As we are now in the dead of winter (it is actually snowing outside here), it is time to get out to the garage and get the upgrades on the car done. I have just over 6 weeks till the SCCA Annual Tech session and that is my goal to have the car completed by then. I have have several items planned for the car this winter and I will reveal them as they are completed.

The theme to this year's upgrades is: Stronger, Lighter, Faster!

The first issue to address is historically a weak link on these cars....the CV joints. I have opted to upgrade to 944 CV's on both the inboard and outboard joints. These units as readily available, don't require adapter plates, and are relatively lightweight compared to some of the alternatives.

I didn't take many pictures of the conversion parts, but I have a few pictures I took from another thread. The parts I used for this conversion include:

• (2) new 914 rear wheel bearings
• (4) new 944 100mm 6-bolt CV joints including mounting bolts, boots and grease
• (2) 911 ('75 - '79) 100mm 6-bolt coarse spline transmission output shafts
• (2) 911 ('75 - '79) 100mm 6-bolt stub axles
• (2) 911/912 ('69 - '73) hubs

The first step was to remove 4mm of material behind the spline to fit the wider 944 CV. I actually removed just a bit less and deleted the spring washer.

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Here is the machined axles when completed.

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The difference in the thickness and diameter of the 944 CV as compared to the 914 CV can be seen here:

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Here are the 911 coarse spline output shaft and 911 stub axle used for the conversion:

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When completed, this is a comparison of the stock 914/4 set-up (top) and the 944 CV set-up (bottom):

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The only issue I came across with this conversion is that the 944 CV bolts suppied with the CV kit were just slightly too short and were not getting enough thread engagement as I would have liked. I actually ended up stripping one of the holes on the output shaft while torquing the bolts. I pulled the axle out of the car and the output shaft out of the transmission to timesert the stripped threads. I then reassembled with longer M8x50mm Grade 12.9 bolts and that did the trick. I am much more confident with this arrangement.

More to come after I feed my kiddo's dinner.

-Britain

I just weighed the 914/4 axle and it came in a 13.5lbs. The 944 Conversion axle comes in a 15.0lbs. Therefore, the total additional weight added with 3lbs.

-Britain

Yes, Dan...there will always be a weakest link. Curious, what parts in the transmission did you keep breaking?

-Britain

While the 944 CV's fell under the stronger category of my theme, the next phase is making the car lighter. At the end of last season, the car sat at 1725lbs with any ballast weight and without driver. My goal is to get the car closer to 1700lbs, preferably under that barrier.

I have a plan for that that pesky first gear.

-Britain

Hi Britain,

What are you using for rear brakes?

Yea, it uses the stock 914/4 axles.

You could also do the same machining mod on a set of 914/6 axles and used 911 CV's.

It is the lenght of the 914/4 and 914/6 axles compared to 911 and 944 axles and require you to either machine the stock ones or go with Sway-A-Way custom axles.

-Britain

The rear brakes are 'M' 911 calipers.

The front brakes at 911S calipers.

-Britain

So, back to my lightening efforts, I decided to reduce the rotating mass of the flywheel/pressure plate set-up. The car had a '69 911 stock flywheel and a Kennedy Stage 1 pressure plate. This combination weighed in a 25lbs.

To replace this, I obtained a discontinued WEVO Street-Lite flywheel that uses a Tilton 7" pressure plate and organic friction plate. This combination weighs 14.5lbs for a weight savings of 10.5lbs.

Stock flywheel and Kennedy Pressure Plate:


WEVO StreetLite Flywheel and Tilton Pressure Plate:

One part of this conversion that was tricky was the throw-out bearing. I had to obtain a 356 throw-out bearing carrier and remove the actually bearing to replace with a custom bearing designed to be used with this set-up.

Researching this 356 part, I found new ones to be north of $250 which was not acceptable. I then found a guy on the 356 registry happening to be selling a used one along with a rusty flyhweel and pressure plate. However, to send him a message on 356 registry, they required a subscription for somewhere are $35 a year. I searched the guys screen name on Google and found him selling other parts on The Samba. I sent him a message through there and was able to get the throwout bearing for $50!

When I got the parts in hand, it was pretty obvious how everything went together. Just needed some Locktite retaining compound for the bearing (which took a couple of places to locate) and I was good to go.

-Britain

Now, as with any project...there is that ol' Murphy's Law creeping up. While the flywheel was off, I noticed that the rear main seal was leaking just a bit. There was also lots of crud in the bellhousing when I took it off. I decide to go ahead and replace the rear main seal while I was there. Jeff at Rothsport was kind enough to provide a seal and installation tool on a Friday afternoon and I went at it.



As you can see from the images, the rear main seal was pushed in slightly too far. It is supposed to be flush with the outer raised surface. I am not sure if this lead to premature failure, just pointing out a fact that I learned.

Ok, now for some more extreme upgrades. In a pure AX application, you really don't need that many gears to navigate the course. In addition, that dreaded 1st to 2nd gear shift in the middle of a corner after the start line really sucks when you hit reverse or whatever. I believe that the time you lose making that shift and the comprises you have to make to ensure that the shift is not done with the car is loaded can really make an impact on your times.

Now, last season JP and I regeared the transmission to use a stock 914/4 mainshaft with the welded "F" 2nd gear and a "KA" 3rd gear (flipped 5th). In this configuration, we had the shift rod on the side of the transmission locked out from moving between gates using a homemade teflon bushings. We would launch the car in 2nd (low gear) which could propel the car to ~54mph which is acceptable for many AX courses at smaller venues like Portland (PIR). The 3rd gear would be our "high" gear and would take the top speed to 78mph which we will probably never hit and if we do, it would bounce the rev limiter for a split second before a apex or something. I have ran the car at Packwood (which is 15acres of asphalt) at both SCCA and PCA events and never hit the rev limiter in 3rd.

Anyway, now that out theory proved feasible, it was time to take it to the next level. This involved removing all the unnecessary gears, sliders, syncros, shiftforks, and other misc stuff out of the transmission. I got rid of reverse, 1st, 4th and 5th gear stacks and replaced them with machined spacers. Now, the final outcome looks simple enough, but let me tell you that it required a lot of custom parts to deal with the shift rod detents, gear spacers, shift forks, and clearence issues with the new parts. It also required the transmission to be completely dissassembled and then during the rebuild, I had to reset the backlash and pinion depth. I am not sure how many people would recognize the name, but Gordon Ledbetter did the rebuild. The best part is, he lives not 10mins from my house. I could tell he got really interested in this project as it was something different that he had not seen or done before.

Here is the final gear stack as it sat before being installed in the case...looks like it is missing something doesn't it?



Here is the reverse idler gear after I had the center removed to be used as a spacer to hold the pinion shaft together. It is harded and a lathe barely made a dent, so I had it wire EDM cut...really cool process. You can just barely see the cut from the outside of the gear to get to the center and cut it out.

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-Britain

I will let you guys digest this before getting into the "aero" work I am doing.

-Britain

You see Dan, I just got rid of 1st gear...now it can't break!

-Britain

That's great! You figure you will never need reverse? never ever?

Maybe one of the "aero" mods is a hole in the floor so he can Fred Flintstone it

We haven't had a reverse in the car for 2 season...no real issue. Why would you need one on an AX course?

-Britain

I think that his legs would increase drag

-Britain

OK, done digesting. On with the aero mods...

That is really EFFIN cool!!!!!!!!!!!!!!!!!!!!!!!

word show me the AERO!!!!!!!

BTW I'm 1683 pounds on the button with 50 lbs of ballast

Yea, but I a carrying around 2 extra cylinders.

-Britain

If you plan to Hillclimb ever you will want to keep reverse and enough gears to get to 100 mph.

Yep. Purpose built is, just that. I think it's great. That box looks just right for what you want to do... win an AX event.

Hillclimb cars get up to 100mph round here? YIKES.... Not too sure I want to do that. Just me, I'm sayin.

I've been known to change my mind.

I agree, that this set-up is not for anything other than AX. However, given the ease in which one can pull the transmission in a 914, if I ever want to do track events or hillclimbs, I will build/purchase a close ratio box with a clutch style LSD. In fact, I know of one right now that I have my eye on.

Everything is a comprimise, but I believe that I had made the comprimise in such a way that the car can be convert back rather easily. Everything else I am doing will work on a Hillclimb.

-Britain

Why would I need reverse on a hillclimb? Just in case I nose off into a ditch?

-Britain

Yea, like an AX...you do that and your not doing something right.

However, in an AX all you hit are cones and stuff.

I agree, a Hillclimb box needs to have reverse.

-Britain

Without a muffler, the tail section of the 901 can be accessed and real gears for 1st and reverse thrown in within 15 minutes. A power socket driver would cut that time in half. Assuming of course that area is near stock configuration and shift forks still work there.

Real cool spacers there to eliminate the un-used gears. I was thinking you could just leave all those roller bearings under the gears in place, but that spacer is slick.

Just curious, if you break 2nd gear and need a new shaft, does that require a re-set of the pinion depth?

Keep up the good work!

The shifter forks were modified, the shifter rods removed, and the detent mechanisms altered to make this 2-speed transmission function properly. Therefore, I can't just open it up and put in a 1st/Reverse gear.

Regarding the 2nd gear on the mainshaft...if you break that you will probably just need a full rebuild cause other stuff will get all screwed up.

-Britain

Really? I think if you are parked against a tree, the last ting on your mind will be "damn, I wish I had a reverse right now.."



B

Nice work Brit.. I would of thunk you would of relieved the OD of the spacers to remove more OZ off the assembly and reduce spinning weight But otherwise nice custom work ..

did you know how much it weighed before mods?

care to share ?

The spacers OD is specifically that size to line up with the thrust washers and the landings on the gears themselves. Yea, they probably could be slightly smaller, but as a first pass it works well. They are made out of heat treated steel, 4140 I believe.

As for the weight, I don't have the total weight, but I removed 12lbs of stuff.

-Britain

Cool. That's over 22 lbs of rotating mass gone (clutch,PP, gears etc).!!!
!!!!

Yeppers, that was the goal!

I will get into the aero mods and some of the suspension mods soon.

-Britain

Hillclimbs in our parts have very narrow turn arounds. It's just you and the car often. ...and yes 100 mph is common in quick cars. I was in 4th gear in both the boxster and the 914-6 hanging on for dear life at Hoopa.

Guess you could have two boxes but what a hassel.

The last serious SCCA FProd 914 road race car I was involved with had 3 tranny's. Two complete and one with a diff in it ready for gears. The owner had 15k in the 3 boxes + gear sets.

How fast do you want go?


B

You going to travel from SF to Ohio for the Runoffs without a spare tranny and some gearsets? Nobody I know would go that far without a backup and spares



B

Two boxes is essential for my plan to work out. I have one already built for AX. Just saving parts and stashin lil bits of cash away for the second one right now. Should be very cool. Heck, it only takes 2 hours to swap in my driveway. That's the easy part. Figuring out what to build... that's another thing all together

That's nice. Still a hassel for most low budget AX guys. I can see it for road race guy going to runoffs. 2nd gear only ax car probably has less of a chance of issue if gearbox is well maintained.

When I (er my shop) first put the short gears in my car a few years ago, I figured before long I would need at least one other box with taller gears. However with essentially no aero being gear-limited to 130 or so is not necessarily a bad thing. I know a couple other 914 guys (John R. and Andy R.) ran the same gears as me for years, on a variety of tracks. So I'm sticking with this one for now but I may add a cooler setup.

Now IF I actually drove this car on the freeway for more than 10 minutes at a time it would effin drive me crazy and I would HAVE to get another box.

So now that we have beat the 2-speed transmission to death, I will move on to what I am working on for Aero improvements. Now, I know that aero in AX has a questionable effect, however if it didn't doing anything then why are so many SCCA National Champion cars have wings and splitters?

The rear of the car already has a 10" lexan spoiler sitting at a high angle of attack. This is the maximum allowed by the SCCA rules and when we added it I could definitely feel the difference in high speed sweepers and slalom's. The rear spoiler is further benifited be the fact that we have no windsheild to deflect the air as it passes thru the car. The only thing in the way is my big head.

Now it is time to start addressing the front, specifically a splitter. I agree that a convention splitter that would be found on a street car or road race car that extend about 2" at the most is not going to be as effective at low AX speeds. However, the SCCA rules allow a much larger splitter which I beleive would amplify the effects and be effective a lower speeds.

In the SCCA prepared classes, the ruling states the following:

Front splitters are allowed and shall be installed parallel to the ground (within +/-3 degrees fore to aft) and may extend a maximum of 6 inches forward of the front bodywork/fascia as viewed from above. Splitters may not extend rearward past the centerline of the front wheels. No portion of the splitter may extend beyond the widest part of the front bumper/fascia as viewed from above.

The illustrative interpertation this rule look like this:
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My path towards this design first started with creating a duplicate set of bumpers and valance assemblies that can be interchanged depending on the venue and even the course design. I can retain the current set-up which provides ample ground clearance for local events at our bumpy PIR facility and switch to the "aero" package at locations such as Packwood or Qualcomm. In addition, the assembly needs to be easily removed to allow loading and unloading on the trailer.

Here is the current set-up on the car, you can see that there is a lot of daylight underneath the front of the car.





So, I started with the purchase of a front fiberglass bumper with no holes cut for the foglights or oil cooler. I then obtained a used aggressive lower valance from Brett Laurila. The valance was in rough shape, but usable. The first thing I did was delete the brake ducts as they are not needed in AX and added a large lip on the bottom for a place for the splitter to bolt to. Here it is attached to the car.







As you can see, it is much more aggressive and a lot lower. The only issue, if you look at the last picture long enough, you will notice that the cut-out on the valance for the oil cooler inlet is not centered. Now, I didn't make that cut-out, it was part of the valance but to think that somebody went into production with the inlet offcenter is embarressing. I wonder how many cars out there are running around with this valance?

Well, being off center is not acceptable to my level of standard. Therefore, I decided to section the inlet out and move it over the required 1/2" to make it centered. It now looks much better.





Now, before you say anything, I know that the body will need to be opened up a bit to line up to the valance. I haven't done it yet but it will be done.

Now I am at the point in which I can mock up the splitter and determine out far out I will extend it within the specified rules. I laided out a peice of cardboard and translated the bumper profiles down which as in itself gives me a 4" lip. I can effectively extend this out another 6" to give me an effective 10" splitter. Now, I believe this is a little overkill, but I am interested to see what your opinion is. I have a lenght in my head, but we shall see. The marks on the cardboard are at 2" intervals as measured from the translated bumper profile. The farthest mark is 6" which is the max lenght to the rules.

When youre talking national championship level cars every little bit counts. Suspect aero component of XP cars is fairly minimal in comparison to 400 to 500 HP the national championship cars make. I'd focus on HP and better rear suspension if Nationals are youre aim, but aero looks cool!

For practical matter more spoiler you have more potential damage you will incur upfront at your local events where aero is less a factor. I love Boxster urethane front end. Just bounces cones off with little damage. Poor fiberglass spoiler on my 914 was abused from some of those 60 MPH direct hits. Also do you really want anything that makes car wider or longer down low where cones are likely to be hit?

Well, I agree on the wider part...the splitter is not allowed to go past the body line of the front bumper, the drawing in the picture is a bit too wide. In addition, the actually splitter will be very stout...I will show more of that when I get there.

-Britain

This was my concern. In theory the one piece front bumper and air dam sounds good, but in practice.. it sucks. When you hit something? it wipes out the air dam AND the bumper. I'd rather just have the air dam break away and not take the bumper with it.

Ask Roger Sheridan why he split the front nose on his wide body kits. Easier to repair a removable lower air dam.



B

The splitter will be made out of a material called Poly-Metal. It is a very strong, but lightweight sheet with a solid thermoplastic core switched between two sheets of aluminum. The splitter will be mounted to the body and take the majority of the abuse. There will be three splitter supports from the valance down to the splitter. I think the final outcome will convince you of the strenght.

Here is the Poly-Metal details:
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-Britain

So I'd encourage you to test the theory, but my (limited) experience is telling me that you might run into some issues with the large splitter... Thoughts:

I once did a front splitter project similar to what you're working on. It worked well- too well. The extra front downforce wasn't balanced by enough extra rear downforce, and the center of pressure moved forward, ahead of the center of gravity.

Normally the center of pressure is slightly behind the CG- this results in slightly more understeer as speeds rise, which is very nice for high speed stability- quite confidence inspiring. When the COP moves ahead of the CG the opposite happens- the fronts stick while the rears don't, resulting in instability- the rear steps first on high speed sweepers and braking (the nose dives, the front splitter gets closer to the ground, the COP moves forwards further).

My personal approach would be to concentrate on maxing out rear downforce first, then add as much front downforce as you comfortably can without upsetting the balance. Are under body tunnels, side skirts or diffusers allowed per your rules? If you've maxed out your wing that's where I'd look if you are allowed; ideally you'll add enough downforce to the rear to be able to use your full 6" splitter while still keeping the COP behind the CG.

Of course you may find that you're not making enough downforce at AX speeds to upset the balance, of course, so I might be off in the weeds, but I'd still max out the underbody if I could- I agree that aero can be big at the AX, especially of a light car.

-Pete

Remember, the splitter is allowed to extend back to the centerline of the front axle. It will mount to the underbody tray that goes over the master cylinder. That is where the majorty of the load will directed when it hits a cone.

-Britain

Thanks for the information Pete.

I have thought about this in lenght. I am doing additional "aero" items to maximize the effect of the rear wing...to be revealed when I am a little farther along. I also agree that going the full 6 inches might be a bit much, which is why I probably won't go all that far out.

I am not allowed to do any underbody diffusers in the rear or anything like that so I am limited to either the current spoiler or an actual wing with a limited surface area.

-Britain

In addition, the design will allow both set-ups (the new splitter and the previous bumper) to allow switching at events.

-Britain

Well, if you're gonna do it, you may as well go for the gusto.

Get it low enuff in front so you can run it up the maximum 3 deg in the rear. I'd go back to the front edge of the tire. A couple-3-4 dzuts to hold it up on the aft end. It's gonna need to be stout....... enough to cut cones in half if they get in the way.
I'd also put rubber dough nuts on the body mounts behind the bumper to help absorb impacts with mother earth. They are already there,IIRC

There is no rule against canards that don't stick out past the body work.....think about that for a bit.