Drag racing setup vs Street Rod? Shocks or ??

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Kent mosby

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I have a 1973 scamp with a 512 that dynoed at 406 hp and about the same torque. I have since changed the rocker arm ratio from 1.5 to 1.6 with new rockers. Hopefully that will improve the numbers a bit. We are also dialing in the EFI as well. There were some tuning and timing issues prior to this year. Here is a video of the best race we had so far, (October 2020), tracks were closed this year. It doesn't seem to shift weight much but it also doesn't lose traction. Only a 12.89 and 107 or so.




Currently I have the following setup. Only change was the rockers. and drag radials

RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.6RR, Trick flow single-plane intake. Holley Super Sniper EFI, HyperSpark ignition, coil and distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with transgo TF2 valve body mods. B&M Quicksilver shifter. Gear vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs. Competition Engineering race shocks. Pypes Exhaust 3" into 2.5 inch. RacePro mufflers. Cooper Cobra 275/60-15 28.2 inch diameter tires, will have drag radials for track. Current cam specs 244°/252° @ .050”, 282°/290° adv, .516”/.537” lift (1.5:1 rocker), 112° LSA, .016”/.018” lash, Solid lifter from Oregon Cams.

The Rockers will change the cam a bit. I have not gotten it to the dyno due to weather.

So, I really do not like the comp engineering shocks as I cannot adjust them very well at all. I want to replace them front and rear with adjustables that I can use 90% of the time on the street and 10% on the dragstrip. I don't really want to change the 1.03 inch, PST torsion bars or the SS springs as they are brand new. Future plans are replacing the torque converter but that will not happen this winter.

What would you recommend for this setup? I am not doing class racing and do not plan to get into 10.99 seconds or faster if that matters.

Shocks or what else is a must for a street rod that goes to the track? Especially if not trying to break 11 seconds
 
If it were me, disconnect the front sway bar at the track, loosen up the front shocks to the lightest setting, and increase the front tire pressure to about 40 psi or so.
 
Professor Fate said:
If it were me, disconnect the front sway bar at the track, loosen up the front shocks to the lightest setting, and increase the front tire pressure to about 40 psi or so.
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No sway bar. And you have to remove the shocks to adjust. There are only 3 settings. So the shocks at least in the front have to go
 
Kent mosby said:
No sway bar. And you have to remove the shocks to adjust. There are only 3 settings. So the shocks at least in the front have to go
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The Vikings are adjustable on the car.
 
Part of the issue is you have way too much spring up front. You are way over sprung for a drag car and no shock will correct that. You’ve already been burned once buying an effectively untunable shock. You can buy double adjustable shocks for about the same price as a single adjustable. Always buy DA shocks. I don’t know what the spring rate is for that big bar, but you have to take a bunch of weight off it (meaning pitch rotate the chassis) just to move it an inch. What I’m saying is (using made up numbers) that lets say your torsion bars have a 500 lb/in spring rate. That means to compress the spring 1 inch you need to add 500 pounds to it. The opposite is true. If you want to raise the front of the car 1 inch you have to take 500 pounds off the spring. It’s as simple as that. Now let’s say you change out the bars to 250 lb/in bars. Now it only takes 250 pounds off the spring to make it move 1 inch. That means is takes less weight to get the car to pitch rotate with the spring with less rate. To get the ride height back, you adjust the bars up. If it was a coil over spring car you’d just raise the platform the spring sits on to get your ride height. With out addressing the torsion bars, in my opinion you’ll never get what you want. You’ll have to chose between street ride comfort and track ET. With the percentages you posted above, I’d leave what you have in there and live with the ET.
 
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Rat Bastid said:
Part of the issue is you have way too much spring up front. You are way over sprung for a drag car and no shock will correct that. You’ve already been burned once buying an effectively untunable shock. You can buy double adjustable shocks for about the same price as a single adjustable. Always buy DA shocks. I don’t know what the spring rate is for that big bar, but you have to take a bunch of weight off it (meaning pitch rotate the chassis) just to move it an inch. What I’m saying is (using made up numbers) that lets say your torsion bars have a 500 lb/in spring rate. That means to compress the spring 1 inch you need to add 500 pounds to it. The opposite is true. If you want to raise the front of the car 1 inch you have to take 500 pounds off the spring. It’s as simple as that. Now let’s say you change out the bars to 250 lb/in bars. Now it only takes 250 pounds off the spring to make it move 1 inch. That means is takes less weight to get the car to pitch rotate with the spring with less rate. To get the ride height back, you adjust the bars up. If it was a coil over spring car you’d just raise the platform the spring sits on to get your ride height. With out addressing the torsion bars, in my opinion you’ll never get what you want. You’ll have to chose between street ride comfort and track ET. With the percentages you posted above, I’d leave what you have in there and live with the ET.
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PST bars are 230 lbs/inch. 6 cyl bars are 100 lbs/inch each. So I have a difference of 260 lbs/inch for both.

I guess I could have asked my question a bit differently. If my current setup does not break the tires loose, is there any benefit to changing shocks? Either front or rear? If by doing so, What would I see as far as the change in both the drag strip and on the street? FWIW, I do have my original 6 cyl torsion bars. I changed them because they were riding almost on the bump stops. Perhaps they are worn out or defective. If I am understanding your reply correctly, I could use smaller torsion bars with adjustable shocks that would help improve both street and drag, but adjustable shocks set at a lighter setting would still not help with the heavy torsion bars. What about the rear setup? Any help there? Any improvements with adjustables?

I have an extra set of rims that I can even go to drag slicks instead of drag radials. I had MT SS street radials in 255/60-15 with a bit of mileage left, then I will need to replace them.
 
When you get that 512 sorted out traction will be a problem.
I'd switch to the .890 or .920 bar.
 
Kent mosby said:
PST bars are 230 lbs/inch. 6 cyl bars are 100 lbs/inch each. So I have a difference of 260 lbs/inch for both.

I guess I could have asked my question a bit differently. If my current setup does not break the tires loose, is there any benefit to changing shocks? Either front or rear? If by doing so, What would I see as far as the change in both the drag strip and on the street? FWIW, I do have my original 6 cyl torsion bars. I changed them because they were riding almost on the bump stops. Perhaps they are worn out or defective. If I am understanding your reply correctly, I could use smaller torsion bars with adjustable shocks that would help improve both street and drag, but adjustable shocks set at a lighter setting would still not help with the heavy torsion bars. What about the rear setup? Any help there? Any improvements with adjustables?

I have an extra set of rims that I can even go to drag slicks instead of drag radials. I had MT SS street radials in 255/60-15 with a bit of mileage left, then I will need to replace them.
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At this point, I wouldn’t change anything. You want way more performance for your street driving, evidenced by your percentages above. If you are happy with your track performance then I’d leave it be. If you buy shocks that allow for changing rebound (extension) dampening, you will only change how fast (or slow) the suspension acts and reacts. The shocks control the motion of the springs. You can either slow down or speed up that motion with the shocks. If you want to transfer more load (or less) you start with the springs. I’m not suggesting you change anything yet. I suggest spending a bit more time learning about springs, spring rate and shocks and shock tuning before spending any money. That way you can save yourself some money by not making a change you don’t like and then needing to change that change too.
 
Rat Bastid said:
At this point, I wouldn’t change anything. You want way more performance for your street driving, evidenced by your percentages above. If you are happy with your track performance then I’d leave it be. If you buy shocks that allow for changing rebound (extension) dampening, you will only change how fast (or slow) the suspension acts and reacts. The shocks control the motion of the springs. You can either slow down or speed up that motion with the shocks. If you want to transfer more load (or less) you start with the springs. I’m not suggesting you change anything yet. I suggest spending a bit more time learning about springs, spring rate and shocks and shock tuning before spending any money. That way you can save yourself some money by not making a change you don’t like and then needing to change that change too.
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When you say springs are you referring to the rear leaf springs or the spring rate of the torsion bars?

As evidenced here. My setup can work except the bars. I don't know what he has. This is from FABO. I copied the post info from him. @B3422w5 posted in September 2021


https://video-sea1-1.xx.fbcdn.net/v...XiuhGosSPZ542jWMHi-4Ige9gj-vsn94w&oe=61C78583

this is me in my old car( blue duster, 422W5 deal) dialed 9.85, racing a 9.92 car, he went red
Serious SS/AH type wheelstand

002/003 leafs, no snubber, CE 3 ways all around, tripping beams with the backs
 
What I'm going to say is for reference, not to brag.
I have a 64 Sport Fury with a 440 has a cast crank. .505 intake, .515 exhaust
3.91 locker rear, 3000 stall converter. Rpm intake, with a 750 race demon. 1 3/4 headers. 1 1/8 front sway bar, .920 bars, KYB shocks. Nothing removed, or disconnected.
I went 12.12 @ 110 mph.
So, I think your combo has some serious issues. Changing the suspension will improve the performance, but will not fix whatever is the main problem. I'm not sure the rockers will either.
 
furyus2 said:
What I'm going to say is for reference, not to brag.
I have a 64 Sport Fury with a 440 has a cast crank. .505 intake, .515 exhaust
3.91 locker rear, 3000 stall converter. Rpm intake, with a 750 race demon. 1 3/4 headers. 1 1/8 front sway bar, .920 bars, KYB shocks. Nothing removed, or disconnected.
I went 12.12 @ 110 mph.
So, I think your combo has some serious issues. Changing the suspension will improve the performance, but will not fix whatever is the main problem. I'm not sure the rockers will either.
Click to expand...

yep, it did have some serious issues. When we did the run seen above, that was the last of the season. When I got it home, one plug wire was off and one was shorted/burnt by the header and the tune for the efi was awful. My son was on his second race ever and left off idle. Much room for improvement. When the weather clears we will get it to the dyno for some tuning.
 
Well, that's alot of problems. I can see why you had issues. I'm rooting for you, because I am building a 505 stroker from 440 source.
Merry Christmas.
 
Kent mosby said:
When you say springs are you referring to the rear leaf springs or the spring rate of the torsion bars?

As evidenced here. My setup can work except the bars. I don't know what he has. This is from FABO. I copied the post info from him. @B3422w5 posted in September 2021


https://video-sea1-1.xx.fbcdn.net/v/t42.1790-2/1301447_10200852643291245_61459_n.mp4?_nc_cat=101&ccb=1-5&_nc_sid=985c63&efg=eyJybHIiOjY1OCwicmxhIjo1MTIsInZlbmNvZGVfdGFnIjoibGVnYWN5X3NkIn0=&_nc_ohc=885vnNG5mWYAX988dQy&rl=658&vabr=366&_nc_ht=video-sea1-1.xx&edm=AIbDutUEAAAA&oh=00_AT9T80W7neJK_XiuhGosSPZ542jWMHi-4Ige9gj-vsn94w&oe=61C78583

this is me in my old car( blue duster, 422W5 deal) dialed 9.85, racing a 9.92 car, he went red
Serious SS/AH type wheelstand

002/003 leafs, no snubber, CE 3 ways all around, tripping beams with the backs
Click to expand...


I’m talking about the torsion bar spring rate. Like I say, you have a preference for ride on the street. If that’s the case, I’d leave everything alone for a bit and tune with what you have. Once you get things a bit more sorted out you can look at shocks. I’m always for anything that is adjustable but it needs to be an adjustability that makes sense. Those 3 and 9 way shocks make no sense if you are changing bump and rebound at the same time. That makes the assumption that the tire/chassis wants both a change in bump and rebound, and in proportion that the shock changes it. I hope that makes some sense.
 
I think you're working backwards, you should be looking to why you have good traction.
With 512 CI , you should be spinning through all three gears.
 
fishmens67 said:
I think you're working backwards, you should be looking to why you have good traction.
With 512 CI , you should be spinning through all three gears.
Click to expand...

Perhaps I am. In Idaho the weather will be cold for another 3-4 months. I would consider this a winter project prepping for the next season. If nothing else, food for thought for me in advance.

I do know we are at over 500 hp at the crank. The last race was a dog but we have made tremendous progress with the tune and got an exhasut leak fixed that was causing misread but the O2 sensor as well. Also the cam was installed 8* retarded in that video. I corrected the cam timing since then. I suspect we will be traction restricted in the future. Part of the bad tune I mentioned before
 
I am running Competition Engineering 3 way shocks with a .920 torsion and S/S springs. My car will come off the line straight as can be with no spinning. Competition Engineering shocks work for me. I can not see buying a more expensive shock if these work. I will say they are not the best shock on the street if you leave them in drag race set up. I do not have a Caltrac set up or some other traction bars.
In your video I can see your front end is rising up as you leave the line, now with the smoke I can not see, is the back of your car rising up with your revs up at the starting line? If not you shocks need adjusted lighter.

race2 md 001 (2).jpg
 
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68dodge said:
I am running Competition Engineering 3 way shocks with a .920 torsion and S/S springs. My car will come off the line straight as can be with no spinning. Competition Engineering shocks work for me. I can not see buying a more expensive shock if these work. I will say they are not the best shock on the street if you leave them in drag race set up. I do not have a Caltrac set up or some other traction bars.
In your video I can see your front end is rising up as you leave the line, now with the smoke I can not see, is the back of your car rising up with your revs up at the starting line? If not you shocks need adjusted lighter.

View attachment 1715846807
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nice car. Do you happen to have video of the launch?
 
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