Chassis Tuning Question - 460 Ford Forum
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post #1 of 4 (permalink) Old 06-09-2006, 09:11 PM
TopSportsman916
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Chassis Tuning Question

Alright guys(Dave,Buddy,etc), give me your input. I discussed before that I loosened my shock settings to see if it would help my loading/unloading the chassis. I ran one weekend with the looser settings & the next weekend went back to the tighter setting. Car pretty much was the same but I believe it was slightly better with the looser settings. I believe the car is oversprung also. I thought it last year & was going to change springs when I had the lifter failure. Mike Balf, a local chassis builder, pretty much thought the same, that the springs were too heavy.Car was porposing off the line. I had 300# springs up front & 110# springs in rear. I could get the chassis close to ride height but would run out of threads with the spring seats all the way to the bottom. I am about an 3/16" high in front & 1/4" high in rear. I now have 250# springs on front & 95# in rear. I plan on setting ride heighth in the morning. My question is do I go with my original stiffer shock settings (struts-2 from full loose, shocks-ext-4 from tight & comp-2 from tight) to get a spring baseline. Then try a softer setup or try the softer set up off the bat. I am leaning to go with the original shock settings since I have more of a baseline with it. What do you think? :?
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post #2 of 4 (permalink) Old 06-10-2006, 05:25 AM
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long.

If it's a test & tune outing where you have all day & as many passes as you want.....go crazy and try a bunch of things. But if its a money race where your only guaranteed passes are two time trials & first round...then big changes are out.

Actually if you were running nitrous I would lean toward staying with the 110 lb spring (or 100's) on the back. But 95's might be a good choice W/O nitrous because if you have to crank them up more to get your desired ride height, that will store more usable spring energy.

Rear extension/re-bound: leave them at 4 sweeps from full tight for now. The softer springs storing more energy might help the suspension "pop" the sidewalls a little faster.

Rear compression/bump: back them up to 4 clicks from full tight (from 2). this could help the car some if the wheelie bars were un-loading the slicks. Plus a softer bump setting should help the slick stay in contact with a rough-bumpy track surface down course.

Struts: when you say "2" from full loose, are you counting full 360* turns (or 1/4 or 1/2 turns)? As an example the older Lamb struts are about 2.5 full 360* turns full loose to full tight. A usable starting point for nitrous cars is to set the strut valving at about 50% tight, w/o nitrous start at about 20-30% tight. Of course the required strut valving depends a lot on how violent the rear suspension combo is.

Good luck next outing.

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post #3 of 4 (permalink) Old 06-10-2006, 06:55 PM
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Dave, I got the ride height set today & now all the springs are about centered on the threads. I agree a high HP nitrous/prostock/clutch car needs stiffer spring/shock set up. Not being a chassis expert(but it is the part that most interests me) I got to thinking about why the car was poisposing. The original springs had the spring seats all the way to the bottom with about 2 threads left under them. None of the springs had little to any compression(is this normal nowadays??) on them. Seems to me that when the engine would lift the front end, it wasn't getting any help from the springs. So when the front came down the stiff spring would bounce it. I believe the same effect was going on in the rear also. I set the shocks per VPRC's suggestions. I think they may have overestimated my HP. I know they are use to super high HP & my puny 850 ponies aint quite in that ballpark. I am not "knocking" them for this. Plus I have been enjoying trying to figure things out to make the car qicker & more consistant. It says alot for VPRC's chassis considering I haven't found the right set up yet & the car is deadly. But it can be better. Anyway on my last car I started with the Koni's at the softest settings(ext & comp) & worked my way up until the car worked the best. How many usable compression settings did you say the Santhuffs have? Wasn't it 11 or 12?While I was setting up the car, I thought about setting the shocks in the middle(6 from full tight) on both settings & leave the Strange struts where they are(2 from full soft).When I say 2 turns that is 2 full sweeps across the window, not a full 360.Oh yeah the wife & I are talking about going back to Texas to visit her aunt & uncle. They live in North Richland Hills. Is that anywhere near you? Thanks for the post
 
post #4 of 4 (permalink) Old 06-11-2006, 05:07 AM
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Porpoising can be a pain. One situation that I think Buddy has mentioned before is where the car dead hooks & winds-up the sidewall, then can't keep the pressure applied as the car tries to get "up on the tire". The car then "falls off" the sidewall, and then re-winds the sidewall all over again, in a continous cycle.
Another is more of a "skipping" tire shake, where the car winds-up the sidewall, then spins, then re-winds again in a continous cycle.
And as you said a over sprung car can do this too, as it tries to use the sidewalls as a makeshift spring.

I think the Santhuff's top shock window has around 18 sweeps from full tight before you can't get a tool in the window anymore, & the bottom knob is at least 20 clicks from full tight. But I doubt that most people will really need any settings looser than 10 sweeps (or clicks) from full tight. Going past 10 from full tight might not have any real effect anyway, only a shock dyno could tell you for sure.

There's a few people on here that are around the D/FW area, I'm in Kennedale. Duane & Glenn are also in the D/FW area, but I seem to recall that others on this site are also in the larger general north Texas area.

D.I.L.L.I.G.A.S. Dave::
460 street '66 Ranchero.......................finished someday.
460 race '70 Maverick..........................finished someday.
All 'glass Top Sportsman '69 Mustang......ummm, check back when I win big playing the Texas Lotto, or online poker.
My youtube page. Some ancient & newer local race video.

Join the Poker Players Alliance (theppa.org). US online poker should NOT be turned into a crime.
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