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Old 07-19-2007, 11:21 AM   #1
Aubrey N Bruneau
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Red face 62 Chevrolet, STILL No Traction

I am very much afraid to even bring this up... actually stalling for a week now.

Car is back together.
I did EVERYTHING I was told to do... including spending every last cent I will ever see, on chassis related components that are permissible in Stock.
Moroso front springs
Loose, firm control arm bushings
Thousands of dollars in QA1 adjustable drag race shocks
MANY thousands of dollars in state-of-the-art wheels and tires
MORE thousands of dollars on light weight disc brake components
( already had the 2.83 Jerico, aluminum flywheel, aluminum soft lok clutch )

I also relocated the upper control arm at the housing, about 2 1/4" upward.

The difference ?
At least now, I don't have to let off the gas pedal in first gear. Engine actually hovers at around 6200 RPM, until the car catches up.

So, I started scouring the Internet, looking for a couple good diagrams and brief, direct pointers, as to where a person needs to have the "instant centre", yadda yadda.
What I found, is that like everything else about this hobby... that elusive information, will cost $100 - $200 ???????????????!!!!!!!!!!!!!!!!!!!!!!!
IE, books, programs, ect.

My problem appears to be that the rear tires aren't receiving the neccessary intial "hit".
Yesreday, I did a full series of measurements. Here's what I came up with:
( it's a factory "4 link" )
Distances from ground:

lower mount at housing... 8.75"
Upper mount at housing... 19.75"
Lower mount at frame... 12.125"
Upper mount at frame... 19"
Rear rocker to ground... 12"
Front rocker to ground... 9.5"

Lower control arm length... 23.75"
Upper control arm length... 13.75"
The lower mount at housing, is located approximately 1 1/2" behind the centre of the drive axle. The upper, 4.5" behind.

Car has 119" wheelbase.
Weight distribution is 50/50
Total weight, with me, is 3750 pounds

Rear tires are 29.5" X 9" M/T "stick" compound... front actuall effective diameter 27".

From my calculations, the point of intersect of the two "imaginary" lines extending forward of the two rear control arms, is located: 53.5" ahead of rear axle centre line... 16" from the ground.

SURELY this is enough info ???!!!

Can someone PLEASE advise me as to what might be wrong, and where it should be ?
( please PLEASE don't ask things like shock settings... I understand enough to have them adjusted for lift, ect. ! Tire pressures have been moved from 13 - 19 pounds )

I just don't get. EVERYBODY else gets traction...
I get laughed at
( can you tell I'm at my wit's end with this thing ? ! )
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Old 07-19-2007, 11:30 AM   #2
Glenn Briglio
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Smile Re: 62 Chevrolet, STILL No Traction

Stupid question but how did you set up the clutch or adjust it?
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Old 07-19-2007, 11:39 AM   #3
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Default Re: 62 Chevrolet, STILL No Traction

DAMN !
forgot to add that into my "please don't ask" list !

slips alot low RPM... especially cold. Never get any kind of "shock" feeling from it.
Has good centrifugal... no slippage at tp end in high gear.

What I failed to mention, is that I am releasing the clutch at about 5000 ( 7000 RPM engine ).
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Old 07-19-2007, 11:46 AM   #4
Dick Butler
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Question Re: 62 Chevrolet, STILL No Traction

Contrary to thoughts, you could be getting too much "hit " on the tires. Need to know if the car squats, Balls up tires, if you tried uping pressure, lowering pressure? Result of pressure. Have you experimented with Rpm you leave? Dick Butler
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Old 07-19-2007, 11:51 AM   #5
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Default Re: 62 Chevrolet, STILL No Traction

Here is another foolish question. What is the rim width for your slicks?
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Old 07-19-2007, 12:20 PM   #6
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Smile Re: 62 Chevrolet, STILL No Traction

I guess I should have asked what is the base pressure or static preload and what if any cetrifugal weight is added? Clarify what RPM you are leaving at.
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Old 07-19-2007, 12:41 PM   #7
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Default Re: 62 Chevrolet, STILL No Traction

HOLY !
I appreciate the replies, guys

in reverse order:
Dick...
Takes the tires off with a 3500-4000 RPM launch ( peak torque is at 4700 ). Should be able to leave at 6000... like everyone else
As stated, moved pressure from 13-19 pounds ( lower is REALLY REALLY dumb )
Tires seem to be wearing VERY smooth ( my old ones peeled up the tread badly )
I am completely alone, so no one to view. No sensation of "up" or "down" from the rear of the car.

Mark...
rims are American Racing Pro Series Trackstar, 15 X 10 / 5" back spacing.

Glen...
actual measured "pressure" has not been calculated ( this doesn't mean... "NO WONDER.... YOU'RE AN IDIOT" !... it means this clutch setup is very much common sense. A person can feel the slippage on engagement... the "torue converter" philosophy )
There are 11 full "turns" of the adjuster bolts, from nothing to max.
This is set 4 1/2 "in".
Counter weight... I'll go weigh what I put in there...
Since retarding the cam 4 degrees, the lower end torque has dimminished some.
Can't really launch below 3000 ( would be freakin' ridiculous anyhow... car has "super duper" slicks for crying out loud ! ).
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Old 07-19-2007, 12:51 PM   #8
Steve Calabro
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Default Re: 62 Chevrolet, STILL No Traction

Are you testing at the track or on the street?
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Old 07-19-2007, 01:46 PM   #9
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Default Re: 62 Chevrolet, STILL No Traction

Does Higher pressure make any effect on 60? Are you on good track. None of this will matter if not at track though.Also an awful lot of first gear I think on a 10 tire. especially when starting out. Dick
Try a trans with a lower first and see what happens Maybe you are just so far up on power, torque at this point you need to creep up on this kind of ratio making one or two adjustments at a time. If the tail drops try Air bag on Rt. Helps with rotational movement and picking up rt tire.Its like preload for SS cars or ladder cars...Are you allowed the Bolt on Comp ladder bars? They really helped my heavy chevelle wagon. Made it press the tires down instead of lifting the slicks up(SQUAT)
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Old 07-19-2007, 02:58 PM   #10
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Default Re: 62 Chevrolet, STILL No Traction

Steve, yes, everyone seems to think the track is best.
One thing that I have confirmed for absolute certainty, is that the only place this car EVER spun more than on good, clean, new highway pavement... was on a prairie track, concrete "launch pad".
A little video in Saskatoon, with the old slicks:

Granted, that spinning completely through first and second, was a little extreme ( usually only goes an additional 20 feet in second ). If I remember correctly, the 60 ft was a 1.78 that time. So far, the track performance has proven to be a joke, largely due to the fact that the traction is always so poor.

Dick, I'm told that I'm WAY off on 1st gear in the trans. Saying I should have 3.08 or even 3.22.

Tires seem to "plant" dead-on even left/right ( has slight weight jacking in RR spring )
Car goes straight as an arrow.

No traction device permitted, which has a front mounting point ahead of the factory lower control arm mount.

Still can't seem to find the info on the 4 link, which indicates the optimum geometry for effective initial planting of the tires, resulting in weight transfer, which should perpetuate itself. PLEASE don't tell me the "every car is different" story !
At this point, I'm not looking to tune the chassis in order to go from a 1.50 60 ft, to a 1.49 !
I'm trying to go from 1.75 to 1.50. I don't think this discrepency is due to being out half a pound on tire pressure, or the like. It's a BAD problem, from a very fundamental error in design. Just need to know the "rules" !
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