Operation Bad Penny version 2.1T (track edition)

[bwhinnen]

Steve are you getting more timing advance up high compared to the old tune? Also I assume the fuel injectors are sized with enough headroom etc?



Other than that the curve looks brilliant, torque is on hard and fast, would be lovely to see it stay for another 500rpm at least though

[Steve1968LS2]

Steve are you getting more timing advance up high compared to the old tune? Also I assume the fuel injectors are sized with enough headroom etc?

Other than that the curve looks brilliant, torque is on hard and fast, would be lovely to see it stay for another 500rpm at least though

Yea, injectors have room left. They are FAST 39 lb units.

I think the timing was a tiny bit higher.. 26 rather than 24 but I would have to review the data.

The cam is done by 6500... maybe down the line that would be cool to try and hit. The main thing I wanted was down low torque.

[David Pozzi]

Steve, Your subframe uses C5 suspension correct? The Corvette suspension has different spring motion ratios than a Camaro sub. It may be closer to a Camaro than a C4 though. A 600 lb spring on a C4 would be very very stiff.

What rate front coil was on there?
A 300 rear coil is probably good. Springs don't change roll rates much however.

[Steve1968LS2]

A 600 lb spring was on there at the Super Chevy event. Now the fronts are 550 lb.

The shocks are at more of an angle compared to a shock on a stock C5 'Vette. I think that's why I can get away with 600 (or 550). The ride really isn't bad.

We now have the option of rasing the Watt's knuckle if we wish one notch. I think the valving is going to help as well.

[Payton King]

sub. The bump steer was dialed out of the car with the caster set at 5 degrees. If you have rolled 6 or 7 degrees in you will get a little bump steer. I know the alignment specs should be set like a 2000 Corvette, except for the caster setting....that should be at 5 degrees like previously stated.

I would be curious to know why chevy went from 6 degrees of caster in 2000 to 7 degrees in later years?

I would also be curious as to what the corvette team was running on the C5 race cars.

What alignment specs are you running for the auto cross and the track day?

[Payton King]

With the caster set at 5.7 yielded 1/32 toe change with 1 inch of compression....which is 1/64 on each side. He got 1/32 going up an inch and 1/16 at 2 inches.

No good way to compress more than 1 inch without taking the shocks off.

[Steve1968LS2]

Forgeline just sent me over this picture of the rear wheels..

[David Pozzi]

I doubt the C5R used the stock spindle, but perhaps the same dimensions. I did hear they use more agressive camber gain than stock to suit their race tires.

A web search turned up the C5's use rates in the 600 to 625 range.
Did you find it toed out under bump or in?
David

[Damn True]

I'm certain that LG motorsports did not use the OE spindle on their cars. I'd assume the same for Pratt & Miller.

[Payton King]

and spent a good amount of time going through Corvette Forum getting information. Here is a quick run down on what I found.

The stock rubber bushings deflect up to 1/4 inch in Autocross and Track days using R compounds or better. This can be fixed 3 different ways. Use the GM T1 bushings for the Corvette, after market poly bushings or full on spherical race bushings.

Under hard load the lower eccentrics can move changing your alignment. You can drill the eccentrics and put a 1/4 inch bolt to hold them in place. I think it would be cool to do a street alignment and drill a hole, then do a track alignment and drill a hole. That way you could change it with out having to go to the alignment shop. Get a set of toe plates to adjust your toe when you make the change.

A company also makes camber plates that replace the lower eccentrics. This locks in more camber than you get with the eccentrics. Then you shim the top like a conventional car to get the amount you want.

Alignment specs:

Dual Street/Track-aggressive for R compound tires minimal street driving. This setting will cause wear on the inside edges of steet tires.

Camber -1.6
Caster 5 to 8 degrees
toe 0.0

Dedicated Track car with race tires, DOT or slicks

Camber -2.5
Caster 3 to 6 degrees
toe 0.0

Some were saying to run up to 1/8 toe out as it will make the car turn in quicker but sometimes in will cause a mid turn push.

Since you have the Pozzi's in your corner there is no doubt you are in good hands and they know what they are doing. Since the 21st is C5 stuff I pulled info for the C5. Hopefully these are good starting points for y'all to get the car right.

As far as parts go: WWW.pfadtracing.com for bushings and camber plates

David, that was toe out on the compression.

[Steve1968LS2]

My bumpstear..which was minor and only under compression...



My alignment specs.. his "aggressive street C5" program:




Thoughts? I will be getting it re-aligned before the event/SEMA

[hotrdblder]

steve, .08 is not aggressive, i run -2.0 on the street with no or very minimal inner tire wear after 2000 miles, for your event i would look to have at least -2.5 and if you have r888 on there go for 2.75 , caster looks good, also put an 1/8th inch toe out in it before event, helps turn in, etc. at event set tires to 30-32 psi cold, check them after running, should be no more ten 20 degree spread across tire if set up properly for the track your running.

[Payton King]

LG Motorsports did do their own spindle (steering knuckle) but the only difference in was it had a 1 inch drop built in. Nothing else was changed. Cool think about a corvette is the same knuckle on the front is used in the back. On the front you use the bearing pack and on the rear you run the half shaft through the hole.

I agree with Jake. I would dial in as much static camber as you can get and let the caster fall where it may. I am not sure how much you can get with the eccentrics full over...just for the competition.

I would also change out the bushings to the polys from Pfadt. I think they are $280 for a set, but it also does the rear for a corvette. You may call them and see if they will sell you a set just for the front.

I would definitely pin the eccentrics so they do not move. Once the alignment is set, drill a hole and tap it, put a screw in it for insurance.

I would use Jakes recs on the front bar. The Speedway bars all work with the same pillow blocks that you have and arms. May want to get a bigger bar and try it out. On Speedway's site they have a chart with bar sizes and arm lengths. I am guessing the bar that Jake is using on his will be right on the money for your car.

Have you driven you car with the new motor yet?

Are the shocks finished?

[Bow Tie 67]

" This setting will cause wear on the inside edges of steet tires. "

The Camber is set at 1.7 my 69.

1 A/X 3 track days and 1200 miles

The tires have a noticeable list when off the car.

[Steve1968LS2]

Burning the midnight oil at Best Of Show...

[David Pozzi]

Payton, Great info!

I like this recommendation:
"Dual Street/Track-aggressive for R compound tires minimal street driving. This setting will cause wear on the inside edges of steet tires.

Camber -1.6
Caster 5 to 8 degrees
toe 0.0"

The A arm bushings would help, I'm not fond of Poly bushings, but they would be better than stock bushings.

I'm not up on what Corvette's need, but do recall autoxers bending the front cradle inward to get more neg camber. Of course it was illegal for stock class but they were doing it.

I saw Corvettes at the races using a billet fabricated front upright, the guy told me they were a lot stronger, didn't break like stock spindles under racing conditions. I wonder if they were LG spindles?
David

[69camarokid]

Those new wheels are godly...

[Payton King]

bending the cradle to get more camber. David Farmer is a corvette racer that is local and Pettigrew said that some use to do that, but for some reason I think it was on the C4...probably on the C5 as well. There is not a lot of camber adjustments with the eccentrics.

I am not sure you can get as much camber out of a 21st sub frame as Jake reccommended. I know his frame has a lot built in and is a much more agressive piece....which I like!

[Steve1968LS2]

Found my radiator has FOUR leaks in the core.. can't be fixed.. I'm having a new one fabbed up.. argh!

My powder paint was delayed a day so that Robbie Gordon could get his damn racecar chassis coated..

Gotta love it!

[hotrdblder]

always something steve
what caused the leaks? work hardening? can't wait to see penny done