Sunday, December 8, 2019

Debating Front Suspension Changes

My front coil springs are made by Eaton Spring and are sold by NPD as part number 5310-8.  The springs are rated at 428 lbs to compress an inch at 11" tall.  They were originally used on big block cars and on those with a 289 with A/C and the heavy duty suspension option.  

When I originally purchased the springs, I cut a bit off at a time and ultimately ended up with 3/4 coil removed.  At that point, I thought the ride height was about perfect.  a few years later, while I had the engine out for work in December 2011, I decided to do the Arning drop which is supposed to lower the car a little.  While I had the suspension apart, I cut another quarter coil off the coil spring for a total of a full coil removed. 

As time has gone on, the car has continued to change.  When the engine went back in, it had an aluminum intake and heads.  In the last year, I added more weight back in with the air conditioning system and the big block style radiator.  I can now only fit one of my two jacks under the front of the car as it is so low.  

At this point, I think the front suspension is too low.  I took the front wheels off this afternoon to inspect everything, I noticed the upper control arm is hitting the bump stop.  I don't drive crazy but at times I hit a bump and there is a hard thud noise.  I thought something was loose which is part of the reason I was checking but now I wonder if it is because the suspension is bottoming out.




I've not really considered how much space exists between the upper control arm and the bump stop.  I put the wheel back on and rolled the car around a bit to get it leveled.  It seems I only have about 2" of travel before the front suspension which is not all that great.  From some quick reading, a street car should have about 2.5 to 3" of travel which would be measured at the wheel.  With all of this in mind, I'm not sure if I bottom out or not.  



For later reference, I decided to take a few pictures of the ride height with a measuring tape.  The fender well opening is right at 24 3/8" at the highest point.   The lower control arm is essentially parallel to the floor at ride height. I'm not sure how high I should take the front suspension but perhaps 25" would be good as that would increase my travel on compression at the UCA to 2 5/8".  I'll continue to think on it as I save some cash for the parts.
  


While looking everything over, I noticed there was some play in the passenger side wheel.  I'm not sure where it is coming from but it looks like the steering linkage.  I'm going to see if I can't check the torque when I get everything a once over.  For when that time comes, I dug up the torque specs...

1) Tie rod end to spindle arm: 30-40 ft/lbs*
2) Steering tie rod to center link: 30-40 ft/lbs*
3) Pitman arm to center link: 35-47 ft/lbs.
4) Idler arm to center link: 60-80 ft/lbs*
* Tighten to the low limit of the specification, then tighten the nut to the nearest cotter pin slit and insert the cotter pin.

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