In the fully convertible top of a 75...

[eighteenninetytwo]

in the side posts behind the doors that sit on the rails, there are two threaded bolt holes about a third of the way up on each side , each covered by a small grommet.. Does anyone perchance know what thread these are? I'm making a half cab out of a wrecked top and these are pretty handy for bolting an aluminum strip across the width to stiffen the assembly.

[Irish1941]

Yep. Those holes are for optional shoulder belts.

[eighteenninetytwo]

Any idea what thread they are though? I figure using them to fit a brace across the back inside a fiberglass cover is a good move.

[eighteenninetytwo]

Bump. Any idea of the thread? ? Bueller?

[tony58]

7/16"-20
Keep in mind that's a bracket that's held in place with two rivets in the fiberglass, not sure how strong that really is.

[eighteenninetytwo]

if it was designed for seat belts you'd hope reasonably strong. I'm only going to put an aluminum brace from one side to the other to help shape fiberglass over. it won't be a safety thing.

[mgchevyparts]

Originally Posted by eighteenninetytwo

if it was designed for seat belts you'd hope reasonably strong. I'm only going to put an aluminum brace from one side to the other to help shape fiberglass over. it won't be a safety thing.

My top (1975) has those two nuts covered with a round plug, one on each side. If they're for shoulder belts why don't the trucks have shoulder belts then?

[Irish1941]

Originally Posted by mgchevyparts

My top (1975) has those two nuts covered with a round plug, one on each side. If they're for shoulder belts why don't the trucks have shoulder belts then?

It was an option.
Wasn't mandated until '76 or '77.
You could get shoulder belts as far back as '70 if memory serves me right. I have pix of a '71 Blazer with optional belts. Rare as can be.
The plug is there as is the threaded hole and plate behind it in any '73-'76 pickup.
Go look at one
http://67-72chevytrucks.com/vboard/s...d.php?t=419042

[mgchevyparts]

Originally Posted by Irish1941

It was an option.
Wasn't mandated until '76 or '77.
You could get shoulder belts as far back as '70 if memory serves me right. I have pix of a '71 Blazer with optional belts. Rare as can be.
The plug is there as is the threaded hole and plate behind it in any '73-'76 pickup.
Go look at one
http://67-72chevytrucks.com/vboard/s...d.php?t=419042

Have you seen one installed? Was the shoulder belt removable? in order to remove the top it would have to have some type of detachment.

[Irish1941]

Yep, I have seen 3 in my days. All base trucks. And have I owned NOS RPO A85 Blazer belts in the GM box. They are weird.
RPO A85 started as early as 1966 and by '67 in all platforms, trucks included.
And it was removable in Blazer...sorta.
It was a two retractor deal with one retractor on the floor and one on the bedside.
If roof was off, toss upper d-ring/retractor in back and still be belted in.

Now take that info and go look at a '76-'91 Blazer. It was no accident the newer belt d-ring just happen to be in the exact same place on the half cab versions. All that changed was belt design as there was no need for the retractor up top. In fact, the newer '76-'91 belt retractor bolted right where the roll bar used too bolt in on the '73-'75 Blazers.
Have a look at this thread:
http://forum.73-87chevytrucks.com/sm...p?topic=6288.0

Meant to add, in '73-'75 it seems a roll bar was optional depending on what truck you got. 2wd or 4wd made no difference as I've seen bone stock with and with out one.
That being said, a roll bar makes the A85 impossible. I've heard but yet to see a roll bar was standard on ALL '75s thanks to Mr Nader.
Plus the Blazers, once topless, had a known problem of the to the 1/4s spread and the doors wouldn't close or tailgate stay shut from the '69-72 production run.

[special-K]

The optional shoulder belts were in addition to the lap belts already provided. In other words,You would have two sets of buckles & straps to deal with separately.

[tony58]

Don't know about 73-74 but roll bar was standard on all 75, probably 73-74 as well. The roll bars main function was for body stiffening due to removable top. The roll bar won't interfere wit the mounting holes on the top for a shoulder belt.

[eighteenninetytwo]

Hmm i have a bolt in roll bar which still has to be bolted in for the 75. Would the recommendation then be to also weld it to the side of the body in addition to bolting it through the floor? it further seems that the recommendation would be to actually install it and affix it to the sides when the hard top was ON. am I right in this?

[Irish1941]

Originally Posted by tony58

Don't know about 73-74 but roll bar was standard on all 75, probably 73-74 as well. The roll bars main function was for body stiffening due to removable top. The roll bar won't interfere wit the mounting holes on the top for a shoulder belt.

Dad's brand spanking new '73 didn't have roll bar.
I meant the retractor wouldn't fit on the upper hole on the 1/4 where the bar would tie in. The d-ring on the top would clear the bar.
Check these out too. Pretty cool.
Here is '73

And '74

And here is the standard roll bar for '75. I was a little foggy on that one last night. Here is proof of that one.

[Irish1941]

Originally Posted by eighteenninetytwo

Hmm i have a bolt in roll bar which still has to be bolted in for the 75. Would the recommendation then be to also weld it to the side of the body in addition to bolting it through the floor? it further seems that the recommendation would be to actually install it and affix it to the sides when the hard top was ON. am I right in this?

It was bolted to the sides from the factory.
This might clear up your question…
[IMG][/IMG]

[tony58]

"Don't know about 73-74 but roll bar was standard on all 75, probably 73-74 as well"



My '75 comment was correct and my "probably" was off but I knew I didn't know about 73-74


Was there a Nader situation or did they finally figure out they needed more body strength with the open top?

[Irish1941]

Originally Posted by tony58

"Don't know about 73-74 but roll bar was standard on all 75, probably 73-74 as well"



My '75 comment was correct and my "probably" was off but I knew I didn't know about 73-74


Was there a Nader situation or did they finally figure out they needed more body strength with the open top?

Yep, you had the '75 part for sure.
And it was pretty much Nader. His safety crusades killed the convertible.
'75 was the last yr for ragtops from GM and the Blazer fell with the rest of them. I think the Eldorado was still offered in convertible in '76 but that was the end.
The word at the time was Nader was pushing hard for roll over standard laws but sales were way down & new design model lineup coming out anyway so GM just killed them off. You'd think the half cab would have had to be a design idea from at least '74. Another thing is the full vert Blazers leaked like a screen door on a submarine from brand new. The body spreading was more than likely another reason too.

[mgchevyparts]

This all makes a lot of sense to me now and clears up a few things. My 75 has a roll bar so I was wondering why I mostly never see these with roll bars, well because they (pre 75) pretty much didn't come with them. Keep in mind this is the only Jimmy (Blazer) I have ever owned. I was a little concerned about removing it for body sag or what ever you want to call it. Since GM apparently wasn't worried about it from 1969 through 1974 I won't either.

[Irish1941]

As long as your floors and rocker boxes are in good shape you should be alright. Any real off road stuff and you will tweak the body. Frames flex like a wet noodle and the body flex with it. When the doors start to get hard to open & close you'll know the body has twist in it.
Owned more than a few '70-'75s and rust free rocker box is key to the body staying lined up. The 1/4s like to spread too with the roof off.

[mgchevyparts]

Off road stuff? Lowered 2 whl drives don't do that. I owned a four wheel drive truck once, Never knew if the 4 whl drive worked or not.

[Irish1941]

Ha! Sorry man, just looked at your sig...
I'm just used to dealing with Blazers and off road type stuff. Haven't had a 2wd K5 in about 10yrs.