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the end of the frame / front . where the bumber brackets bolt to the frame horn . the 4 bolts , 2 use welded nuts and the other 2 use a nut , these fasteners are what i would like to discuss , the 2 welded nuts use an 11/16 bolt with what head mark and the other 2 are an A" headmark , the 2 that use a nut should be a smaller bolt 5/8 or should they also be 11/16 bolt.
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Re: c3 69 front frame brace or bumber brace
Kelly, bolt size of 11/16" or 5/8" does not compute for that application. I think you probably stating the wrench size that fits the bolt heads/nuts.
My late 70 takes used two 1/2"(diameter of thread) NC X 1 1/2" inch long bolts, and one 1/2" NC X 1" long bolt to attach the front bumper brace; the shorter bolt was in the center hole of the three hole pattern. These three bolts also pass through and attach the frame extension. Two of these bolts (one 1 1/2" long and one 1" long) thread into weld nuts on the inside of the frame channel. The remaining bolt of these three has a nut (only) inside the frame channel. A fourth bolt and nut (1/2" NC X 1") attaches only the frame extension.
FWIW, head stamps on my late 70 are "M" with three radial lines (Grade 5) for the 1 1/2" long bolts , and "WB" with three radial lines on the 1" long bolts. -
Re: c3 69 front frame brace or bumber brace
thanks for the tech on the 1/2 inch bolts , i have once again glanced at the upc 14 and have a couple questions,
#1 the bumper guard shows a #22 special washer on the atatchment to the air dam glass portion. between the guard and the glass , what style of washer are we dealing with? and you did say that a lock washer was used in place of the split-L/ washer , did that just use outside teeth ?
the second question is dealt with in upc #8 "fuel tank filler neck the drain hose on my vehicle ends up at the rear frame crossmember . " the note states insert shield into hose end even with lower end of hose . What are they meaning when they say shield ? is there an additional hose that atatches to the hose?Comment
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Re: c3 69 front frame brace or bumber brace
Kelly,
I don't know about the bumper supports, but the shield they are referring to is, I think, a spring that is inserted into the rubber drain hose to keep it from kinking.
TerryTerryComment
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Re: c3 69 front frame brace or bumber brace
Kelly, going back to my first post on the frame extension/bumper brace: After you read the post, I deleted the post and removed the part about the "special washers"...reason: my car had two on each side under two of the frame extension bolts, but I don't know in which positions they were installed.
It's not a problem for me on re-assembly because the frame extensions have been permanently marked by the washers' serrated teeth. Unfortunately, as the frame extensions are temporarily installed now, I can't see the marks. These special washers are really thick, heavy duty 1/2"(nominal id size) flat washers with teeth on the face to be mounted toward the frame extension. I mentioned in my first post that these "special washers" are contrary to my AIM, which shows cut lock washers under the frame extension bolt heads.
Regarding your question on the bumper guards, there may be differences between 69 and 70 bumper guard configurations. My AIM (Sheet 14A3), however, also shows a "special washer" between the lower end of the bumper guard and the fiberglass, but this special washer is nothing like the one described above for the frame extension.
This "special washer" appears to be a simple flat washer, zinc plated, 3/4" OD X 7/16" ID. The bumper guard bolt threads in from behind the air dam through a bracket attached to the front cross member, and uses a flat washer and a cut lock washer under the head. GM's use of the terminology "special washer" for an ordinary garden variety hardware item like this washer is not unusual in my experience; I am not sure why...maybe these were items outside their standard fastener specs.Comment
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Re: c3 69 front frame brace or bumber brace
Thanks for the work, the special washer/normal , your manual does show also that it goes inbetween the guard and the fiberglass, ? as what a spacer ? and thanks for the special large on the frame rail , i thought they were only used on the rear , so you say they may belong on the front as well excellent , sure would like some others to jump in and support these findings ,Comment
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Support These Findings...
Yeah, Kelly, I am still hoping for your sake that somebody out there has completely disintergrated a 69 Corvette, and will share notes they carefully kept during the process.
I believe the "special washer" shown in the AIM between the bumper guard and the fiberglass is a regular flat washer, but my notes show no thickness. If it's not a plain flat washer, then that is probably as close as you're going to get. The washer probably does serve as a spacer to keep the sharp edges of the bumper guard off the fiberglass; it's real difficult to weld the end plate (with weld nut) on the guard without leaving a little clearance on the end for the weld bead.Comment
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Re: Support These Findings...
thanks again , very supportive of you! thanksComment
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Re: Support These Findings...
Those bumper support bracket washers Chuck speaks about are very common on seel bodied GM cars up until the beginning of energy absorbing bumpers. A salvage yard with old GM cars should be loaded with those washers. They are designed to dig into the frame and the support bracket to lock the bolt and all the chassis pieces in place. I've never had the chance to look for them, so I don't know if they are reproduced.TerryComment
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Re: Support These Findings...
thanks MR McManmon , SIR yes i purchased them previous to the posting at C.C and i believe Paragon stocks also, i understood them to only be present on the rear, my knowledge grows .Comment
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