Hello all,
Can I use my 1987 300sdl glow plugs in a 1991 350sdl head. My glow plug system was working perfectly when the 300 head was on the car but I now can buy a 350 head for my car. Isn't it just a matter of switching plugs to new head? thanks all

There's a little difference in glow plug length between 300- and 350SDL. I don't know which are longer. I suppose you can use shorter plugs in place of longer plugs. For the effort involved, why not get a proper set of plugs?

Sixto
87 300D

91 has afterglow, 87 does not. May be a factor.

It has to do with the angled injectors in the 3.5L engine.

Are there other differences to consider with the later cylinder heads? Injectors, injector lines, prechamber differences, etc?

__________________
1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting

Yes, all of those are different. The injector nozzles themselves might be the same, but the bodies have a different thread pitch. And, because they are angled the lines are different too.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Nozzles are different. 3.0 have fine threads near the tip like 617 nozzles, 3.5 have coarse threads further up the shank. They only work with their respective prechambers. Also need corresponding compression tester prechamber adapters. Same compression tester glow plug adapter.

3.0 prechambers will not sit properly in a 3.5 head without modification per gsxr's specs.

Injector lines can be gently persuaded to fit but application specific lines are less likely to leak in the future.

Sixto
87 300D