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Arning drop - drilled holes but UCA doesn't quite fit

Rex66

Rex66

Member
So I bought some new UCAs, roller spring perches, and springs from Open Tracker, along with the Arning drop template. I drilled the holes using the template and a 1/8" bit. Then I removed the template and enlarged the holes with a step bit, and then finished with a regular 1/2" bit. When fitting the new UCA, it will only go in a very short distance without applying any force. I did my best to drill straight and prevent the bit from wandering, but it appears one hole must be slightly off. I took my old UCA and used a hammer to tap/pound it in to place part way, then I pulled it back out. One of the old bolts now has a shiny spot on the threads that I presume indicates the area where it's interfering. I'm thinking I should either use my 1/2" bit, or maybe a rat tail file to gently open the hole in that area. The directions indicate that I should use a 17/32" bit instead of 1/2", but I've also seen advice to just go to 1/2". So what do you think I should do? Work the one hole a bit, or drill them to 17/32"?

Thanks!

1966 coupe, 302, C4
 
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Use the correct size drill. Would you try and pound a square peg through a round hole? Seriously. The hole needs to be sized to the arm stud for proper positioning. Don't think you can just hog out the holes and make it fit. Do it right. You can order the correct drill on Amazon tonight and have it in your hands as early as tomorrow depending where you live.

Now, depending on how badly you screwed up the threads on the arm you tried to pound in you may need to get the correct die and fix them too before installation. DON'T USE THE NUT and a big wrench to try and fix them either. Do it right.
 
Thank for the response!

While the instructions say to go up to 17/32", Opentracker (John) posted somewhere that he drills to 1/2" because that's the size the UCA bolts are. So I followed his advice as best as possible. I can get the correct bit from my local hardware store no problem. Based on the info I had, I wasn't sure if 17/32" (or 1/2") was the correct size.

In my previous post, I mentioned that I used my old UCA to test the fit - I did this so that I wouldn't munge the threads on my new UCA. The new UCA is just fine.
 
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I think with a 17/32 you have enough room to mount the UCA. With a 1/2 you can establish a perfect fit with no play at all , presumely you drill it perfectly.
And thats what John tries to achieve so the UCA can't move at all under all kind of conditions in particully the track. My2 eurocent.
 
Nope a drill. No such thing as a "drill bit". Being technical but accurate. You use a drill motor to spin a drill when making holes.

In all likelihood, you will not find a 17/32 at any local store. At least here around Chicagoland I couldn't. A 17/32" drill will give you .031" total clearance for the studs. That's pretty damn tight in this type of fit. It won't cause you any issues but will allow you to mount the arms without a hammer!

Glad to hear you used the old one when attempting to force fit it (missed that when reading the first time).
 
Come on, does anyone really think 1/32” makes a whits bit of difference here? The cars flex way more than that. Use the 1/2” and ream it to fit or get a 17/32” DRILL BIT. Once you torque it down, they are not going to move.


Mark
 
1/32” oversize is industry standard for clearance hole loose fit bolt and nut applications, even in military and space flight hardware unless a tighter tolerance is needed for limiting movement. In this case, like Mark said it ain’t moving once you torque it down. The 1/32” oversize also allows for caster and camber adjustments due to the UCA studs being angled into the holes.

BTW, the proper term is “twist drill” per Machinery’s Handbook.
 
FWIW, I had no problem picking up a 17/32” twist drill / drill / bit at my local hardware store last night. I’ll give it a go. Thanks for the responses.
 
Horseplay said:
Nope a drill. No such thing as a "drill bit". Being technical but accurate. You use a drill motor to spin a drill when making holes.

In all likelihood, you will not find a 17/32 at any local store. At least here around Chicagoland I couldn't. A 17/32" drill will give you .031" total clearance for the studs. That's pretty damn tight in this type of fit. It won't cause you any issues but will allow you to mount the arms without a hammer!

Glad to hear you used the old one when attempting to force fit it (missed that when reading the first time).
Click to expand...
Patrick Stapler said:
1/32” oversize is industry standard for clearance hole loose fit bolt and nut applications, even in military and space flight hardware unless a tighter tolerance is needed for limiting movement. In this case, like Mark said it ain’t moving once you torque it down. The 1/32” oversize also allows for caster and camber adjustments due to the UCA studs being angled into the holes.

BTW, the proper term is “twist drill” per Machinery’s Handbook.
Click to expand...

Finally someone came through with the correct term for a twist drill. How in the world can you simply call it a drill? I was born with a drill, a twist drill, not so much...

I wouldn't sweat the 1/32", you've got things on that car 64/32" out would be my guess...you're good...

Allen
 
Hey, just thought I'd follow-up on here. Got all of the suspension work done, replaced the tie-rods, and got an alignment. Had to use Granada outers and shorten all of the tie-rod ends a bit due to the Granada disc brake swap, but everything is now in spec... +2* caster, 0* camber, and 0.15* toe-in.

New UCAs, LCAs, roller perches, springs, adjustable strut rods, roller idler arm, tie-rods, and a rebuilt steering box. Arning drop.

It's amazing how much better it feels. Corners well. Much easier to steer now that energy isn't being wasted via worn-out parts. Under hard acceleration, it has a tendency to lift the nose, but it comes back down when I back off the gas (either maintaining speed or decelerating). Kind of like a boat planing. How abnormal is this? I know my front tires are crap (badly worn on outer edges prior to alignment), and I intend to go from 14" steel wheels and tires to 15" aluminum wheels & tires in a couple of months.

Anyway, thanks for all of the help!
 
Under hard acceleration you want weight transfer front to back. What you don't want is it wasted energy to do it. That's why drag racers use different springs and shocks with variable rates (open/close) to make the shift quickly and effortlessly. Whatever springs and shocks you've installed are contributing to the nose rising as you describe.
 
+1

Weight transfer is normal. Worn out springs and shocks will result in more of it.

I have 4.5-leaf mid-eye springs on the back of my fastback, 540lb grab-a-trak coils up front, arning drop, with Edelbrock IAS shocks all the way around, and I'm very happy with the way the car handles. It still pitches up a bit on acceleration, but not excessively.
 
Please forgive my ignorance here... Stiffer shocks (front and back), and stiffer rear springs would help resist the nose lifting under hard acceleration, right? What about the front springs? I would think stiffer front springs would only encourage squat under acceleration and resist nose dive under braking. I did change springs from drop springs that had 1.5 fewer coils, and were about 3" shorter and somewhat stiffer than my new stock V8 springs. The shorter springs would shift weight towards the front and reduce pitch - perhaps I should try putting the drop springs back on.
 
Front springs are trickier. Stiffer front springs are generally shorter at full natural extension. So while they will encourage faster nose lift, it won't be as much lift as a weaker spring with a longer full extension.

When I switched from original, worn out coils to the 540lb 1" drop coils, I noticed much less nose lift in general, both under acceleration and at high speeds.

The other factory is center of gravity. The higher the CG, the more the car is going to want to pitch. Keep the CG low (drop springs), the car will have less tendency to pitch.
 
Shocks can also have different dampening rates for both extension (car nose goes up) and compression. Drag racers like to swap in 90/10 pieces for use at the track when you want that instant weight transfer, for example. The rate numbers are indicative of how much force is required to compress/extend the shock. A shock with more resistance to extension would help keep the nose from rising as easily.
Your rear springs can also play a part in how the nose rises. If the springs are weaker, they allow the weight to shift fore to aft more rapidly as well. It's all a balancing act. I too have 4.5 mids which are pretty stiff. On top of that I lock them up with a set of CalTracs so they don't wrap when I step into it.

I would put the shorter, stiffer front springs back in. The stock springs always made the cars sit too high, IMHO. This certainly adds to the weight shift issue.
 
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