Violent bouncing on launch.

[fordified]

You can calm the rear end with limiters up front. You can make a set for $20. They’ll limit weight transfer. I use 1/4” stranded cable connected to the control arm and the frame. On the frame side I use a strip of 1/8” steel with holes drilled every 3/4 of an inch so I can adjust the limiters.

I have those even with very expensive shocks front and back.

If you don’t want to call Randy at least go over to class racer and ask the stock eliminator guys what they think in the tech section.

[rfoll]

It is not wheel hop. The front of the car does not bounce. I tried setting the rear shocks on full dampening, but all it did was make the bounce stiffer, like there was no spring at all. Some have indicated the front isn't coming up quick enough, possibly because the rear of the car is now 1.5" higher than before. Just as an experiment I might try some spring spacers in the front to re-establish the previous stance. The gear change puts 20 percent more torque to the axle, possibly aggravating a problem that was barely under control before.

[fordified]

Wheel hop usually describes rapid up and down movement of the rear suspension which causes the slicks to literally hop on and off the track surface. If you tightened the rear shocks all the way then it's almost definitely not wheel hop. You need video up close in the water and at the line.

Did you buy new slicks? Radial or bias-ply? Bias-ply is way more forgiving than radials. Check the circumference on both sides. It's important that they match.

Are you feeling anything different in the water?

I just read that you broke your trans case. Do you have enough clearance between the yoke and the trans to account for suspension movement? Usually 1 1/2". Look for witness marks on the tail shaft housing to see if it’s hitting. Also check your trans mount.

It’s not the rake of your car that’s doing this.

[rfoll]

I have been running 10X26 Hoosier slicks, and went to 10X29 Hoosiers. Same tire different diameter. The back tires are not coming of the ground, but the bounce causes them to loose traction enough to raise the rpm to about 7500 and back down to about 6000 when it lands. It does it twice before I shift to second gear. In the only relevant video, (from 5 years ago), you can see the front bounce slightly. https://www.youtube.com/watch?v=l21jY7CohH8

[rfoll]

I have been running 10X26 Hoosier slicks, and went to 10X29 Hoosiers. Same tire different diameter. The back tires are not coming of the ground, but the bounce causes them to loose traction enough to raise the rpm to about 7500 and back down to about 6000 when it lands. It does it twice before I shift to second gear. In the only relevant video, (from 5 years ago), you can see the front bounce slightly. This with the 26" tire 3.73 gear combo https://www.youtube.com/watch?v=l21jY7CohH8

[fordified]

I'm trying to help you as best I can, but you need to answer the questions. There's a reason I'm asking them. I know this is the internet, but I've been doing this a long time and have learned a thing or two along the way. There are guys who've been racing longer than I have but never seem to go any faster. They'll spend money on stupid shit and ignore the real problems with the car especially when it comes to suspension.

I asked if the slicks are radial or bias. I'm not talking about the radial street car crap. There are slicks that are radials like the ones on my car. They're light and I can run 20 lbs. or more of air pressure in them. They're 3-4 hundredth faster than the bias ply, but they can cause problems when they're not right. Whether you run bias ply or radial slicks, you have to measure roll out/circumference of the tires. It's important that they match. Take a piece of string, wrap it around the tire, mark it and measure the string with a tape measure. Compare the two tires.

Are the slicks new or used? That matters a lot. Did you get somebody else tires that look good but are all used up? Are they new, but the diameters are not the same? These things cause problems.

If you broke your transmission because your driveshaft is too long, then you have a binding situation that affects the suspension. Maybe you do maybe you don't. That's why you have to check. Did the case break for whatever reason, or did it break because you don't have a torque strap on your engine or the drive shaft is slamming into the tailshaft?

When I see bounce, I see shock settings. It doesn't matter the rake on your car. With good shocks, you can tune your suspension. Weight transfer is a big thing, but it's most important only on the starting line. My car is front heavy. I use the 4-link bars to move the IC back and to soften the rise so I don't wheelstand past the 60' clocks. The rest is shock settings.

You have to begin with basics. You need to check whether the rear is straight in the car. You typically compare it to a crossmember. You have to make sure the trans, driveshaft and rear are aligned. You need some string, a plumb-bob, some chalk, a square, a good tape measure and a flat concrete floor.

Take off the shock, including the adjustables. Push up and down on them to see if they're working right. Do the left and right sides move the same up and down? Are they blown out or valved wrong? You can fix that for cheap.

I think you have caltrac bars. They're good and on just about every A, B, C stock eliminator car that I've seen with leaf springs. They also tend to run his split monoleafs. Those are 9-10 second cars on 9" slicks that usually weigh a lot and have to run a class-legal stock engine. The guys who go fast spend a lot of time on their suspension.

Start with the basics and check everything. Just because the pieces fit together and are the way they came from the factory doesn't mean they're square and move correctly. It will take you a day in the garage to check. Take notes and look for parts that are rubbing, binding, dented or whatever. Also, check your bushings including the bushings on the leaf springs, and check the springs mounts on the car and on the rear. Don't assume they're right or not damaged in some way.

[fordified]

By the way. If you do what I posted above and you spend the time to make sure that your suspension is aligned and has free movement up and down that nothing is bent, broken or binding, you will pick up. Usually more than you would expect. Everything has to be right. Then you can tune with your shock and go even faster.

[fordified]

I looked at the video. The front end bounce is due to shocks. The extension is good but the compression is too light. The front end should go up, stay up and drop gradually.

I also noticed you have a lot of body separation at the rear. You're hitting the tire too hard. You need to lower the angle of the caltrac bars. You can do this by changing the setting but you should also try to lower the car.

Can you get a set of monoleafs or run the springs you have as monoleafs? Multi leaf springs are not helping you. You're not driving a pick up or going to the market. You need monoleafs with a spring rate that holds up the back of the car and no more. Getting rid of those multileafs will be a move in the right direction. They'll lower the angle of the caltracs and let your shocks work.

If you look at the rear tires they seem to be climbing up the front of the wheel well which changes the geometry of the rear, the driveshaft angle and the shock extension. You got to fix that suspension.

Watch how this car leaves and then compare it to yours. Both foot brake cars. Look at the rear tire and body separation then watch the front. The rear is much more important. Notice the angle of the caltracs.

https://www.youtube.com/watch?v=d9Yvw5Jku5k

[rfoll]

I wrote a long response to your suggestions, but it didn't post. It's too late and I'm too tired to try to re-compose my response. I agree with things you said. The front should go up and stay there. The Caltrac bar has already been lowered to the bottom setting. It was clearly hitting the tires too hard. With that done, and leaving at just enough to clean up the engine rpm, the problem goes away. I will post again later when I car collect my thoughts again.

[1980RS]

I wrote a long response to your suggestions, but it didn't post. It's too late and I'm too tired to try to re-compose my response. I agree with things you said. The front should go up and stay there. The Caltrac bar has already been lowered to the bottom setting. It was clearly hitting the tires too hard. With that done, and leaving at just enough to clean up the engine rpm, the problem goes away. I will post again later when I car collect my thoughts again.

I watched your video that you posted and it does not look like the car bounces too bad. Do you still have the rubber dampeners that GM put in the upper control arms as a bump stop? if so get rid of them. I added an inch of front end travel and it really helped out my car launching a lot. You can also add 100lbs. of weight in the trunk at the rear of the trunk area to help with weight transfer to get your car to pitch better. My buddy has a '69 Camaro A/ Stocker and has about 200 lbs. in the trunk.

[rfoll]

I wrote a long response to your suggestions, but it didn't post. It's too late and I'm too tired to try to re-compose my response. I agree with things you said. The front should go up and stay there. The Caltrac bar has already been lowered to the bottom setting. It was clearly hitting the tires too hard. With that done, and leaving at just enough to clean up the engine rpm, the problem goes away. I will post again later when I car collect my thoughts again.

I watched your video that you posted and it does not look like the car bounces too bad. Do you still have the rubber dampeners that GM put in the upper control arms as a bump stop? if so get rid of them. I added an inch of front end travel and it really helped out my car launching a lot. You can also add 100lbs. of weight in the trunk at the rear of the trunk area to help with weight transfer to get your car to pitch better. My buddy has a '69 Camaro A/ Stocker and has about 200 lbs. in the trunk.

That video is 5 years old with completely different tire and gear combo. The engine and converter are the same but it does not show anything like the bounce I have been getting. Thanks for the tip on the A arm bumpers. I will have to look for them. I haven't been to the track this year to test other changes and get more video because of the crack in the trans case and the non-stop rain we have been getting. Add a 2 week bout of sciatica to the mix, (hard to imagine tying shoes can be so painful), and I have projects stacked up waiting for me.

[1980RS]

I wrote a long response to your suggestions, but it didn't post. It's too late and I'm too tired to try to re-compose my response. I agree with things you said. The front should go up and stay there. The Caltrac bar has already been lowered to the bottom setting. It was clearly hitting the tires too hard. With that done, and leaving at just enough to clean up the engine rpm, the problem goes away. I will post again later when I car collect my thoughts again.

I watched your video that you posted and it does not look like the car bounces too bad. Do you still have the rubber dampeners that GM put in the upper control arms as a bump stop? if so get rid of them. I added an inch of front end travel and it really helped out my car launching a lot. You can also add 100lbs. of weight in the trunk at the rear of the trunk area to help with weight transfer to get your car to pitch better. My buddy has a '69 Camaro A/ Stocker and has about 200 lbs. in the trunk.

That video is 5 years old with completely different tire and gear combo. The engine and converter are the same but it does not show anything like the bounce I have been getting. Thanks for the tip on the A arm bumpers. I will have to look for them. I haven't been to the track this year to test other changes and get more video because of the crack in the trans case and the non-stop rain we have been getting. Add a 2 week bout of sciatica to the mix, (hard to imagine tying shoes can be so painful), and I have projects stacked up waiting for me.

Be prepared for a little noise when the control arms hit the frame after removing the bumpers, my Camaro has been making the smack noise for years but it sure helped launching the car up.