Manifold and choke question

[Rij Martin]

I have a 1978 280z that I am switching to early SU carbs (and for you FI guys there is no changing my mind, I already bought them) I am putting the carbs on the stock L28 and while shopping for the manifold gasket I found that the 240-260 has a specific gasket and the 280 has it's own gasket. I would assume that I need to buy the 240 gasket when doing this swap correct? I also have a question about how to run the choke cable through the car, what is the best way to do it, and can anyone with experience with this tell me how they did it?

[siteunseen]

EDIT: I don't know which you need.  

'77 & '78s have round exhaust ports but ive always read the square port for carbeurators  will work for the round ones. The EFI gasket has notches up top for the injector tips. 

There's a couple of guys that have done the switch recently that would help you out. Try searching for a thread "SUs on 280" I think. 

Edited February 3, 2017 by siteunseen

[siteunseen]

Here's a TECHNICAL ARTICLE that I found. Looks pretty thorough too.

http://www.classiczcars.com/topic/20038-fuel-injection-to-su-carb-swap/

If you have the n-47 head that came on the '78, the fuel pump sounds like the hardest part.

Edited February 3, 2017 by siteunseen

[rossiz]

i did the same thing w/my '78 - absolutely love it, wouldn't go back ever. do a search for my threads, pretty much shows everything i did.

there's a plug in the firewall below the throttle linkage, i pulled it and drilled a pair of holes (make 'em tight to the cable so it won't leak) and the cables run behind the dash right into the console - easy. i don't recall anything special about the gasket, hold it up to the carb manifold and check. you will need to get yourself a carb bolt kit, i think the carbs use a couple different bolt holes - or maybe my memory is foggy...

do it - you'll love it!

[rossiz]

some light reading for you - hopefully it will be helpful:

 

i never liked the steel fuel rails or their routing around the front of the engine, so when i started from scratch w/the fuel lines in the engine bay. i bent up the feed line that comes up under the battery 90 degrees and put a rubber line up the fire wall, mounted an old-school "filter king" glass bowl filter/pressure regulator with a bottom input/right side output and ran rubber fuel line across the firewall (up under the windshield washer hoses) over to the carbs, fed both and dead-end at the front carb. i rolled a strip of aluminum sheet into a tube and loosely wrapped the piece of rubber line in between the carbs to act as a radiant heat shield for it. the system is fed by a little electric pump mounted in place of the stock efi pump. my round-tops came with a steel heat shield which is installed. it really got rid of a lot of clutter and it works great.

btw: i also ditched the vapor canister and associated plumbing/clamps.

[siteunseen]

There it is!  @idgemartin

[Rij Martin]

some light reading for you - hopefully it will be helpful:

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i never liked the steel fuel rails or their routing around the front of the engine, so when i started from scratch w/the fuel lines in the engine bay. i bent up the feed line that comes up under the battery 90 degrees and put a rubber line up the fire wall, mounted an old-school "filter king" glass bowl filter/pressure regulator with a bottom input/right side output and ran rubber fuel line across the firewall (up under the windshield washer hoses) over to the carbs, fed both and dead-end at the front carb. i rolled a strip of aluminum sheet into a tube and loosely wrapped the piece of rubber line in between the carbs to act as a radiant heat shield for it. the system is fed by a little electric pump mounted in place of the stock efi pump. my round-tops came with a steel heat shield which is installed. it really got rid of a lot of clutter and it works great.

btw: i also ditched the vapor canister and associated plumbing/clamps.

 

That sounds like an awesome design, could you send some pictures over?

 

[rossiz]

i'll snap a few for ya.

[rossiz]

here are a few pics - no comments on my filthy bay please! it's winter and i drive her every day... 

kinda hard to see, so i've included a set w/notes to call out the fuel system. i cut the steel feed line from the tank/pump and bent it up 90 at the firewall, then used rubber line up to the filter. i removed the evap canister and left the steel vent/return line in place and just capped it w/a bolt in a piece of rubber hose clamped onto the end.

as for the fuel pump - i used a little electric airtex unit mounted in place of the original (above passenger side rear wheel) and used the efi pump wiring to power it.

the fuel filter is by "filter king" and comes in a variety of configurations - i got it w/the feed from bottom left and output from right horizontal to follow the path of my lines. comes with a little mounting bracket to fasten it to the firewall and it has a built-in adjustable diaphragm-style pressure regulator (adjustment screw on the top) i like the glass bowl - easy to see when to change the paper filter (i also have an inline paper filter at the tank, which i change every 4-6 months).

 

you can also see i used some flexible aluminum heat shield around the vacuum line for the brake booster as it's above the exhaust outlet and gets hot. i actually bent up a piece of steel tube (old bits from the original efi rail) and slid it inside the rubber vacuum hose b/c when it got hot i noticed it would collapse. also used the same shield material on the pcv hose. the vacuum balance tube is a stock unit that i cut off all the egr and other crap, welded up the holes and ground/polished to look like a euro-style tube. i left one port on top for the vacuum gauge and fed the brake booster from the end.

let me know if you have any other questions - i can't tell you how happy i am w/these little carbs, as they work fantastic and are sooooo simple. i never could get the stock efi to work right w/my modified engine and exhaust, and the su's do the job with no drama.

 

Edited February 18, 2017 by rossiz

[Rij Martin]

That's a awesome post, thank you. It looks like you aren't running a return line but from what I have read if you are using an electric fuel pump you need the return line. How are you getting around that?

[rossiz]

the little airtex just purrs away with no problem - between the light output of that pump and the diaphragm pressure regulator on the filter it's all good.

i've been doin' nothing but putting in gas and driving day after day and it runs great. middle of the winter, 30 degrees (cold for us in seattle) and just pull the choke, she starts right up and off you go. middle of the summer, 90 degrees (hot for us in seattle) and never a hint of vapor lock or hot-start issues. this is of course with a header (runs cooler than the cast iron stock manifold) and the stock round-top heat shields in place.

[Patcon]

I suspect the little electric pump is kept in check by the filter's pressure regulator. If the engine isn't consuming enough fuel it is basically "dead headed" but probably isn't much of an issue on a lower pressure pump. It would be on a higher rated pump though...

rossiz beat me to it...

Edited February 18, 2017 by Patcon