if they're not going to be chromed.
Damn, 9 inches? Right now I'm looking at less than 1" of clearance from the primary to the water pump. I am planning on thermal coating the header and building a heat shield that will have Thermo-Tec's 2000 degree aluminized heat barrier on as well. I might even go so far as to slide Thermo-Tec's high velocity exhaust jacket over that section of tubing.
The steering box on a tri-5 Chevy runs less than an inch from most headers without ill effects. Of course there's not a lot of area-to-area involved to transfer heat, like when all 4 tubes on a set of headers run along the length of a starter. For most purposes I'd say if the exhaust is less than a couple of inches from something sensitive it'd be a good idea to put a heat shield in between.
Welp, I dunno but I found if you install 2, 100 amp alternators on a 460 ford truck, set the RPMs at 2250 mid-day in mid July, [to power up the signal lights at an intersection where the power has been cut] after about an hour and a half, the plastic inner fenders will melt and the rubber floor mat will begin to smoke so badly the air inside can't be breathed...even with the hood opened. Don't ask..
Just Gary, the answer is NO. 5/8" is plenty enough clearance between a single header pipe and the oil filter, as long as you can still get the oil filter off and on without interference from the pipe. Now, if you intend on letting it idle for several hours without moving, it might raise the oil temp a few degrees. Clearance between exhaust and other items can change depending on how much air is flowing around the items involved. It will also depend on what items you are concerned about. Weather your talking about exhaust manifolds, head pipes, or header tubes also makes a difference. Manifolds hold heat and usually have a higher temp then header tubes, unless 3 or 4 header tubes surround the item. Exhaust head pipe (just off the manifold) are usually hotter the individual header tubes because all the exhaust off the one head travel through the head pipe where only one (or sometimes 2) cylinder(s) exhaust is (are) traveling through the header tube. More cylinders, more heat. My general rule of thumb is clearance should be enough you can fit a finger (1/2" -3/4") between the exhaust and the item of concern, except for fuel lines and wires, they need more clearance. You don't want the insulation to melt off the wires, and excessive heat near fuel lines can boil the fuel in the lines. You need enough clearance hoses ans such do not start to deteriorate. Gene
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