The last races I went to a couple of months ago saw me hit a 10.04 and a 139.96 mph. Bad part was the car was quite a handful in first/second gear because of the suspension "porpoising" during the launch as it loaded/unloaded. Once I hit second it was fine and usually showed daylight under both fron tires on the 1-2 shift.

Since then I've made a few changes. I had Vette Brakes build me a custom 6 leaf steel rear spring to replace my previous 'glass one. It had done well, but I think I was at the point of just needing more. I then added a set of QA-1 12 way adjustable shocks and then extended my snubbers closer to rear trailing arms to limit travel.

I got a chance to make it to an 1/8th mile track in Houston last night finally to try it out. Never been to it before. Turned out to be a really neat place with great folks. Of course after the 4th run I got "invited to the tower" to discuss my lack of proper NHRA safety equipment. Rollcage (not a roll bar!), safety net, firesuit, neck brace, NHRA license etc etc. But they allowed me to keep making passes as long as I didn't return without proper stuff. Great! They even allowed me to take my wife for 2 runs as long as I shut it down after I hit second gear and didn't go too fast. She really enjoyed that....she had never been in the car with slicks.

I don't want to give away all the times yet, there are more races coming up soon and the competition could be serious...but I will tell you that even with terrible weather conditions...muggy and it started to rain just as we were heading home......I ran my fastest 60's and 1/8th mile times ever!

The neat part was that on almost every launch, all my buddies that were there confirmed 10-12" of daylight under both front tires through first gear and serious air under them on the 1-2 shift and often on the 2-3 shift! The guy who was bringing the video camera couldn't make it at the last minute, but one guy had a digital camera. Hoping he got some good shots do I can have a new screensaver! The new setup does not "porpoise" anymore. It actually appears to have rear of body "lift" instead of squat and it drives the rear tires down into the pavement as it lifts the fronts off the ground. I'm sure there is more in it with some work, but it sure feels nice to have it work this well first time out!


Anyway, I just wanted to say thanks to VB for great support and great parts. I even bought some new trailing arms from them at the Houston Vette show last weekend. Not installed yet, but I will soon. Everyone says I'm going to bend the stock ones soon! Plus just wanted to let everyone know that you really can make an IRS Vette hook pretty well even with a stick with just a little work and the right part selection.

So, I'm really confident that the elusive deep 9 second time slip on 93 octane pump gas with my 3600 lb. 3.07 geared(Viper Hunter!) convertible street Vette is just around the corner!

Gotta get to a "long" track soon. Hopefully I can get some good weather soon!


JIM

 

Jim.

Just how different is the rear setup in your car compared to the C4s?

This is in a early year vette right?

CAn you take some pictures of how your suspension is configured to compare it to the C4s for me.

My belief too in these cars is to keep the rear suspension as stiff as possible for best results. Sounds like you made it rediculously stiff and the results are good.

I have even given thought to LOCKING it so it can't squat at all, but unfortunately that also keeps it from driving the rear end downward also.

Good job..

 

Well, I suppose there are some similarities, but the real difference is the trailing arms. Old stuff like mine uses a single trailing arm instead of the 4 links the C-4 uses. I think with some playing, you can create the same effects as a 4 link drag setup almost. You could play with instant center etc. On the old stuff, I'm basically locked to the basic configuration overall. The "lift" points so to speak, are not perfect for forward acceleration.

Early cars seem to work well going stiffer. You can actually hook very well with the typical 'Corvette Squat", but depending on HP, it can cause some bouncing and weird geometry changes as the suspension moves that far. Unless corrected, that is what breaks lots of u-joints. Not hard to correct....just have to lower the inboard mounting points of strut rods.

I haven't run a C-4 through the entire arc of travel, but it would be interesting. Need to unhook spring and measure it from full compression and then to full droop. If suspension travel is limited somehow, it's not as critical, but only slight camber changes can really screw up the hook.

You also want to monitor toe-changes as it launches. I know early stuff has a tendency to toe-out and it can really make it dart around under power.

Most C-4's I've seen as well as C-5's are just incredible how they hook with basically stock stuff. I "wish" I had it so good!


The new setup on mine seems to "drive" the tires downward and the whole body is actually lifting rather than squatting. So far so good!

BTW...killer ride you have there!



JIM

 

Awesome, keep us posted.

 

Not sure if you mentione it or not,, is your car an auto or man?

If its an auto, what converter/trans are you running?

I just went to a racing 8" and it seems to hit alot harder, but its hard to tell on the "street" - it just blows the tires off like your on ice at nearly any MPH < 60, if you boot it.

I will have to examine my setup in a little more detail here and see what I can turn up.

Thanks.

Jesse

 

I'm jealous. That is all...

 

Mines a stick...it's a G-Force GF5R trans...straight cut gears etc.

It would be "smarter" to put an auto in it....but it's just so much more fun to bang gears! Plus it's only got 3.07 gears, so I can still cruise on highway at 2600 rpm or so and play with the top end guys too!

I'm just a die hard "3 pedal" guy!!


JIM