DuPuis Family Cobra Build

IK04 said:
The four-cam 4.6L in my Marauder has a clutch on the alternator that disconnects the drive above a certain RPM or when the throttle is WFO. less inertia and spinning mass during the .5 second upshifts.
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Huh, I've never heard of a clutch on the alternator for that reason. That's interesting. I've heard of that linkage (disconnecting the AC compressor with full throttle) but not alternator.

I have a Meziere electric pump, but it still has a pulley on it that spins freely, so there is a little loss there...
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I imagine that's essentially the same as an AC compressor with the clutch off, which is something close to zero. I'm assuming that pump has been reliable for you? That's what I have, although minus the pulley.

That cam sounds pretty sporty, but since you have an intake system that can suck huge CFM, you might be right. Again, driveability will be what you want it to be and if a screaming top end is paramount, then plan for the nasty cam and accept the soggy low end...
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Isky lists the cam that I bought as 2-6k RPM. However I'm pretty sure they calculate that for a 302 vs. a 351W (since they both can use the same cam, and do in this case). The bigger cam is advertised for 3-7k RPM, again, I think for a 302 vs. a 351W. The heads I have have 2.02"/1.60" valves and 190cc intake runners as I recall.

in a 2400 lb car with 3.73 gears, low end torque really isn't a concern and I wanted it to be more on the sporty side. Basically, I'm not going to do any changes now, but I think that low end driveability is something I'm willing to sacrifice for higher end power in a fun car, but I'll need to see how it drives. If the engine feels like it's really running out of steam at 5k RPM, I'm going to want a new cam. If it pulls well up to 6k, I will probably be fine with it as-is. But if the cam gets wiped out or I have an excuse to change it, spending a few hundred bucks to experiment and try a different cam sounds like something I might do. It's all for the future - for now I'm getting the thing driveable so I can drive it.
 
Yeah, when they put the freewheeling alternator on the Mustang and other SVO cars, drivers were concerned when they heard the weird whining sound n deceleration. It was a foreign sound to all of us. It sounded like something was broken. :eek:

Two inch intakes and over 3/4 inch of lift @7,000 RPM will dictate some serious springs and those solid lifters will be getting a workout! How much overlap is the 270 degree cam?
I have run 290 cams, but without the low-end killing overlap. I'd love to see a dyno curve on your setup when you get it dialed in. Sounds like fun!
 
IK04 said:
Two inch intakes and over 3/4 inch of lift @7,000 RPM will dictate some serious springs and those solid lifters will be getting a workout! How much overlap is the 270 degree cam?
I have run 290 cams, but without the low-end killing overlap. I'd love to see a dyno curve on your setup when you get it dialed in. Sounds like fun!
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The springs on there are the ones Edelbrock sends, and from talking to their tech support I should be fine as-is for the cam I chose. But you're probably right that if I went to the bigger cam with higher RPM that I'd be running into some potential valve float issues and needing bigger springs.

This is a fun car so longevity/ultimate reliability doesn't need to be supremely high. Obviously I don't want to be putting new cams in every 1,000 miles, but needing to do some level of maintenance on it over the winter is fine.

Overlap, I'm not sure the exact spec there, Isky might have it. But both of them have 108 degree lobe separation angles. Also remember those 270/290 numbers are advertised, not @0.050" lift, and it's a solid flat tappet not a solid roller. I felt that a flat tappet was a better value for this application and I could get sufficient performance for a much lower cost with that vs. a roller cam.
 
Outstanding. I will always love the rumble of an engine like that. Drives my wife nuts when we stop at a light next to someone's old muscle car and I roll down the window to listen.
 
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Matthew said:
Outstanding. I will always love the rumble of an engine like that. Drives my wife nuts when we stop at a light next to someone's old muscle car and I roll down the window to listen.
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The engine idle sound was a big part of what I was going for with my specs. I need to play with it some more to see final sound, but initial sound has me very happy.
 
Matthew said:
I see the YouTube shows you have 100 views. I think 30 of those are me.
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If you can subscribe another 350 times then I’ll hit the 1k subscriber mark. :)
 
Ted said:
If you can subscribe another 350 times then I’ll hit the 1k subscriber mark. :)
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You know, I’m computer incompetent. I don’t even know how to subscribe.
 
Kritchlow said:
You know, I’m computer incompetent. I don’t even know how to subscribe.
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If you have a YouTube account (which you can make independently or have it tied to your Gmail account, I’m sure there are other ways too) you simply go to my channel:

https://youtube.com/channel/UCaQHHoLTPa5QGklGwqXCoYw

And click the “Subscribe” button at the top.

You do need to have an account of some sort to subscribe.

1k subscribers is a goal for me, but it’s also where I can start monetizing. Not that I expect to get rich off of any of this like @SixPapaCharlie (who’s given me some really great tips on how to make better videos that I mostly haven’t implemented), but it would be cool, and I think the kinds of projects I do could be interesting to some audience.
 
This evening I spent a couple hours resetting the valve lash. This gets complicated since I made everything difficult with pedestal mounted rockers and a solid flat tappet cam, and therefore have to make shims to get the adjustment just right.

Isky provides a hot valve lash setting of 0.020”, which I’m running a little tight (aiming around 0.014” per the Isky tech recommendation) to get a hair more lift and duration out of the cam. With an iron block and aluminum heads, the clearances loosen up as the engine gets hot. Looking at the measurements I took when hot, it seemed that the exhausts didn’t loosen up quite as much as the intakes, which makes sense since the exhaust valves will absorb more heat and then the stems expand a hair more. At least, that sounds logical to me. So I set cold lash at 0.008” for intake and 0.010” for exhaust, and that seems to be about right. After my next run, I’ll pull the valve covers and check again.

One thing that was concerning was that a couple of the rocker bolts were loose. I did a Google search and apparently Ford issued a TSB on this and said blue thread locker should be used to keep them from backing out. So, what I’ll do is check the hot valve lash after my next run and put blue thread locker on all the bolts at that time.

I also ground down one side’s valve cover spacer to make it fit with my coil pack brackets. Need to do the other side, and then bolt the whole things together.

Next task on the car will be wrapping the headers, and once that’s done I can run it again and work on finishing up the wiring.
 
Ted said:
Next task on the car will be wrapping the headers, and once that’s done I can run it again and work on finishing up the wiring.
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Sounding good! No spring bind with the closer tolerances on the lash? It's small, so probably not a big deal, but good the check after another run.

As for header wrap... I hate that job! Double gloves and I still itch at times. Any thoughts of ceramic coating or using a header sleeve instead of the wrap?
 
rtk11 said:
Sounding good! No spring bind with the closer tolerances on the lash? It's small, so probably not a big deal, but good the check after another run.
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The springs are supposedly good for up to .570" lift, and with the 1.7 vs. 1.6 rockers (that's the bigger one) and running slightly tighter lash, that should get me around 0.515". Good point that it's worth checking, but I think I'm fine.

As for header wrap... I hate that job! Double gloves and I still itch at times. Any thoughts of ceramic coating or using a header sleeve instead of the wrap?
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Well, at this point I already have the wrap. The goal is mostly to reduce heat in the engine bay, specifically reduce heating of the brake line and master cylinder by the headers. I think the wrap will do a better job of that than ceramic coating. It's been probably 15 years since I did header wrap, which means I've thoroughly forgotten how much I didn't enjoy the job. :rofl:

I thought about doing that today, although I wonder if that might be pushing my 20 lb lifting limit a bit much.
 
Bill said:
OK, that lopey idle sounds totally bad ass!
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I spent a lot of time pouring through different cam specs to get a cam that I thought would get that the lopey idle sound I was looking for. With only 108 degree lobe separation angle on this cam, it's got a good amount of overlap and being a solid lifter flat tappet cam, that profile and valve opening and closing are hard and direct. Once I get things tuned better, we'll see what it sounds like. But So far, I'm quite happy with the sound.

Really, I put a lot of effort into looking at what the characteristics of the parts I chose would do for the visceral sensations of the car, not just the horsepower and torque curve. Maybe that should be what I open a shop to specialize in. ;)
 
I have an mp3 file I need to send you of an engine a friend in Boston helped build. 351 Cleveland, 4-barrel carb, pump gas, no nitrous, it pulled 700hp at 9500rpm. It doesn't even come on cam and clear it's throat until it hits 6000rpm. The customer wanted a street drag engine. Too bad we can't attach .wav or .mp3 files in posts.
 
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Bill said:
I have an mp3 file I need to send you of an engine a friend in Boston helped build. 351 Cleveland, 4-barrel carb, pump gas, no nitrous, it pulled 700hp at 9500rpm. It doesn't even come on cam and clear it's throat until it hits 6000rpm. The customer wanted a street drag engine. Too bad we can't attach .wav or .mp3 files in posts.
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I'd strongly considered making a really high revving 302 for the Cobra in that 6-9k RPM range. But the parts you need to support those revs get exotic (read: expensive), well above budget. Plus, then it really is a race engine that's not going to have very good street manners no matter how you tune it, and while I'm willing to give up a lot in street manners for this car, I can't give up everything.
 
This is the longer video on the preparations I did for first start, just published:

 
Matthew said:
Outstanding. I will always love the rumble of an engine like that. Drives my wife nuts when we stop at a light next to someone's old muscle car and I roll down the window to listen.
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My wife sometimes beats me to it, lol. Product of her having been raised around her father's muscle cars her entire life.
 
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Ted said:
Maybe I should make that my ringtone...
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The COO at my former company had a Harley idle/rev for a ringtone for his kids (not sure what the connection was-they didn't ride). But it was recognizable...
 
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Did the header wrap over lunch and after work today. I’ll need to do a couple of details before putting the header back in.

79C35B4E-3BD5-466B-BB1E-9F013C12F2D1.jpeg
 
Matthew said:
I I forgot: what’s the body color scheme?
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The plan is black with ghost black stripes (basically charcoal color) and then a red pinstripe where the ghost stripes meet the main body color.
 
Ted said:
The plan is black with ghost black stripes (basically charcoal color) and then a red pinstripe where the ghost stripes meet the main body color.
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Ahh, yeah. I remember now.

This will be awesome.
 
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Two comments on alternator clutches.

If you are the factory, and you want to cut the HP draw of the alternator, it is probably easier, more reliable and in line with other manufacturer initiatives to just have the ECU cut the field current at WOT/high RPM

The other part is something that the Crown Vic Police Interceptors have had to deal with for a while. With 200A alternators, the rotating inertia of the stator is enough that when the automatic up shifts, the engine drops RPM fast enough that with the high inertia stator, it would chirp the belt. The CVPI solution is a simple mechanical one way clutch to allow the alternator stator to overrun the belt drive RPM.
 
-KLB- said:
Two comments on alternator clutches.

If you are the factory, and you want to cut the HP draw of the alternator, it is probably easier, more reliable and in line with other manufacturer initiatives to just have the ECU cut the field current at WOT/high RPM

The other part is something that the Crown Vic Police Interceptors have had to deal with for a while. With 200A alternators, the rotating inertia of the stator is enough that when the automatic up shifts, the engine drops RPM fast enough that with the high inertia stator, it would chirp the belt. The CVPI solution is a simple mechanical one way clutch to allow the alternator stator to overrun the belt drive RPM.
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That's really interesting. I never knew that the P71 CVs had that in. Interesting!
 
Ted said:
That's really interesting. I never knew that the P71 CVs had that in. Interesting!
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It isn’t something unique to them. Many cars built in the last 20 or so years have one way clutches on the alternators. I don’t know what the ratio of vehicles with vs. without is but I believe every post 2000 MY car I own right now has one.
 
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mondtster said:
It isn’t something unique to them. Many cars built in the last 20 or so years have one way clutches on the alternators. I don’t know what the ratio of vehicles with vs. without is but I believe every post 2000 MY car I own right now has one.
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That, too, is interesting to me. I haven't replaced an alternator on a 2000 or later vehicle in quite some time, maybe never, so that may be why I haven't seen it.
 
Ted said:
That, too, is interesting to me. I haven't replaced an alternator on a 2000 or later vehicle in quite some time, maybe never, so that may be why I haven't seen it.
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The clutches are typically built into the pulley, so they don’t really stick out. It’s not surprising that you’d miss the clutch since alternators last so long these days and a quick glance under the hood wouldn’t reveal anything obvious.
 
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One of the modifications when installing the twin screw supercharger on the Marauder engine requires turning the alternator around so it is facing the rear. That requires replacing the pulley with a direct drive version:

woodward_defyant_2.jpg
 
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Could cut the current in the alternator field at WOT with a Hobbs switch at the throttle-body?
 
455 Bravo Uniform said:
Could cut the current in the alternator field at WOT with a Hobbs switch at the throttle-body?
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I’m really not worried about it. But, we’ll see once I start driving it.
 
Ted said:
This is the longer video on the preparations I did for first start, just published:

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Just now catching up on this thread... Great video! My dad would be quite jealous of your MaxJax. He’s been wanting a lift for quite some time.
 
RyanB said:
Just now catching up on this thread... Great video! My dad would be quite jealous of your MaxJax. He’s been wanting a lift for quite some time.
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My wife bought them for me about 8 years ago. I’ve been very happy with them, work great for smaller cars and projects. I’ve had 1/2 ton trucks on them too without issue.

Being used to full height lifts as a mechanic, originally I’d thumbed my nose at half height lifts, but it’s really been great.
 
Over the weekend I managed to get some more wiring work done on the Cobra. I ran out of two gauges of wire that I needed, so that stopped me. However, that didn't stop me from running some more of the remaining wiring/circuitry, including for the rear lights.

One thing I had been working on figuring out was how I wanted to run the horn and headlight relays. I've got most of the relays for the car in the trunk, but for the horn and headlights it really didn't make sense to do that, but I also didn't want them to be in a location that was going to be easily visible under the hood since much of my goal is to keep that area pretty clean. There's an area in the driver's footwell that I'm placing them that should be accessible enough if I ever have to replace them, but still hidden/out of the way. So I got those mounted and started running wiring as much as I could for them.

First drive could be this month, depending...
 
IK04 said:
One of the modifications when installing the twin screw supercharger on the Marauder engine requires turning the alternator around so it is facing the rear. That requires replacing the pulley with a direct drive version:

View attachment 96757
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You made me look. At first I assumed that was a roots type blower. I didn't know screw type superchargers were a thing. Quieter?
 
Sac Arrow said:
You made me look. At first I assumed that was a roots type blower. I didn't know screw type superchargers were a thing. Quieter?
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Like @SoonerAviator said, the Lysholm Twin Screw supercharger is more efficient, cooler charge temps. Same boost = more horsepower.
 
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