After reading the post by old iron and seeing the afermentioned term "porpoising", I must say my car does this horribly. I was racing this weekend and my racing partners are continually telling me the car is unloading and porpoising. I have a 67' Barracuda with SS springs, non adjustable mopar 452914 rear shocks, about a 1"+ lowering block, and an adjustable pinion snubber that is touching at the lowest possible setting. I have .870 torsion bars and C/E 3 way adjustable shocks that seem to be a mystery where they are set. The car has a big block, I drove to the track and ran a 10.59 but with a horrible 1.630 60' time on nitrous. This weekend my tires showed little to no holes in the treads and they are spent, the car has went from a 1.69 non nitrous 60' to a 1.73 and still running a 7.20 1/8 mile at 99 mph. I checked the shocks length at ride heigth and they are 16"..... is this where the 452914 mopar shock is supposed to operate. I will be getting a new set of slicks for my August 4th weekend race and hope to get the porpoising fixed, I expect its the rear shocks, I have to get this problem fixed! Im putting down what I think is 700 horse and cant seem to get a good 60' and this porpoising is horrible, im disappointed its not pulling a wheelie

Any video?

I might, my wife said she videod "all my races" Saturday.....I made it to the quarter finals, 5 rounds.....and then red-lighted.

2 things can cause this... tire pressure real high
and shocks... and in some cases its both... you will
need to get adjustable shocks... you can do a band-aid
and lower the tire pressure BUT it might get loose
on the top end..... oh... I'm not a fan of snubbers...
they were made to a crutch for worn out springs

Ive got some video showing it, how do I post it?

also you could be bottoming out the shock.

first attempt at a youtube video


http://www.youtube.com/watch?v=zShFQpnca9s

11 lbs http://www.youtube.com/watch?v=WyEKrmLElZU&feature=BFa&list=ULzShFQpnca9s

Looks like the back shocks aren't working for you.

How much front end travel do you have(from it sitting
there and jacking it up)

when my car was doing that i had too much spring in the front.
i am running caltracks and their springs.
i did not have the 5 to 6" they wanted and i would hit it and
the springs with all the windup would throw the front in the air.
not the car lifting it. it only went up 4" or so. then it would come back down and it would act up after that.
i got rid of some preload and got qa1 adjustable shocks to fake the front spring rate by stiffening them up a tad if it does it again.
you may be in a different situation with new slicks.

get good hardware. nothing sucks mor than limiting your self because you do not want to get better parts. the 10 need a little bit more attention to detail i am finding to get the car to leave well all the time.
get rid of the snubber just try it on the springs and see how that is. does your car leave twisted? the snubber makes it a tripod. launch and then roll over to the passanger side.

I saw a few things in the video.When you were running the camaro,it looks like his car is doing the same thing but worse.look close.How was the track prep that day?The tires are no help if they are done.Shock travel will cause this,also I had a similar prob. years ago with a GTX,SS springs,and long shocks.The car would wheel hope bad,& unload itself over & over.Took the pinion snubber off.Problem solved.just my

I think most of your problem is in the front end...
you need more travel
EDIT
Like I said before... I'm not a fan of those CE shocks...
the Caltrac fronts seem to work on most cars for a
cheapo shock

Have you walked the track? Almost appears to have frost heaves?

I was thinking my culprit was the rear shocks, the track isnt perfect, but giant heaves it doesnt have. I looked at the Calvert front shocks in the Mancini flyer and they say they are for maximum weight transfer and I was considering them. Im going to fix this problem, if I have to keep throwing money and parts at this thing then so be it. Do I need to measure the existing front shock ride heigth or will the standard A body shock work just fine. I am not afraid of buying some adjustables eitheir, I seen for $300 you can get a set!

I tried Mopar auto drag shocks on the rear with SS springs on my car a long time ago and it would wheel-hop under certain conditions. I switched to Rancho shocks and never wheelhopped again. Harder leaving, higher HP cars seem to need stiffer shocks. Of course it would spin occasionally depending on track conditions, but it spun "smoothly". Rear shocks have to control the winding up and unwinding of the leaf springs and the regular shocks couldn't. But working on the front end should help also. I found OEM style shocks tended to raise the front end too quickly and compressed too easily. Koni adjustable drag shocks are on mine now. But you have a big block which makes transfering the extra weight that's on the nose and keeping it transferred more difficult.

It was a totally different set-up, home built chassis with ladder bars, but I found that adding 100+ lbs in the trunk of my old bracket Challeneger helped it be much more consistent.

I had the same thing happen years ago with my Dart and it turned out the shocks were worn out. Once I replaced them the porpoising was gone.