1986 951 LS1 Conversion

Greetings everyone!

I have been working on collecting parts for a few weeks and have now started on the project.  Parts continue to slowly roll in.  Just thought I would post up some pics/info as I go for the entertainment and benefit of all.

Thanks!
Mike


Out With the old:

[You must be registered and logged in to see this image.]


Parts Coming in.....

[You must be registered and logged in to see this image.]

Engine Build......

[You must be registered and logged in to see this image.]

So the engine build will be basically built as the 500 hp one listed here:

[You must be registered and logged in to see this link.]

I plan to do the following:
-Total Engine Airflow stage 2 5.3L heads
-Mild comp cam
-Fast intake
-Kook's long tube SS headers
-36 lb injectors
-Custom tune of course

-The trans is out for professional rebuild, 0.73 fifth gear, and Wavetrac TBD LSD install.

-Torque tube is with Constantine for rebuild (he's the expert)

-Conversion parts from TPC trickling in now, thanks to Kent!

-I am planning on coilovers all around with a torsion bar delete and would welcome spring rate suggestions. Still working that out.

-I did spring for front/rear sways 30mm/19mm adjustable.

-Also have cross drilled rotors coming.

-XSchop is getting me some 4340 axles and a trans mount.

Thanks for watching. Will update as I can.

Mike

How do you plan to use the car? That'll drive your spring rates...

Good luck with the build.

docwyte wrote:How do you plan to use the car?  That'll drive your spring rates...

I say that I will be using it for the track but realistically it will be street/autox/and DE type car. Unless I become more stable (military now and move around a bit). So I am trying to be on the upper end of stock/stable suspension setup that will be useable but not extreme. As I type this I realize I am not helping to narrow it down at all lol. I am currently thinking 350lb springs in the front and a comparable set for the rear without the torsion bars (plan to delete them). If that sounds too high/low let me know. Any thoughts are welcome and if you read this far thanks for your time

Mike

If you're planning on deleting the torsion bars you need more spring rate in the back. I'm currently running 450 front, 700 rear with no torsion bars. If I was going to take my car to track only I'd move the 700's to the front and run 800 or 900's in the back...

Doc,

Were the 450 lb springs tough to live with on the street?

Would you go softer if you were using it more on the street?

Let me know what you think.

Thanks!
Mike

In my experience, while spring rate does matter some it is the damper choice that really dictates how usable the car is on the street. Investing in quality dampers tends to be it's own reward.

With my Evo, I went through three different suspension set-ups. The first was a track focused coilover set-up that rode like a pogo-stick on public roads and freeways, it was essentially useless off the track. Since my Evo was doing both time trials and street duty, I invested in a better quality set of coilovers with about the same spring rates, but much better dampers. The cost was over twice what the first set cost, but suddenly my ride was almost OEM quality, even with the very aggressive spring rates. The final set-up was a set of very good quality dampers and and very stiff lowering springs after the car had been returned to street use only. Almost as fast as the coilovers on a track, but even more road friendly without the maintenance headaches that come with coilovers. If you've never had to live with them, coilivers tend to like a fair bit of shock-body thread and piston rod cleaning to keep them in top condition.

If you dig around the internet a bit you can figure out how to calculate your wheel rates, and use that to figure out how to choose your springs based on a frequency value. For an aggressive road car, I'd probably start with somewhere between 2 and 2.5 hz with the rears about 10% softer than the fronts. You don't want the front and back to have identical frequencies .. that can lead to the car feeling like it's rocking or bouncing from front to back when it goes over larger bumps.

I have Bilstein Escort Cup coilovers and I sent them back to Bilstein to get rebuilt and revalved to the spring rates that I'm using.

As such, the ride is firm, but not bad...

Anyone have any opinions on the Koni Sport Kit from Paragon?

[You must be registered and logged in to see this link.]

That's the front runner right now.

Mike

I'd recommend keeping the torsion bars. Other parts of the car were built around their presence.

For a strictly DE car, I'm running 600-650 up front and a 30mm torsion bar in the rear with the Paragon Koni set up in back. I went with 250 or 300 lb springs on the back. It's been so long I forget.

It's too stiff for any long distances on the street, especially for the crappy Pennsylvania roads I drive but it is tolerable for the drive to and from my mechanic's shop.

cjbcpa,

I was not planning on removing the torsion bars but when I looked for torsion bar replacements in different rates they were unavailable . Only option was to install elephant racing quick change plates and 911 type torsion bars. That is all well and good and I may still go that route but it's more costly and more work to adjust the bars while "tuning" the setup so I am leaning to coilovers all around and no torsion bars as others have done.

Mike

Removing the torsion bars and going to strictly coil-overs places all the rear suspension load on the bottom damper bolt and top shock tower mount which is contrary to how the car was designed.

The bottom damper bolt is probably the weaker of the two contact points in this set up and more problematic because it can't be visually inspected easily. Even though I kept the torsion bars, I used a Racers Edge lower shock adapter which is beefier than the stock bolt. Went a step further and had the surface of the trailing arm and the shock adapter machined to create a mild pocket and shoulder where those two tie in.

BTW, Paragon's website lists sway bar sizes up to 30mm as individually available as well as up to 34mm as part of a full suspension kit.

I called Paragon and spoke with Jason at length, he recommended the current plan and stated he has trouble getting the torsion bars and most are NLA. I am not sure why there are still listed on the site. I also spoke with Steve at 944 Online and he sourced me some big sway bars and cross drilled rotors. Still working on some parts from elephant and then the shock/strut/spring combo.

Big thanks to all who are reading and giving input. More input will help make a better car and hopefully less headaches.

Mike

I think these guys are getting the TB's here:
[You must be registered and logged in to see this link.]


I have 28mm ones from here in my DD.

Gord.

Paragon sources them from sway away. I doubt Jason would lead me astray on the bars. Anyways, I will keep digging and I welcome all input. Decisions decisions decisions

Check with Elephant Racing for torsion bars also; they have a line that they make in house.

ElephantRacing.Com

Some VW bars will fit.... [You must be registered and logged in to see this link.]



These guys have cheap torsion bars

[You must be registered and logged in to see this link.]

Thought I'd share this post in case it was overlooked. Even with Torsion bars and quality hardware, stuff happens:

[You must be registered and logged in to see this link.]

that's a TB delete car. Not uncommon either, I've seen a few break once the TB's are removed.

I must have misread, I thought the TB's were still in. Proves my point I guess. I'm very reluctant to second guess Porsche engineers unless its a well documented flaw, e.g. Boxster & 996 IMS bearing.

cjbcpa wrote:I must have misread, I thought the TB's were still in. Proves my point I guess. I'm very reluctant to second guess Porsche engineers unless its a well documented flaw, e.g. Boxster & 996 IMS bearing.

I've not had torsion bars on any of my 944 race cars.  Don't have time to reindex when I'm busy corner balancing, changing spring rates, etc.

Well that doesn't make any sense to me. Installation and indexing are only need to be done once to set the proper ride height. Spring rates can be changed, if necessary, by changing the spring on the coil over. Done right, there is still ride height adjustment available in spring arm as well as the coil over rings. Yeah, corner balancing would need to be redone but that's it. TB spring rates range from 320 to 550 lbs using 30-36 mm bars so there's plenty of range.

Point is, it's quite easy to get to nearly any desired suspension set up without removing the TB's and without deviating from Weissach's engineering design which I'm sure was done this way for a reason.

Lots of cars are done and work well with full coilovers. But I'm with you on keeping the torsion bar design, cjbcpa. My car has 31mm torsion bars and coilovers with 100 lb helpers. Corner balance and ride height is perfect.

Rich

Well, it's been a bit since I posted. I see the thread has gotten a bit off track

Updates:
Engine rebuild completed and topped with a FAST LSXR 102mm intake
Transmission completely overhauled by California Motorsports and new wavetrac differential installed as well as AN fittings for an external fluid cooler
Torque tube rebuilt by Constantine with super bearings and new shaft

Waiting on some swap parts still and tinkering away on the odds and ends.

Will post some pics when I get a little time......