Determining bump stop length
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Determining bump stop length
My car's been off the road for a few years and is soo very close to coming back out.
I have an 89 Z51 with a 383 and a ZF6 using a McLeod Street Twin clutch.
This clutch hits hard and I have broken a few spindles and half shafts.
I have read about running longer bump stops, like the Energy Suspension 9.9143 to control how far the rear squats and to make sure the half shafts don't drop below parallel with the ground.
http://www.energysuspensionparts.com...sp?prod=9.9143
I also plan on grabbing a new set of Bilstein Z51 shocks due to the fact that my car is 25 years old and I believe they are still original.
How do I measure how much bump stop to run, because I have heard about people trimming to fit their desired lengths?
I haven't tracked the car much in the past due to fear of breaking parts, etc. and the engine I have recently dynoed (engine dyno) at 480 hp/506 tq (but operator was using a battery pack like the kind you boost a car with and we had multiple pulls starting at zero degrees timing working our way forward and the time I hit those numbers, the battery pack was fluttering around the 11 volt mark....long story short, I believe there is more in it than the numbers show.)
I have an 89 Z51 with a 383 and a ZF6 using a McLeod Street Twin clutch.
This clutch hits hard and I have broken a few spindles and half shafts.
I have read about running longer bump stops, like the Energy Suspension 9.9143 to control how far the rear squats and to make sure the half shafts don't drop below parallel with the ground.
http://www.energysuspensionparts.com...sp?prod=9.9143
I also plan on grabbing a new set of Bilstein Z51 shocks due to the fact that my car is 25 years old and I believe they are still original.
How do I measure how much bump stop to run, because I have heard about people trimming to fit their desired lengths?
I haven't tracked the car much in the past due to fear of breaking parts, etc. and the engine I have recently dynoed (engine dyno) at 480 hp/506 tq (but operator was using a battery pack like the kind you boost a car with and we had multiple pulls starting at zero degrees timing working our way forward and the time I hit those numbers, the battery pack was fluttering around the 11 volt mark....long story short, I believe there is more in it than the numbers show.)
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 275
From: Melbourne, Victoria, Australia
My car's been off the road for a few years and is soo very close to coming back out.
I have an 89 Z51 with a 383 and a ZF6 using a McLeod Street Twin clutch.
This clutch hits hard and I have broken a few spindles and half shafts.
I have read about running longer bump stops, like the Energy Suspension 9.9143 to control how far the rear squats and to make sure the half shafts don't drop below parallel with the ground.
http://www.energysuspensionparts.com...sp?prod=9.9143
I also plan on grabbing a new set of Bilstein Z51 shocks due to the fact that my car is 25 years old and I believe they are still original.
How do I measure how much bump stop to run, because I have heard about people trimming to fit their desired lengths?
I haven't tracked the car much in the past due to fear of breaking parts, etc. and the engine I have recently dynoed (engine dyno) at 480 hp/506 tq (but operator was using a battery pack like the kind you boost a car with and we had multiple pulls starting at zero degrees timing working our way forward and the time I hit those numbers, the battery pack was fluttering around the 11 volt mark....long story short, I believe there is more in it than the numbers show.)
I have an 89 Z51 with a 383 and a ZF6 using a McLeod Street Twin clutch.
This clutch hits hard and I have broken a few spindles and half shafts.
I have read about running longer bump stops, like the Energy Suspension 9.9143 to control how far the rear squats and to make sure the half shafts don't drop below parallel with the ground.
http://www.energysuspensionparts.com...sp?prod=9.9143
I also plan on grabbing a new set of Bilstein Z51 shocks due to the fact that my car is 25 years old and I believe they are still original.
How do I measure how much bump stop to run, because I have heard about people trimming to fit their desired lengths?
I haven't tracked the car much in the past due to fear of breaking parts, etc. and the engine I have recently dynoed (engine dyno) at 480 hp/506 tq (but operator was using a battery pack like the kind you boost a car with and we had multiple pulls starting at zero degrees timing working our way forward and the time I hit those numbers, the battery pack was fluttering around the 11 volt mark....long story short, I believe there is more in it than the numbers show.)
I am not quite running the h/p you are but even the Dana 44 is not bulletproof.
You may want to talk to 383vett, he has been drag racing for some time with a high h/p 383. See the link to his missing teeth thread. and send him a message
http://forums.corvetteforum.com/c4-t...ken-teeth.html
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
I also forgot to mention that I now have Denny's Nitrous Ready half shafts as well.
I think I'm ok for the half shafts, but first time I bust a spindle, I'll prob go Summers Brothers beefy 32 spline spindles.
I think I'm ok for the half shafts, but first time I bust a spindle, I'll prob go Summers Brothers beefy 32 spline spindles.
Le Mans Master
Joined: Feb 2005
Posts: 6,479
Likes: 565
From: Clearwater Florida
..... Put the car on jack stands ... disconnect/remove the spring bolts ... jack the knuckle up to where you want it ... remove the tire-wheel and measure the gap 'tween the rubber bump stop and the chassis and adjust from there ... remembering that you need some suspension travel for cornering and those occasional rough roads ... trying to level the halfshafts is a drag car kind of deal and will result in great anti-squat but will also dramatically limit suspension travel ... creating a potentially dangerous driving condition ..........
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
You want the bump stop long enough that it keeps the halfshaft level - when the suspension bottomed out on it.
All this does is prevent the halfshaft U Joints from being placed at an angle under max power/load during launch. By allowing the halfshaft and it's U Joints to be perfectly straight, you put them in as strong of a position as possible.
As C409 stated - Just disconnect the rear spring and it's easy to figure out how long you will need to trim the bump stop.
I have said this before and I'll say it again.
The car squatting down on the rear spring is NOT the kind of weight transfer to the tire you need (or want) in drag racing.
When drag racing the idea of weight transfer is transmitting all that force or motion of the car directly into the rear tire. When you have soft springs that allow the car to squat down - they take away from that force and it's just wasted motion.
Now - I won't say that the bump stop mod will solve your problems - because in all reality your problem is too much clutch IMO.... but it will give your stuff the best chance it can have.
Will
All this does is prevent the halfshaft U Joints from being placed at an angle under max power/load during launch. By allowing the halfshaft and it's U Joints to be perfectly straight, you put them in as strong of a position as possible.
As C409 stated - Just disconnect the rear spring and it's easy to figure out how long you will need to trim the bump stop.
I have said this before and I'll say it again.
The car squatting down on the rear spring is NOT the kind of weight transfer to the tire you need (or want) in drag racing.
When drag racing the idea of weight transfer is transmitting all that force or motion of the car directly into the rear tire. When you have soft springs that allow the car to squat down - they take away from that force and it's just wasted motion.
Now - I won't say that the bump stop mod will solve your problems - because in all reality your problem is too much clutch IMO.... but it will give your stuff the best chance it can have.
Will
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Would it be simple enough to cut the bump stop to the desired length and then just use that particular bump stop at the track and swap it out for my current one for road use?
So, when I'm at the track, I'll just change bump stops?
So, when I'm at the track, I'll just change bump stops?
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
No problem at all. The bump stops are just held on with one nut.
Also I just want to be clear that the Energy Suspension PN 9.9143 will need to be modified a little to "bolt on" the C4 Corvette....
It's round at the top and the factory frame bracket is square.... You will have grind/cut 2 flat spots (one on each side) about 1" deep and 2" tall on the top of it so it will seat in the factory frame bracket. I did both of mine with a 4" angle grinder in about 5 mins.... It's messy and molten Polyurethane will burn the crap out of you so wear gloves and face shield.
I trimmed it to length with a hack saw but sawszall or grinder would work there as well.
Will
Last edited by rklessdriver; Apr 30, 2014 at 03:05 PM.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
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Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario