C20 to C10 conversion question, wanting confirmation
 

I have a 67 C20, and I just bought 70 lower control arms. I will be converting from drum to disc in the process, and converting from manual to power brakes as well. The way I understand is this:

Use a standard or dropped spindle from a 73-87 C10 w/1.25" rotor
Use upper and lower ball joints from 73-87 C10
Use brake hose for 73-87 C10
Use an outer tie rod as an inner tie rod from my 67 C20.
Use an outer tie rod as an outer for a 73-87 C10
Use POL HPAS6570 tie rod adapter to mate the two different tie rods.

So do I understand this correctly? Or is there a tie rod combo that doesn't need the special POL adapter?

And what about the hard brake lines? Are they the same size, or do I need to buy new ones?

Re: C20 to C10 conversion question, wanting confirmation
 

Instead of using the adapter for tie rod ends, I used the cross link bar from the 86 donor truck. That way everything for parts wee from same truck. If you are cahnging to power steering you'll need to do pitman arm also.

Re: C20 to C10 conversion question, wanting confirmation
 

What he said :mm:

Re: C20 to C10 conversion question, wanting confirmation
 

If you are using 70 LCAs you will need lower ball joints for a 70. 73-87 ball joints are different.

Re: C20 to C10 conversion question, wanting confirmation
 

This is incorrect.
The upper and lower need to match the year of spindle he is using.
The 73-87 c10 balljoints will work in his 67 c20 upper control arm and his 70 c10 lower control arm.
His plan is spot on.

The only additional thing to address is the fact the 67 frame doesn’t have a indent in it for a power steering box.
They make spacers for this issue.

Re: C20 to C10 conversion question, wanting confirmation
 

Keith, thank you for correcting me. I thought 73-87 ball joints were larger than 67-72.

Re: C20 to C10 conversion question, wanting confirmation
 

All the 63-87 c10 control arms have the same size balljoint holes and mounting locations for the upper control arm balljoint bolts.
The only difference is the diameter of the hole on the c20/c30 lower control arms. They are bigger.

The tapers of the balljoints are different through the years.
Divided by these years:
60-62
63-70
71-72
73-87

Re: C20 to C10 conversion question, wanting confirmation
 

I converted my 69 C10 from manual drums to power discs 30 years ago, using parts from a mid-80s C10. As I recall, my center link came from a late 70s C20, but as I recall, it's identical to a mid-80s C10. Tie rod ends are stock mid-80s. I don't see a need for adapters. I also used 71-72 booster, brackets, master cylinder, and combination valve.

Looking at the attached .pdf file, the mid-80s Pitman arm is different than the 67-72 C10, but idler arms are the same.
A while back, someone on this forum pointed out an error or two in my table, but I think I corrected the problems.

Re: C20 to C10 conversion question, wanting confirmation
 

Just us the whole front crossmember for the 1/2 ton, unbolts ,like 16 bolts , bolts right into the 3/4 ton frame , I’ve done it ,gives u everything u want

Re: C20 to C10 conversion question, wanting confirmation
 

Idler Arm is not the same all the way to 87. GM Changed the center link (have no idea why) in 1983 on the 1/2 ton. K6247 +/-T is from 83 to 87. K6096 is from 82 and down.

Smitty

Re: C20 to C10 conversion question, wanting confirmation
 

think it just went to metric thread, was the change. But cannot remember as all my squares were 82 up.

Re: C20 to C10 conversion question, wanting confirmation
 

Thanks for the corrections to my table. I'll do some further investigation.

Speaking of metric, an 82 C10 I used to own was a crazy combination of SAE and metric. Small screws had 7mm hex heads, and some under-hood body bolts were 8mm with 12mm or 13mm hex heads. But I don't remember if suspension and steering hardware was metric or SAE.

I guess GM was just dipping their toes into the metric pond, while driving mechanics nuts!

Maybe Keith will jump in here.

Re: C20 to C10 conversion question, wanting confirmation
 

Stud taper on the link side is way smaller in diameter than previous years.

Smitty

Re: C20 to C10 conversion question, wanting confirmation
 

Thanks guys, just as I thought. Use adapter or change the center link.

But what about the hard brake line for the front? Does it change size from drum to disc?

Re: C20 to C10 conversion question, wanting confirmation
 

My set up was from an 86 Cab-n-Chassis and the center link was about 1" too long or short (can't recall) so I used my original 70 and everything on the center link fit with no problem.

Re: C20 to C10 conversion question, wanting confirmation
 

Yes,

Drum lines are larger than the disk lines for the front application.

Smitty

Re: C20 to C10 conversion question, wanting confirmation
 

From what I have found, C and C models also have quite a few differences from the regular platform. I am using some of those parts for my 72 Motor Home build.

Smitty