Big Dave

It may be a simple process to most of us, but I documented the process with pictures anyway. I found information already about converting from H5s to H4s, but nothing on the coversion from 7 inch lights to H5s.

Here's the link

Alan

Dave,
Nice write up - But - where are those comparison pictures of the H4 vs H5 patterns you promised?

We all want to see it...

When I changed my H5's for H4's I really wished I'd initially done just one side & compared the resulting brightness & pattern but I was in hurry to see the "full effect" and besides I was even more distracted by installing & getting the electric headlight adjusters to work...

My next project is to add 100W/55W H4 bulbs - these are oddballs - I already have them - they are intended for a Harley Motorcycle (just 1 bulb - so brighter...). High beams should be like daylight!

Alan

AO

Nice write up. Really helps the looks of the car.

Big Dave

Alan:

I didn't have a bulb for the H4 unit. As soon as I get one, I'll do the comparison. The quick-change wiring plugs I used were in anticipation of it.

bd0nalds0n

What's the difference between H4 and H5?

Jim bailey - 928 International

ONE...

Shane

Alan

Brian,
Ahh - works every time. Its like night & day - uh I jest!

H4 & H5 are just bulb styles. But in the 928 world there is an implication of lens
version also. US OB's have 7" H4 lights ( and surrounding plastic "chrome" trim rings)
designed for the US DOT standard. S4's & newer have 8" H5 DOT standards lights
(different conector & bulb attach).

In Europe Porsche uses 8" H4 lamps with a very sharp vertical beam cutoff and equips cars
with remote headlight aim adjustment so you can keep them adjusted right regardless of
car loading.

In the US these lighs and aim adjustments were illegal in case you adjusted them badly
and blind oncoming vehicles - since they give out a lot of focussed light.

(Apparently the DOT thinks Americans are quite stupid, Europeans must be smarter
to be able to use these corectly I guess...)

When adjusted right H4's throw a lot of light down the road but have very little spill
above a tight cutoff horizontal line that rises to the right side to illuminate the side of
the road. These are truly excellent lights - quite illegal to use for quite odd reasons.

Mine shine a sharp cutoff line on a garage door at the end of my road from 150' away
- impressive (useful for aiming too). Working headlight adusters means your car is
really equipped the way the original designers intended....

In order of goodness 7" H4's are the least desireable 8" H5's are better - more light - but a relatively
blobby focus pattern while 8" H4's are the real deal (the way the car was designed to be!)

Alan

Jim bailey - 928 International

Actually the USA 78-86 used simple sealed beam headlights just like an old Chevy truck 7 inch high low beam and basically useless at any speed over about 60 MPH... The chrome plated plastic trim ring was a USA "special" !

Alan

Jim ,
Yeah I kind of glossed over my lack of detailed knowledge of the OB's. The sealed beam did use the H4 socket connector style but it isn't really an H4 Bulb which would be removable. Anyway not a highly desirable item and the chrome ring is odd in that there is no other chrome on the car!... I guess they just couldn't find an 8" sealed beam at the time...

As you can tell this seems a bit of a botched job to federalize the car - likely they were surprised they needed to make such major changes to the standard Euro lighting and had to scramble to do it...

WRT the H4 vs H5 its interesting to see that new H4's are cheaper than new H5's... if you bust an H5 its a good time to get H4 replacements - very easy swap out! Ebay the remaining H5... I sold 2 H5's for $270 on ebay vs $500 for a pair of brand new Bosch H4's. So net they only cost me $115 each - screaming deal!

Alan

SanDiego928

I want to do this someday and thought I would fix the first link since it went no where for me.

Link to Big Dave Swap out Here

Now just need to save money and find some cheap H4 or H5. Get rid of that ring....

linderpat

wow, just in time for a thread revival. Took a stone thru my driver's side H4 and need to replace it. Was wondering what was involved. Looks pretty simple since my car is already converted. The question I have is whether I will need to realign the light after the install?

SanDiego928

Thread Revival Once Again;

I am thinking of converting from 7 inch with chrome ring to the H5 "Used" 8 inch. Big Dave's write up is so great. My Son offered to buy them for Xmas.

Comments really appreciated.

Is this a good idea? The looks alone I think is worth it. Is there a downside to this at all?

Thanks, Mark

Big Dave

Downside? None that I can think of!

You'll need to re-aim after installing the new lights.

Bill Ball

Debate: 8" H5 vs 7" H4 ? I think the 7" H4 is inexpensive (widely available Hella housing) and better beam pattern. H5 requires a plug change too. H4 does not - same plug as OB's sealed beams.

Here's Alan's assessment: https://rennlist.com/forums/8978799-post39.html

With H4, even 7", aftermarket HID kits are a nice option. Not so with H5 due to the diffuse beam pattern.

Anyway, I would go with 7" H4 before 8" H5.