[lamans71]

In prepreation for replacing my gas tank I was looking at the trunk floor and thinking that perhaps now as a good time to tackle this issue. I've known that the floor has a few holes and weak spots but its been way on the back burner. So my question is how difficult is it to replace the trunk floor in a convertible without removing the quarters and while the car is on the frame? Am I kidding myself that its possible? I've watched a few you tube videos and in those the quarters were off or it was just the center section of the pan that was replaced, and all the videos I saw the work was on hardtops.

In my case I think I really need to replace the full pan from where it attaches to the rear valance up or as close as possible to the cabin floor pan. My thought is to replace it in sections (partly due to size) starting with the two sides then the center section. One huge concern is will I have problems with the quarters twisting (or worse) if I attempt to do this without removing the body from the frame.

I have never replaced a floor pan before so this will be my biggest body work challenge by far. I welcome any thoughts or insights from anyone who has done this before.

[Farrell in Vancouver]

If you can do it in sections I would reccommend it.
Without removing at least some of the car, a full piece would be difficult.
My 70' Lemans Vert is getting quarters but I only had to repair a few spots in the trunk so purchased the left side only. Check the trunk braces from underneath carefully and if they are weak replace them as well. I failed to recognize this issue and should have ordered the left trunk brace. Ended up rebuilding it from scratch as it would have been a few weeks to get one.

[lamans71]

Yes I do agree that doing it in sections is the only way I could see doing it without having the body off the frame, just curious if anyone had found a way to do so in the past. And also to see if I need to worry about bracing or supporting the quarter on the side I cut away, it seems that at the least I would need to support the quarter from underneath so that it does not droop or twist as I cut out the old floor on the sides. And thanks for the brace suggestions, I am indeed going to replace all the braces. Both of the braces that support the gas tank look in rough shape and I suspect the side braces are also toast.

[ZeGermanHam]

A full 1-piece trunk pan replacement isn't possible with the body on the frame and nothing else removed for access. You'll have to do it in sections, which isn't that big of a deal.

[Greg Reid]

I replaced the full trunk pan in my '68 and if I had it to do again, I would still choose the 1 piece without a second thought. A LOT less welding as all braces are in place on the replacement pan.
I did not have to completely remove the car from the frame and both quarters were in place. I cut a good portion of the trunk out of the center and then removed all of the body mount bolts except the front ones... just loosened the front pair. Jack the car up by the differential, put jack stands under the body near the rocker panels and let the jack down. The frame/differential will come down (keep and eye on the distributor to firewall clearance)... Finish cutting the old pan out as needed.
Finally, slide the new pan in from the rear. Once you get it where you want it, spot weld around the perimeter and let it back down.
Not saying it was easy.., physically, removing the old pan was the hardest thing I did to my car during the resto but was well worth it. Installing the new one was a comparative breeze.

[bluejudge]

Originally Posted by Greg Reid

I replaced the full trunk pan in my '68 and if I had it to do again, I would still choose the 1 piece without a second thought. A LOT less welding as all braces are in place on the replacement pan.
I did not have to completely remove the car from the frame and both quarters were in place. I cut a good portion of the trunk out of the center and then removed all of the body mount bolts except the front ones... just loosened the front pair. Jack the car up by the differential, put jack stands under the body near the rocker panels and let the jack down. The frame/differential will come down (keep and eye on the distributor to firewall clearance)... Finish cutting the old pan out as needed.
Finally, slide the new pan in from the rear. Once you get it where you want it, spot weld around the perimeter and let it back down.
Not saying it was easy.., physically, removing the old pan was the hardest thing I did to my car during the resto but was well worth it. Installing the new one was a comparative breeze.

Looks great. Nice job!!! Marc

[lamans71]

Originally Posted by Greg Reid

I replaced the full trunk pan in my '68 and if I had it to do again, I would still choose the 1 piece without a second thought. A LOT less welding as all braces are in place on the replacement pan.
I did not have to completely remove the car from the frame and both quarters were in place. I cut a good portion of the trunk out of the center and then removed all of the body mount bolts except the front ones... just loosened the front pair. Jack the car up by the differential, put jack stands under the body near the rocker panels and let the jack down. The frame/differential will come down (keep and eye on the distributor to firewall clearance)... Finish cutting the old pan out as needed.
Finally, slide the new pan in from the rear. Once you get it where you want it, spot weld around the perimeter and let it back down.
Not saying it was easy.., physically, removing the old pan was the hardest thing I did to my car during the resto but was well worth it. Installing the new one was a comparative breeze.

Awesome, thanks for your reply Greg the pictures also are super helpful. I was curious if it could be done that way but was not sure if there would be enough room to slide the new one in or not. Now I know it can be done and I think that will be the way I go as well. One question did you buy your replacement floor from Ames?

[lamans71]

Well bummer, after some searching today it seems that nobody makes a one piece trunk floor for the 70-72 cars only the 69 and earlier models. I looked at Ames, OPGI, and Year One but could not find a one piece floor at any of those sites very disappointing. If anyone has any other recommendations for a supplier of a one piece unit please speak up, otherwise I have no choice but to do it in sections like it or not.

[BB70]

I put a one piece in my 70 GTO, had to get a Chevelle unit and reuse the very rear part from my car. I cut up a decent shell for the trunk and a quarter, but could not use the trunk after it got cleaned up.It was alot of work. If you have rust problems where the rear bumper brackets bolt to the trunk, nobody makes that piece and the Chevelle stuff is different. You have to do some fabbing or find something out west.

[lamans71]

I don't know just yet how far the rot extends, it does go up from where the gas tank straps bolt onto the brace. In looking at the photos of the three piece replacement floor available from Ames it seems that those pieces extend all the way up and then out to where the floor is spot welded to the body just under the trunk opening. But I've never done a trunk floor before so I might be interpreting what I see in the photos wrong, really will not know for sure until I have the parts in hand I suppose.

The biggest headache with the three piece floor over a one piece (actually its seen pieces when you include the two side braces and the tank braces) is all the extra welding that will be involved. I'll have to stich weld together all seven pieces, a ton of extra welding which is not my best skill.

I am wondering if it would be easier to stich together all the pieces on the bench then install as if it came as a one piece unit. Anyway you slice it lots of extra work that could be eliminated with a one piece unit.

[Greg Reid]

The one I got was from Tamraz and purchased through ebay.
I do recall that for some year models, this same pan was used but had to be spliced into the original metal at the rear. Basically, you have a trunk pan that is the same for a lot of years but the change in tail lights causes you to have to modify that.

[gtojeff1967]

Get the chevelle one and use the gto rear section and the hump between the wheel wheel is correct were the 68-69 the hump is different.

[lamans71]

Thanks for that additional info Greg. GTOJeff, that would require buying two full pans which is way too much , I will just have to purchase the 7 seven piece set as that is all that is available for my 71. It may be possible to stich the three pan panels together on the bench with the four braces and then install as a single unit. Not sure and I really won't know for sure until I have the new stuff in hand and the old floor cut out.

[mrennie]

I wouldn't recommend welding anything on the bench...many of the multi piece panel sets have extra material that need to be trimmed and unless you are fitting to existing sheet metal you may end up with something that is too short or too long making things worse.

My opinion (I am not a bodyman so take this for what it's worth), if I was doing a 7 piece set, I would start by cutting the old braces off (leaving the existing floor pan installed), then weld the new braces in and screw the old floor plan to the braces. Then, cut the side sections of the floor away, replace the drop offs and install new side sections, screwing the pieces together and tack welding to keep things from moving. Once both sides are done, cut out the old centre section and graft in the new one, then weld it all up.

There are multiple ways to do this, but the key thing is not to take too much of the original structure out at once, to keep things aligned. The one piece panels are welded on a jig and you will have a very difficult time welding the 7 piece kit together and getting it straight and with correct dimensions.

[400 4spd.]

^ Absolutely.
I've seen several multi-piece trunk floors that people have installed. A common problem I've seen is getting the floor flat vs. a roller coaster surface. If you can make a one piece work, I think you will be pleased. Good luck with your project.

[lamans71]

Thanks mrennie and 400 4spd for your thoughts and experiences. Welding the 7 sections together is only an idea at this point, I'm not sure it would be done either. Mostly just thinking out loud as it were. I wish there were a one piece but that does not seem to an option at all. I looked that the 69 floor from Ames and here is what the description notes:

WILL WORK FOR 1970-72 MUST REUSE ORIGINAL TAIL SECTION. RIBBING DOES NOT MATCH 70-72. FOR 1971-72 FRONT UPPER SECTION MUST BE FABRICATED TO ACCEPT EMISSIONS BOX

If I'm reading this correctly the ribbing would not line up so mating this floor to the tail section of my current floor (assuming its good enough) does not sound like it will be easy or look at all correct. Plus I have no idea what would need to be fabed for the emissions box . The one big plus is that this part does come with the braces already welded, I just cannot figure out why nobody makes or carries this for the 70-72 cars??

As this project is still in the planning phase I have not ordered or made any plans just trying to wrap my head around it and find the best way to produce the correct aesthetic and functional results.

[mrennie]

If you can make the splice at the rear of the floor pan about 6" up the back, making the rear ribs line up with the factory section isn't that bad...sheet metal is easy to move if you go slow.

I replaced my trunk floor with the 3 piece set and the rear edge of the replacement panels did not line line up at the ribs either. I made a small dolly out of 3/4" flat bar to match the rib width, marked where the ribs should be, and using a body hammer I slowly tapped down the ribs flat that were in the wrong spot and made ribs in the correct spot on the replacement panels. A few hours work and they lined up fairly well. The ribs at the back fade away as you get to the floor area so this helps to hide your work. The challenge of doing this with a one piece pan will be putting it in and out to test fit and do the dolly work.

What they are saying about the emission box is that the 70 floor has a somewhat flat area behind the seat back (except for the hump over the differential) while the 71 & 72 have the big emissions tube that comes up through the floor area and goes into the seat back, and this isn't reproduced.

If you truly need to replace the section over the differential, your options are more limited, but if you only need to go halfway up the front and back vertical sections it will be much easier to match up with the original metal.

If you could sandblast the floorpan where it goes up the front and back, you would quickly find out for sure how far you need to go and this would help guide you. This may not be reasonable on a car that is still being driven...

[lamans71]

Thank you so much for detailing your experience with the three section replacement panels. That is just the sort of information that I was hoping to hear about and learn from before tackling this job.

And again thanks to everyone for all your thoughts and experiences with the different replacement panels available. IT really does help to hear and learn from those that have done the replacement.

[Va68goat]

I know I'm a little late to this thread but I'm just about done replacing the trunk pan in my 68 GTO and I'm in the process of researching spatter paint. I think the blk/aqua is correct for the car but I believe I'm going to go with the blk/gray instead. Any thoughts on name brand of paint? I think we're going to spray the paint but I'm not opposed to rattle can. Any ideas?