Need Advice - Cut the Top or Not

[Feldsine]

I'm starting to think about fixing the rust along the top of the A pillars and the roof on my 71 C20. As the pictures show, there are gaping holes. The rest of the truck is very solid, only surface rust and no rot.

What I am thinking of doing is cutting the top off and replacing it with the top off my 69 C10 donor truck, which is in great shape. The plan I have at this point is to carefully measure and cut the A pillars about 6 inches up from the bottom, and cut along the seam on the back of the roof and around the B pillars to separate the top.

What I am not sure of is if cutting the seam is going to allow the top to separate. It looks like from the inside of the cab, that the inner panels are just butted against each other and should separate without cutting???

Would it be better to cut the top off lower say mid rear window, or below the rear window or some such place?

I'm thinking since I have a donor top in good shape that is a better way to go than trying to fix the hole in the roof and tops of the A pillars...???

I'm not body work guy, I have a friend who is going to help, but he also is wondering what is under that seam. Would appreciate the guidance of any who have gone down this road before.

[alsriv2]

I would think that for the least amount of pain and greatest benefit, you would be in good shape to just cut out the bad metal in your roof and splice in repair patches. Your roof is not all that bad considering. The effects of not doing your roof replacement correctly will result in a junk cab and much more expensive work.
Get the appropriate tools and give the splice a try. With careful work, you will have a good repair and a notch in your belt for the experience gained.
Take a look in the forum for other members who have done the patch repair work. The end results are fantastic and they give good write ups with pictures on how they did what they did.

At the end, by not cutting up your parts truck, you will have something you can use for parts or sell to another person for some money in your pocket.

[Feldsine]

You know, I guess we could always try patching it first, nothing lost, and if that turns out to be a less than desired project, we could always consider a top swap afterwards.

[hugger6933]

I have a cab on the tipper flipper dolly in my shop now that had the roof cut through the A and B pillars. I would not hesitate to do it again. It is just metal work, cut and weld. The more of it you do the more comfortable with it you will be.

[swamp rat]

I think if you have not already you should remove the front clip and take a close look at the floor, lower A pillars, rockers, inner rockers, cab supports and inner kick panels and around the vent openings, Also look closely around the heater body and master cyl, usually much more rust that most realize.

Water can and will get in thru the gutter seam and work its way along the inner roof windshield and down the A pillars, also usually what rust you see on the outside is only about 1/3rd of the actual damage. Look under the dash and up at the seams below the window.

Most roof top repairs are below the rear window on the back of the cab, and about 3-6" down the A pillar.

[Chknlyps2]

Originally Posted by Feldsine

What I am not sure of is if cutting the seam is going to allow the top to separate. It looks like from the inside of the cab, that the inner panels are just butted against each other and should separate without cutting???



I'm not body work guy, I have a friend who is going to help, but he also is wondering what is under that seam. Would appreciate the guidance of any who have gone down this road before.

That seam is spot welded, if it stops snowing for a bit before it gets dark I will try to get a pic for you from a cab top I have looking up the B pillar.

[ss454conv]

Swamp Rat is right on the money. I just did a roof replacement and mine did not look nearly as bad as your pictures look. I thought I would get by with a roof skin until I cut it off. The inner structure looked like it had been at the bottom of the ocean with the titanic. I got a donor roof but instead of just cutting through the A and B pillars, I decided to separate all the spot welds and put all the pieces in individually. I still had to cut the A pillar but I was able to offset the cut in the inner and outer structure which should make it stronger then a straight across cut.
It is a big job. Which ever way you go make sure you weld in some support before you cut it off and measure carefully. It can be done.

[LockDoc]

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Here is the location of the spot welds on the rear cab seam....

LockDoc

[swamp rat]

Looking at Loc Doc's pic i have seen then cut across by the gas cap, and also along the floor but ether case leave your vin plate intact and dissect around it to not disturb it.

If your good at fitting then yes you can cut at the pillars and at the roof seam but i would inspect closely at all the inner roof panels

[Chknlyps2]

This is not the greatest picture but it is looking up the B pillar, I can stick my hand in there and feel the dimples where the spot welds are. Circled in red is the lip where the outer skin seam is spot welded together, yellow is the inner skin seam and the little plate with the wings is the shoulder belt mounting point. If you take out your dome light you can see the outer skin seam right there and you can feel the inner seam just above the opening.

Like what swamp rat said, what you see on the outside is probably 1/3 of what is there. The outside of this roof looks great with no rust and what looks like original paint but the inside of the A & B pillars are rusty and rough as heck. I can feel pitting in some spots also... on the left of the pic is the back side of the door jamb area and that is where the pitting feels the deepest, the painted side looks wonderful.

[Feldsine]

I'll take another look around the truck in the places swamp rat suggested. I've crawled around the truck pretty much, and I didn't see much rust. This truck was stored for 15 years under cover, but this is in Humboldt County, CA near the beach and I think the years of moist air just got to it in the exposed sections up top for the most part. I'll check it out and see if I can post more pictures of what I find in the lower places on the truck.

[cooperhw]

I just did the same type roof swap on my last truck last year. It was called "Meet Homer" in the 67-72 trucks "build thread".
I show detailed pics of how I cut off my trucks roof and back of cab. I had to take off way more of the back of the cab that you probably would because mine you could walk through the hole and I wanted to preserve the portion of the vin pillar.
If I was not worried about the vin I personally would cut the A pillar about 3 inches down and right across the bottom of the cab under the seat where it didn't show. Put new outter rockers on and good to go.
P.M. me if I can be of any assistance. Hugger 6933 does this stuff all day, every day, so he's probably forgot more than I know, so he would be the guy I would be asking (if I was you).

[Feldsine]

Wow cooperhw, that is a lot of great info!!! Found all the pics on page three of your build sheet. Thanks a bunch, that is inspiring, and you make it look easy.

Perhaps Hugger 6933 will weigh in here. I'm thinking that it makes more sense to cut the back like just under the window rather than along the seam at the top....???

[Feldsine]

Duh, I see Hugger6933 already posted above.

I guess a follow on question. If I were to cut the top off, where in the back would be the best place to do that, I.E. simplest with best chance of success? Above back window, mid window, under the window were that ridge is?

Here are a few more pictures from up under the dash and around the doors. I realize I'd have to pull all this apart to see what is behind the carpet and sound proofing, but initially it doesn't look bad.

[cooperhw]

Originally Posted by Feldsine

Duh, I see Hugger6933 already posted above.

I guess a follow on question. If I were to cut the top off, where in the back would be the best place to do that, I.E. simplest with best chance of success? Above back window, mid window, under the window were that ridge is?

Here are a few more pictures from up under the dash and around the doors. I realize I'd have to pull all this apart to see what is behind the carpet and sound proofing, but initially it doesn't look bad.

If the vin isn't an issue for you, you could just slice it through the middle of the window. You will only have to fix/weld, bodywork from the edge of the window to the doorframe. Bad news is it's gotta be perfect when you are done cause it's right in your face. That's one good thing about doing it below the bed is that you only see what shows from the edge of the bed to the door frame. Easiest in my opinion is top of A pillar and right down the middle of the cab under the seat. Install new rockers when done and you only see a few inches from the rocker to the edge of your carpet or sill plate.
IMHO