DuPuis Family Cobra Build

Regarding the Speedo. I am not sure what my son's Speedo was connected to, but calibration was a simple connection of two pins on the back, drive a measured two miles and connect the pins again. This allowed an easy way to recalibrate if gears were changed or different size tires were introduced. The issue with his installation was that no one had the forethought to install a simple momentary push button to make re-calibration easier

The problem then becomes installing the electric speedo sensor, cable, etc. I did that on my Jaguar and it didn't work. Now, I'm a better mechanic than I was then so I'm sure I could make it work, but it adds wiring and complexity. I use a GPS for ground speed in the plane, I like the idea in the car, too. It seems most custom builders are going that route too.

I'd go with the digital TFT display. It ain't no classic car anyway, I'd have more fun programming and playing with the digital gauge.

Please post links to options you like. :)

Having used a Koso digital gauge package before, I would not go that route.

First and foremost, aesthetically it doesn’t meet your desires. Second, it’s a compromise.

So now looking at those Koso gauges, I actually really like the form factor of some of their all-in-one units. Gives me analog for the tach, digital on the speedo (which I can accept), in a modern sport-bike-looking thing at a good price. So what's your issues with them from a technical perspective?

This one is interesting:

https://kosonorthamerica.com/shop/motorcycle-mx/rxf-multifunction-speedometer/

So is this one:

https://kosonorthamerica.com/shop/motorcycle-mx/rx-2n-gp-style-multifunction-10-000-rpm/

I’ve had good success with auto meter before and there’s a wide selection of styles and colors to meet your desires.

I've had good success with them too. But I haven't found any that jump out at me and scream "This is it!"

Gauges:

I'd go Stewart-Warner Deluxe. Simple, clean.

https://www.stewartwarner.com/products/deluxe/

Simple and clean, many use them for that reason. Doesn't do it for me though.

I vote for Sport Comp. That’s my era.

That's my era as well, but they don't offer any with a GPS speedo, which is a criteria for me.
 
So now looking at those Koso gauges, ...So what's your issues with them from a technical perspective?

This one is interesting:

https://kosonorthamerica.com/shop/motorcycle-mx/rxf-multifunction-speedometer/

So is this one:

https://kosonorthamerica.com/shop/motorcycle-mx/rx-2n-gp-style-multifunction-10-000-rpm/

Here’s the one I had:

https://kosonorthamerica.com/shop/motorcycle-mx/xr-sr-multi-functions/

This was probably 10+ years ago on a cafe conversion of an SV650. Biggest reason I didn’t suggest it for you is the speedo was Hall effect driven. Wasn’t aware they had a GPS driven speedo now.

The backlight was brighter than I cared for at night on a motorcycle and the fuel level display just wouldn’t accurately display the level in my bike no matter what I tried. Full tank = 3/4 on the display and the low fuel indicator wouldn’t illuminate ever. No ability to flush mount the unit I had, which may or may not be a concern for you.

Manuals back then were a poor translation from an Asian language.

That’s the big stuff off the top of my head. For perspective, I kept that rig setup like that for five years before I reconfigured to original cluster so I could sell the bike easier. And yes, I did disclose the discrepancy on the odometer, but it wasn’t a big deal as the bike was >10 years old by then.

Oh yeah, since they’re a powersports focused company, they may not have an 8-cyl option for the tach.
 
Here’s the one I had:

https://kosonorthamerica.com/shop/motorcycle-mx/xr-sr-multi-functions/

This was probably 10+ years ago on a cafe conversion of an SV650. Biggest reason I didn’t suggest it for you is the speedo was Hall effect driven. Wasn’t aware they had a GPS driven speedo now.

The backlight was brighter than I cared for at night on a motorcycle and the fuel level display just wouldn’t accurately display the level in my bike no matter what I tried. Full tank = 3/4 on the display and the low fuel indicator wouldn’t illuminate ever. No ability to flush mount the unit I had, which may or may not be a concern for you.

Manuals back then were a poor translation from an Asian language.

That’s the big stuff off the top of my head. For perspective, I kept that rig setup like that for five years before I reconfigured to original cluster so I could sell the bike easier. And yes, I did disclose the discrepancy on the odometer, but it wasn’t a big deal as the bike was >10 years old by then.

It actually isn't clear to me whether those ones I linked have GPS speedometers in them or not, so that is an issue that may not meet my requirements. Either way, good points to know and it does look like something that's got Asian translation issues. I'd like to see some more info on how it actually works and some of the sensor inputs, etc. before making a decision. But, that could be an interesting alternative to traditional gauges.

My wife used to have a Triumph Daytona 675 with a similar style panel, something like this:

daytona_675_stock.jpg


We did really like it. It was very clean, gave you the info you needed. Another option would be something like that in concert with another gauge/gauge cluster, but would require something that's coordinated for it to not look completely awful.
 
Don't recall it being squarish, but it was huge. Lots of leverage for turning the wheels at parking lot speeds. It also had a climber speedometer, which was cool. Wish he didn't sell it.....oh well. Those slant-6's ran really well in the pre-smog era.

A friend had a slant 6 in an early Duster that he built up. It ran 11.90s in the quarter mile. Not bad at all for a street car. A 6 cylinder street car at that. It was an awful green color. Almost like an army green.
 
Ted, some pretty cool digital panels to consider. Amazing stuff.
 
Ted, some pretty cool digital panels to consider. Amazing stuff.

My wife really liked that Koso one I linked above. May be worth considering.

It lacks fuel pressure and WBO2 (I realize I left that one out) but I could add those if I wanted with separate gauges.
 
Parts have been starting to come in, and it's fun. Yesterday I got most of my Summit order from Monday which included my head gaskets, head bolts, lifters, and timing gears. Everything looks good and it's all very exciting. The short block and intake manifold are supposed to show up on Monday.

Unfortunately I still have some major parts that I'm missing. Biggest one is the cam, which is at least a week away from showing up and I'll need that before I can check for and order the appropriate length pushrods and check the piston to valve clearance on the engine to make sure I'm good to assemble everything. So the reality is I probably won't make much progress on the engine over the next week, but I can hopefully get the rear end installed and get the brakes and maybe fuel lines completed. Still, very exciting.

Since I have July 4th off I expect we'll use that as an extra day to work on it. Or maybe I'll decide I need a mini-split in the garage... which would be really nice.
 
Don't you just love it when man toys start arriving?

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I shot this video last weekend but just uploaded it:

 
Loved the video, you don't need to worry about editing, your videos are easy to follow and just flow naturally

Sent from my SM-N920V using Tapatalk
 
Loved the video, you don't need to worry about editing, your videos are easy to follow and just flow naturally

Thanks :)

I try to think about what I want to say before I start the video to hopefully make that flow easier.

My next rear axle video will endorse steel toe boots.
 
I didn't expect to get anything done on the Cobra this weekend. But after spending all morning outside in the hot sun yesterday (and all day outside on Saturday), the kids were really tired and wanted to veg. My wife had some cleaning up to do, so that gave me an opportunity to work on the rear axle. I'd been hoping to get a full afternoon to work on this because I've never set up a rear axle before, and I'd expected it to take a bunch of iterations.

When setting up a Ford 8.8 (and I think most other rear axles) it's commonly an iterative process. You make an educated guess as to the shim you need under the pinion bearing to set its location correct. Then you put the differential in with its shims to get its location correct. The possible issues are that the pinion is too low or too high, or the differential is too far left or right. In the end you have to get the backlash correct and the engagement pattern.

Changing the backlash really isn't too big of a problem. You've got the 4 bolts that hold the differential carrier in place and then you pull it out and mess around with the shims. At the end of it, you have to check the gear tooth pattern and if it's good, you're good to go. If not, you have to at least change the backlash, but might need to change the pinion shim. That's a lot harder and more involved, more than anything because you then need a new crush spacer (those are one time use) and you also have to pull the bearing off the pinion, which often results in destroying it.

Oh, and here's the other fun thing with the pinion installation. You have to torque it down based on a preload, so specifically how much torque it takes to turn the pinion. This is a moving torque so you need a beam style torque wrench, which I bought. And, as I found, it's extremely sensitive - only a couple of degrees of turning can make a big difference.

Because of all of this, I decided I wanted to try to get the pinion together once and hopefully get it right. Most people set things up with the plan of taking it apart, putting it back together, etc. etc. I had two crush washers and two new pinion nuts so that would give me one additional opportunity if I had an issue.

When I took this rear axle out I immediately noticed that it felt like it had too little backlash (essentially zero) and also way too little resistance to turn (also essentially zero). While I didn't know the official spec on those, it didn't feel right to me - it felt like everything was freewheeling. Of course these were older, original bearings and old, leaky seals, but it still didn't feel right. When I took everything apart, the pinion shim was 0.030" (which I suspect was the stock shim) and the shims for the differential carrier were sticking out. What I'm now realizing happened was they set this up for zero preload, and probably reused the crush spacer on the pinion. They definitely didn't set anything correctly. Because of this I was basically setting it up blind.

However, most people say that the stock shims are usually what you end up needing with new gearsets. I also saw another video where someone from Ford Performance said that 0.024-0.028" was the typical pinion shim range.

So, I picked out a pair of shims that were good for 0.028" (a hair less than what was in there) pressed the bearing on, and crossed my fingers that it would work. Tapped in the forward seal, bearing, slinger, and got ready to tighten it down.

But before that, I had to figure out some spacers for the differential carrier and this time set it up so there was some preload on the bearings. I was going 100% from scratch on this. There's not good documentation (and no spec) on preload for the differential bearings, but Ford Performance gives you some thicker spacers (2 per side) and you put the thinner shims between those. I more or less guessed on a preload where it felt like the shims and spacers could get in and out easily enough, but also that they were solidly in there and wouldn't slip out like the did before.

On my first try of tightening down the pinion I ended up over-tightening it. Spec is something like 16-28 in-lbs of preload. I wanted a hair on the high side, had it at 20 in-lbs (right in the middle). Then I torqued it a hair more and it went up to 50 in-lbs. Well crap. Also for some reason when I moved the differential back and forth I heard a little metallic "clink". So took that all apart, put it back together. I couldn't figure out what the clink was, so I just put more oil in the bearings figuring maybe I didn't pre-lube them enough and maybe having it overtightened was causing something odd. Put it all back together, got it to about 22 in-lbs preload, called it good, and crossed my fingers that I wouldn't have to mess with it again.

I then split the shims between the left and right side on the differential carrier and put it in, which resulted in zero backlash. So I put both spacers on the right side (moving the ring to the left, increasing backlash) and that resulted on about 0.015" backlash, a bit above the spec of 0.008"-0.012". A few more rounds of playing and I ended up with the backlash right at about 0.009-0.010". Then I did the gear paint.

The gear pattern looked good. I'll admit I had a hard time really seeing it and I didn't get any of the super pretty patterns that you see on videos from people who've done it a bunch of times before, but I could tell that none of the patterns looked like the examples I found that said "need to [increase/decrease] pinion shim". So I got the backlash set, pattern looked good, and then put in the axles and called it a day. The setup has a good, appropriately level of resistance but is also super tight. The limited slip looks like it works correctly and well.

Now that the axle at its core is back together, it's time to put on the lower control arms, the 3rd top link, the coil/over assemblies, brakes, and then put in fluid, put the cover on, and put the whole thing under the car and attach it. I'll probably do that tomorrow or Wednesday night when my wife is back on shift. At that point I'll have a "roller" although I'm not putting wheels on it yet.

Today my intake manifold setup arrived, and the short block is supposed to arrive, too, although that's LTL freight and I haven't received a phone call to schedule delivery. I'll need to be home for that one.

On Friday I heard from the machine shop working on the heads and they confirmed that the springs were of the correct pressure (as recommended by Isky) so they're all back together. I'll pick those up probably tomorrow. Reality is until I have the cam, those heads don't do me a whole lot of use since I can't torque them down (or at least won't torque them down) until I have the cam installed and can check the piston-to-valve clearance. I can put them on with the head gaskets and snug the head bolts down, but won't do much beyond that.

In the end, the heads are a savings of about $1200 vs. if I bought them new, so I think that's a pretty good number.

There's a lot to do, although part of me feels like I need more parts still. :)

2019-07-01.jpg


2019-07-01.jpg
 
Nice progress on the diff!

While you’re waiting, go ahead and cc the heads, the pistons, measure the deck height, gasket thickness, and use all that to calculate your final compression ratio (vs plan).
 
Nice progress on the diff!

While you’re waiting, go ahead and cc the heads, the pistons, measure the deck height, gasket thickness, and use all that to calculate your final compression ratio (vs plan).

I let the machine shop go ahead and cc the heads - 56.5cc was the number they came up with. I'm using head gaskets with the same thickness that ATK uses for their calculations for compression ratio. Really what I'm concerned with is the piston-to-valve clearance at this point and so long as that's good, I'm going to be putting it all together and torque things down.

One thing I do need to decide on is what I want to do for an oil pan. I have the stock SN95 pan which is aft sump and I like that setup. However it doesn't include any baffling in it, which has me wondering if I should do something else in the even that I track the car (which I very likely will at some point). I'm inclined to stick to the SN95 pan, though... or maybe even add some baffling to it to help. I have a welder and I'm not afraid to use it.
 
I'd definitely want baffling if I were tracking the car at all, and possibly a bit of extra capacity if space is available.
 
I'd definitely want baffling if I were tracking the car at all, and possibly a bit of extra capacity if space is available.

That's more or less the question. The bottom end is new so it should last the longest without issue, and of course the oil pan is about the hardest thing to change once it's all bolted together. Hence why I'm thinking about whether I want to do that or not.

I also have that Milodon oil pan that came off of the first parts car still, I may look at that and see if it's got some potential to be used, I forget what it has in it for baffling etc.
 
My engine (short block) is in the general KC area, but it didn't make it to my house yesterday. All that happened was it made it from KC to Clinton KS, which is actually a bit further away. This is LTL freight and UPS at that, so I get that things are sometimes slower. If it still seems stale by tomorrow then I'm going to call and try to find out what's going on.

The big thing that arrived yesterday was my Speedmaster downdraft individual throttle body EFI setup. I didn't spend too much time looking at it but I did take it out of the box. Initial impressions are very positive. This is a lower cost unit (I paid $858 with free shipping). They offer more expensive units that are polished, but I didn't see a point in spending extra money there. The "wow" factor will already exist when opening the hood just from the setup itself.

The unit looks and feels better constructed than I was expecting. The base is a nice cast aluminum, and the linkage on the throttle bodies is solid. Everything seems well sync'd and the throttle bodies open smoothly and accurately from what I can tell.

There is no plenum whatsoever. I didn't expect there to be one, but it's worth noting that one simply does not exist. The lack of a plenum will hurt certain performance aspects but that's fine. This is truest to the Weber-style of induction without the finicky nature of carbs. The unit is assembled other than the intake horns, which are nice as well.

I need to look through and see if there's any cleaning up of the ports that I want to do and also do a good once-over to make sure there aren't any metal shavings too.

I will need to buy fuel injectors. I don't know enough about Delphi vs. Motorcraft fuel injectors, but I think dimensionally they're all about the same. My plan is to go with Ford Performance fuel injectors, and probably 47 lb-hr ones. That's bigger than I need (I want 42 and could probably get by with 39), but the 47 lb-hr ones are popular and it's about $275 for a set of 8 new ones. I like the Ford Performance products. Good quality and you know what you get so it makes sense for what I'm doing.

One thing that I am noticing is this intake does not have any vacuum ports built-in. So if I want to add vacuum ports (such as for a MAP sensor, syncing the throttle bodies, or vacuum brakes if I were to eventually do those) then I will have to drill and tap those myself. Not a big deal and I think I'm probably going to want to do that, I just have to figure out exactly how I want to. I would prefer to use a MAP sensor with MegaSquirt vs. Alpha-N (throttle position sensor based) for many reasons. Something to look at and think about.

Here's a short clip showing the linkage working on the intake:

 
Just picked up my heads from the machine shop. Total damage was $420. Ultimately the only things they actually did that could constitute as changes were cleaning the heads and also decking them. I will say the deck surface looks better than it did before, and it's nice having a known good surface to start from. When you figure that these heads were $900 each new, that's a good savings for heads that are effectively new and, thanks to the decking, produce a bit more compression than they would have out of the box. Since they did a 3-angle valve job when they did the valves up they should also flow a bit better than stock, too.

Interestingly, when I was looking up the current MSRP on these heads, I ended up at the Jegs website with some technical info:

https://www.jegs.com/i/Edelbrock/35...VAtvACh1pWg8OEAQYASABEgIfIvD_BwE&gclsrc=aw.ds

What I found interesting was the flow numbers that they have on the head. If you notice, above .500" lift the flow numbers essentially are the same, even going down slightly from .600" to .700". With 1.7:1 rockers I'll be just over .500" lift, so I think I'll be in a good spot there. Duration might be a hair on the low side, but my gut says this will come together nicely.

The freight company also called and told me that they'll be planning on delivering the engine tomorrow midday, which is exciting.

This is all coming together nicely. I think having the engine and transmission together and physically in the car and physically connected by the end of the month is pretty doable, assuming Isky gets me my cam in a reasonable timeframe.
 
I bet she'll run just fine with the EB RPMs. You did order the SpeedMaster EFI intake for the 351w, right?
 
I bet she'll run just fine with the EB RPMs. You did order the SpeedMaster EFI intake for the 351w, right?

I wasn't thinking about the Edelbrock heads, I know those will make plenty of airflow. I was more thinking about the size of the cam. We'll see.

Yes, I bought the Speedmaster EFI setup for the 351W. One of the benefits is that, for reasons I don't fully understand, the 351W intake is much cheaper than the 302 variant. I'm not sure how they price these - it seems to be all over the map.
 
Injectors- get make and size with the best spray pattern at its lowest flow/pressure (idle and off idle). You’re gonna spend the most time at low part throttle and you want the most atomized fuel stream possible.
 
Injectors- get make and size with the best spray pattern at its lowest flow/pressure (idle and off idle). You’re gonna spend the most time at low part throttle and you want the most atomized fuel stream possible.

Correct. That's also part of why I want those Ford Performance injectors. They're good enough at idle that they can meet the driveability and emissions for the GT500, which they come on stock.
 
I wasn't thinking about the Edelbrock heads, I know those will make plenty of airflow. I was more thinking about the size of the cam. We'll see.

Yes, I bought the Speedmaster EFI setup for the 351W. One of the benefits is that, for reasons I don't fully understand, the 351W intake is much cheaper than the 302 variant. I'm not sure how they price these - it seems to be all over the map.

No clue there. Technically the 351w intake should contain slightly more material (due to being slightly wider) and lower sales volumes due to sheer number of them in the marketplace. Ah well, chalk it up to a win!
 
No clue there. Technically the 351w intake should contain slightly more material (due to being slightly wider) and lower sales volumes due to sheer number of them in the marketplace. Ah well, chalk it up to a win!

Near as I can tell they have a sort of shotgun approach to what they make and it's based off of how much they think they can get for anything they sell with little regard for cost to produce. Given that it's all made/cast in China (or somewhere in that part of the world) I imagine they all cost the same to build and have the same level of (non) complexity.

The exact same unit that I bought from them for $858 they first quoted me $1200, and that's what it costs from Summit or Jeg's. But another place online sells them for $858 so they matched that for me without flinching. That sort of a pricing disparity makes no sense to me and I would think would infuriate their dealers.

Whatever. I'm not going to think into it too much other than I win, like you said.
 
My engine (short block) is in the general KC area, but it didn't make it to my house yesterday. All that happened was it made it from KC to Clinton KS, which is actually a bit further away. This is LTL freight and UPS at that, so I get that things are sometimes slower. If it still seems stale by tomorrow then I'm going to call and try to find out what's going on.

The big thing that arrived yesterday was my Speedmaster downdraft individual throttle body EFI setup. I didn't spend too much time looking at it but I did take it out of the box. Initial impressions are very positive. This is a lower cost unit (I paid $858 with free shipping). They offer more expensive units that are polished, but I didn't see a point in spending extra money there. The "wow" factor will already exist when opening the hood just from the setup itself.

The unit looks and feels better constructed than I was expecting. The base is a nice cast aluminum, and the linkage on the throttle bodies is solid. Everything seems well sync'd and the throttle bodies open smoothly and accurately from what I can tell.

There is no plenum whatsoever. I didn't expect there to be one, but it's worth noting that one simply does not exist. The lack of a plenum will hurt certain performance aspects but that's fine. This is truest to the Weber-style of induction without the finicky nature of carbs. The unit is assembled other than the intake horns, which are nice as well.

I need to look through and see if there's any cleaning up of the ports that I want to do and also do a good once-over to make sure there aren't any metal shavings too.

I will need to buy fuel injectors. I don't know enough about Delphi vs. Motorcraft fuel injectors, but I think dimensionally they're all about the same. My plan is to go with Ford Performance fuel injectors, and probably 47 lb-hr ones. That's bigger than I need (I want 42 and could probably get by with 39), but the 47 lb-hr ones are popular and it's about $275 for a set of 8 new ones. I like the Ford Performance products. Good quality and you know what you get so it makes sense for what I'm doing.

One thing that I am noticing is this intake does not have any vacuum ports built-in. So if I want to add vacuum ports (such as for a MAP sensor, syncing the throttle bodies, or vacuum brakes if I were to eventually do those) then I will have to drill and tap those myself. Not a big deal and I think I'm probably going to want to do that, I just have to figure out exactly how I want to. I would prefer to use a MAP sensor with MegaSquirt vs. Alpha-N (throttle position sensor based) for many reasons. Something to look at and think about.

Here's a short clip showing the linkage working on the intake:


You needed to make motor sounds when you opened the throttle plates.
 
So I was looking into this Koso RXF that is appealing to me. I found the following video and the unit looks to be of good quality:


I do really like the display and the overall form factor. Nobody seems to have installed this in a car, I only see it in motorcycles and the like. That's not necessarily a bad thing - after all the Cobra doesn't have a top and I may get caught in the rain - but it is an interesting note.

I figure that I'm going to get further along with the wiring before I make a decision on the gauges. I at least want to get the brake and fuel lines in, as well as the engine, transmission, rear axle, and driveshaft. Basically get it to where all the physical parts are (at least mostly) in place. Something to continue pondering on in the meantime, and look at some analog gauges too.
 
So I was looking into this Koso RXF that is appealing to me. I found the following video and the unit looks to be of good quality:
Unlike the video itself. Had to mute the stupid thing.
 
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Ted, it seems the Superlite guys are using a Koso RX-2N in LS-based cars. There might be hope.

http://slc-wiki.squarespace.com/gauges

Good deal, thanks. I figured that someone somewhere had done it, I had only been searching for the RXF in a car.

Looking at some videos I see some lag in the tachometer display, but nothing that's unexpected I think. I will say that when I had a an AutoMeter Sport Comp tach in my V12 Jag it felt like the response was instantaneous, however it looks like the Koso's display is no worse than any stock gauge. While a GPS speedo was a requirement, there were some good points made regarding the inherent lag GPS speedos tend to have, so I may rethink that. The Koso setup comes with its own pickups for measuring speed at the wheels. I'd have to look at how to best handle that, but I think it would be doable.

Unlike the video itself. Had to mute the stupid thing.

Yeah, I left the music playing hoping he would talk at some point. No such luck.
 
RXF in a car..

Here’s someone who’s done it:
https://www.gt40s.com/threads/new-koso-gauge.52634/post-531941

Honestly, my biggest concern for you was the tach; the unit I had was limited to 6 cyl. It appears after close reading of the RXF manual that it supports up to 8 cyl.

As for the Hall effect sensor, I recall there being a dedicated bracket in the kit with an oblong opening to fit a wide variety of applications. You could probably fab your own.

I seem to recall a decent length cable run for the sensor, though.
 
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Here’s someone who’s done it:
https://www.gt40s.com/threads/new-koso-gauge.52634/post-531941

Honestly, my biggest concern for you was the tach; the unit I had was limited to 6 cyl. It appears after close reading of the RXF manual that it supports up to 8 cyl.

As for the Hall effect sensor, I recall there being a dedicated bracket in the kit with an oblong opening to fit a wide variety of applications. You could probably fab your own.

I seem to recall a decent length cable run for the sensor, though.

That looks good, and as pointed in that link out more supercarish look. I would need to add gauges for the oil pressure and also for WBO2 if I wanted to have those. I suppose the ones I'd be more interested in would be oil pressure and fuel pressure.
 
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