DuPuis Family Cobra Build

Discussion in 'Hangar Talk' started by Ted DuPuis, Aug 3, 2018.

  1. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Got the lift located and leveled. It still works after sitting dormant for about 3.5 years!

    [​IMG]

    Yes my garage is a mess.
     
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  2. -KLB-

    -KLB- Pre-takeoff checklist

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    Are there even lift points on the frame that this lift can reach? The photo makes it look like a bit of a stretch.

    And I'll admit I have fewer square feet of garage floor visible at the moment.
     
  3. SoonerAviator

    SoonerAviator En-Route

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    Still would go with a belt-driven water pump. Electric power steering is fine, but I don’t see much reason to bypass the normal water pump in favor of an electric model. I can’t imagine there’s any benefit to going electric there.


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  4. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The frame itself doesn't have lift points on it like on most cars. I haven't figured out what I want to do for that long term, my guess is I'll add some closer to completion. For now what I'll do is put cardboard between the posts and the frame itself. What I'll be more interested to see is how easy (or difficult) it is to get the car on the lift once it's completed and I have tires on it. I may have to put some mini ramps or something on to get it a little bit further off the ground so I can swing the arms under it.

    I may change my mind on this, but remember part of my goal is to have as rev-happy of an engine as possible. A water pump is a parasitic drag that will hurt that (yes I realize the alternator will be providing power, but that'll be a constant). Another advantage is that I'll have a constant water flow regardless of RPM, so that'll help with cooling especially after a hard run. Plus I also just want to experiment with an all-electric setup. I may change my mind on this and I don't have to make a firm design decision yet.
     
  5. SoonerAviator

    SoonerAviator En-Route

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    I don't see it "freeing up" anything regarding the revs, at least nothing significant at these power levels. The belt-driven water pumps won't cause any noticeable parasitic loss that an alternator drawing the increased load (to run an electric water pump) would be doing. I get that you want a clean engine bay, but I don't think the extra pulley above the crank with no mechanical fan attached will look much different than stuffing an electric pump somewhere in the engine bay. I just wouldn't want to introduce another failure point, especially on a component which is typically fails rarely and has fewer failure modes than an electric pump. If this were a pure drag car, or possibly a road-race car that you needed every ounce of HP and wanted high water flow at low engine speeds, I could see it. However, it's tough to beat the durability of a belt-driven pump on a mixed-use vehicle. Just my .02 you didn't pay for! :)
     
    Last edited: Jan 7, 2019
  6. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Oh I get it. The high water flow at low engine speeds is another benefit, and like I said much of it is just for the novelty.

    The biggest thing that might convince me on a standard belt-driven water pump is the pulley aspect. The water pump and alternator can be driven by a single belt so while it would be another pulley it wouldn't be another belt. I've heard some people say that the electric water pump can make it difficult to put in belts for powering anything, but obviously that's not insurmountable. I haven't figured out where I want to mount the alternator yet, but I'm thinking I want it mounted low.
     
  7. SoonerAviator

    SoonerAviator En-Route

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    I don't know how your setup will go, but my 351w has a single belt driving just the water pump (no fan) and alternator (marine application). Granted it's a V-belt, not a ribbed, but I'd think you can get a pulley to run off of one belt instead of multiple.

    (Notice the alternator mounted low, single belt despite dual belt crank pulley)
     

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  8. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    That's more or less what had come to my mind as the ideal setup, especially since that keeps things clean up top. A lot of folks are pulling engines more or less directly out of Mustangs and putting them on, which keeps the alternator and power steering pump further up. Not very clean at all.
     
  9. -KLB-

    -KLB- Pre-takeoff checklist

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    The Ford modular V8 philosophy, put the alternator top front center, and bury everything else under the heads. At least it makes mustang, truck, and crown Vic alternator changes a walk in the park, but it doesn't suit your application at all.

    I will say that I don't find the duratech alternator location below the head, trapped between the firewall, block, and half shaft to be remotely fun to deal with. Unbolting subframe members and lowering 3/4 of an inch, and taking out a half shaft aren't things I expect to have to do to change an alternator.

    At least it seems to beat what I heard had to be done on last generation mercury cougars, and cutting wheel well sheet metal.
     
  10. Bill Jennings

    Bill Jennings Touchdown! Greaser! PoA Supporter

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    At least they're not water cooled alternators like on some BMW models. Water cooled alternators, WTF??? Only the F'n Germans come up with overengineering crap like that...
     
  11. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I've changed some really crappy alternators in my day. I can't remember the worst off the top of my head, but a low mounted alternator usually isn't too terribly awful if there's not too much other junk around. So I figure this will work well.

    I had a 4.6 in my Town Car, and the top-mounted alternator and water pumps were incredibly easy. I changed those preventatively once on that car but didn't need to. Like you said, everything else on the 4.6 was underneath and hard to get at.

    I will say that I think the 4.6 is an overall better engine design than the pushrod engines in many ways, but for me the biggest reason for sticking with pushrods is the sound and the weight.

    That was the one saving grace of my 740iL. It was one of the earlier models with a conventional alternator.
     
  12. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    With the weekend approaching, I've been giving some thought to what I want to work on with the car. The polyurethane steering rack bushings arrived from FFR, so I think the one item I'd like to check off is the steering rack and get that done, as well as connecting the tie rod ends. At that point the steering system will be "complete." I put it in quotations since I'm still planning on adding power steering, but I've decided not to spend money on that unless it 1) goes on sale 2) I get more to a point where it's something I need to do.

    With the lift in I contacted the guy who wants the engine and transmission from my parts car to see if he wanted to pull it this weekend. He wasn't available, so we'll pick another weekend to get it pulled out. I also sold the extra set of 351 headers that FFR sent me. My total invested at this point is just over $19k, which when you consider that a "complete kit" costs $20k without shipping or options is pretty good. At this point the only major items that I need to buy are the engine and transmission.

    I've also been thinking some more about engine options for the car and looking at various short block options. I know that I want a roller cam, and by the time I get myself to a 351W rebuilt roller block with decent pistons, it's not that much more to do a 408W stroker, and a 347 stroker short block is in that range. My heads will work for any of those engines, and they're all popular choices. One of my friends has a Cobra that he built with a 351W and then after he blew that up he put in a 408W. At first he'd said the 408 was a bit too much as he was breaking tires loose in 3rd and 4th, but he said that since getting stickier tires he's really enjoying the 408. That gives me some things to think about. The 302-based velocity stack EFI that I'm wanting to use costs around $1k more than the same setup for the 351-based engines (I have no idea why), which pushes towards the 351/408. But the 347 saves 50 lbs, and less weight is a good thing, and the engine is smaller which makes it fit in the engine bay better.

    I suspect I'll be happy either way, but it's something to think about. What I think I'm more likely to do once I get the rear end in is look around for a driving Mustang that's got a motor and transmission on the order of something I'd want and try to pick that up as donor car #3, but it would have to be a running and driving car (or at least running), unlike the first two. Any Mustangs that fit that criteria seem to be priced such that I probably can't do much better vs. buying the parts I need new anyway, but we'll see what's out there.

    Another item I've been kicking around is the idea of rebuilding a T-5 with an upgraded straight cut gearset and putting that in instead of a TKO. I've always wanted to do a straight cut box in a car, and that would be an opportunity. The benefit of this is the T-5 saves 15 lbs over the TKO, and rebuilt it has similar strength, plus it fits right in. The negative is that to do the mid-shift conversion is a bit more involved as it requires a tailshaft swap, and ultimately the casing isn't as strong. Also, then it's a straight cut gear transmission which is harder to run on the street. Not that I've ever let such things bother me too much, but Laurie is going to be driving it some. I generally figure if I go 408 it's a bad idea, if I do 347 it may be alright to do.
     
  13. FormerHangie

    FormerHangie Pattern Altitude

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    I take it that this straight cut gearset also uses dog ring engagement, and thus is non-synchromesh. The Formula Ford I drove had a Hewland Mk 9 gearbox that used a similar setup. It works very well on the racetrack, but it would make for a pretty hard edged street car. In my racer, I used a 17:33 first gear and either a 24:26 or a 24:25 fourth gear, depending on the track, so the ratios were very close, 1.96 to 1 for first gear and 1.04 to 1 for top. I was shifting at 6700 rpm when going from first to second and 6400 for the 2-3 and 3-4 shifts. If I remember correctly, the rpm drop from first to second was about 1100 RPM and about 900 RPM for the other two, so it was a close ratio setup. In a street car you'd typically want a low first gear for parking lot duty and a fairly tall top gear for highway cruising. When you get a bigger RPM drop it's more challenging to pull off a smooth shift in with non-synchromesh transmission, hence the nickname "crash box". Old cars and heavy trucks have slow turning engines, and it's fairly easy to match the engine and gearbox speed, but with a high revving engine this gets much harder.

    If you're building a track focused car, I think that would be a good transmission, but if your driving is mostly going to be on the street, it's not something I'd want. There is a certain amount of appeal to being able to upshift without the clutch, and the gear whine is pretty neat, but for a street car I'd want a synchromesh transmission. Of course, if the straight cut gearset you're thinking of using does keep the synchros, then it's mostly just a cost issue.
     
    Last edited: Jan 13, 2019
  14. SoonerAviator

    SoonerAviator En-Route

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    T5 (TKO or otherwise) are synco-trannies. I can’t imagine it’d be beneficial to drive a non-synchro tranny anywhere but the track. Just getting into reverse/1st can be a chore if you didn’t stop at the right spot in the gear mesh.


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  15. FormerHangie

    FormerHangie Pattern Altitude

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    Let the clutch out briefly with the transmission in neutral, then put the pedal back down. If you're wanting first, guide the gear lever gently into first, it will engage. If you need reverse, wait a few seconds for the input shaft slow or stop, then try for reverse. With reverse, you're pulling an idler gear into the driveline, and they're relatively fragile, with first, you're just trying to get the dogs to engage, and they're stout.
     
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  16. SoonerAviator

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    Right, I just mean to say that slow moving/stops become a bit more of a chore with non-synced transmissions. Once you learn the tricks with any tranny it becomes easier, but every now any then it can be a pain, especially if you miss a gear. If I’m driving something on the street as much as it’s on the track, I’d rather not worry about trying to keep the gears from ratcheting on every shift that didn’t have revs matched perfectly. I did like the whine from the ‘67 Vette we had with the M-22 “rockcrusher” which was synchro’d but had straight-cut gears.


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  17. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I ended up doing absolutely nothing on the Cobra this weekend, best laid plans and all. I had some house projects that I wanted to get done, plus we got about a foot of snow between Friday rush hour and Saturday afternoon/evening. So Saturday and Sunday both we spent a lot of time outside playing in the snow and playing with the tractors (more on that in my runway thread).

    What I really want to do next is get the steering rack in since that will let me throw another box away and I'll feel accomplished. In reality I could do that or keep moving on the aluminum panels and be doing just as much towards getting things moved along. I doubt I'll get much done this week, though. Laurie comes home from her type rating Thursday midday, and what I want to get done during my evening projects is make progress on the last of the iron pipe light fixtures I'm making for the kitchen.

    It's worth noting that in my truck transmission, and even sometimes in a TKO, I have to do some level of double-clutching when shifting if the transmission is cold. And I'm talking about starting out on a winter day, with temps around or below freezing. The 1-2 upshift on my truck almost always requires double-clutching in that scenario. Other upshifts are usually fine, but downshifts then benefit from double-clutching - it just goes together a lot smoother. Also when it's cold (and even sometimes when warm) it regularly won't go into 1st or 2nd, I'll have to put it in another gear, let out the clutch, push the clutch back in, and then it'll go in.

    If I just try to force it in, yeah, I probably could and it'll probably go in, but it's hard on the machinery.

    Now, that is a transmission with synchros (and so is a TKO), but point is even then these techniques can be beneficial and I use them. That said, I generally agree that I'm probably better off with the TKO. For one, I'm not THAT concerned about 15 lbs that's more or less in the center of the car, the TKO I know will work without issue, and Laurie will be driving it so a more conventional transmission would be better for that.
     
  18. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    This weekend I managed to make progress on a few items related to the build. On the infrastructure side, I put in the LED garage lights in the aft portion of the 3 bays. Now, the light in the garage is exactly what I wanted, and brings me to what I had in Ohio light wise. I actually have a full on shop again. Of course, the aesthetics of my garage now aren't great like they were in my last garage, but I have all the function I need. I'm very happy about that.

    Cobra wise, I only got minor items completed. I cleco'd some of the aluminum panels that were painted back in place. Other than the driver's footwell, I've got everything firewall forward painted. Well, I say that, but I also don't have the "bird box" for the HVAC completed. Realistically I just need to drill more aluminum panels at this point.

    I also got the steering rack in. I had ordered a brand new steering rack, and the rack bushings didn't match what the Mustang bushings are supposed to be. This rack was used in a lot of other Fords over a number of years, and my thought is they put the wrong bushings in. FFR stepped up and sent me their polyurethane custom bushings that they send with the complete kits free of charge. Of course, probably only cost them about $5, but it sure adds a lot of goodwill to me as a customer. So I pulled the bushings out (easy enough being new, rubber, and not glued in), hammered in the new bushings and the steel spacers. I also pulled off the hydraulic power steering lines, which does a lot for cleaning up the appearance of the rack and also gives a little bit more room to work once it's installed. I don't expect working on the car is going to be much of a problem, but I want to keep it looking as clean as possible.

    I've also been toying around with some of the engine ideas, specifically relating to the valvetrain. The goal with the car is to have things be as direct and lag-free as possible, especially with the drivetrain. That's part of why I've wanted to have nothing belt-driven besides the alternator. So, I've been thinking also about going with timing gears instead of a timing chain and also thinking about a solid lifter cam. For the application there isn't any reason why I need either of those. I'm not revving high enough to get to a point where they make a technical difference. However, since my goal for this car is to have minimal lag and a really tight, instantly responsive valvetrain, I'm thinking there's some merit. I've heard that the problem with timing gears is they just end up being ridiculously loud, to the point of making a vehicle unpleasant to drive loud. However, I do love gear noise, so I may be crazy enough to enjoy it.

    The solid roller cam of course adds the extra complexity of having to adjust the valves every so often.

    I know, most would argue that the benefits of those aren't worth the cost for what I'm doing, hence why they don't use them in any production vehicles, but this car is all about the visceral aspects for me.

    Decisions I don't need to make yet anyway.
     
  19. Zeldman

    Zeldman Final Approach

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    We used reverse rotation cams in our race engines. Only gears are one on the crank, one on the cam. Even with race mufflers the exhaust noise covered up everything, so I can't say if there was any gear noise. I think the timing gear sets that use an idler gear make a lot of gear noise.
     
  20. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The idler gear ones are the kind I'd be using. They do make ones labeled "quiet". I've never been around one so I really don't know what sort of noise they make. I DO know that what I like is often not in-line with what others like in that regard, and I do enjoy a nice gear/supercharger whine, so I think I would enjoy that sound.
     
  21. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude

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    You’re nuts (in a good sort of way). With that chassis, you’re gonna get instant dis-traction, regardless of how “soft” some of your other components are (timing chain, hydraulic lifters, belt driven parasites). I’d bet you wouldn’t feel the difference, only cuz the rest of the setup behind the engine isn’t exactly soft. But that’s what will make this ride personal and unique.

    Crazy-on dude.

    P.S., need more pics of car now that panels are on, and pics of the lit garage (the messier the better, so I can feel better about mine).