Question about early vs. late tops Options

[DC_neun_vierzehn]

I know there are two different tops (early vs. late).

My question is can an early top work on a late car IF the rubber seals on the sides have been updated (to match the late windows) AND the bump stops have been swapped (to match the late latches)?

The reason I ask is that I have two spare tops (one early and one late). I have them both stripped down (no rubber, no hardware, no felt headliner, etc.). Just the fiberglass top. And I noticed that the early top much lighter. I weighed them and the early top is approx. 17 pounds whereas the late top is approx. 23 pounds.

I'm not looking to shed weight for performance (although that's a bonus), but a lighter top would be less cumbersome to take off and put on the car.

TIA

-Kris

[Literati914]

Not only are the side seals different but the channel mounting points are different because the top of the glass position is different.

Even if you can get the channels to line up, early seals won't seal against late glass and late seals won't seal against early glass.
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Really interested in doing a bit more of a technical deep dive on this as I have not noticed everything you have mentioned to be the case.

As so much bad information has just been parroted on this board over the years id like to nail this down (with data to back it) once and for all.

I'm not saying what is right or wrong at this point just proposing a more in depth root cause investigation. The reason being some of the things you are saying conflict with some of the things I know.

Specifically:

1. Side windows and roofs changed to the newer style sometime in 73 however the later style roof side seal was not implemented until 74. This means that a not insignificant number of cars from the factory got the late roof, late windows, and early seals, and I in fact have one of these cars and its probably the most water tight 914 I have owned.

2. The forward window guide rails (Part# 914 542 013 11 and 914 542 014 11) are the same part for all years. This means the location of the junction between the top/front corner of the window and the Targa, should be the same for all years. Same with rear seal, the upper rear corner of the window should also be in the same location for all years. This should mean the upper edge of the window should be the same for all years (but i will confirm this)

3. The PET may be wrong on this but the side seal attachment strips are listed as the same parts for all years. ( Part#s 914 531 865 10 & 914 531 866 10 )

4. In the factory manual Porsche lists the new side seals ( 914 531 185 10 & 914 531 186 10 ) as superseding the early part and specifies it for use on the early cars.

So, If the seal support rail didn't change, the seals are interchangeable between years as proven by the 73 cars using the early seals and per Porsche themselves in the factory manual, the window depth didn't change (couldn't have as the chassis and window guide didn't change dimensions) then what changed?

Despite not being documented in the PET we know there are 2 versions of the rear rubber supports and 2 versions of the Targa latches that coincide with these blocks. A mismatch here can absolutely cause leakage.

You mentioned the location of the seal mounting strip screws changed. This I have never looked at but doesn't make sense to me as to why it would given the window depth should be the same for all cars. I will verify this though as we currently have 7 tops torn down for refurbishment (both early and late) at PMB, it shouldn't be to hard to verify.

Also worth noting in addition to my 73 car with late roof and early seals, I have a 72 car with 73 doors and an early top, also without issue though on this one I am using the later rear latches and rubber blocks.

Given all this it seems worth a deep dive to figure out why things are/are not working in some cases.

James I'm interested in seeing what you can discover about all this. I purchased the only side targa seals available via 914rubber and I've got gaps (I doubt that's 914rubber's fault, the seals seem like quality parts tbh), that I'm gonna have to go back and address at some point.

I get your point about the vertical window rails not changing, and that sems like a good point but surely the factory changed to taller rubber blocks at the latches for a reason.. or maybe it was the other way around? Anyway, thanks for the effort - looking forward to your report - (IMG:style_emoticons/default/popcorn[1].gif)