DuPuis Family Cobra Build

Ted DuPuis said:
Another thing I've forgotten to talk about was coolant. There's standard green coolant, Dexcool, or something more exotic like Evanscool. Jay Leno uses the Evans coolant in his cars, and has talked about the fact that it's waterless so it doesn't expand, system therefore runs very low pressure, no water so you don't have internal corrosion/rust issues. There are some seemingly reasonable advantages to it.

Coolant is honestly something I've never spent much time thinking about because the cars I've worked on have always had something already in there that I've pretty much had to put in to stick with what the thing has in it already. But this time, I'm starting from new, and get to decide.

Most people I think stick with the green stuff just because it's simple and cheap. It's also universally available. OEMs have mostly switched over to some sort of DexCool/orange coolant, which is apparently because there are adavntages ot it vs. the green stuff. The Evanscool stuff looks interesting, but you can't mix it with anything else and it's $45/gallon on a system that will probably take 3-4 gallons. If a hose pops off, that suddenly gets really expensive.

So, something new to think about. If anyone has thoughts, I'm all ears.
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Start with water only. That way you can just let it go when (not if) there are problems that need to be addressed or a hose blows off.

I’d also consider staying with water. It does a better job cooling than a mix of water/antifreeze. When we do head crack testing at work we intentionally use a mix of 75/25 coolant to impede heat transfer.
 
mondtster said:
Start with water only. That way you can just let it go when (not if) there are problems that need to be addressed or a hose blows off.

I’d also consider staying with water. It does a better job cooling than a mix of water/antifreeze. When we do head crack testing at work we intentionally use a mix of 75/25 coolant to impede heat transfer.
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Although the Cobra will always be garaged (and the garage is now heated) and I’m unlikely to drive it any significant amount when it’s below freezing, the consequences of water freezing up if it happens are high enough that I don’t think I want to take that risk.

I do agree with the “when not if” part about the cooling system though. Food for thought...

One other thing with this car is that I do hope to keep it a long time. But while I’d like to think I won’t do any engine work to it, the reality is that I’ll end up doing something at some point.
 
Ted DuPuis said:
Although the Cobra will always be garaged (and the garage is now heated) and I’m unlikely to drive it any significant amount when it’s below freezing, the consequences of water freezing up if it happens are high enough that I don’t think I want to take that risk.

I do agree with the “when not if” part about the cooling system though. Food for thought...

One other thing with this car is that I do hope to keep it a long time. But while I’d like to think I won’t do any engine work to it, the reality is that I’ll end up doing something at some point.
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Don’t forget that antifreeze also contains a corrosion inhibitor. Running straight water is fine for shaking out any bugs, but I’d rather have coolant mix in it to add a layer of protection.
 
My brother sent me these pix of what drove into his shop today. Someday you’ll have to take your Cobra there, too.


BB52B833-C762-4195-9466-92DEBDD624E9.jpeg3D2DFB7E-6705-4426-AF98-A79637031D2C.jpeg9FC77118-B49B-46A5-A2A5-C38E679A362E.jpeg
 
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Forgot to mention that it took a second trip to the auto parts store to get the belt figured out. I had figured 32-34". 31 1/4" (per Gates) was the size I ended up needing. So now I have to figure out how exactly I'm going to make the bracket for the alternator. That part I'm still trying to figure out, and I may find that I have to go back to one of the bit longer belts. I think I can make this work fine where it is, and I like having the alternator tucked in closer to the engine so long as it doesn't interfere with any other maintenance.

Once the crank position sensor I ordered comes in, I can see if that's the correct one and check that off the list (hopefully), and maybe then figure out some hoses for the heater.

Laurie heads back to work tomorrow, so maybe I'll pick up a few more details at the auto parts store during the week and keep moving forward over the weekend. But I also need to order the manifold pressure sensor.
 
And I knew I was forgetting a couple other details.

I went ahead and picked up a distributor for an '84 F-250 with a 351W. This was the cheapest rebuilt distributor that'll serve the purposes of plugging the distributor hole and (more importantly) spinning the oil pump. However first I'm going to put it in to make sure that it does, in fact, fit and do what it's supposed to.

Ultimately I don't want a distributor, though, since I won't need one. A friend of mine is going to machine the distributor to make it smaller and not look like a distributor that's not hooked to anything. So I'll do a test fit and send it off to my friend.

Along with that, I'm going to send the emergency brake handle. My friend also said he'd machine an aluminum cover for it that would look better than either the plastic that Ford sends from the factory or the cheap aftermarket ones, make it more like the original hand brake handles these came with.

So, yeah, more details.
 
Dunno if it would help, but I can take a pic of the alternator bracket on my 351w to see if it would inspire you. It's just a curved/L-shaped arm which pivots at the bottom and uses one bolt in a slotted section to set belt tension. Also a single-wire alternator/v-belt, but that doesn't really affect the mounting orientation.
 
SoonerAviator said:
Dunno if it would help, but I can take a pic of the alternator bracket on my 351w to see if it would inspire you. It's just a curved/L-shaped arm which pivots at the bottom and uses one bolt in a slotted section to set belt tension. Also a single-wire alternator/v-belt, but that doesn't really affect the mounting orientation.
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I appreciate it, but I think I can figure out what I want to do - just may take a bit. The part that confounds things is the fact that I will need to bolt it to where the timing cover is bolted to the engine, but the crank position sensor is also there. There are a few ways I could do it. I think once the car is in the air it will be obvious which one I should go with.
 
Ted DuPuis said:
a 351W.
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Speaking of the 351, it's too bad we can't upload .wav files here, a mechanic buddy of mine who occasionally builds engines sent me a .wav of a pretty wild 351C build dyno pull. It sounds glorious!
 
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Bill Jennings said:
Speaking of the 351, it's too bad we can't upload .wav files here, a mechanic buddy of mine who occasionally builds engines sent me a .wav of a pretty wild 351C build dyno pull. It sounds glorious!
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It can't be uploaded directly but you can insert it if it's uploaded someplace else (YouTube, Vimeo, etc.).
 
Didn't get much time in the garage today, but got to work on the Cobra a bit. Did two things:

1) Replaced the thermostat housing (90 degree) with the "new" one I bought (45ish degree). Much, much better. Really a thermostat housing with a completely horizontal output would be ideal, but the 45 degree angle makes the in-line filler neck significantly lower, and just looks better all around. The 90 degree housing took eyes away from the velocity stacks, which is something I want to avoid.

2) I made the brackets for the AC condenser, and started making the brackets for the cooling fan. Having about a 3/4" spacing is arguably not ideal for optimizing airflow, but I think it will be fine. One other benefit of the spacing is it will hopefully minimize (or at least ease the cleaning of) leaves that will get in there. A lot of older cars that I've worked on have had significant radiator blockage because of leaves that get in between the condenser and the radiator. Especially on a car with no grille and a 45 degree (roughly) slanted radiator, I see this being a concern on the Cobra. With this spacing I'll at least be able to get a tool up in there to help keep the area clean. Plus, with how oversized the cooling system should be, I think it'll be fine.

2a) Going with that, I bent the hard lines for the AC a bit, and I figure I'll have to bend them some more. The hard lines as they arrived overlapped eachother and wouldn't work. So I bent them a bit to get them out of the way a bit further, and also allow for moving the AC condenser to a more optimal mounting location. It's not quite centered (which would obviously be ideal since it's visible from the front with the lack of grille) but it should look acceptable.

Another thing I'm thinking about is whether I should go for an oil cooler. Right now I'm not, and for a ~400 HP 351W with a racing oil sump and as much cooling capacity as it has, I'm not sure it's truly necessary. On the street it's definitely not, more a question of whether it's needed on the track. One thing I'm figuring I want to do is take the car to the track over the summer with the body still in gel coat, since I plan to do the body work over the winter. If I start to see the oil getting too hot, then that'll be my indication to add one when the body comes back off for paint. Or maybe I should do it now. Maybe I'll ask the Factory Five group.

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Ted DuPuis said:
Didn't get much time in the garage today, but got to work on the Cobra a bit. Did two things:

1) Replaced the thermostat housing (90 degree) with the "new" one I bought (45ish degree). Much, much better. Really a thermostat housing with a completely horizontal output would be ideal, but the 45 degree angle makes the in-line filler neck significantly lower, and just looks better all around. The 90 degree housing took eyes away from the velocity stacks, which is something I want to avoid.

2) I made the brackets for the AC condenser, and started making the brackets for the cooling fan. Having about a 3/4" spacing is arguably not ideal for optimizing airflow, but I think it will be fine. One other benefit of the spacing is it will hopefully minimize (or at least ease the cleaning of) leaves that will get in there. A lot of older cars that I've worked on have had significant radiator blockage because of leaves that get in between the condenser and the radiator. Especially on a car with no grille and a 45 degree (roughly) slanted radiator, I see this being a concern on the Cobra. With this spacing I'll at least be able to get a tool up in there to help keep the area clean. Plus, with how oversized the cooling system should be, I think it'll be fine.

2a) Going with that, I bent the hard lines for the AC a bit, and I figure I'll have to bend them some more. The hard lines as they arrived overlapped eachother and wouldn't work. So I bent them a bit to get them out of the way a bit further, and also allow for moving the AC condenser to a more optimal mounting location. It's not quite centered (which would obviously be ideal since it's visible from the front with the lack of grille) but it should look acceptable.

Another thing I'm thinking about is whether I should go for an oil cooler. Right now I'm not, and for a ~400 HP 351W with a racing oil sump and as much cooling capacity as it has, I'm not sure it's truly necessary. On the street it's definitely not, more a question of whether it's needed on the track. One thing I'm figuring I want to do is take the car to the track over the summer with the body still in gel coat, since I plan to do the body work over the winter. If I start to see the oil getting too hot, then that'll be my indication to add one when the body comes back off for paint. Or maybe I should do it now. Maybe I'll ask the Factory Five group.

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I've never come across a track driven car that didn't need an oil cooler. If you only do one or two track events per year you may get away without it, mainly because your skill level will never get high enough to where you're pushing the car hard enough to need one. If you do more than that, you'll be driving hard enough to where you're most likely to need it, especially where you live.
 
FormerHangie said:
I've never come across a track driven car that didn't need an oil cooler. If you only do one or two track events per year you may get away without it, mainly because your skill level will never get high enough to where you're pushing the car hard enough to need one. If you do more than that, you'll be driving hard enough to where you're most likely to need it, especially where you live.
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Those are all good points. And of course it would also depend on the track that I was driving, and the duration of driving at a single stretch. 10 minutes vs. 30-60 (I'm also not sure how long most of these sorts of events are). The fact that I have a racing oil sump that holds something like 10 quarts also influences things there.

I asked the question on the Factory Five Facebook group and got mixed answers. Mostly people who clearly had no clue gave me answers that were useless. Some also think that oil should be much cooler than it really should be. A few folks said that even with big blocks they didn't find they needed coolers, but I don't know how much they were racing.

I figure what I'll do is run the first season without and see what my oil temps really are, and then when I pull the body to do body work I can put it on if I find it useful. That was also my plan with power brakes and steering, so I think it's a good plan.
 
Ted DuPuis said:
Those are all good points. And of course it would also depend on the track that I was driving, and the duration of driving at a single stretch. 10 minutes vs. 30-60 (I'm also not sure how long most of these sorts of events are). The fact that I have a racing oil sump that holds something like 10 quarts also influences things there.

I asked the question on the Factory Five Facebook group and got mixed answers. Mostly people who clearly had no clue gave me answers that were useless. Some also think that oil should be much cooler than it really should be. A few folks said that even with big blocks they didn't find they needed coolers, but I don't know how much they were racing.

I figure what I'll do is run the first season without and see what my oil temps really are, and then when I pull the body to do body work I can put it on if I find it useful. That was also my plan with power brakes and steering, so I think it's a good plan.
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Most track day sessions are 20 - 30 minutes, with 45 minutes to an hour between sessions. Depending on the length of the day, there will be three to six sessions, so between one and two hours on track for the day. Two hours on the track is a very full day. There are a few events that do have more than two hours; I haven't been to one.

You have lots of motor and a big oil pan, so you may get away without needing an oil cooler. We were running relatively low powered cars (10-12 lb/hp) with racing tires, so the great majority of a lap was at 100% throttle. We used to shoot for 210 degrees water and 230 degrees oil temperatures. You probably don't need to run the water that hot and that can run the oil a little hotter, since oil is better than it used to be, but I wouldn't want to see more than 250 degrees oil temperate for any length of time.

If you do need some oil cooling, Canton (the folks that make Accusumps) make an oil to coolant heat exchanger, which is neat because in addition to it cooling the oil, it helps bring up the oil temperature at the beginning of a session. It plumbs into the cool side our your radiator hose.
 
FormerHangie said:
Most track day sessions are 20 - 30 minutes, with 45 minutes to an hour between sessions. Depending on the length of the day, there will be three to six sessions, so between one and two hours on track for the day. Two hours on the track is a very full day. There are a few events that do have more than two hours; I haven't been to one.

You have lots of motor and a big oil pan, so you may get away without needing an oil cooler. We were running relatively low powered cars (10-12 lb/hp) with racing tires, so the great majority of a lap was at 100% throttle. We used to shoot for 210 degrees water and 230 degrees oil temperatures. You probably don't need to run the water that hot and that can run the oil a little hotter, since oil is better than it used to be, but I wouldn't want to see more than 250 degrees oil temperate for any length of time.

If you do need some oil cooling, Canton (the folks that make Accusumps) make an oil to coolant heat exchanger, which is neat because in addition to it cooling the oil, it helps bring up the oil temperature at the beginning of a session. It plumbs into the cool side our your radiator hose.
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Yeah, I tend to feel that full throttle in the car will be reserved for straights. There won't be the traction for full throttle in most turns, at least I don't think so. Maybe if I had some super sticky tires.

I had thought about the oil/coolant heat exchanger idea. A lot of radiators have transmission coolers built in to the end tanks, and I would probably run oil through that if it was an option (and appropriately sized/rated for the pressure and flow). My radiator doesn't have that, but I could do something in-line like you're talking about. That said, there's also a nice kit that looks very attractive for an oil cooler in the front of the car.

So, I'll probably just evaluate and see.
 
What was the decision on the expansion tank? I think it would be a must have, if you want to avoid a wet mess and constant radiator topoffs.
 
Sac Arrow said:
What was the decision on the expansion tank? I think it would be a must have, if you want to avoid a wet mess and constant radiator topoffs.
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The SCCA, for one, will require a overflow container for any vent that could leak fluid: https://cdn.connectsites.net/user_f.../238/TNiA_Tech_Sheet_-_Atlanta.pdf?1503432989

That form is specific to Atlanta Motorsport Park, because AMP requires Snell SA2010 or later helmets, but the generic one for all the other tracks have catch can requirements as well.
 
Officially I haven't come to a conclusion yet. That said, an overflow container is one of those things that I could put in a lot of different places fairly easily, so if I do add one, it will be towards the end.
 
@Ted DuPuis

Did you receive the sparkplug wire crimping tool? It's been three weeks since I mailed it, and since I hadn't heard from you, I'm wondering if the USPS lost it.
 
3393RP said:
@Ted DuPuis

Did you receive the sparkplug wire crimping tool? It's been three weeks since I mailed it, and since I hadn't heard from you, I'm wondering if the USPS lost it.
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Yes I did, I apologize. I thought I had messaged you to thank you - apparently I didn't.

So, thank you! :)
 
I haven’t made much progress the past couple weeks, but last weekend I did get the radiator fan and the AC condenser mounted. I like the solution I came up with, hopefully the airflow is sufficient.

Among the other details I need to start working on, I need to do some work on the dashboard. I’ve decided that I want to go ahead and do a keyed ignition but I need to look at options. No steering lock is required (nor could it even be used) but I would like to find something with a more interesting key (and overall aesthetic) than the typical universal tractor ignition key you can find at the parts store. That would be period correct I suppose but I’d still like something more interesting.

Similarly I‘ll just get a standard headlight switch with built in dimmer for the dash lights.

I’m trying to figure out what I want to do for the high beams and horn. There’s a turn signal stalk I plan on using with a button at the end, which people often use for high beams or a horn. The center of the steering wheel doesn’t support a horn button (specifically the electrical to go with it). The manual has you place a physical button on the dash, but that doesn’t make it readily accessible.

I’m thinking the turn signal stalk is the place for the horn button (that’s also something I’ve seen on British cars before - the 88-92 I believe Jaguar XJ6s has it there) and is accessible. Where to put the high beams then? Not sure. There’s not really room for a foot switch as was done on old cars and on the dash itself would be less convenient. I’ve thought about a button on the shift knob, which would be convenient but I think get in the way and hit too much. So it’ll probably be on the dash itself.

Oh, and I need a horn...
 
Doing a search indicates that I'm probably not going to find an ignition switch that has Ford keys on it. There is a universal one with GM keys on it:

https://www.amazon.com/Universal-3-...ith+key+universal+ford&qid=1581430304&sr=8-13

Which seems kinda wrong in some ways (GM style keys on a "Ford"ish car). I could just go with generic keys, but what I like about proper automotive keys is that it makes it easy to make copies of them anywhere. And if they don't see GM on them, then I won't feel so bad. Maybe there's something else out there.

Horns... not sure. Want something small and loud. Preferably a British sounding horn. Or maybe the one that the Ford Excursions had... that thing was really loud. I definitely want a loud horn.
 
Ted DuPuis said:
I’m thinking the turn signal stalk is the place for the horn button (that’s also something I’ve seen on British cars before - the 88-92 I believe Jaguar XJ6s has it there) and is accessible.
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I had an Impala that had it there. It was fine if you didn't need it in a hurry as very muscle memory non-intuitive.
 
I think I'd rather have the high beams on the stalk, and a horn button on the dash. Maybe it's my experience with boats, but the horn is almost always on a panel switch. I also use the horn once a year, tops, on any vehicle so I'd rather have the convenience of the high beams up close since I use those constantly.
 
Pugs said:
I had an Impala that had it there. It was fine if you didn't need it in a hurry as very muscle memory non-intuitive.
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I think I'll get used to it quickly enough, and then probably just put a button for the high beams on the dash.

Bill Jennings said:
IMHO something like this would be cool, maybe with a hidden key somewhere to turn on/off master power to the car.

https://www.jegs.com/i/JEGS/555/110..._U1Nk_kC5MA6cymvepZuT3JTuu4R6oJxoCW5oQAvD_BwE
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I've thought about that as well and it was my initial idea. I am planning on a full on battery disconnect/master power, but I'm planning on that in the trunk.

I could defer on the decision for a while until I get a bit further along and mock up to have a better idea of what I could put where. I want to be able to pull up someplace and get out of the car with at least a medicore level of security without having to open the trunk. The key provides some of that.

Another option would be putting some hidden switch in an under/behind the dash area that I could reach. I suppose such a thing would only need to kill something particular, like the ECU, but I'd still prefer to have some level of semi-security (like a key).

Another way of going about it could be having a keyed ignition switch and then a start button. But that adds clutter to the dashboard without necessarily adding much on a street car.

SoonerAviator said:
I think I'd rather have the high beams on the stalk, and a horn button on the dash. Maybe it's my experience with boats, but the horn is almost always on a panel switch. I also use the horn once a year, tops, on any vehicle so I'd rather have the convenience of the high beams up close since I use those constantly.
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I think that's your boat experience talking. For me other than those Jaguars, the horn has always been on the steering wheel. Yes, my boat had the horn button on the dash, but that seems to be a boat thing.

I'll agree that I use the high beams more than the horn, but I use them less as far as a more urgent "don't run into me" moment. High beams are more deliberate for me.

Doing some searching, it does seem like a number of people did successfully install a floor switch for the high beams. So maybe I need to look into that more and see if it is doable...
 
Fords n the early to mid 80s had the horn honked by pushing in on the turn signal lever; I had a 1983 LTD like that. Worked fine, just like the 1969 Renault 10 I once had.
 
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Ted DuPuis said:
Doing some searching, it does seem like a number of people did successfully install a floor switch for the high beams. So maybe I need to look into that more and see if it is doable...
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I have always liked the high beam switch on the floor. For me, it takes too long to find the stalk on the steering column to dim the lights. And I left foot brake.

Horn. Mid 70s Cadillac high/low horns. Not one of those wimpy stick boy sounding horns like the one on my Subaru...

https://hornblasters.com/collection...ers-nathan-airchime-k5la-5485k-train-horn-kit
 
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Zeldman said:
I have always liked the high beam switch on the floor. For me, it takes too long to find the stalk on the steering column to dim the lights. And I left foot brake.

Horn. Mid 70s Cadillac high/low horns. Not one of those wimpy stick boy sounding horns like the one on my Subaru...

https://hornblasters.com/collection...ers-nathan-airchime-k5la-5485k-train-horn-kit
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I'm a fan of the floor hi/lo as well. I need to sit in the car on a milk crate or something and see if that seems like it would actually work.

...but I'm not spending over $2k on a horn.
 
^^^
No.
 
You could bring back the floor switch that engages the starter motor.
 
How difficult is it to wire in a clockspring or horn button for the steering wheel? What about mounting a low-profile momentary switch on the steering column? Use a PTT switch for an aviation tie-in, lol.
 
ja_user said:
You could bring back the floor switch that engages the starter motor.
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My primary concern there would be hitting the switch when driving by accident. Less of a problem if that switch is the high beam.

SoonerAviator said:
How difficult is it to wire in a clockspring or horn button for the steering wheel? What about mounting a low-profile momentary switch on the steering column? Use a PTT switch for an aviation tie-in, lol.
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That's a good question, and I'm not entirely sure of the answer there. Maybe worth looking into to see if anyone else has done it. The steering column isn't designed to have wires going through it, but that doesn't mean it couldn't be done. I can't remember whether the top half of the column is hollow or not.
 
What about having the horn work how most modern dimmer flash to pass switches do? Personally I think that would be an easier habit to develop, and maybe less fiddly than trying to push a button on the end of the turn signal stalk.
 
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