70 wiper door, grill, questions,

[Warren L.]

Just working on the wiper door and have some questions. Some of 10/24 bolts (4 pcs) that hold the door on at the ends through the plastic bushings were broken off in the wiper door so drilled them out and put in 10/24 stainless inserts drilled from the outside. The holes seen on the outer edge of the door were then too large from the insert so filled it with filler and drilled it out to the original size hole and assembled it with anti seize. In the mid America manual page K76 the bolts are number part #5 4 pcs #3922099, the GM number for the bolt is 3945216.

The two screws that adjust the stop for the wiper access door assembly were seized so heated and cooled and finally got them out just barely without breaking them. Cleaned them up and put them back with the nut with some antiseize, I did not re tap the holes.

Is there info on refurbishing this assembly in the archives? Yeah I should have asked that before doing this.

The screws that hold the wiper grill on (8pcs) are 8/32 as far as I can tell. I put in some 8/32 screws and they fit well but a bit snug from a bit of corrosion, I retapped the holes 8/32 and then checked the screws and they are a bit loose. I noticed this on each of the holes I tapped.. Not a problem, snugging the screws but since running the tap through the holes they are not as tight as I would like.
Am I doing something wrong chasing holes with a tapered tap? should it be a flat bottom tap or is there something else used for chasing holes?

For the grill bracket Part 2 on page K74 Mid America what is the screw size for the two screws part 8 that go through the firewall? Am hesitant to tap anything else, I tried a 10/24 screw and it fits then loads up, think it is a 10/24 though.

Do most cars end up with shims on the wiper assemble where it bolts up to the firewall? marked as part number 5 page K74, I am not sure if this car had these originally or do they all have them?

I noticed that the grill is lower at the back edge than the front edge of the wiper door, I can preload the grill with the moveable bracket 2, is this normal to have to put pressure to raise the grill up so that it is closer to matching the contour of the front edge of the wiper door? Thinking of it now need to check how the grill matches the back edge of the hood.

From what I can tell my assembly was painted a lower sheen than ralleye black but a bit than more than flat black. Is that correct and do they paint over the white nylon washers that are there? Or were they painted first then the assembled after so the washers did not have paint on them.

Sorry for so many questions at once,

Thanks,

Warren

[Chuck S.]

Re: 70 wiper door, grill, questions,

Warren, my experience with taps sold to home shop users is that they provide a "sloppy" hole. It could be because the taps are general purpose taps providing a sloppy "general class" of fit to insure everything fits, or...it could be that my hands are getting shaky.

In any event, the wiper door, cowl vent panel, and wiper door linkage are all made of SOFT metal. Running a cutting tap through soft material is very likely going to give you a sloppy hole unless you are EXTREMELY careful (sans shaky hands). Some contributors here have suggested using "chasing" taps which are specifically made for chasing boogered holes without removing material, but I haven't tried them...the regular taps and dies are enough expense for me. Another option is to use a poor man's "chasing tap"...just turn a PROPERLY threaded fastener through the hole with penetrating oil until you can easily turn it through with your fingers. Get the thread wrong, and you'll be installing some more heli-coils.

Shims in that location are like shims everywhere else on the cars...the number varies from car to car, but they are not unusal at that location. Use as many shims as you need to get it right. Shims, however, will not help remove a front to rear bias since they are constant thickness. You will have to find the source of that problem and correct it. Avoid trying to make any "strong arm" adjustments on the door linkage...it is easily broken and expensive to replace.

[Jack H.]

Re: 70 wiper door, grill, questions,

Screws to mount the wiper door grille to the wiper door platform originally had thread cutting tips. Mechanics in a hurry over the years typically managed to get them started into existing holes, off-thread thus 'wallowing out' the tap.

What's sold in the aftermarket as replacement screws are typically standard screws without thread cutting tips. With these, repair is simple, drill and install helicoils. To reused factory originals, it's time to fill the existing holes, drill small guide holes and let the thread cutting tips of the screws take a fresh bite.

[Warren L.]

70 wiper door, grill, questions,

Thanks for your response.

I used very high quality taps, and had a steady hand, will talk to a tool and die maker, I think the taper at the front of the tap rubs on the threads as it goes in and preloads the tap, then it is scraping some .000`s off as it goes. I haven`t come accross this in the past but I was always doing larger sizes. I also found flat bottom taps which would have just matched the threads right away with no taper on the front, anyway I will get this confirmed by the tool and die maker. I did check on chasing taps and my one supplier does not have those, putting a screw through would have been better, the holes were fine, just a bit too tight and I wanted room for anti seize to be in there. Gee wish GM put anti seize on all my bolts when they assembled the car! Yeah I know.

As far as the wiper door, I didn^t see any shims but this was years back so maybe they were there, just wondered if cars came without them but will see how it fits. The relationship of the grill to the door is in the height, the grill sits lower in the center, it does not match the ww wiper door but I am thinking this is normal factory how it came stuff.

Do you know about painting the wiper door assembly? if they were painted after they were completely assembled with some sort of flat black. Mine seems to be flat black and the paint is over the nylon washers. I don't think this was painted by either of the two previous owners. If that is correct then will blast it lightly, epoxy primer it and put on some low gloss urathane.

Thanks,

Warren

[Jim T.]

Re: 70 wiper door, grill, questions,

Reference the 8 wiper grille screws. Nuts on the bottom of the screws will hold them in place.