Porsche 944: Actually there is a substitute

[CherokeeC10]

You sir are my kinda crazy. My first car was an '83 944 non turbo w/ the fatory mags that I drove the piss out of and always got a special kind of confused only German mechanics working on U.S. trucks can understand.

[sparkydog]

Getting verrrrry close to finished with the prep work. The awning is functional. I just need to tweak a couple of more things and it will be off the list!

And the yard/driveway will soon be organized and more attractive. I was reaching my limit for visual mayhem.

I also finished fabricating two jack extensions (yes that sounds funny) so that I can get the 944 waaaay up off the ground. One is 8" and the other 16".

[sparkydog]

The 944 is high.
The Mustang is on the dolly and more stuff comes off every day.
Look what followed me home from the wrecking yard today.

[cAlvis165]

So your going with IRS? What is it from?

Chad

[aussiejohn]

Updates, please?????

Regards from Down Under.

aussiejohn

[sparkydog]

Originally Posted by aussiejohn

Updates, please?????

Sorry to say that all I have are "down-dates" instead of updates.

I've messed up my neck to the extent that I now have numb fingers and arms so I haven't been able to work on ANYTHING let alone the Porsche. Recovery is going slow because I keep ignoring the Dr. and working on stuff and blowing out my back/neck.

Secondly I have made a series of blunders in my selection of donor rear-ends for the Porsche and I am pissed off at myself so I'm busy trying to figure out what to do next. The over-all "lesson" I am teaching myself is that I don't seem to be able to do the proper amount of research before I pull the trigger. My first blunder was not understanding that Ford 8.8 rear ends only came on V8 models. So my donor car doesn't have an 8.8 it's a 2.77 ratio 7.5". Then I tried to recover from that, got all side-tracked over IRS on Tbird/Cougars and again, thought I had all the info I needed but nooooo. Effed up again and bought an 8.8 but can't use the sub frame and thought it was a posi diff but it's not.

Plan A is to use the 7.5" non-posi straight axle that came with the Mustang and just live with it for now. I continue to believe this is the best design for adapting to the Porsche.

Plan B is to tear down the IRS I bought and tear down the Porsche swing arms/spindle and see if there is any "easy" way to adapt the Ford IRS diff & axles to the Porsche IRS swing arms. This is along the lines of what Frizzlefry suggested.

So assuming that my neck recovers some day then I am going to focus on grafting the Mustang front K member over to the Porsche first instead of last. I've got to give myself more time on the rear end before I screw it up any more.

I also hope that I can learn from these mistakes and do a more careful job of fact finding before I buy my donor LS motor vehicle.

That's all I've got for now guys. Talk but no walk.

[Zoomin]

Hey man, sorry to hear about all that. Hope you get things turned around soon.

[67ChevyRedneck]

Probably be hard to find, but mustang Cobras came with IRS from 99-04. Supposedly the 03/04's are the best to use, would that work for you? Don't know if that would help or not...

[NONHOG]

Originally Posted by sparkydog

The over-all "lesson" I am teaching myself is that I don't seem to be able to do the proper amount of research before I pull the trigger.

I swear I could have , with a few details changed, written that entire post.
Not laughing at you, laughing with you. I bought the wrong donor car going into my engine swap thread (here on A.T.) Bought mismatched components.
etc. etc.. Can't count how many days I could not crawl under the car because my back was out. "Again".

Hope you heal well and quickly! Love this build!

[aussiejohn]

Sparky,

So sorry to hear about your neck. PLEASE listen to your doctor and take it easy for a while and let your neck heal. I'd rather not hear any progress on the Porsche than find out that your condition worsened because you disobeyed good medical advice.

Take a break and learn a new card game or take up knitting or something, the car can wait and so can I.

Best wishes for a speedy recovery.

Regards from Down Under.

aussiejohn

[sparkydog]

One of the last things I have done before becoming a cripple was to get the brake rotors and calipers off of all 4 corners of the Mustang in order to render the front and rear suspensions as light as possible for mocking up under the 944.

I was going to fabricate some mockup struts in the front (to hold it at ride height) but realized I would spend un-necessary hours and $'s doing this when I could just weld up the struts that came with the Mustang. So I drilled and drained out the oil, then used the spray paint reference marks to calculate where ride height should be and then welded them up and re-installed.

[sparkydog]

My original plan was to graft the rear suspension into the 944 first as I thought it would be a little more simple than the front and I could get my mojo going before tackling the front graft.

But with the problems I had with buying the right parts I'm going to leave the rear alone for awhile and shift my plans and do the front graft before the rear.

If I can't do any actual work on the car at least I can sit around and stare at it. Here is a comparison shot of what the engine bay of the Mustang and the 944 look like. The two photos are roughly to scale. You can see where I posed my tape measure on the top of the shock towers in each photo.

In order to do a CARB legal engine swap here in California I have to use stock LS headers and I want as much room in the engine bay as possible. The 944 bay is very narrow between the frame horns and the firewall has a 4" jog on each side. But the biggest space hog in the 944 are the gigantic inner fender tubs.

For comparison, the width across from fender pinch weld to pinch weld on the 944 is about 1.5" wider than the Mustang but the width between strut tower sides is almost 4" wider on the Mustang than the 944. The Mustang firewall is flat and is almost in the same location as the rear-most face of the 944 firewall (above the trans tunnel).

Bottom line is the Mustang engine bay is more roomy than the 944's. So the plan is to graft most of the Mustang's engine bay sheet metal from the firewall to up near the radiator and from fender pinch weld to fender pinch weld.

[sparkydog]

Originally Posted by 67ChevyRedneck

Probably be hard to find, but mustang Cobras came with IRS from 99-04. Supposedly the 03/04's are the best to use, would that work for you? Don't know if that would help or not...

Yes good suggestion. The Cobra IRS or the Cobra straight axle would work very well for me. But the ones I have seen on Ebay and Craigslist are $1500-ish. For me that is big money. They are also a little too wide for the 944 body unless I was wanting to do some body mods. The 94-98 V8 rear was the perfect thing for me but I screwed the pooch and bought a V6 instead. The V8 would have had an 8.8 and now that I know how to read the damn tag on the diff I could have easily figured out if it was posi or not.

[sparkydog]

Oh yeah... Sparky's back in the ring to take another swing.

Welded some support into the Mustang's engine bay and then...
Whamo the Mustang lost it's nose. Guess I crossed the point of no return again!

[sparkydog]

Next I had to lower the 944 back down and get it on the dolly so I could spin it around. Then back up in the air. Then leveling it all up. Put "Righty" and "Lefty" the wheel locator gauges back on the sides of the 944. Then I tucked the Mustang's donor metal up under the Porsche and sat back for awhile (OK I sat back for a long while) and studied the situation.

[hgs_notes]

While you're sitting there pondering, did you change to a fresh blade on the sawzall? Cause you're not done yet.

[sparkydog]

Good news:
If all I had was 2D to fit the Mustang engine bay into the 944 I would be a lucky guy. From a bird's eye POV the graft will go well. The 944 and Mustang firewalls are almost at the exact same location. The Mustang inner fenders and strut towers give me more motor clearance yet fit inside the envelope of the 944's hood footprint. The Mustang and 944 floors are almost exactly the same height relative to the wheel CL.

More good news:
Even in 3D I have most of the issues going my way. As mentioned the floor heights are almost the same. The Mustang frame horns are approximately the same height as the 944. I think I am going to be able to keep enough of the 944 firewall and trans tunnel so that I may be able to re-use the 944's HVAC module. I think I will keep some of the 944 firewall and use the mouth of the 944's bell housing section of the fire wall but mod/replace the section just aft of the mouth so that there is more room for the GM tranny.

Bad news:
The Mustang strut towers are 3.5" taller (at stock ride height) than the 944. I was hoping to shoot the moon and do about a 1" body drop while I was at it so if I tried this too then the strut towers are 4-5" too tall to clear the 944 hood.

After 3 hrs of staring and schemeifications I have some ideas but before I belch them out - does anybody have suggestions on how I can get 4" out of the Mustang's strut length?

[sparkydog]

I also went back to the 6 X 944 guy's house and got my 944's rear suspension and brought it back to my chop shop. In my spare time I will study, measure and probably even render it in 3D CAD to see if there is a somewhat simple way to mate the Ford IRS spindles/brakes/axles/diff into the 944's swing arms. Here's a shot of the two rear ends trying to make nice with one another. (The Porsche engineers are probably rolling over in their graves.)

[rcbildr]

Just stumbled on this thread and have yet to read it entirely. But I had an 84 944 for a while and was dreaming about stuffing a V8 in it...spent a lot of time at renegade hybrids (I think) website looking at parts for the conversion. Not sure if this will help at all, but IIRC 84 and older 944's use steel suspension arms (from the VW super beetle I think) instead of the cast aluminum parts you have.

[hgs_notes]

Can you use the porsche strut in the mustang tower? It was made for a similar ride height but has shorter towers. Or are there other fords with shorter struts, like the focus or even other brands of car that have shorter struts? Just modify the mounting point on the towers to match the shorter strut style.

[sparkydog]

Originally Posted by hgs_notes

Can you use the porsche strut in the mustang tower? It was made for a similar ride height but has shorter towers. Or are there other fords with shorter struts, like the focus or even other brands of car that have shorter struts? Just modify the mounting point on the towers to match the shorter strut style.

Yes I am headed in a similar direction to what you said. The main choices I have are 1) shorter strut units that just bolt in, 2) modify a strut to change the location of its bracket on its body, 3) aftermarket drop spindles or 4) a combo of 2 or more of the other choices.

4" drop spindles would solve everything but I do not believe they exist for my model and if they do then the old economics thing comes up (they are expensive). I have been doing a little web research and I may be able to get most if not all of the 3-4" I want simply with another PN strut unit. I for sure can get 4" if I do a combo of using a different PN along with some slight mod to the strut mounting bracket. If I go this route I will first get a set of the new PN out of the wrecking yard and make sure it will really work, then buy a new set.

I will be proceeding with the graft of the Mustang engine bay metal over to the 944 bay. The stock Mustang struts and towers will come along and will initially be tacked into the 944 at correct ride height which will reveal the exact amount the struts are too tall. Once I have a workable solution to shorter struts I will figure out how to section (lower) the strut towers without messing up the suspension geometry.

[sparkydog]

First picture is what the stock Mustang strut looks like and has a catalog body length of 12.375".

Second picture is of a similar strut (not quite the same bracket) that I think I can make work. A version of this was used on the front of 2000+ Impala and Monte Carlos. It is approx 2" shorter and I can just shave off the coil perch. Another version of this is used on the front of early 2XXX LeSabre and DeVilles. It is even shorter and might give me a total of 4".

[67ChevyRedneck]

Does anyone sell a dropped one to lower the car (mustang)? Maybe for a racing application? 3.5" is a lot though... but it would be extra cool to include some GM parts instead

[hgs_notes]

Because of the geometry and strut mounting points I don't know how much shorter the strut would have to be. Such as a 2" shorter strut giving a drop of 3", similar to what you see by cutting front coils on our trucks. It's probably not a 1 to 1 ratio but you probably already considered this. You may be able to get what you want with a slightly shorter strut and by nipping the spring a bit or swapping the coils to a shorter stiffer set.

[sparkydog]

The top of the strut housing or tower or whatever you want to call the thing on the body that the strut bolts to is what needs to go lower by 3-4" in order for the Porsche hood to close. So I could hillbilly my solution by just sectioning the strut tower and dropping it and re-welding it. However the next problem would be that the (stock) strut would bottom out either at ride height or slightly compressed because the rod would be 3-4" deeper in it's travel.

Ride height is determined by the coil springs on a Mustang and the strut does two other things - dampen the springs and function as the upper pivot point of the spindles during turning. The location of the strut attach point also plays a part in the roll center and a bunch of other geometry stuff I barely understand. I would start out using the stock Mustang coil springs and cut coils or change springs as needed once the GM V8 is in. I would then buy a different PN strut so that it still has the correct travel in both directions but will fit into a tower that I shorten by 3-4". I will then have to carefully cut and re-weld the top of the strut tower (where the strut bolts to) so that it not only is lower in the engine bay but is also still on the same travel axis that it was before I cut it out. This should preserve the geometry. If I dork it up then caster, camber and roll center will all be screwed.