Wheelies - Hypothetical Combo

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71GSSDemon

71GSSDemon

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So, a discussion (winter bench racing about making the cars quicker) with friends came to the topic of a street strip car capable of a wheelie. We would like to do some track time soon. Yes, each set up is different, but what does it take? Also, I know with SS springs, the idea is lift in the rear vs squat so there is some fighting that too. More gear? More HP/TQ?

We can use my car as an example as an "average" car:

1971 Dodge Demon - all steel except hood, full stock interior
440 9:1 compression
ported iron heads
hyd flat tappet LSA 107° installed at 102° .518" lift duration 229/242 @50.
Weiand tunnel ram with Holley 660s
MSD Pro Billet ready to run distributor
2" headers, automatic RMVB
Current converter is incorrect 2500 - needs to be 4000-4200 tight (in my belief - also I would be willing to add a trans brake if needed) - next on my list
3.91 SG with 29.5x12.5 Hoosier Quick Time Pro
Super Stock springs (my case 002 spring on both sides).

*** PLEASE NO "6000 CONVERTERS, 6:17 GEARS, 4SPD CONVERSIONS, LIGHTEN THE CAR 1000LBS, 500HP NITROUS, TURBO, ETC. THIS IS FOR THE SAKE OF A CONVERSATION PLEASE"
 
You didn't say anything about moving the engine :lol:

LADart.JPG
 
Yeah, just make a wheelstander. lol
 
A friend of mine in high school had a 1968 firebird with a built 400 ( pontiac ) and a turbo 350 transmission. He didn't have any trick suspension system and he got daylight under his front tires with no problem. I think that all he had was ladder bar's, spring clamps, pinion snubber. The car ran strong, but he was the type of guy that didn't talk about what was done to his car
 
MomsDuster said:
Good driveshaft and u-joints (1350’s)
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Thanks Mark. I am more wondering about the combo. I know I need better brakes, better driveshaft and overall stout parts. Wallace calculator estimates it could go 11.2-11.5 ish. I am thinking about the launch itself.

**Dumb life goal of a knowing what a wheelie in a car is like - without a purpose built wheelie only car. Budget (lack of) says to try with the big block A body I have.
 
Long, low, ladder bars. Geometry matters. You want the leverage pushing to the front and below the front tires, not lifting the rear like ss springs. See traction tutorials on you tube that explain cg, and lift/squat line, instant center.
Got my first wheelies in an aluminum head small block car with ladders, ENTIRELY different chassis reaction from my iron head big block ss spring car.
 
33IMP said:
Long, low, ladder bars. Geometry matters. You want the leverage pushing to the front and below the front tires, not lifting the rear like ss springs. See traction tutorials on you tube that explain cg, and lift/squat line, instant center.
Got my first wheelies in an aluminum head small block car with ladders, ENTIRELY different chassis reaction from my iron head big block ss spring car.
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Thanks. Yes I am very familiar with the suspension styles, instant center, squat, etc. I would like to work with what I have in that matter. Plenty of SS leaf spring cars do wheelies. I don't want to re-engineer it all.
 
1/4" steel plate on the bottom of the oil pan.
 
33IMP said:
Long, low, ladder bars. Geometry matters. You want the leverage pushing to the front and below the front tires, not lifting the rear like ss springs. See traction tutorials on you tube that explain cg, and lift/squat line, instant center.
Got my first wheelies in an aluminum head small block car with ladders, ENTIRELY different chassis reaction from my iron head big block ss spring car.
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One of the best answers ever on a forum. EVER.

Geometry matters and IF you want the chassis to pitch rotate (wheelie) you want a fairly long, fairly low Instant Center.

On my 4 link with a 4 speed I needed my IC (going from my memory because once I learned how stupid the starting point for IC that was used in 1989 was dead wrong and that was half the wheel base out and cam high up…which is great for tire limited, low HP, foot brake stuff as a starting point…maybe…so I had my IC all over the place getting it right) was 107 inches out and 4-5 inches up.

Most cars run the IC way too high and way too high IMO. Then they end up using up the shock adjustment trying to control the axle.
 
So, if leaving leaf springs, what would be the direction. Paul Rossi Challenger and many others did 70' plus wheelies with leaf springs.

20221120_105822.jpg
 
+ .030 318, W2's, Enderle Injected/methanol, 5500 stall, Glide, 4.88's in a 9", 2750 with driver.
Ran 9.95 @ 135
Al Bouska.jpg2.jpg
 
71GSSDemon said:
So, if leaving leaf springs, what would be the direction. Paul Rossi Challenger and many others did 70' plus wheelies with leaf springs.

View attachment 1716040258
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If you don’t have the MoPar chassis book, see if you can find I copy of it.

I have one at home but I’m not there.

Off the top of my head, the FIRST thing you need to do is buy some nice Double Adjustable shocks the front.

I say that because next up is /6 torsion bars. Unless the car is REALLY light you NEED them. If you don’t understand why let me know and I’ll type it out, but the short answer is: just like geometry matters, spring rate matters.

Once you get the /6 torsion bars you need to rebuild the front end using POLY bushings, and that included the lower control arm bushings. Poly is smoother than rubber, doesn’t bind like rubber and reacts more consistently than rubber.

To run poly LCA bushings you need to use adjustable strut rods. I use QA-1 strut rods. You can run poly LCA bushings with OE strut rods but that’s a bad idea.

You need to be able to get the front end to rise as easily and smoothly as possible. Once you get that, you use the double adjustable shocks to control the rate at which the car pitch rotates.
 
Rat Bastid said:
If you don’t have the MoPar chassis book, see if you can find I copy of it.

I have one at home but I’m not there.

Off the top of my head, the FIRST thing you need to do is buy some nice Double Adjustable shocks the front.

I say that because next up is /6 torsion bars. Unless the car is REALLY light you NEED them. If you don’t understand why let me know and I’ll type it out, but the short answer is: just like geometry matters, spring rate matters.

Once you get the /6 torsion bars you need to rebuild the front end using POLY bushings, and that included the lower control arm bushings. Poly is smoother than rubber, doesn’t bind like rubber and reacts more consistently than rubber.

To run poly LCA bushings you need to use adjustable strut rods. I use QA-1 strut rods. You can run poly LCA bushings with OE strut rods but that’s a bad idea.

You need to be able to get the front end to rise as easily and smoothly as possible. Once you get that, you use the double adjustable shocks to control the rate at which the car pitch rotates.
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Thanks! That's the type of info i need. I have the Mopar High Performance Book. I have the understanding of weight transfer and front end rise. I have the small block torsion bars (340 car). How much lighter are the /6 spring rates?
 
71GSSDemon said:
Thanks! That's the type of info i need. I have the Mopar High Performance Book. I have the understanding of weight transfer and front end rise. I have the small block torsion bars (340 car). How much lighter are the /6 spring rates?
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I forget the actual spring rates but it’s a big change. I think either @crackedback or @Mattax can tell you the actual rates. They may be in the chassis book. Or maybe not.

Just using a simple example with simple math let’s say you have a spring with a 100 lb/in rate.

That means it takes 100 pounds to compress it one inch. 200 pounds, 2 inches etc.

If you have a 200 lb/in spring it takes 200 pounds to compress it 1 inch and 400 pounds to compress it 2 inches.

Now think about that in terms of what we are talking about, which is pitch rotation.

If we look at that same 100 lb/in spring, if we want it to EXTEND 1 inch we need to take 100 pounds off of it. Simple math. I love it. Simple math is the best math lol.

If we have our 200 lb/in spring, we know to get it to extend that some one inch we have to take 200 pounds off of it.

So which is easier to lift???? 200 pounds or 100 pounds????

Its the same for your front suspension! You want it to rise as easily and quickly as possible. In fact, you want it to rise too fast and too violently. Why??

Because you spent the money up front for the nice double adjustable shocks!!! Now you can slow the front end down where you need it to be by a simple shock adjustment. You turn a dial. Simple is good.

And if you have adjustment up front you have the ability to tune for track conditions.

Lets say you end up at a Division race for some reason. Or you hit a National Event some day. Those tracks are prepped to the balls. The car should hook like it’s on cogs.

And it does. And you can see nothing but blue sky as the rear bumper is dragging the ground. For the next pass you don’t want that pan smashing wheelie. So you grab the knob on the shock and now the shock can’t extend as fast and you are back to a nice 10-12 inch wheelie.

The opposite can happen. You can go to a test and tune and the only prep the track gets is some dude walked up and looked at it and said send ’em, it’s ready.

And the starting line has about as much hook as the local car wash.

Your first tuning move is to turn the knob and make the extension setting on the shock looser. That will let the front end raise quicker and it goes back to a nice 10-12 inch wheelie.

Shocks and springs and geometry go hand in hand in hand.
 
Thanks Man...this all helps. Exactly what i am looking for. And welcome back from FABO jail
 
DIA Rate Part Number fits
0.81 90#/in P5249148 drag bars
0.83 100#/in 2535888-9 slant six bars
0.85 110#/in 2535890-1 slant six w/air - 318 w/o air
0.87 120#/in P5249149 (2535892-3) 318 w/ air - 340 std bars
0.89 130#/in P5249150 383 std bars
0.92 150#/in p5249151 *h/d handling
0.99 200#/in p5249152 solo/road race
1.04 250#/in p5249153 h/d solo road race-oval track
1.09 300#/in *p5249154 oval track 1/4 mi--optional 1/2 mi
1.14 300#/in p5249155 oval track 1/4 and 1/2 mile *

Drag car, run the /6 bars in it would be my suggestion.
Think about spring rate like this. If you have a valve spring and a spring from a Bic pen. Compress the valve spring with 20# (barely budge it) of weight and knock off the weight, see how spring react. Then do the same with your fingers (nowhere close to 20#) with the bic spring (fully compressed). That bic spring is going to FLY. The stored energy in the bic spring can release. The bigger spring needs much more weight on it to have a response.

Fast rise rate is good. Too fast is BAD... Many cars need the front end rise slowed to keep from unloading the rear suspension. The rise should be controlled and not a sudden jerk to a stop, jerky is bad unless you have a bunch of HP and tire to overcome it.
 
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crackedback said:
DIA Rate Part Number fits
0.81 90#/in P5249148 drag bars
0.83 100#/in 2535888-9 slant six bars
0.85 110#/in 2535890-1 slant six w/air - 318 w/o air
0.87 120#/in P5249149 (2535892-3) 318 w/ air - 340 std bars
0.89 130#/in P5249150 383 std bars
0.92 150#/in p5249151 *h/d handling
0.99 200#/in p5249152 solo/road race
1.04 250#/in p5249153 h/d solo road race-oval track
1.09 300#/in *p5249154 oval track 1/4 mi--optional 1/2 mi
1.14 300#/in p5249155 oval track 1/4 and 1/2 mile *
Click to expand...
So it would be dropping from 120# to 100# doesn't seem like much of a change
 
16% That is a decent sized change in spring rate. Going to require a couple extra turns on the adjust to maintain same ride height, loading that spring even more.
 
But is it worth the change vs 340 spring? I know everything helps, but...
 
From video of my car with stock springs, the front end lift was (maybe) three inches, the rear lift was close to six inches.
When I mounted the ss springs in the ss front mount, I moved the mount hole down as much as I dared, to adjust the instant center as much as I could. Rear lift is down to about 3 inches now. I still have way less front end lift than I would like, even with Slant six no-ac bars, and 90-10 shocks.
 
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