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  #401  
Old 05-29-2021, 12:54 PM
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heinke heinke is offline
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Originally Posted by Steve Hamilton View Post
Hi Joel
could the tube be squeezed to an oval in the tight area?

Steve
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Originally Posted by 123pugsy View Post
Just grind 1/8 off the top of the elbow to zero on the bottom of your elbow. It need not be exactly square where it joins.
Thanks for the suggestions. After thinking this through some more, I think there's a better way that's a variation on what Pugsy suggested. Simply put, use an extra thick flange and carve the start of a bend in the flange itself having the primary tube exiting at an angle.
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  #402  
Old 05-29-2021, 12:57 PM
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Post Header Design Progress

This is a progress update on the Miura engine headers.

I’ve been working with Vince Roman at Burns Stainless on header design options and specifications. Burns offers free header design services if you buy the various header pieces from them. The primary objective on the Miura header design is to make the Coyote V8 sound as close to a V12 as possible and feasible. A 180 degree header design (primary tubes mixed across engine banks) would do that but it just isn’t feasible given the transverse engine orientation and configuration. So the next best design option to achieve the v12 sound is 4 into 1 headers followed by Y pipe with all primary tubes equal length along with equal length secondary tubes into Y pipe.

The spec Vince worked up on their header design software is 28.5” tapered primary tubes starting at 1 5/8” going to 1 ¾” and then up to 1 7/8” prior to a merged collector. If the left side header is routed under the oil pan, it looks like there’s barely enough room to fit headers of this specification and keep them equal length. It will require a “flat collector” instead of the standard stacked collector design but that should be all right.

As to the right side header and maximizing the transaxle shift mechanism clearance, Vince confirmed that starting a short radius bend in the flange is a viable design and it’s used in some racing engines that also have tight clearance issues. He confirmed they can provide a ¾” thick header flange with 1 ¼” pilot holes for the ports. This way there will be sufficient metal in the flange to cut in the bends and have the primary tubes exit at an angle to the flange instead of perpendicular. It will likely be time consuming to grind out the flange for a good flow match but this appears to be the best way to maximize the clearance over the shift mechanism without compromising exhaust flow.

In addition, I’m having the shift mechanism made up from a single piece of aluminum billet which should shorten it by 3/16”. Between these two measures, it looks like a clearance of something like ½” will be possible where prior it was 1/8”.
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  #403  
Old 05-31-2021, 07:44 PM
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Post AC Compressor & Engine Mount Progress

When it comes to mounting the engine/transaxle package in my Miura, it’s coming down to fractions of inches, literally fractions of inches. The critical spot is between the upper suspension joints, specifically the heim joints at the front of upper A arm. To make room for the AC compressor, the engine/transaxle needed to be moved 3/8” to the drivers side from where I originally intended to place it. Fortunately I hadn’t yet fabricated the engine mounts so it’s become a matter of making room for the AC compressor and then building out engine mounts for that placement.



My first choice was the Ford AC compressor that came with the Coyote engine as it mounts directly to the engine block with 3 long M8 bolts; nice, simple and clean. I couldn’t make it work though as it has some sort of hub that sticks out about ¼” as part of the electro-mechanical clutch and this hits the suspension mount prior to all 3 mounting bolts lining up. I had already moved the engine/transaxle as far to the drivers side as possible.



There’s 1/8” clearance between the transaxle case and the heim joint and that’s as close as I’m comfortable running them. Like I said, fractions of inches. I’ll shave a bit more metal off the chassis so there will be the same 1/8” clearance there as well. So plan B is to use the Sanden 508 AC compressor that came as part of the Old Air aftermarket AC system. While the Sanden unit is a nicer piece from an eye candy perspective (it’s polished to a nice shine), nobody makes the hardware to mount it to a Coyote engine. Oh well, in for a penny, in for a pound. I’ll have to spend a couple of days fabricating mounting brackets for it.







After building part of the mounting bracket and lining up the serpentine belt with the crank pulley, there’s 3/16” clearance, just enough to sneak a belt through and hopefully with good engine mounts enough to keep the AC clutch from hitting the chassis. I knew clearances would be close but I didn’t envision they’d be this close.

Ok, onto engine/transaxle mounts. The primary requirement for the mounts is to control the potential lateral movement for the engine/transaxle with a secondary requirement to dampen engine vibrations. So I decided to use “biscuit style” mounts that are secured with a 7/16” bolt through the middle. Ideally, the engine/transaxle package could be suspended at 3 mounting points, but I decided 4 points would be better given the tight clearances. I started building mounts at the back side of the final drive.





I started with a scrap piece of 6” by 4” by ½” rectangular tubing and with some machine work, it slips snuggly over the final drive case and through bolts can be used to fasten in place. I’m thinking 3 bolts are better than just 2 so I’ll add some ears to the bottom to pick up a 3rd bolt hole. As often happens when starting from metal scrap pieces, it has a couple of extra holes in it, maybe they will come in handy for some sort of mounting bracket. I’ve ordered up some more metal and special bolts to complete the engine mounts.

More to come…
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  #404  
Old 06-01-2021, 04:50 AM
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Gojeep Gojeep is offline
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Some times hard to know where to start with things like this. I start with what can't be moved or changed and then go to the next critical thing. You get there in the end but can be a real juggling act.
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  #405  
Old 06-06-2021, 11:19 AM
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heinke heinke is offline
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Originally Posted by Gojeep View Post
Some times hard to know where to start with things like this. I start with what can't be moved or changed and then go to the next critical thing. You get there in the end but can be a real juggling act.
You are right Marcus. I just knew I didn't want to move the suspension mounts, so my only choices were limited to the other components.
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  #406  
Old 06-06-2021, 11:29 AM
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Post Engine Mount Progress

I’ve made more progress on fabricating engine mounts with 2 of 4 now complete.

On the mount attached to the final drive case, the metal cut away from the main part is used to extend the mount downward for the 3rd bolt attachment. The metal was cut to shape, a ¼” bevel made along the weld zone, and a big fat bead laid down. I used a ½” thick steel backer plate during welding to minimize the warpage from shrink in the weld bead.



After metal finishing the weld, some extra metal was cut away in a curved cut to match curves in the final drive case. The surface was cleaned up with a belt sander and 100 grit sanding belt leaving a satiny “grained” finish.





The next mount to be fabricated was the drivers side front. I started with a scrap of 3/8” thick aluminum angle. I was able to cut it to pickup 3 bolts on the bellhousing and this time all the extraneous notches and holes in the scrap went away with the cut. After welding on a foot and a gusset, it was drilled with lightening holes to remove some weight and belt sanded to get the same finish as the other mount. The short piece of channel the biscuit mount sits on still needs to be welded to the chassis but I’ll wait to do that until all the engine mounts are completed.





2 mounts down, 2 to go. For some reason I always think fabricating stuff like this should go quickly but they really do take quite a bit of time to make.
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  #407  
Old 06-06-2021, 05:18 PM
Charlie Myres Charlie Myres is offline
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Pardon me for mentioning it, but the lightening holes have created a lot of stress-raisers. In steel it may not have mattered quite so much, but in aluminium I think that it may weaken the mount enough, for it to break one day.

I do admire your perseverance and creativity in this build. I have just watched one of Ian Tyrell's films on a Miura and even the designers of the original cars had their issues, which were not solved easily, or not at all,

Cheers Charlie
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  #408  
Old 06-07-2021, 11:06 AM
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Quote:
Originally Posted by Charlie Myres View Post
Pardon me for mentioning it, but the lightening holes have created a lot of stress-raisers. In steel it may not have mattered quite so much, but in aluminium I think that it may weaken the mount enough, for it to break one day.

I do admire your perseverance and creativity in this build. I have just watched one of Ian Tyrell's films on a Miura and even the designers of the original cars had their issues, which were not solved easily, or not at all,

Cheers Charlie
Charlie: I'm curious as to why you think the lightening holes are stress-raisers. Each hole is radiused on both sides so no sharp edges were introduced with these holes. The mount is vertical so the main force going down through the aluminum is compression. I don't think there will be much if any shear force against it. I'm not an expert in this area and I'm asking to learn something not to question what you've said.
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  #409  
Old 06-07-2021, 05:21 PM
Charlie Myres Charlie Myres is offline
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Radiusing the hole edges was a good move, but the fact remains that if it starts to crack it will be at a hole.

I guess it gets back to an engineering and design question – is the gain of losing a few grams of aluminium, worth the risk of of the mount breaking?

I always ask myself – what is the worse thing that can happen if it fails?

Hopefully I am wrong and there is little risk, or consequence, to worry about,

Cheers Charlie
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  #410  
Old 06-14-2021, 02:52 PM
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Post Engine Mount Completion

The engine mount fabrication is now complete; all that remains is to weld the mount pedestals to the frame rails. I’ll need to pull the engine out to get access for the welding so I’m going to try to complete more things that need the engine in place before pulling it. The front passenger side mount was the hardest to make as it is wedged between the oil filter and oil pan. I probably made more than 25 trips under the car on a creeper to get it sorted out.





I would have preferred to have only 3 engine/transaxle mounts instead of 4 but I was worried that the transaxle would contact the chassis and the 4th mount is to ensure that doesn’t happen. The transfer case part of the transaxle has about 3/16” clearance above the lower A arm pivot. The cedar door shim in this picture was used to set the clearance while the engine mounts were being fabricated.





It’s back to the transaxle shift mechanism and header mock-ups now.
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