DuPuis Family Cobra Build

[Kenny Phillips]

While I am not inherently against a homebuilt (and may build one someday myself), the RV-10 is not on the list. It's a good airplane for a lot of people and a lot of missions, but does nothing that I want to do. If I wanted something like that, I'd buy a Comanche 250/260. Or maybe find a 400.

I appreciate that, but I was more commenting on how that picture looked. I'll bet you could sneak that into someone's build blog and it would go unchallenged!

 

[Ted]

I appreciate that, but I was more commenting on how that picture looked. I'll bet you could sneak that into someone's build blog and it would go unchallenged!

Ahh, ok. That makes sense, and having never built (or been around) a -10, I didn't get the reference.

 

[Ted]

Made a bit of progress on the Cobra this evening. I finished drilling the holes for the panels for the heater core and AC condenser, and then I drilled the holes for the panels in the left side trunk panel.

I'm getting to the point where I'm about to run out of panels. I have 5 more panels remaining (all in the trunk). After that there are some smaller panels, but those all come much later in the build process. So really, I'm getting to the point where I'm going to have to start pulling some parts out of the parts car soon and/or buying some other parts that I'll need to put on the thing. Really, the things I need to be working on next are pulling the rear end and pedalbox out of the parts car so that I can get working on that. I'm also running very thin on clecos, but given that I'm almost done drilling aluminum panels, I think I'll survive with what I have.

However one thing that's come to mind as a tool I need, and that's something that's good for cutting holes in the aluminum. I have to cut a retangularish hole in the firewall panel for the HVAC, and then I also am thinking I'm going to cut a hole in the rear seat panel to provide some access to the forward trunk area. I have a jig saw but I don't feel like that would do the job very precisely. Any recommendations for an appropriate tool to consider?

If I were to follow the instructions, I would be using the Mustang wiring harness. I don't want to do that because 1) it's 25 years old and going to be brittle/broken if I remove it and 2) it's got a lot of functions I don't need/won't use. So I'm planning on making my own wiring harness. The electrical system is going to be pretty simple. Circuits will be for the EFI, fuel pump, ignition, lights (probably a couple different circuits to split up the lights), starter relay, HVAC, and heated seats. I'm planning on putting a master battery cutoff as those are recommended for the cars as a general safety/anti-theft precaution. There won't be anything that needs a "keep-alive" circuit anyway. I think what I'm likely going to do is find some marine switch and fuse panels. Something like this looks pretty appealing, having circuit breakers and fuse panel in one - make things simpler:

https://www.amazon.com/VETOMILE-Wat...F8KC59ZAF73&psc=1&refRID=03E437665F8KC59ZAF73

For some of the higher amperage things I might have to put in a relay and then a separate fuse, but I think mostly that'd probably do the trick. I'm somewhat debating when I want to start work on the electrical system, but I think that probably will come pretty far down the road. I at least want to get the car rolling and steering and run the brake and fuel lines before I get into the electrical system. If nothing else, I think that will make it more apparent where the wiring needs to/should go.

One of the problems I'm having at this point is that I'm running out of the things to do that can be done in a shorter block of time and am more at the point where the things that I'm going to do will require a dedicated day, or at least dedicated morning/afternoon to do well. Fortunately the weather is getting warmer and it's staying light later.

 

[SoonerAviator]

How big of a rectangular hole are we talking about? If nothing too expansive, a Dremmel with a cutoff wheel ought to do it pretty easily. You could clean up the corners with snips or file if needed.

 

[Ted]

How big of a rectangular hole are we talking about? If nothing too expansive, a Dremmel with a cutoff wheel ought to do it pretty easily. You could clean up the corners with snips or file if needed.

The big one is maybe 12”x6”. The Dremel idea came to mind.

 

[Tarheelpilot]

Does painless make a harness you could use as a base?

 

[SCCutler]

While I am not inherently against a homebuilt (and may build one someday myself), the RV-10 is not on the list. It's a good airplane for a lot of people and a lot of missions, but does nothing that I want to do. If I wanted something like that, I'd buy a Comanche 250/260. Or maybe find a 400.

Comanche 400. Hubba.

 

[Ted]

Does painless make a harness you could use as a base?

I've looked at their products, but really anything I've seen of theirs is really more than I'm looking for in terms of capability/wiring, and not particularly cheap for what you get. I think their stuff makes more sense if you're wiring a normal car that has more "normal car" things like power windows and locks.

I may change my mind, but when I take a look at the various pre-fabbed options and what they actually provide, it seems like it makes more sense to buy a plug-n-play EFI setup, not so much for the main wiring harness.

 

[Tarheelpilot]

I've looked at their products, but really anything I've seen of theirs is really more than I'm looking for in terms of capability/wiring, and not particularly cheap for what you get. I think their stuff makes more sense if you're wiring a normal car that has more "normal car" things like power windows and locks.

I may change my mind, but when I take a look at the various pre-fabbed options and what they actually provide, it seems like it makes more sense to buy a plug-n-play EFI setup, not so much for the main wiring harness.

I have come to the same conclusion about their pricing over the years. Nice products but I never could pull the trigger.

 

[FormerHangie]

The big one is maybe 12”x6”. The Dremel idea came to mind.

How big of a rectangular hole are we talking about? If nothing too expansive, a Dremmel with a cutoff wheel ought to do it pretty easily. You could clean up the corners with snips or file if needed.

I have a RotoZip saw, and I see that there is a metal cutting bit available for it. I've never tried it on metal, but I can testify to its effectiveness on wood and especially sheetrock. The challenge in cutting with a RotoZip is that its rotation makes cutting extremely easy in one direction, maybe a little too easy. My experience with reciprocating saws on sheet metal isn't positive, they tend to beat the edges up pretty badly.

Have you considered one of those nibbler attachments for your drill? They appear to do a pretty decent job.

 

[Ted]

I have a RotoZip saw, and I see that there is a metal cutting bit available for it. I've never tried it on metal, but I can testify to its effectiveness on wood and especially sheetrock. The challenge in cutting with a RotoZip is that its rotation makes cutting extremely easy in one direction, maybe a little too easy. My experience with reciprocating saws on sheet metal isn't positive, they tend to beat the edges up pretty badly.

Have you considered one of those nibbler attachments for your drill? They appear to do a pretty decent job.

That RotoZip looks like that could be a good potential option, thanks. I'd want to try on a scrap piece first probably. I'm not familiar with the nibbler drill attachments, that could be another option, any links to ones you'd recommend?

 

[jesse]

I would just cut it with a cutoff wheel on a dremel. It will make VERY quick work of aluminum and is easy to control accurately if you trace the line.

I’ve cut everything from plastic to wood to aluminum to steel with a dremel. It’ll cut anything if you’ve got enough wheels...steel goes through them fast but I’ve cut through some pretty thick ****.

 

[Ted]

I would just cut it with a cutoff wheel on a dremel. It will make VERY quick work of aluminum and is easy to control accurately if you trace the line.

That'd probably the simplest option since I already have cutoff wheels for my Dremel. But... then I don't get to spend money on another tool.

 

[Matthew]

Is the firewall panel already mounted?

If not: Is it flat? How thick is it?

I know a guy with a laser.

 

[Ted]

Is the firewall panel already mounted?

No.

If not: Is it flat?

Yes.

How thick is it?

Not very thick... I'm not sure the exact thickness but it's fairly flimsy.

I know a guy with a laser.

Is it a shark?

 

[Matthew]

^^^ This isn't it, but it's similar. I'll check on it, we use it a lot for Lexan and a few other materials. I'll see if it's the right beam and wattage for aluminum and what thickness it can cut. I'm pretty sure we'll need to put together a .DXF file or similar for the holes you need. The XY gantry is just a plotter with a laser instead of a pen. Getting the holes placed properly would be the trick. You only get one try. In the image above, the parts and associated holes are cut in a sheet, so the holes are already aligned with the parts because they are all the same drawing. Adding holes to an existing part is a little trickier because you have to get everything properly oriented first.

edit:

The guy I need to talk to is stuck in MSP.

My guess - yeah, we can do it, but it's probably going to be more trouble than getting a Dremel or Rotozip.

 

[Ted]

My guess - yeah, we can do it, but it's probably going to be more trouble than getting a Dremel or Rotozip.

That would be my guess as well. Plus the piece is painted, which probably is bad with a laser.

Appreciate the thought, but I'll figure out a RotoZip, Dremel, etc. I think.

 

[Matthew]

... the piece is painted, which probably is bad with a laser.

It would char the paint around the edges regardless of which cut side is up. I'd probably have to make a jig to hold it, do test cuts on paper for placement, then put the panel in the jig and let 'er rip. I could program it to etch your signature on it too, for the "Banhammer Signature Edition".

 

[Ted]

I could program it to etch your signature on it too, for the "Banhammer Signature Edition".

Now THAT could be cool... maybe somewhere along the lines we could find a place to put in a fun little personalization for the Cobra if it wouldn't be much trouble.

 

[Matthew]

Now THAT could be cool... maybe somewhere along the lines we could find a place to put in a fun little personalization for the Cobra if it wouldn't be much trouble.

I can probably etch that on a small piece you could attach somewhere. You want an etching of your picture? That might personalize it too much!

 

[PaulS]

You need a nibbler tool, I believe that's what my buddy used when he built his. You can get electric or hand operated. Just drill a hole and go to town.

 

[Ted]

You need a nibbler tool, I believe that's what my buddy used when he built his. You can get electric or hand operated. Just drill a hole and go to town.

That’s it! I used one of those at some point years ago.

 

[FormerHangie]

That RotoZip looks like that could be a good potential option, thanks. I'd want to try on a scrap piece first probably. I'm not familiar with the nibbler drill attachments, that could be another option, any links to ones you'd recommend?

I don't have any personal experience with nibblers. There was a thread a while back where someone was asking about which hand nibbler to get, and it got me investigating them. I wish I'd known there was such a thing back in my racing days, it would have saved a lot of time if we'd had one.

 

[-KLB-]

Wait, this doesn’t currently have ignition issues?

There are air powered nibblers that make quick work of holes like that. Be aware that all nibblers, especially the air ones make a bunch of razor sharp crescents (especially if cutting steel) that will pierce shoe soles and hitch rides to lots of places to atttack bare feet. So use them someplace you can hopefully contain the mess, and clean it up right away.

 

[Ted]

Wait, this doesn’t currently have ignition issues?.

Well the engine doesn’t run and there is no engine therefore there is no ignition system so it kinda has ignition issues.

 

[MIFlyer]

Made a bit of progress on the Cobra this evening. I finished drilling the holes for the panels for the heater core and AC condenser, and then I drilled the holes for the panels in the left side trunk panel.

I'm getting to the point where I'm about to run out of panels. I have 5 more panels remaining (all in the trunk). After that there are some smaller panels, but those all come much later in the build process. So really, I'm getting to the point where I'm going to have to start pulling some parts out of the parts car soon and/or buying some other parts that I'll need to put on the thing. Really, the things I need to be working on next are pulling the rear end and pedalbox out of the parts car so that I can get working on that. I'm also running very thin on clecos, but given that I'm almost done drilling aluminum panels, I think I'll survive with what I have.

However one thing that's come to mind as a tool I need, and that's something that's good for cutting holes in the aluminum. I have to cut a retangularish hole in the firewall panel for the HVAC, and then I also am thinking I'm going to cut a hole in the rear seat panel to provide some access to the forward trunk area. I have a jig saw but I don't feel like that would do the job very precisely. Any recommendations for an appropriate tool to consider?

If I were to follow the instructions, I would be using the Mustang wiring harness. I don't want to do that because 1) it's 25 years old and going to be brittle/broken if I remove it and 2) it's got a lot of functions I don't need/won't use. So I'm planning on making my own wiring harness. The electrical system is going to be pretty simple. Circuits will be for the EFI, fuel pump, ignition, lights (probably a couple different circuits to split up the lights), starter relay, HVAC, and heated seats. I'm planning on putting a master battery cutoff as those are recommended for the cars as a general safety/anti-theft precaution. There won't be anything that needs a "keep-alive" circuit anyway. I think what I'm likely going to do is find some marine switch and fuse panels. Something like this looks pretty appealing, having circuit breakers and fuse panel in one - make things simpler:

https://www.amazon.com/VETOMILE-Wat...F8KC59ZAF73&psc=1&refRID=03E437665F8KC59ZAF73

For some of the higher amperage things I might have to put in a relay and then a separate fuse, but I think mostly that'd probably do the trick. I'm somewhat debating when I want to start work on the electrical system, but I think that probably will come pretty far down the road. I at least want to get the car rolling and steering and run the brake and fuel lines before I get into the electrical system. If nothing else, I think that will make it more apparent where the wiring needs to/should go.

One of the problems I'm having at this point is that I'm running out of the things to do that can be done in a shorter block of time and am more at the point where the things that I'm going to do will require a dedicated day, or at least dedicated morning/afternoon to do well. Fortunately the weather is getting warmer and it's staying light later.

You probably want a fun radio and console phone charger?


Sent from my iPad using Tapatalk

 

[Ted]

You probably want a fun radio and console phone charger?

I’ve decided no radio for this car. Lots of people put them in, but general consensus is you can’t hear it while driving anyway. Our Harleys have radios and we can hear those fine, but reality is these days I’m more of a “turn the radio off and enjoy the drive” type. I figure I can use ear buds and my phone if I want to listen to tunes. Maybe not entirely legal but I’ll be using ear plugs of some sort when driving much of the time I suspect. No reason to make the tinnitus worse any faster than necessary.

I do figure I’ll put in a USB charger and cup holders. Some of the marine switch panels I’ve looked at have USB chargers built in, so that seems a logical step.

 

[SoonerAviator]

I own both a Dremmel and a Rotozip, as well as pneumatic cutoff tools. For fine cuts less than a foot, the Dremmel is much easier to control and it won’t get away from you. The Rotozip makes quicker work of things and can handle thicker materials, but if it snags or hangs up it can make a mess of things. Pneumatic cutoff wheels are more easily handled than the Rotozip, but don’t have the consistency in wheel speed or torque. Choose wisely.

Nibblers are fine, especially the pneumatic type, but for a rectangular 12x6 hole I’d pass on them. If you have more complex shapes they’re a better option.

 

[Matthew]

I found a parts car for you:

 

[Ted]

I found a parts car for you:


View attachment 73474

Perfect! I was wanting velocity stacks...

 

[FormerHangie]

I've looked at their products, but really anything I've seen of theirs is really more than I'm looking for in terms of capability/wiring, and not particularly cheap for what you get. I think their stuff makes more sense if you're wiring a normal car that has more "normal car" things like power windows and locks.

I may change my mind, but when I take a look at the various pre-fabbed options and what they actually provide, it seems like it makes more sense to buy a plug-n-play EFI setup, not so much for the main wiring harness.

Have you looked at the Ron Francis harness for your car? $550 is not an insignificant amount of money, but if it's plug and play I can see where it would be worth the money.

 

[Ted]

Have you looked at the Ron Francis harness for your car? $550 is not an insignificant amount of money, but if it's plug and play I can see where it would be worth the money.

I’ve been told it’s not very good and isn’t worth the money. I figure for a couple hundred bucks I can build my own that does exactly what I want.

 

[Ted]

Today I managed to get some more drilling done with the help of my kids, almost finishing up the trunk panels. The only reason I didn’t finish fully was because I ran out of drill bits, I only have around 5-10 holes remaining to drill, at which point I’m done with drilling aluminum panels until final assembly.

I’m somewhat concerned that I may have screwed up by reading the manual on the steering rack. Specifically it said to cut 1.75” off of the end of each of the inner tie rods. I did, but it looks like there’s a major tow in now. Of course there’s no weight on the suspension but I’m not convinced weight will fix that. It’s a minor issue if it turns out to be a problem.

I also cut the hole in the firewall for the HVAC. Then when I went to smooth out the edges with my grinder, the grinder caught the aluminum and ripped it. Fortunately it was in a corner and after mocking things up with clecos I might have to make a patch but it’ll be fine. It’s in an area nobody will see anyway.

At this point I really can’t do anything else significant until I either buy more parts or start pulling parts off the parts car. I need to pull the rear suspension and the pedal box first, so next good day to work outside that’s probably what I’ll be working on.

 

[Ted]

I've now had something come up that makes me rethink my engine a bit. I had been planning on trading the 302 and T-5 out of my parts car for some parts he sells for the Cobra. I checked in with him and he's decided he doesn't need another project. I completely understand and respect that, no hard feelings.

So now I'm back to thinking about drivetrain, especially since I have this engine and transmission combo that works (other than the bad clutch). The description for the engine included that it was rebuilt, GT40P heads, E303 cam, flat top pistons, new rods. Since my aluminum heads (that I want to use) have 2.02/1.60 valves I don't think flat top pistons will work. I have no idea if what he said was truthful, and I also don't want to use the E303 cam as I want to go with a solid cam of some sort (whether roller or flat tappet) just for the fun of it. I don't want GT40P heads mostly because I don't want iron heads. So if the bottom end is in good shape, I could either get different heads with smaller valves (which might not be a bad idea on a street car anyway), or maybe hone/bore it for different pistons with valve reliefs.

Transmission wise, I had been planning on a TKO. I'd also been thinking about doing a T-5 with straight cut gears to get more strength out of it. So this gives me a potential to do that.

The car's going to weigh around 2400 lbs, and my goal is lightweight and responsive, high compression. So what really appeals here about this idea is that the 302 would theoretically be a bit more responsive with about a 1/2" shorter stroke, the T5 is lighter than the TKO (provided it's strong enough to handle the power). T5s are around 15 lbs lighter than the TKO so that makes for a good weight savings option.

It's easy enough to pull the engine, pull the heads and the oil pan and do a basic inspection, so that might be a worthwhile first step. I need to start pulling apart the parts car anyway.

From doing some Googling of various dyno runs, getting 400 HP from a 302 is still pretty doable it seems (which is my goal). And if the bottom end is sound on the thing, it's a roller cam 302 that I can easily enough swap another cam into, swap some heads on, either reuse or put the different intake on, and call it a day.

 

[SoonerAviator]

I’d still sell the 302/T5 on Craigslist or similar. Those are easy to flip. I’d still go after a stroked 302 or a 351w with aluminum heads and a TKO if you’re concerned about saving weight. I wouldn’t even consider trying to salvage whatever is in that unknown 302 you have. If anything I suppose you could still use the engine you have and strip it down to a bare block to rebuild to suit your specs, but it’s not going to save you much money and zero time. I’m the type who’d rather build what I want the first time instead of just accepting whatever I had lying around, so you may have a different outlook. I’d just hate to get it all buttoned up and be wishing I had invested a few hundred more to get the drivetrain I really wanted.

 

[Zeldman]

My experience back when I used to buy used race engines was I never got a good surprise when I opened the engine up to see what I had bought.

 

[Ted]

I’d still sell the 302/T5 on Craigslist or similar. Those are easy to flip. I’d still go after a stroked 302 or a 351w with aluminum heads and a TKO if you’re concerned about saving weight. I wouldn’t even consider trying to salvage whatever is in that unknown 302 you have. If anything I suppose you could still use the engine you have and strip it down to a bare block to rebuild to suit your specs, but it’s not going to save you much money and zero time. I’m the type who’d rather build what I want the first time instead of just accepting whatever I had lying around, so you may have a different outlook. I’d just hate to get it all buttoned up and be wishing I had invested a few hundred more to get the drivetrain I really wanted.

My experience back when I used to buy used race engines was I never got a good surprise when I opened the engine up to see what I had bought.

Valid points, and we all know what happened on the last engine that I tore into found. Of course, that engine wasn't running. This one is running, and running at least reasonably well. So that's a good start. No rod knocks, good oil pressure (at least according to the Ford factory gauge), and I haven't observed any leaks under the car (yes it has oil in it).

To correct a few things, though, I wouldn't just be using what I have around, and there are some benefits that I'm thinking of.

Transmission: The Cobra is really designed around the T-5, although TKOs are popular because you can buy them and they're turn key. However they don't fit great into the transmission tunnel. The TKOs add 15 lbs as well, and since the bellhousing is different from a T-5 I have to buy a new one of those. The T-5 out of the box isn't strong enough, but various replacement gear setups that reduce the helix are available. While they aren't cheap, they are cheaper than the full cost of a TKO. I've always wanted to do a transmission rebuild, and also wanted to run a closer to straight cut gearbox - I love transmission whine. I also love TKOs, I've owned two of them, but that also loses some appeal since I've done it before. The T-5 also has an 0.59 5th gear as opposed to an 0.62 or 0.68, and the 0.59 will fit with 3.73s better. So this seems like it could save some money and get me a result that fits this car better, as well as some goals I've had. The one negative I'll give is I love the harder shifting nature of the TKO, although a modified T5 will probably get closer to that.

Engine: I've been going back and forth on this since the beginning of the project. I'd initially been thinking 351 because they're cheaper/easier to buy and MORE POWER! But reality is the goal of this car is lightweight and well balanced, which pushed me towards the idea of a 302-based engine and thus was thinking the 347. Again, this is a lightweight car, so lightweight is a good thing. Really if I had my way I would be doing an aluminum block. But this is a 94 roller block, so it's a good starting point. What's inside? Good question, unknown. I wouldn't be leaving the cam (E303) or heads (GT40P) on. I want aluminum heads (mostly for weight) and I want a solid roller cam (mostly for the sound, I realize that it's unnecessary technically for my application), so I'd change those out. Either using the aluminum heads I have now, or swapping them for some different aluminum heads.

Obviously a 302 would have less torque than a 347. It would also have a shorter stroke and theoretically be a bit revvier. In a 2400 lb car and with 3.73 rear gears, I'm not too concerned about having insufficient torque, either.

The engine and transmission essentially have to come out of this car anyway. I suppose I could make an argument that they could stay in the car if I'm not using them, but pulling them isn't too bad to do. From there pulling the transmission to look at things there, and then pulling the oil pan again isn't too bad. So at least having a look-see seems reasonable. Of course, doing compressions as well to make sure there are no red flags there.

The other option is to try to find another buyer for these bits as-is, and then stick to the previous plan.

 

[jesse]

I would sell the engine as-is. Then I would order a short-block off the InterWebs. After that, I'd be slowly ordering parts and simultaneously building up the engine while I built the car.

At the end of the day....if I was going through the work to literally build a whole car...I wouldn't stop short of building the engine...that would never sit right with me and I'd never be happy about what was under the hood. Building the engine would be more interesting to me than building the car..and I like new parts.

The above is how I plan to do the boat engine when I do it. One of these days I'm just going to order the short-block and get started. I like the idea of having a spare engine and sterndrive ready to go sitting in my garage.

 

[Ted]

I would sell the engine as-is. Then I would order a short-block off the InterWebs. After that, I'd be slowly ordering parts and simultaneously building up the engine while I built the car.

At the end of the day....if I was going through the work to literally build a whole car...I wouldn't stop short of building the engine...that would never sit right with me and I'd never be happy about what was under the hood. Building the engine would be more interesting to me than building the car..and I like new parts.

"Hi, My name is Ted and I built this car, except for the engine". That just doesn't make any ****ing sense and doesn't sound like something Ted should be saying.

The above is how I plan to do the boat engine when I do it. One of these days I'm just going to order the short-block and get started. I like the idea of having a spare engine and sterndrive ready to go sitting in my garage.

Valid for sure, and that's another option I've been considering. I am trying to build this as much of a "new" car as possible with as many new or otherwise refurbished parts as possible. The engine in some ways is the most scary part of that as I want it to work and never have to take it out again, at least not for a long time.

To me the transmission makes more sense to upgrade and reuse since there are more technical benefits there for me, and I think it's a better solution. The engine I have a harder time with since it's a turn-key unit (literally) and has a lot of things I'd be changing. Could sell it as-is probably to someone building a Cobra locally, and then easily enough procure what I need to build an engine myself, either buying the short block and going from there.

 

[Zeldman]

This one is running, and running at least reasonably well. So that's a good start. No rod knocks, good oil pressure (at least according to the Ford factory gauge), and I haven't observed any leaks under the car (yes it has oil in it).

Are you able to drive it? If so, are you happy with the feel of acceleration it has? If the compressions are good and you are happy with it then put in the cam you want and the heads you want. Save the new engine for a winter project down the road when you have a better idea of what you want. On the other hand, with the heads off and the cam out you are not that far away from a rebuild.

The T-5 should work out Ok. Most people that break them do so with a bad shift. (ask me how I know) The 41% overdrive gear will really make a highway trip less stressful on the ears as well as the gas tank.

I had an '69 Nova with a built 396, 3:73 gears and a Muncie 4 speed. The national speed limit was 55, and at that speed the motor was really wound up. Buuut..... at 55, slip it back to 3rd gear......

Good thing gas was only around 38 cents a gallon.....