GTM roll cage modifications and race car build log

[kabacj]

It's Thompson Raceways inaugural race weekend. An exciting day for track lovers in the north east where we needed some variety. I had a host of changes to test on the GTM including stiffer rear toe link mounts.

Lucky for me I was pitted with the factory five brain trust. . Mark Dougherty (aka the traveling builder) ,John George( FFR challenge series national champion) , Jim Schenck (engineer responsible for the GTM), Pat Maddigan who runs a heavily modified challenge car, Brendan Dougherty who has been working on factory five cars his whole life and Chris Allen who owns a factory five coupe and is racing the spec e-30 class. Talk about a crew of guys who know what they are doing.

Friday am we had a drivers meeting and track walk. The first session was a bit hairy as nobody knew the racing line. The pace of the lap is relatively slow. The track is tight. Several turns where the camber falls off as you exit and and six pavement transitions as we enter and exit the oval.

Friday practice the verdict was good. The car was stable when transitioning from hard G turns to full throttle and off throttle. Seems like I fixed that problem.

Next step was to start tuning the car. I really should have aligned the car after all my welding, but I had marked all the suspension points and mounts to put it all back together with the same settings I started with. I know it was low probability, but work and travel ate up all my garage time in the past two weeks. It's all I had time for.

I had some instability around 120 as I went over some big dips in the front straight.

Thompson has many places where it cycles the suspension through its travel top to bottom. Our theory is that was cycling the rear toe through changes due to bump steer and getting the car into a setting range it did not like.

A toe change and addition of more shock damping and we got the car to settle down over the high speed dips on the front straight.


One thing I learned this weekend is that if you mess up the rear toe/ bump steer on this car you completely change how it handles. It's been said before but it's worth repeating. The car even turns differently when the rear toe is wrong.

The few people who have complained about stability of the car most likely had their rear toe incorrectly setup.

By mid day Saturday I had the car working well enough that I was comfortable pushing. We all had found the fast line around the track and learned where we could pass. The only bad thing was we also started ripping up the new pavement. This made passing a real challenge. Off line was covered with the small stones that make up the track surface. Marbles in the true sense. I think everyone in our group went off the track at least once on Saturday.

I spun for the first time in the GTM and the second time and drove the car sideways like a drifter countless times. One time the car swapped from left to right 5 or 6 times before I caught it. I'll have a hi-lights video soon.


Skip to my rookie race on Saturday afternoon.

Ill admit it was a little scary. Its been 10 years since I have raced anything. I don’t really know the racing protocol. Sure I learned it in the racing school but that’s not the same. We never did rolling starts or standing double yellow restarts on motorcycles… ah hell how hard could it be?

Since the track was super slick. Off line was basically unusable in many corners and nobody wanted to wreck their car on lap one. The first turn was very reasonable. HUGE difference from motorcycles. Turn one is a hairball every time, every race, regardless. You have a bunch of kids 20-30 and a few adults from 40-60 fighting to win the race in turn 1 going 5-10 wide from a standing start. Bumping is normal.

Not so with cars. Much higher dollar investment in the equipment and cooler heads prevailed. . I was the only guy out there on full tread DOT tires. That was not ideal but I did not let that stop me from trying to match corner speed with cars on full slicks. That usually worked. One lap I tried to make a pass in an off camber turn off line. Note to self, don’t do that. I instantly spun on the marbles but luckily was able to get the clutch in and lock the tires and release when I was going forward again. I didn’t need to restart the car. I don’t think I even stopped moving, just down two gears and I was off again. No flat spots . Cool! Dodged that bullet.

I only had one other close call during the race. After I was out of traffic I kept pushing my lines wider to try to carry the most speed through the corners. Of course that got me very close to the slick line. Acutally into it a few times. Its possible to drift a GTM! Not the fast line, but its fun.

I ended my rookie race without further incident. To my surprise I got 3rd place in SU.

The two winners were driving 850+ hp TA1 Trans Am cars. Im not in their league yet, but ill get there Lots of folks driving the high horsepower cars spun off including me. I was just lucky enough to limit the time penalty .

My first car racing trophy.



John

[Mark Dougherty]

John
It was awesome meeting you. and being able to put a face to the name.
You did great at the track.
Keep tuning and you will find alot more in that car.
Later
Mark D

[carbon fiber]

Excellent write-up John. I can't wait to see the vids on this one. Glad the frame beef-up helped, I'll be doing the same mods, thanks for pioneering.

[kabacj]

John
It was awesome meeting you. and being able to put a face to the name.
You did great at the track.
Keep tuning and you will find alot more in that car.
Later
Mark D

Thanks Mark

It was great meeting you as well. Guess what! You know how you were saying I should go full stiff on the shocks. I did that on sunday am and ran a half a second faster!

Thanks so much for your help.

For the group ill spend some time on the suspension setup I used as soon as I have time to measure it at home. Measurements i take at the track are always suspect so I want to verify them all before I post them.

I made at least one mistake with the toe settings and boy was that noticeable. a few turns in the wrong direction on the toe link and the car transformed from good to un driveable. Oops. Oh well. A good learning experience.


John

[crash]

Great write up. Glad you are having fun.

[Fraser D]

Congrats John!
I am looking forward to seeing your vids.

[fastthings]

Good show, can't wait to see some of the video.

[kabacj]

Thanks guys. Ill have the video done ASAP. I have a few hours of video to watch and edit.

While we are waiting im looking to add the dry sump and a set of wider front rims shod with race slicks.

I need to step up my game now if I plan to be successful in Super Unlimited.

Shopping for the dry sump setup seems like I have quite a few options.

Anybody have an endorsement for a particular system?


Thanks
John

[crash]

I use ARE stuff, my buddy and my engine builder both swear by the Daley stuff, and the FFR PDG GTM runs the ASA spec engine setup. The ASA stuff is BY FAR the cheapest way to go. Give Richard Migliori a call and he can give you some contacts to help in tracking down the parts. We just set up a complete spare engine so I know he just spoke with the supplier back east. If you need his number PM me.

ARE can be found here...www.drysump.com

[Plebeian]

Great report. What was the lap time difference comparing your car to the Trans Am cars?

[kabacj]

I use ARE stuff, my buddy and my engine builder both swear by the Daley stuff, and the FFR PDG GTM runs the ASA spec engine setup. The ASA stuff is BY FAR the cheapest way to go. Give Richard Migliori a call and he can give you some contacts to help in tracking down the parts. We just set up a complete spare engine so I know he just spoke with the supplier back east. If you need his number PM me.

ARE can be found here...www.drysump.com

I was also leaning to the ARE setup. I have two quotes. One for a 2 stage and one for a 4 stage system. Am I correct in my understating that the 4 stage simply creates more vaccume when compared to a 2 stage?

And with that extra vaccume I'll actually pull the oil through the motor instead of depending on gravity to return the oil to the bottom of the motor?

Thanks for the help

John

[kabacj]

Great report. What was the lap time difference comparing your car to the Trans Am cars?

Well since I'm not yet up to speed in the GTM I'd say my times are a bad example. I dropped 5 seconds over the weekend and was still making changes on Sunday when I dropped into the 1.19s. John George on the other hand is a very good driver running a well setup car. He was 3 seconds slower then the TA cars running a 1.16 in a challenge car with 1/3 the HP and no aero. My theory is that the GTM is lighter and has better aero and I have more HP. Well setup the GTM will be a good match for the TA1 cars doing 1.13s . At 1/3 the price and far more reliable. We will see how that theory works out


The top 10 fastest cars this weekend spanned 1.13 to 1.19.

The good news is the factory five cars made a very good showing this weekend against a field of well funded and well prepped race cars.

John

[crash]

Not trying to be a Richard, but if JG or you are anywhere near a REAL Trans Am series car then the people running them haven't a clue. Those should be 900 HP with huge tires and great suspensions. I was talking with a friend that used to run the Trans Am series and was saying how we were very happy to be running 148 down a particular straight. His reply was "Let me know when you reach 187". That's a HUGE difference, and challenge cars are no where near our times out here. Again, not trying to be a jerk, and comparing to TA cars is fun(obviously I am doing it also) but they should be 10 seconds faster than a challenge car, easy.

Now the ARE stuff. Really all I use of theirs is the pan. I run a 3 stage Auto Verde pump with a separator. The low profile pans from ARE require a bit of modification for a supply line attachment. I have suggested to Gary that he change/update his castings as it would be very nice to not have to weld on a brand new cast pan to make it work, but last time I checked, he had not done this. You can get one of those long block adapters, but the fitting ends up below the pan and the lowest thing on the engine/trans combo. Not a real good thing for the oil supply line to the engine. Be careful/aware of developing too much vacuum. It can starve a piston of oil. Also, the number of stages does more than create vacuum, it also gets the oil out of the engine better so it helps with crank windage. Segmented pans are another way to go if you want to go with a 4 stage scavange pump. This just makes the pan like four separate little pans and prevents sloshing.

The ASA stuff uses a single stage pump and vacuum is not created in any substantial amount.

I'll look for some pictures of my components.

IMG00060-20110411-1806.jpgAuto Verdi Pumps.jpg

One of the things ARE has that is nice is a multi stage pump that bolts right to the A/C compressor block bosses. In my case I had to make a front engine plate to mount the pump, which was a hassle. ASA pump mounts this way also, and the Daley stuff doesn't need a mount as the pump is part of the pan.

[johngeorge]

Not trying to be a Richard, but if JG or you are anywhere near a REAL Trans Am series car then the people running them haven't a clue. Those should be 900 HP with huge tires and great suspensions. I was talking with a friend that used to run the Trans Am series and was saying how we were very happy to be running 148 down a particular straight. His reply was "Let me know when you reach 187". That's a HUGE difference, and challenge cars are no where near our times out here. Again, not trying to be a jerk, and comparing to TA cars is fun(obviously I am doing it also) but they should be 10 seconds faster than a challenge car, easy.

Not trying to be a Richard either, but thanks for the props Its 1.7mi with 10 turns and not a long straight thus suiting the Challenge Car on Hoosier A7 extremely well.. ohh and and here is the TransAm guy's incar: http://youtu.be/QC7d4ovEFgA

[crash]

Not trying to be a Richard either, but thanks for the props Its 1.7mi with 10 turns and not a long straight thus suiting the Challenge Car on Hoosier A7 extremely well.. ohh and and here is the TransAm guy's incar: http://youtu.be/QC7d4ovEFgA

Video is not loading. Other YT videos are fine. I'll try again later. Anyway, again really not anything against you in that I KNOW you are great at getting everything out of the challenge cars and have enjoyed running with you at the 25. Wish you would continue to make the trek out west but understand why you don't. 10 turns, 1.7 miles? Yeah that sounds pretty tight and with your abilities against a "normal" guy in a Trans Am car I can see how you all may be close. That said, under NORMAL racing conditions with the best TA cars/drivers and you or us, I would still favor the TA car heavily. They are intense...and fast. I was a crew chief for a TA team in the 90s and a fabricator for much longer. Best finish was a podium at Limerock. The TA guys(and gals) are a fast bunch.

[tachman]

I believe ARE makes a 2 stage setup that has 2 scavenge stages and uses the stock crank driven pressure pump. I think it can be driven by a serp belt with stock AC pulleys. It may even clear the motor mount but I don't know for sure. This is a major upgrade from the circle track pan ASA setup we're using.

One thing we found with our ASA single stage setup is that when the scavenge only pump failed the crank driven pressure pump continued until the tank was emptied. By this time the engine was so full of oil the performance and sound changed alerting the driver to look at the guage (we since have a warning light). Even with no oil pressure, splash lubrication with nearly 2 gallons of oil in the engine avoided major damage (we changed rod bearings but they weren't seriously damaged). This makes it nearly fail safe. A bit down the road from here Team QRP had an ARE 3 stage pulley failure (get the collet mounted one for 3 stage) and even with a bright dash warning by the time Chris shut it down it was seizing and caused major damage to the crank and rods.

If the 2 stage setup is scavenge only I would expect it could be a safer choice and may include an improved pressure pump.

Jim H, PDG

[crash]

I took a look at this video by the same guy...https://www.youtube.com/watch?v=BAh30jmdd_I

Granted I have not been directly involved in Trans Am stuff in over a decade, but that does not look like a Trans Am car. Looks more like a GT-1 car. Definitely not the required dash and electronics setup we had to run.

[kabacj]

I believe ARE makes a 2 stage setup that has 2 scavenge stages and uses the stock crank driven pressure pump. I think it can be driven by a serp belt with stock AC pulleys. It may even clear the motor mount but I don't know for sure. This is a major upgrade from the circle track pan ASA setup we're using.

One thing we found with our ASA single stage setup is that when the scavenge only pump failed the crank driven pressure pump continued until the tank was emptied. By this time the engine was so full of oil the performance and sound changed alerting the driver to look at the guage (we since have a warning light). Even with no oil pressure, splash lubrication with nearly 2 gallons of oil in the engine avoided major damage (we changed rod bearings but they weren't seriously damaged). This makes it nearly fail safe. A bit down the road from here Team QRP had an ARE 3 stage pulley failure (get the collet mounted one for 3 stage) and even with a bright dash warning by the time Chris shut it down it was seizing and caused major damage to the crank and rods.

If the 2 stage setup is scavenge only I would expect it could be a safer choice and may include an improved pressure pump.

Jim H, PDG

Thanks Jim. Your experience is one of my concerns. With a belt driven setup oil pressure and engine rpm are not directly related. If you throw a belt or the pump stops for any reason you have seconds to react before the motor starts to destroy itself.

I need to see if I can program my ECU to shut down throttle to idle if oil pressure drops below a determined value.

I can't believe I need to pull the motor and transaxle again!

Thanks for sharing your experience.

John

[kabacj]

I have suggested to Gary that he change/update his castings as it would be very nice to not have to weld on a brand new cast pan to make it work, but last time I checked, he had not done this. You can get one of those long block adapters, but the fitting ends up below the pan and the lowest thing on the engine/trans combo.

One of the things ARE has that is nice is a multi stage pump that bolts right to the A/C compressor block bosses. In my case I had to make a front engine plate to mount the pump, which was a hassle. ASA pump mounts this way also, and the Daley stuff doesn't need a mount as the pump is part of the pan.

Thanks for that. For once I just want to bolt something on without fab / design work. I don't mind welding, but I would think that it would be possible to warp the pan.

In your setup do you eliminate the stock oil pump?

[crash]

Thanks for that. For once I just want to bolt something on without fab / design work. I don't mind welding, but I would think that it would be possible to warp the pan.

In your setup do you eliminate the stock oil pump?

You can see in the picture...the red caps are scavenge and the yellow cap is the pressure stage. Yes I eliminate the crank driven internal pressure pump. One of the problems with cog belts is tearing the teeth off when decelerating. ATI has a new one way clutched hub assembly for just this issue on super charged engines. I may try retrofitting that into my setup. Definitely the internal pump is a very good and easier solution.

[KeithBoden]

Can you comment on the extent of the oiling issues that has you researching a dry sump setup? Is there a possibility that baffling, running a bit more oil in the pan, restrictors and a lower volume pump (not sure if those are possible on LS motors, that is coming more from BB chevy thoughts), a big accumulator, or a combination of those might help solve the issues? I guess I'd try a lot of things before a dry sump setup, just because they involve a lot of parts and a few of them (like most race parts) require maintenance and rebuilding periodically. I'm sure they are necessary in many applications, just curious if the weight, extra volume of pressurized oil around the engine compartment, and fab time could be avoided.

[crash]

Can you comment on the extent of the oiling issues that has you researching a dry sump setup? Is there a possibility that baffling, running a bit more oil in the pan, restrictors and a lower volume pump (not sure if those are possible on LS motors, that is coming more from BB chevy thoughts), a big accumulator, or a combination of those might help solve the issues? I guess I'd try a lot of things before a dry sump setup, just because they involve a lot of parts and a few of them (like most race parts) require maintenance and rebuilding periodically. I'm sure they are necessary in many applications, just curious if the weight, extra volume of pressurized oil around the engine compartment, and fab time could be avoided.

The definitive answer is NO. That is why the higher end factory Vettes have a pseudo dry sump FROM THE FACTORY and why SCCA and NASA both allow a spec dry sump system for Corvettes running in otherwise virtually stock engine arrangements. The LS has an issue with sustained high lateral loads and there have been people that literally got ONE LAP at a super speedway before their engines went BOOM!

Maybe you can make something work, but I can tell you that you can't do it for less $$ than seeking out an older ASA dry sump system on ebay or whatever. Few hundred $$ will save you thousands.

[kabacj]

Can you comment on the extent of the oiling issues that has you researching a dry sump setup? Is there a possibility that baffling, running a bit more oil in the pan, restrictors and a lower volume pump (not sure if those are possible on LS motors, that is coming more from BB chevy thoughts), a big accumulator, or a combination of those might help solve the issues? I guess I'd try a lot of things before a dry sump setup, just because they involve a lot of parts and a few of them (like most race parts) require maintenance and rebuilding periodically. I'm sure they are necessary in many applications, just curious if the weight, extra volume of pressurized oil around the engine compartment, and fab time could be avoided.

HI Keith,

I also wanted to avoid the dry sump for many of the reasons you mention. Cost, complexity etc.

To keep the LS3 alive on the track I am running the MAST motorsports extra deep and baffled pan. This solves some of the oil starvation issues common in an LS3. MAST claim its good for road race applications. Adding an oil accumulator will also solve for some of the issues with oil slosh in the pan. This is probably a good solution for track days, but not the best solution for racing. I can see the oil pressure dip under G load with my current level of grip. I have decided against the accumulator (even though i alrady have it and all the hardware) as its only going to mask the issue for a short period of time as I step up my game.

Now that I need to complete with other cars I am both driving harder and pushing the car harder. This weekend I will go to limerock and Ill scuff a set of racing slicks and further setup and refine the car. The GTM can hang with many cars on slicks while running DOT R compound treaded tires. Adding Slicks takes you into a whole other area of G loads.

The reason I will swap over to the dry sump is three fold. One without the deep oil pan I can lower the motor and the CG of the car. Two with vacuum in the crank case oil is pulled through the motor instead of flowing via gravity keeping oil in the right places under sustained G load. Three the Vacuum in the motor will lower crank case pressure at high RPM that bored out LS3s are famous for. Sure you also get less drag on the crank from friction spinning through the oil so thats nice.

I look at the dry sump as insurance that no matter how high G load I get I will always have oil pressure. Its possible to get many of these benefits with cheaper / less complex solutions but none that I have found have the full package you get with a dry sump.

As crash says, Its much cheaper getting a dry sump then the motor work required to fix an oil starved engine.

John

[KeithBoden]

Excellent and thorough answer guys, thanks! Pressure drops under high lateral loads. I agree, a whole separate forum could be dedicated to figuring out where the oil is when it isn't where you need it; I have friends that have run clear intake manifolds and without an oil pan on engine dynos (yes, what a mess) to see where it goes in various scenarios. They were worried about longitudinal loads, but you could always tilt your motor over 65 degrees to simulate a 2g load

[Cobra 61]

Hi John,
Been so busy. Congrats on your first competition race! I see there has been no mention of others long ago that attempted to race/track the GTM with oiling problems and eventually killing the motor. I haven't an answer for that and I don't remember what their conclusions were either. Our dry sump doesn't appear complicated or comparatively that pricey vs. engine replacements (plural). The single stage ASA system we have indeed paid for itself as we have run the motor out of oil on two completely different occasions. One when the oil cooler was ripped off in a wreck and the driver drove it back around the track and into the paddock. Two, the gear inside locked up at 6,000 RPM and drove a short time after.

Congrats!!!!!

[kabacj]

Hi John,
Been so busy. Congrats on your first competition race! I see there has been no mention of others long ago that attempted to race/track the GTM with oiling problems and eventually killing the motor. I haven't an answer for that and I don't remember what their conclusions were either. Our dry sump doesn't appear complicated or comparatively that pricey vs. engine replacements (plural). The single stage ASA system we have indeed paid for itself as we have run the motor out of oil on two completely different occasions. One when the oil cooler was ripped off in a wreck and the driver drove it back around the track and into the paddock. Two, the gear inside locked up at 6,000 RPM and drove a short time after.

Congrats!!!!!

Thanks Richard,

After doing the research, I fully agree that a single stage system that uses a dry sump pan, a single stage pump and an external tank to supply the standard oil pump is the minimum way to go on any track ready GTM. Clearly GM agree, as Crash also points out, GM dry sump any corvette that is sold as track ready. Thanks again for all the info that your team have shared regarding what works and the pros and cons of each setup you have used.

Thanks for the inspiration to make the GTM into a race car. I forgot how much fun it is to race. Car racing and motorcycle racing are very different, however both have their upsides. So far one of my favorite parts of car racing are the lovely girls that organize the grid and hand out the trophy’s. We never had this when I raced motorcycles.




Factory five also reported on the race at Thompson in case you missed it here is the link.

https://www.factoryfive.com/whats-ne...pson-speedway/

John

[fastthings]

You stud.

[crash]

Hi John,
Been so busy. Congrats on your first competition race! I see there has been no mention of others long ago that attempted to race/track the GTM with oiling problems and eventually killing the motor. I haven't an answer for that and I don't remember what their conclusions were either. Our dry sump doesn't appear complicated or comparatively that pricey vs. engine replacements (plural). The single stage ASA system we have indeed paid for itself as we have run the motor out of oil on two completely different occasions. One when the oil cooler was ripped off in a wreck and the driver drove it back around the track and into the paddock. Two, the gear inside locked up at 6,000 RPM and drove a short time after.

Congrats!!!!!

And then there were those THREE times on that brand new engine we were testing...that had the ASA setup fitted to it to fit into the FFR PDG GTM...Remember the pulley issues?

[crash]

So far one of my favorite parts of car racing are the lovely girls that organize the grid and hand out the trophy’s. We never had this when I raced motorcycles.




John

That must be a local to YOU thing, as we certainly don't get that type of treatment out here. Trophies are bigger for you guys too.

[kabacj]

I spent most of my time tuning the rear toe and shock damping on my last visit to Thompson raceway.

I did not even come close to testing and documenting the setup changes I planned to test.

This weekend I'll travel to lime rock park ct. Saturday is a double race day and I also will run the TT sessions that don't conflict with the races. That should give me plenty of test time.

On my list was testing the rear ARB. I am starting with the 19mm stock corvette bar. Mostly because my buddy gave it to me for free. I also think it's a good idea to move from soft to stiff instead of jumping in with a very stiff bar.


With some tabs added to the stock frame and some aftermarket c5 poly bushings it's possible to simply bolt up the stock bar in its stock orientation.




The only problem is the tabs on the lower A arm are about an inch too far inboard. The GTM has the A arms mounted more inboard then the c5 , however the wheels are set outboard to compensate. With the low ride height I run the bar pick up point is a little close to the A arm.




To solve for this I could weld a tab on to the lower A arm which might impact the strength of a heat treated part. Or I could make a steel tab and attach it to the factory five shock mount support. Or I could just chop up the bar and place the pickup points in a more ideal orientation.

I went with option 3

Step 1 is flip the bar over and upside down. That both makes the bar match the contour of the GTM frame where it mounts and also gives the bar a more upward sweep on the outboard ends. Of course that also puts the mounting holes on the bar in an orientation that is not ideal.

No problem. I cut about 5 inches off the end of the bar where it makes a bend away from the angle I want. While I had the end off the bar I put it in the press and crushed it flat just like GM did for the end hole. I also added two more holes for adjustment.







It was late so I decided to call it quits for the night. Tomorrow I'll make up a slug to join the ends of the hollow tube that forms the ARB. A few plug welds into the slug and a nice weld around the joint and the joint will be plenty strong I think.

The net of this change will stiffen the bar a bit as well as add some adjustment so I can decide if I need more or less bar then this setup offers.


John

[longislandwrx]

John,

Congrats on your win! Car is really coming together. How's the weather supposed to be Saturday, perhaps I'll take a drive out to CT.

Just wait until you grab a podium finish at Limerock, you should have seen the race day girls at the grand am last year.

[kabacj]

John,

Congrats on your win! Car is really coming together. How's the weather supposed to be Saturday, perhaps I'll take a drive out to CT.

Just wait until you grab a podium finish at Limerock, you should have seen the race day girls at the grand am last year.

Thanks man,

I was very happy to bring hardware and a cool picture home from my first race.

You should come up to lime rock on Sat. Factory Five will be well represented. At least 3 challenge cars and one GTM will be in attendance. When are you going to bring your 818?

John

[kabacj]

Since its a rainy 4th of July courtesy of the remnants of hurricane Aurthur , I got to do a little welding and fabricating instead of drinking beer and having a BBQ. Hmm its a toss up which is more fun...

I had to weld on the sections of the C5 ARB that I had cut off and make up new links to tie the ARB to the lower A arm.

First I welded up the arb.

With the slug inside it was an easy weld. I just built up the area so the bar looked smooth and without kinks.



next i needed to fab up new links to replace the corvette links which unfortunately dont work with the shock support as the studs are too short.

My first idea was to weld two nuts on to a length of tube as a quick and easy way to get a working solution. That process took a while, was heavy, and looked ugly. I decided I could make the part out of aluminum in less time.



That worked out well as the part is both stronger and lighter.

here are the links assembled.



and here you can see them installed.



I spaced the rod ends away from the A arm and nut so they have max mis alignment, but that was not necessary. As I cycle the suspension through its max travel the links stay well aligned to the motion of travel. Actually turned out better then I had hoped.

One of the benefits of flipping the ARB over is now it is more offset from the GTM frame.



We will see how this all works on the track tomorrow.

John

[crash]

John,

I was watching Race Monitor this weekend...what happened?

[kabacj]

John,

I was watching Race Monitor this weekend...what happened?

Funny you should ask Crash. Its a long story, but here goes.

The weather was GREAT following a very rainy Friday I was excited to head out to the track.

First session was the TT group I headed out and there was clearly something wrong as the car was misbehaving badly. I was actually experiencing the same issues I had experienced before I did the toe link re enforcements except now the car was unstable at high speed as well. It was far worse then ever. On and off throttle was scary!

Since I had measured the deflection on the links I was sure that was not the problem. I had just done an alignment at home and I knew that was also in good shape. I could not understand what problem I had. I could not even think of something that could break and cause this.

When i came on off the track, I figured I would just verify the toe settings again. WHAT! I have half an inch of toe out in the rear. How is that possible? I triple checked the alignment at home.

So I carefully adjusted the toe links to bring the toe to 1/8 in on both sides.

Next I went out in Thunder Qualifying. Holy cow this thing is still not working. I did not even do one lap before I came in. The car was barely drivable.

Again measured the rear toe. now I have way too much toe IN on the driver side!

I must be going crazy. I know I measured the toe properly.

Time to call a friend. I called the guys over and asked them to double check what I was doing bc for some reason I cant measure the same settings twice.

They watched what I was doing and double checked my work. Since I was had lost with the toe settings from my careful alignment at home I resorted to measuring off the frame to the rotors. measured both toe links to the frame. Squared the rear rotors to the frame then reset the toe.

I re set the rear tires to toe in - 1/8 on both sides and took the car around the paddock to try to duplicate the toe change. By this point I had missed Thunder qualifying. Lime rock does not have much area to go higher then 5mph. So I just did a few laps of the paddock and a drive out to the skid pad and back. On the way back I heard a thunk... like a bad one. Did I forget to tighten something... I waited for something bad to happen but nothing happened.

Got back and jacked the car up and checked the whole rear over . Then I saw it. The eccentric had moved . I mark the eccentric to the frame to verify that its not moving. They have never moved in many track days. I have kept them in because they are easy to adjust. I looked at the cams and they were polished from moving on the track. What’s worse is I have Crash's kit to eliminate the eccentrics.

So the reason I was having so much trouble was my toe was changing as I drove around the track. That’s bad for handling by the way.

So I took out the camber gauge. Set the camber and verified I was back at my mark on the eccentric and frame. Again set the toe and tightened it all down.

I had a TT session right before the first Thunder race. Normally I would skip that one, but this will be perfect to test the car. Ill just go out for a few laps to familiarize myself with the track I have only been to lime rock once and that was at the early stages of GTM development. After a few laps ill come in and Grid up last for Thunder Race. (since I had missed qualifying)

TT session went well and I roll up to the grid for the race, and I glance at the fuel gauge. Oh man I need fuel I don’t have enough for a 30 min race. I was all disorganized because I was chasing the handling issue all AM. With the wheels on and off so many times I killed the battery in my Impact gun. Back to the pit... very slowly through the crowded pit. I’m all the way by turn 2 on the far side of the pit from the pre grid. By the time I fill up the race has started. By the time I get strapped in and back to pre grid ill have missed another 5 laps. I decided to bag it. I have another TT session and another Thunder race in a few hours.

I started race 2 on the last row since I did not qualify. ( I was not on the grid sheet) THEN Race 2 was cut to 10 racing laps by an extended double yellow flag as a car went off at turn one on to the soaked grass at about 90. He plowed the tire barriers right over the guard rail.

So a lose nut and my forgetting to fill up the car with gas messed up race 1 and race two was super short. On the good side I know for sure what toe change mid corner feels like! It feels just like when you flex the toe link mount.

While I was at the track I mounted up some Hoosier Slicks. WOO HOO traction!! I did not run them in the race for fear of oil starving my motor before I install the dry sump. I am pretty sure Ill be a bit more competitive with these. The toyo r888 are a good street/track day tire, but they are not a great race tire if the track is dry and they are nothing like a full race slick or even a DOT slick. The racing hobby is always a saga, but its fun!

[crash]

I bet I know the first thing your gonna do before the next race...

[kabacj]

I bet I know the first thing your gonna do before the next race...

Yeah that's for sure. The st2 corvette guy pitted next to me was like oh yeah throw away those cam adjusters they are junk on the track. He missed the race because his motor blew up so I felt a little better.
Things can always be worse.
John

[crash]

Yeah that's for sure. The st2 corvette guy pitted next to me was like oh yeah throw away those cam adjusters they are junk on the track. He missed the race because his motor blew up so I felt a little better.

John

He didn't have a dry sump?

[kabacj]

He didn't have a dry sump?

Ha that was my first question too. He has a race built 419 LS 3 like I do, but he put the dry sump in. He also said put the sump in ASAP. He had what seemed like an mass airflow sensor issue that he replaced. Maybe the damage was already done however. The motor smelled like it had overheated. Maybe ran too lean and did the damage that way. But he lost power. Did not sound like a cheap fix.

He said he is going back to a GM crate motor

[LCD Gauges]

You have some great looking linkage parts on your car! Even better than you made most of them yourself.