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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    As with anything, it depends on a lot of factors. Which carb(s) you're running and how they're tuned, which EFI you're running and how it's tuned, some of the ancillary hardware. Back in the day I was into 80s V12 Jaguars, which kept the ECU in the trunk, a good 10-15 feet from the engine. The MAP sensor was located on the ECU, with a vacuum line that ran all the way up to the intake manifold. So the real lag you had was the physical lag of the pressure in that vacuum line changing over the course of those 15 feet, which made the engine noticeably less responsive for rapid power changes. Although I did make it shoot fire out of the exhaust pipes a few times when doing rapid shifts from high RPMs. :)

    In this case, I'm looking at running velocity stack EFI where it looks like Webers (would be my preference but they're too pricey) but is actually EFI. One factor in responsiveness is the distance between the throttle body and the intake valve, and so velocity stacks with independent throttle bodies only a few inches from the intake valve will help responsiveness. Since I'll be programming the EFI I'll also be more generous with the throttle tip-in enrichment which will help.

    If I wasn't going to do the velocity stacks, I'd just pick a conventional intake and probably an Edelbrock carb.

    I think the end result is going to be pretty snappy all around. I was thinking about the closest vehicle to the Cobra that I've driven in the past, and it was the '93 RX-7 twin-turbo. The one I drove was a low mile, completely stock car - beautiful. Now, the rating on that car was about 255 HP (compared to the 400ish I'm looking at), and looking at gearing I'll be a bit taller with 3.73s vs. 3.90s in the back, and then a bit taller gears in the transmission. Tire diameter I'll also be a bit bigger on. The 3rd gen RX-7 is fairly close in weight and overall size to the Cobra, and I thought that 400 HP would've been a good number for that car. So, I think I'll probably find that to be the case in the Cobra, too. I'm more and more thinking the 347 is going to be the way to go engine wise.
     
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  2. SaltH2OHokie

    SaltH2OHokie Pre-takeoff checklist

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    I had a 93 RX7. Loved the car, wife did too... I had the boost turned up a bit, 3in exhaust and otherwise stock and it would flat fly. Problem with them now is most have either been wrecked or butchered... And if they haven't, they're $25,000+ for a 1993 car that makes <300hp to the wheels.

    Since the Japanese FD's are now import eligible (25years old), started seeing RHD options for sale around here. That's just never appealed to me.
     
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  3. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    That's the exact problem with those Japanese supercars of the mid-90s. When I bought my 3000GT VR-4 in 2010, I was lucky to find a 100% stock one that was on its 3rd owner, and the owner was around retirement age. It still had close to 130,000 miles when I bought it, though, and I ended up going through basically the entire car at that point.

    I think the ability to bring in 25+ year old cars more easily now is a good thing, but I wonder how much you really save by doing that. Doing a quick search makes it look like not a lot. You really have to be into Japanese cars from that era to do that, and I have a hard time with that. The first half of the 90s weren't a great time for interior fit and finish in general, but the Japanese and Americans I think did the worst. It wasn't until closer to 2000 that you started to see interiors that were catching up with what the Europeans put out. I like what Jay Leno says about a dashboard - "It's like marrying a girl with a pretty face - that's what you're going to be looking at every morning when you're eating breakfast." Early 90s, not so much for good dashboards.

    The 3000GT had been a bucket list car for me, and I'm glad that I owned one. However that itch has been scratched and I have no desire to buy another one.
     
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  4. FormerHangie

    FormerHangie Pattern Altitude

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    Here's this years Track Night schedule @ Heartland Park Topeka:

    April 25, May 17, June 13, July 12, August 8, September 19, October 17

    I'm planning on doing the May 8th one at Atlanta Motorsports Park, if anyone local would care to join in. The only downside of running at AMP is that you have to have a helmet with a Snell SA2010 or later sticker, no motorcycle helmets are allowed. Most other tracks are OK with DOT approved helmets. I'm not sure why AMP insists on SA helmets in street cars, provided that they don't have a cage installed.
     
  5. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I could take the E55, but I should probably finish the Cobra and use that. :)
     
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  6. Zeldman

    Zeldman Touchdown! Greaser!

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    I don't know the story behind this, but if it is real I would be willing to say don't try this at home....

    [​IMG]
     
  7. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Looks photoshopped, but definitely looks like something I DON'T want to do.
     
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  8. -KLB-

    -KLB- Pre-takeoff checklist

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    Modding a cobra with long suspension travel, and 20+ inch travel king shocks to survive that sort of abuse could be interesting in some pointless way, but sure misses the mark here. Getting that kind of travel out of the drive line currently makes my head hurt trying to conceptualize it.
     
  9. FormerHangie

    FormerHangie Pattern Altitude

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    Clearly he's using flubber.
     
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  10. jsstevens

    jsstevens En-Route PoA Supporter

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    Remember we haven't seen the after picture. I'm sure a Cobra could do that. Once.
     
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  11. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I'm just thinking about how you could even think about going about this. On the front you'd have to start off with some new control arms that were very beefy, and also very long to get 20" of travel within a reasonable angle range. You'd probably have to double the length of those control arms. Figure on custom spindles (not that that makes too big of a deal), and also figure some longer or otherwise custom work with the tie rod ends. The Factory Five cars are known for having bump steer issues, and looking at the steering geometry it's not surprising. I'm honestly not entirely sure why they put the steering rack where they did, (aft of the tie rod mounts by a few inches). The angle the inner tie rods has to take is pretty big and prone to bump steer.

    The rear I think you'd have to go with an independent rear suspension given how the solid rear axle is mounted, and then probably do something similar.

    It would be a fairly hilarious vehicle.
     
  12. FormerHangie

    FormerHangie Pattern Altitude

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    A little like this one, I suppose.

    [​IMG]
     
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  13. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I've been doing my build thread here for a couple reasons. 1) Y'all seem interested in the build 2) A lot of the people building these cars on the FFR forum are real idiots. A number of these people have been trying to install the tapered ball joint end of the outer tie rod into the spindle upsidedown and wonder why they can't thread the nut on. Well, it's because you've got a tapered hole and you're putting the thing in the wrong way.

    Here's the latest gem. One of the well known and respected guys who sells parts and drivetrains recently sold a Coyote 5.0 with transmission attached. Now, if someone's putting a Coyote engine in one of these things to begin with, it usually tells me they have more dollars than sense and are just going for "the best" (i.e. most expensive) option. Not always the case, but it seems to be a common theme among people who go with Coyote engines. Guy said he didn't need a liftgate for the delivery to save money on shipping. So the truck shows up expecting a forklift or a dock, but there is none, and thus no way to get the pallet out of the back of the truck. The buyer seems shocked that the engine and transmission (attached assembly) ARE REALLY HEAVY and you can't just get a couple of guys to pick the thing up out of the back of the truck. He then complains to the seller that these things are heavy.

    What'd you think an engine and transmission were made out of, balsa wood?!
     
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  14. -KLB-

    -KLB- Pre-takeoff checklist

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    Ugh.

    Guess we should all be thankful he isn't building a kit plane.
     
  15. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Some of the people building these things really have no business turning a wrench. It's a testament to FFR how easy these things are to build, but I think I would be equally if not more scared of buying one of these from generic builder than an E-AB aircraft.
     
  16. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Someone screwing around posted this:

    [​IMG]
     
  17. Zeldman

    Zeldman Touchdown! Greaser!

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    When I was racing for a living I saw a lot of ''more money than skill'' cars.

    One guy brought his mechanical fuel injected 331CI '68 Cougar street/strip car. It had a miss at idle/low rpm, then again at higher rpm. We determined that it had a intake leak. We took off the intake manifold and measured. Sure 'nuff the heads had been milled a lot and now the intake no longer fit. We ended up cutting the intake in half, attached it back to the engine to fit it to the heads, then welded it back together and re-ported the intake runners.

    Ok, that cured the intake leak, however there was still a vibration from the engine. We searched and searched, then searched again. We even took the tranny out to check that. Finally in desperation we took the heads off.

    ZOWIEEEE..!!!! The ''engine builder'' had taken a grinder and cut grooves into the pistons into a cross hatch design. The car owner explained to us that the builder did that to improve the fuel/air mixture in the cylinder. I mean ruff grooves almost a half inch wide and almost through the top of the pistons. Hmmm....

    A new set of pistons, a roller cam that was not a ''bigger is better'' cam and a balance job and that little Cougar ran really well.

    I really enjoyed the guy that brought his hot rod truck to us to show that the engine was really hitting 12,000 rpm. Electric tachometer. Change switch from 4 to 8. Now the engine only hits 6000 rpm.....

    I won't even bring up the guys that thought taking the race car out on a 2 mile oval and get it up to speed will make the oil pressure (dry sump system) problem cure itself....Blew the bottom of the oil tank off. Next time you might put a vented cap on that oil tank.....
     
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  18. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    People who have a credit card and a Summit Racing catalog. If you only sold these things to people who were qualified, you'd never sell enough to make money. I should make that my new signature quote. But they can make for good deals later, example the first parts Rustang I got. If nothing else, those heads with 2.02 valves would've been too big for a 302. The 1.90 option would've made more sense. Hence why I'm looking at a 347, which they should be good for.

    I still want a solid lifter cam, but not because I need it, because I like the sound.
     
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  19. FormerHangie

    FormerHangie Pattern Altitude

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    I appreciate you posting this. It's something I've thought of doing, but realistically, I don't have an appropriate space, and the car I'd like to drive (818) looks too much like a kit car for my tastes.

    One of these days I'm going to get something sportier to drive so I can stop abusing rental cars at track days. It's still a couple of years away, I have to get daughter #2 enrolled in a college first, and that's a year and a half away.
     
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  20. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The Cobra/roadster (whichever you want to call it) is unique in that it doesn't look like a kit car, and the Type 65 Coupe I think holds that as well. The other FFR cars to me also look more kit-carish, even the Hot Rod and the Truck kits look pretty obviously not stock to me, even though I think they look cool. I was close to picking the Type 65 over the Roadster, but decided I wanted the open top and my wife liked the look of the Cobra better. Plus, it's cheaper.

    When I look at most kit cars, I tend to feel the same as you that they look too much like kit cars. Jay Leno tends to rag on replicas and kits because most of them are pretty low quality and miss the mark on the driving experience, it's just about the look rather than the full on driving, and even the look is wrong once you get close to it. The Roadster and Type 65 get it pretty accurate.
     
  21. 3393RP

    3393RP Pattern Altitude

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    Do you recall the member 1600vw? He claimed he built a big block Chevy that would turn 12,000 RPM, and the car it was in would lift the front wheels shifting into second gear. It also went 178 MPH.

    LOL!


     
  22. Zeldman

    Zeldman Touchdown! Greaser!

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    :lol::lol:

    I had forgotten about that..!!! 178 mph on street tires....with 3:73 rear gears....:rofl::rofl:
     
  23. SoonerAviator

    SoonerAviator En-Route PoA Supporter

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    I recently discovered that a rental Ecoboost Mustang convertible is electronically limited to 122mph, but has enough power to keep up with a 600cc crotch rocket from 70-120mph, lol.


    Sent from my iPhone using Tapatalk
     
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  24. Bill Jennings

    Bill Jennings Touchdown! Greaser! PoA Supporter

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    Was 600 guy actually downshifting and making an effort or just rolling on in 6th gear?
     
  25. SoonerAviator

    SoonerAviator En-Route PoA Supporter

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    Unsure, we were just horsing around on an empty stretch of 6-lane interstate, but I didn’t listen to see if he dropped down a gear (I’m sure he probably held it in 6th) He was definitely giving it everything it had though, in whatever gear he was in. We had about three runs that each had us neck and neck until I hit the speed limiter. I was impressed that the turbocharged Stang would even hang with it all. I’m sure a liter-bike would have walked away easily on a 70mph roll. The 600cc would have surely walked away from a standing start race, too.




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    Last edited: Jan 26, 2019
  26. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I went back and looked through to see when I’d last reported any progress, which was 3 weeks ago. I actually thought it’d been longer, so that’s better than I thought. We’d been focusing on the office the past couple weekends, so there hasn’t been an opportunity for progress.

    This weekend I probably spent a good 5 or 6 hours (with my assistants) drilling holes in aluminum panels.

    At this point I believe I have 100% of the panels forward of the seat backs forward. I had a few holes I’d missed in the footwell floor pans and did those, as well as the under-door panels, floorpans, transmission tunnel sides, and transmission tunnel cover. Then I ran out of drill bits - my helpers are hard on bits, and drilling into the steel tubes is hard too.

    I’ve made a few mistakes on riveting. For one I’ve got the spacing wrong on a few panels. FFR has a rivet spacing tool with two options for spacing - one for aluminum panels going together and another for panels going on steel beams. I’ve been drilling those in reverse. The end result will be more rivets than prescribed in the manual which is a good thing.

    The bigger mistake is I screwed up alignment on the drivers side footwell/ transmission tunnel side cover (it’s a single piece) causing a gap towards the bottom of the transmission tunnel. Ultimately it won’t be a significant problem but it is a lesson learned.

    There’s a lot more aluminum to go, but it was good progress.

    I’m also thinking more about the wiring harness and I’m thinking I’ll probably end up making my own harness. The generic harnesses don’t quite meet what I want. I’m debating whether to put the fuse box in the trunk or the cabin, but I’ll probaby end up with the cabin.

    Another idea I’ve been toying with is putting the HVAC entirely in the trunk rather than behind the dash, similar to what was done on a lot of older cars or some Vintage Air units, but it seems like it would probably be too much overall effort for not enough of a benefit, but it would clean up the engine bay and move CG aft some.

    Also want to give a shout-out to @FormerHangie who gave me the rolling stool you see in a few pictures. He didn’t need it anymore and it’s proving a very useful tool in the garage, I used it a lot this weekend. Thanks!

    40F3AC61-52F8-4A13-B02F-62D505C5F763.jpeg DCE9CE97-EA60-419D-8E5C-970FEF38DB93.jpeg CE5888E7-47EE-4066-8018-05CECE29D758.jpeg FC5F0FA4-FB1A-49A0-99C1-0CB356C3AF06.jpeg 16027E23-8D04-4C2E-A498-65DBB7FAA8AF.jpeg
     

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  27. Zeldman

    Zeldman Touchdown! Greaser!

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    I have a similar rolling stool. It is a real knee saver, great for an old man.
     
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  28. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Doing a quick look through the manual, I’m probably about 2/3 through the holes to drill for the parts I can do now. Maybe 3/4. Another weekend like this one and I should be as far as I can get, and then I’ll really need to get going making progress on other items, I figure rear suspension will come first.
     
  29. FormerHangie

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    It's great to see something that was collecting dust in our place being put to good use in yours.
     
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  30. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I had a Cloud Nine trip on Saturday, so there wasn't much opportunity for working on the Cobra this weekend. However I did get enough time in the garage to drill the two little panels on either side of the aft transmission tunnel.

    The larger panels towards the outside are the next ones to drill, and then there's a final bigger sheet that goes over that area entirely. I'm supposed to have another trip next weekend so I'm doubtful I'll get those done this weekend or next weekend, but maybe.

    IMG_3067.JPG
     
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