fender mounting tips tricks?

[c20pickup]

front fenders need to get installed! never done this before, was going to have the body man who did the work install the fenders for me, but 7 months later and no such luck. so im going to tackle the project myself! biggest concern here is chipping and scratching my paint, the body work and paint is flawless, to help with that i used a couple strips of masking tape on the door edge to prevent chipping. any tips or tricks to help me out would be great! im told that since the cab was off the frame and i bought new bushings the side to side as well as up and down alignment of the cab could be off, which i understand. i purchased a front end hardware kit along with an assortment of shims from lmc. i ran a thread chaser through the mounting holes in the cab and fender, that didnt seem to do much and the bolts still seemed to go in rather difficult. so i ran a tap through two of the holes as a trial. one being a 5/16-18 and the other being a 3/8-16, this seemed to give me a nice thread to bite onto, is this an acceptable practice after there is piant on the threads? next issue is gap alignment. i mocked up the passenger fender today with two bolt (one 3/8 on the cowl and one 5/16 through the core support) the door to fender cab is very close on the top (maybe 1/16th inch gap) and gets larger on the bottom (around 1/2 inch gap). this would lead me to believe i need to either shim up the front cab mounts or tighten down the bolts that go through the rear cab mounts. i think im off to a good start, refreshing to see my fender back on after almost four years of work. again, any tips or tricks to help prevent damaging the paint, aligning the fender or aligning the cab would be great! shoudl probably mention the passenger fender is new from gmc pauls and the driver side is original to the truck. thanks!

[hugger6933]

OK too bad your not closer I'd help you hang that front in an hour or so. But your gonna need the power of X. X measurements that is. On the cab that is where we start measure the frame to rocker on each side front and rear try to make them as close as possible to being the same. Once you got that done hang the core[radiator] support start your bolts and have them as close to the center of the big hole as possible. Now pick a point on the core support say the bolt head on the corner bracket, and take a tape reading from there to the opposite corner say the cowl bolt hole. Then do that on the opposite side that number should be as close to the same as you can get it. Now with the painted fenders get some BLUE masking tape or kill the glue on the green tape.[To kill the glue= you pull out a section then place it along your bluejeans that will help the tape be less sticky so not to be as strong] Strong tape is not your friend here and could pull up paint and or clear coat.Blue tape isn't as sticky and hence the name lo tack tape.
Ok back to work tape up the points where fender could get a paint bruise and all other joining points to be safe. once you have that done it is a matter of setting on the fender, starting one bolt in the back one in the front. Now you can step back and look at what you've done installing a fender is a big step in moving the project farther along. once you have all the bolts started you can go back and start tightening them up on your first time I'd say start all of the bolts first then put the fender where it has to be setting all the gaps then wrench er down.leave the tape on for the hood and cowl panel install but don't let that tape stay too long or it could be nasty trying to remove transferred glue. If you need any other help let me know and i'll do my best to talk you through it. Jim

[c20pickup]

Originally Posted by hugger6933

OK too bad your not closer I'd help you hang that front in an hour or so. But your gonna need the power of X. X measurements that is. On the cab that is where we start measure the frame to rocker on each side front and rear try to make them as close as possible to being the same. Once you got that done hang the core[radiator] support start your bolts and have them as close to the center of the big hole as possible. Now pick a point on the core support say the bolt head on the corner bracket, and take a tape reading from there to the opposite corner say the cowl bolt hole. Then do that on the opposite side that number should be as close to the same as you can get it. Now with the painted fenders get some BLUE masking tape or kill the glue on the green tape.[To kill the glue= you pull out a section then place it along your bluejeans that will help the tape be less sticky so not to be as strong] Strong tape is not your friend here and could pull up paint and or clear coat.Blue tape isn't as sticky and hence the name lo tack tape.
Ok back to work tape up the points where fender could get a paint bruise and all other joining points to be safe. once you have that done it is a matter of setting on the fender, starting one bolt in the back one in the front. Now you can step back and look at what you've done installing a fender is a big step in moving the project farther along. once you have all the bolts started you can go back and start tightening them up on your first time I'd say start all of the bolts first then put the fender where it has to be setting all the gaps then wrench er down.leave the tape on for the hood and cowl panel install but don't let that tape stay too long or it could be nasty trying to remove transferred glue. If you need any other help let me know and i'll do my best to talk you through it. Jim

used this method today, the cab was already on the frame square, measured the rockers to frame on each side in two spots (front and back of the rocker) then i measure from the back of the cab to the bed mounts on each frame rail, the cab was squared on the frame. I measured my core support to the firewall on the passenger side and also the driver side. The core support originally had a one inch bigger gap on the drive side, so i loosened it to adjust and the best i could get it was 1/16 side to side. both fenders are mounted on the truck and gaps are even on each side, however on each side the gap still gets bigger towards the bottom of the door and bottom of fender. this would lead me to believe i need to shim the front cab mounts upwards to correct this gap?

[hugger6933]

Your cab is either too low or the core support too high. If you just stuck the front bumper on there to see witch one is the case that would help. It sure sounds like the cab is low so yes shimming it up is the best solution I see.

[RenoKeene]

A quick trick to go with these tips...wooden paint stir sticks are about the right thickness for door to fender gaps and won't hurt the paint.

[hugger6933]

Along those lines the back side [top] of a filler spreader will suffice in that instance too. Jim

[Cape Codder]

Before shimming the cab tighten the core support to see if it comes down. You will probably have to tighten and loosen the support a few times to get things right.

[Gmc.guy]

Are you doing inner fenders at the same time or after? I find it easier to do them at same time than after but I've seen it done successfully after fender and good was lined perfect. I always start everything a few turns and work everything a bit here and there as I tighten everything down
Maybe a small dab of antiseize or coppercote will help threading the bolts in and then taking them out again years down the road.
Good tip on the masking tape. I hate leaving it on any longer than I have to. The residue is tough to get off by itself let alone taking it off fresh paint. I use the knee strip method too. If I need better protection where I'm sure it will touch or bump I double wide the masking tape and put duct tape on top of that. I do that when putting bumpers on by myself and things like that

#1 advise from me is do not get discouraged because it can be really tough, but the more you work at it the better it will be. move things a little at a time. Check everything after moving one thing

[c20pickup]

thanks for the replies! the inner fenders are being put in after the fenders are mounted and aligned and gapped, ive been told to do this by several people as it makes mounting the fender easier. i will try the blue tape and also the measurementsas mentioned. thank you!

[Cape Codder]

The paint sticks I get these days seem to be getting thinner.

[kx57]

Don't do what one of our local body shops did....they put a set of fenders on one or our trucks and forgot the shims...then cranked all the bolts so tight they bent the fenders....

amateur hour.

[Cape Codder]

Most body men under 35 never worked on cars with shims. I remember the 70's Caddys had big stacks of shims.