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I wouldn't hesitate to use stainless bolts. I bought a cheap set from 'the bolt locker' and 90% were fine. Exhaust manifold bolts were too short, but sure enough the listing stated "for headers" so assuming thinner flanges. When I brought the issue up they pointed this out and said if I had mentioned it at the time of purchase they would have subbed longer. It is *really nice* to have full heads left on those bolts after ten years of salty new england winters.

I'm sorry, I didn't directly address this. No. You don't have to do crazy mental gymnastics to get an exhaust system that suits your needs. This is not like the threads that start "I NEED a really lopey idle, but want a fuel efficient torque monster... and I want to do it for $150 with bolt on components" My advice is to keep the runner/head pipe volume down and use as large a volume muffler and tailpipe as you like. If you want a sound that is low and throaty go with a big muffler and tailpipe. If you want something that 'barks' then smaller volume and free flowing design. With a 351 -at 'normal' truck engine rpms- 1.75 head pipes and a 2.5 collector are verging on too big for best torque. (IMO) But if the engine is not stock, and you drive it like you stole it, you would be fine and might want more. Headers are always good... except for longevity, and serviceability. Not being able to change a spark plug or starter with the pipes on the engine is hugely frustrating.

CFD modeling has come a *long* way from slide rules in the 1960's... (Yes, the A12/SR51 was designed in that era) There are so many different factors that influence the outcome I would wonder if we could get an *absolute* answer -even today. Plus manufacturing ability is always making new things possible. (Find a few YouTube videos of Nissin CNC tube benders) Wrt exhaust systems there a few basic principles. But even then one needs to account for combustion temperature, pressure when the valve opens, mass and heat coefficient of the material, whatever. Yeah it will make your head swim.

Yes, yes you do have secondary waves, and collisions, magnification due to interference, standing waves, reverberation, constantly changing temperatures affecting the local speed of sound, energy (heat *and* velocity) lost due to expansion, ect... This is why I say it is a very complex equation. That is beyond my abilities -or at least desire- to solve for.

Scavenging happens in a header collector.... You sure aren't looking for right angles there.

The pulse does travel into the other pipe. Ideally we are tuning for the low pressure after the wave passes. Dumbing it down... shock waves happen because the molecules of the medium cannot move out of the way fast enough and you have collision instead of expansion.

I don't think so, but I was very clear that I am not an expert on exhaust system tuning.

Flowing *past* the adjacent pipe is what causes low pressure in the adjacent pipe.... https://en.m.wikipedia.org/wiki/Bernoulli%27s_principle

X crossovers are more common *now* because we have better, cheaper, CNC mandrel tube benders and robotic MIG welders available across both manufacturing and repair shops. It is really the only place to put an aftermarket oxygen sensor in a 'true dual' exhaust. (as opposed to factory bank-1 & bank-2 style) If you've been looking into exhaust you understand that this all has to do with scavenging and that on the whole, long tube equal length headers are going to help top end, where shorties are going to help*loWer* in the rpm range. Also that larger tubes need enough exhaust volume to fill them. (either through displacement or rpm's) In essence you want the shock wave to travel back up the pipe and bounce off the back of the closed exhaust valve. Then the valve can open while the shock wave is helping pull the spent charge through the exhaust port and down the tube. It is a complex equation involving supersonic shock waves, temperature, volume, gas expansion ratios, ect. to determine tube length to the collector. And the distance downstream from the collectors to the crossover. (see Bernoulli effect) **I am not an expert in this but understand the concepts of fluid dynamics from my rocketry experiments** Congrats on your recent purchase! I have an original P220 and find it amazingly reliable and accurate. Edit; lover to lower. Maybe spell check and Valentine's day influence in Chrome?

Laser? Plasma? Water Jet?....

Notice the description says 'fits engines with forward sump oil pans'.. I think you're going to need headers that point back rather than straight down. Those may clear the crossmember in your 4x2 configuration but definitely won't work in a 4x4. Also consider starter clearance. Cooking your starter once a month is not good. There's a reason the passenger side manifold ends where it does. These may be a better choice from the same source. Good advice on putting the exhaust out the back. #1 cause of drone is ending under the bed/turndown tips. If you do want true dual exhaust at least consider an X pipe. If you're going with a 2 in - 2 out design consider a stainless muffler with domed, welded heads rather that a roll crimp. Bear River offers a bunch of lengths and diameters.

I don't see a 'subscribe to this thread' option here.....

Replying mostly to sub this thread. Is it possible to clearcoat over the 'blasted aluminum' PC? Would it flow out and bond in the oven? Giving the valve covers less tooth and a chance to be cleaned. I can see how that finish might not be the best choice for a diesel engine that gets work done.

*Flange bolt* with a reduced head is often because a socket for conventional head would not fit into a recess or some other obstruction. It also assures clamping force is completely axial, where a washer could cock.

You say it is 42% of 12V, but 12V is well below the 12.6V of a six cell LA battery at rest, and even farther below the 14.35V my regulator puts out with the engine running. But I really like your analog solution using discreet components. Newark is another handy source.

Sorry, I didn't mean to hijack your thread. Fixing my gauges is the least of my problems right now.

"MY" sender's are from '85-'86 bullnose, because they are the only two wire (non-pump) senders available with the bigger bung. Just having the top and bottom quarter close to reality would be a vast improvement over below E when full and running empty at around 7/16. I zero the odometer and try to switch or refill when I get to 150 miles. The gauges seem almost like a stepper motor. I'm not sure how they are damped, or what kind of magnet returns them to zero. Maybe I could use a pot for the sink resistor and 'calibrate' the instrument that way?

Gary, Is there some way to implement this in reverse? So that I can use my older senders with the gauge in the bricknose dash. BTW, my old senders read 16.5 -160 ish. The fact that the ohms are inverted had me scratching my head, along with the fact that due to the arc of the float arm the readings were non-linear. I guess this could work with a controller board rather than a processor. But my programming skills are nonexistent (IFTTT)

In your first paragraph you say all you need is the module. But no, you also need a delay switch with the ground wire and the ability to turn counterclockwise. The two speed switch will not plug into the delay module (though it will plug directly into the dash harness)

Can't you get these stickers reprinted? I thought there was some place that would do that from a picture of the original.

That's all good, but I will say that my pic's show a '90 (F0xx) part number that works just fine. Also, I think a wrap of foam rubber will better help isolate the module and keep it from vibrating against anything solid up in the dash. On my truck the mount/stay actually bolts *to* the parking brake assembly. So, you can really understand why it takes a hit every time the truck is driven.

AFAIK later doors will fit an early truck but bullnose doors won't close over the metal hump and seat belt retractor of a bricknose cab.

And what about it???? Maybe I should paint the 450 block blue? But I think it would look out of place in my truck.

I should have known. But I didn't see the question addressed so I thought I should mention it.

I will third the suggestion of using two cables. A large gauge battery cable to the block and something like 6 Ga. from block to frame is fine. My negative cable has a smaller wire incorporated into the battery clamp that goes to the radiator support like Bill's does. Though I don't 'need' a computer ground there I'm sure it helps with the headlight grounding on my relay system. If you want OEM connectors the entire Motorcraft plug and pigtail catalog is available as a pdf online. I can't link it, because my phone will automatically download it from the url, and then I have to delete it (again and again) Find the connector you need and do a web search for the number. Pricing through Ford is ridiculous. They will pop up on Ebay or Amazon.