What changes are needed for H4 headlights in 1977 Porsche 911S

[Diggem]

What parts do I need to convert a 1977 Porsche 911S for Porsche H4 headlights?

[spuggy]

Assuming you want to convert a US spec 911 with "sugar-scoops" and sealed-beam units to RoW Bosch H4's, you'll need a pair of Bosch H4 headlights, and at least the inner half of the 2-piece mounting screw. You can re-use the existing rubber gasket (and you'll probably find life much easier if you do, as later ones are bigger and cause much cursing).

If you don't want chrome trim, optionally add paintable trim rings and the outer part of the 2-piece mounting screw. The Bosch headlights are available with chrome inner rings, or painted with what looks like a semi-matte black primer; some have painted these directly. I haad planned to leave the trim rings off (my car is black), but the visible "step" in profile between the fender and the headlight assembly drove me crazy and I got some trim rings painted body color. Much nicer/finished like factory.

If you get the Bosch headlights with city lights, you may want to make up a little y-harness to feed both the city lights and front markers both from the same feed (loom terminates in the bucket, US has an extra little harness to the front markers), just tee into the factory wiring.

If you only want the improvement in beam pattern that comes from ditching sealed beams for a properly-designed reflector/lens assembly (and/or bulb upgrades), just fit a Hella, Bosch or Cibie H4 reflector into the sugar-scoops.

And fit relays whatever you go with. Tremendous difference and saves the headlight stalk to boot.

[Aloha911sc]

What do you mean by "fit relays".

[mo-mon]

He means install headlight relays. You can buy this- www.jwesteng.com/shop/911/16-911-headlight-relay-kit-74-89.html
or make your own.

[darrin]

and you want to install headlight relays to alleviate the strain on the turn signal/highbeam switch - as delivered/built, our 911s route all of the headlights' current through the high beam switch, which (especially with the higher wattage bulbs you can run in h4s) causes the high beam switch to distort and fail (in an annoying manner -- mine would flash the high beams on and off randomly to the "amusement" of cars in front of me). The relays divert the current away from the headlight switch and frequently provide one with slightly better light output too

Diggem -- are you seeking to change the look of your 911 or simply improve headlight "power"? If the latter, you can add "drop-in" euro-spec H4 headlights to your sugarscoops for a fraction the cost of the Bosch 911-specific h4 assemblies.

[JSV798]

I installed relays recently on my '78 911SC, but used the Porsche relays that slot into the relay panel.

Before:



After:



This makes it look like an original fitting, but is quite a bit more expensive and those relays are a PITA to get in the relay panel. My car happened to have two spare slots and a spare fuse as it doesn't have front fog lights. You will notice that I used #1 fuse to connect my red relay wires (power in) using a 25Amp fuse linked to a new length of red cable to the +ve battery terminal. Otherwise wiring instructions pretty much the same. I have seen other schemes on this forum but they involved much more disruption of the original wiring. If you need any more detail let me know.