pettrix

I noticed on a few convertibles that the area above the trunk lid where the 1/4 panel meets the deck lid. There tends to form stress cracks. I assume this is due to the lack of support from a roof and the torque of the vehicles causing it to crack there.

Anyone else notice this on 455 convertibles?

bccan

pettrix

Speaking of cracks. The factory W-25 hood is notorious for cracking due to the fiberglass tops and metal supports. Two opposite materials both moving in opposition to each other. I haven't ever seen a DRIVEN Olds that had a W-25 hood that doesn't have stress cracks in the fiberglass. Trailer queens don't count since the hood doesn't see the vibrations and bumps a driven car does.

VC455

From the position of most of these cracks, it appears that misadjustment of the hood bumpers and incorrect closing technique are the main causes, not just miles driven.

rand5204

The cracks, in my experience, are from improperly finished welds and lead from the factory. The people building these cars had very limited time to "get it right" When you start with a badly finished seam, add paint and mix in 50 years of use, you get cracks, runt and a mess. Both of my 70 442 convertibles had cracks and issues with these areas. The only solution is to grind it all out, weld it up and finish it correctly

droptopron

My new Thornton hood developed a small crack on the edge of the hood by the pin sitting in the garage over the winter

pettrix

It is what it was for that time. The fit & finish of those 70's cars was not the greatest. Door gaps, trunk gaps, fender gaps, etc. Don't get me started on the interior fit & finish.

I love the old cars for what they were but they sure left a lot not to be loved when it came to fit & finish. Modern vehicles have advanced so much in that realm. Door gaps, interior F&F and reduced rattles and squeaks. My modern car is built tight and rattle/squeak free.

pettrix

That's exactly where my 72 convertible has cracks.

pettrix

I've seen people play with those adjustments for hours/days and cracks still develop. Yes, I believe one can reduce the amount of cracks with proper adjustments but it's a losing battle when you have fiberglass over a metal support on a hood that had questionable engineering to begin with. Fiberglass and steel expand and contract at different rates when hot and cold. Steel is notorious for rapid expansion and contractions when heated/cooled. The fiberglass top is just along for the ride and fiberglass doesn't expand and contract at the rate steel does so eventually the fiberglass will crack due to the movement of steel below it.

It's the laws of physics and fighting it is a losing battle. It is what it was for that time but I've given up battling the hood in trying to stop these cracks from forming.

My442

When I worked in the GM B-O-P plant in Framingham MA in 1972, I saw first hand what the lead line did.

It was an environmental diaster of the first order....fumes and lead dust were everywhere.

The first step was to heat up the body area; and then apply a tinning butter.

The next step was to get a glob of molten lead from a large pot heated by gas.

The glob of molten lead was slapped onto the body seam and roughly spread.

The next operation was to mechanically grind it down to a semi finished state.

The last step was to shape and finish it to be ready for primer.

Nasty, nasty, nasty.

Each operation only had 60 seconds to perform the operation.

No restoration type TLC was applied.

pettrix

Wow, that was a crazy assembly line process. That's for sure. Now it makes sense WHY the 70-72 convertibles get stress cracks in those areas. It wasn't done correctly and it was bound to fail.

No fault of yours as an assembly line worker. It was GM's fault they cut corners. GM actually screwed you by exposing you to the toxins.