Yellow Bullet Forums banner

1 - 20 of 38 Posts

·
Registered
Joined
·
2,670 Posts
Discussion Starter #1
Pro Mod 4-Link, in a 2650# Full Chassis Car.

QA1 Double Adjustables... Anti-Roll...etc.

Car hooked up fine with Lenco and Nitrous Motor... I went to a Blown Alcohol and I cant hook the thing up to save my life.

I tried leaving the line around 4500 rpm... 6.5 Pounds of air in 1022 Goodyears.

It was squating, breaking loose, and jumping the back right off the ground at first... I tried stiffening up the shocks and it just blew the tires off.

I went to the track today... Had a 1.47 sixty foot time, and ran out the traps at a 7.70 @ 186 letting off early.

Car goes down the track nice and straight, I just cant get it off the line.


Any baseline setups I can go to... It just dosnt work the way it is right now.
 

·
Registered
Joined
·
4,629 Posts
QA1's are not much shock for a blown motor..

What are the front and rear weights and where are the 4 link bars and IC
 

·
Registered
Joined
·
1,663 Posts
close to the same problem i had with a local guys camaro it was perfect then he went to a blower, this adds quite a bit of wieght to the front of the car so you might need to rescale it and fudge your IC.
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #6
I agree with the QA1's but they came with the car and I have to work with them... I am gonna check out today and see what the IC is
 

·
Registered
Joined
·
2,024 Posts
ARE YOU TESTING AT OXFORD AND WINTERPORT TAKE THE RIDE TO NEW ENGLAND FOR SOME GOOD BIT ALSO AGREE THAT THE QA1 ARE NOT FOR THAT CAR
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #8
Just ran at new england this weekend.... 1.47 sixty, 7.76 @ 186

I think the clutch is 90 percent of the problem... Need to soften it up!
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #10
That was letting off of course... It spun then I got out of it.
 

·
Registered
Joined
·
5,124 Posts
A couple things to think about is, did the blown motor end up with a lot more low RPM grunt? Two each tire and car want's it's own tire pressure, could yours be a little low?
 

·
Registered
Joined
·
5,124 Posts
What I saw was overpowering the tires, too low a gear at the line and possibly too many RPM on the leave or clutch not soft enough. Your anti squat value is well on the high side. Look at the separation on the rear at the leave.

That blown engine makes a lot of torque at lower RPM, add that to a lower gear, (high numerical gear) and you have a hard time taming it down with your clutch.
 

·
Registered
Joined
·
20,824 Posts
Thats because they took the Santhuffs off when they sold you the car. :) heh

I think we have a winner. There is no way those shocks can control the power you have with the adjustments they offer
 

·
Registered
Joined
·
4,629 Posts
Take the car to a competent chassis shop...

The chassis ride height appears WAY to high... the engine height for a blown motor looks WAY to high...

What is crankshaft height.. and did you ever measure the 4 link locations??
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #17
Take the car to a competent chassis shop...

The chassis ride height appears WAY to high... the engine height for a blown motor looks WAY to high...

What is crankshaft height.. and did you ever measure the 4 link locations??

The car really isnt high.... That is an optical illusion due to the factory corvette body not dropping below the frame rails... A VFN body would have a much different look because they have a 3 or 4 inch drop ground effect.

So anyway, here is the information.

Front of Frame is 4" off the ground ( this will tell you the car is plenty low )

The highest point of the frame all the way in the back behind the driver is 7" off the ground ( This is where the VFN body ground effects come in. They give a uniform appearance 3 to 4 inches off the ground. )

The crankshaft centerline is 10" from the ground.

Top 4 link bar is approx 21"
Bottom 4 link bar is approx 22.5"

Bolt centerline to centerline in rear for 4 link is 10"
Bolt centerline to centerline in the front of the 4 link is 7"

IC is 48" out and slightly down... Maybe 2 inches... It is hard to get an accurate measurement in the garage.

Tire pressure was way to low in the video ( my tire pressure gauge was broken )

Launch RPM was 4500 with a 2.49 Low Gear Lenco 4 Speed.

Clutch pressure is set up at 7 turns ( book says 9 to start then back off from there ) It is set up a little softer than the book says, but it looks like I am gonna have to soften it some more.

Shocks were on #4 of 8 for stiffness.

It also appears I am going to have to put some preload on the passanger side rear to get it to stop twisting... We will see.

I never thought going from a Nitrous Motor to a Blower Motor would have this much effect on the launch.
 

·
Registered
Joined
·
4,629 Posts
If your spread is 10 and 7 your IC is out nearer to 75"

What is the angle of the lower bar.. and how high is the axle centerline and how far up and down from the axle centerline are the rear mounts?

Yes that must be an optical illusion because it looks way high in that video..
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #19
If your spread is 10 and 7 your IC is out nearer to 75"

What is the angle of the lower bar.. and how high is the axle centerline and how far up and down from the axle centerline are the rear mounts?

Yes that must be an optical illusion because it looks way high in that video..

Yeah, the video was taken with a wide angle camera, but it scruntched up into a normal size pic which throws off the perspective.

You could be right on the IC... I was trying to do a string measurement and didnt have a calculator to do the math.

The bottom bar is very close to flat with the ground. It goes up slightly as it goes back.

Would you recomend droping the top bar down a hole in the front? You can see that they have had it in the two holes above in the past which seems to be completely wrong. I have plenty of room to move things around.

What would a good place to start with the IC be?

Does it make a difference that the mounting point on the rear end is further forward on the top?

I am not much of a 4 link tuner... lol. Most of my stuff in the past has been already set up, a hard tail, or didnt have the power I am running now.
 

·
Registered
Joined
·
2,670 Posts
Discussion Starter #20
Alright... some more measurements....

Keep in mind, these are all approximate as I am working around a lot of stuff.

From the axle centerline to the bottom mount is about 7.5 inches.

From the axle senterline to the top mount is around 3 inches.

I have an anti-roll mounted to the rear end as well which should be helping with the twisting.

Here is a pic from the back when the car unloads.

 
1 - 20 of 38 Posts
Top