1974 Fiat 124 Spider: perpetual project

Most of the little ones go to a charcoal canister. The two on the sender are the feed and return.

 

Making a lot of progress on the dual carb swap.

New manifold and carbs are mocked up


Removing the old stuff was a major pain. I now understand why the guys on the Fiat forum told me to remove the engine entirely. I had to disassemble the carburetor to remove it, which is stupid IMO.


Even worse, the intake manifold hits the brake booster when removing it from the cylinder head, and I really didn’t want to remove the brake booster.


So I cut a giant chunk out of the old manifold. This sucked, but these manifolds aren’t rare, sought after, or worth any money. They’re known for being restrictive.


With the manifold out of the way, there was plenty of room to remove and clean other stuff.


The biggest challenge in this swap is assembling an effective and reliable throttle cable setup. The factory ones are rare and won’t work in my car, which means I’m fabricating a custom cable arrangement. There’s not many ways to attach to the throttle pedal and even less to attach to the carbs, so it’ll be a challenge for sure.

Otherwise, setting up and adjusting the carbs should be pretty easy. Once I get the throttle cable done I’ll probably have it running and driving in a few hours.

 

Been spending a lot of time working on the throttle cable setup.

The original pedal system goes through the firewall and has a tall vertical lever, (blue line) that I bent to clear the new intake manifold.


Using an existing threaded hole in the cylinder head, I will create a bracket to hold the throttle cable tucked down low, between the cylinder head and the carbs. Took a couple cardboard templates to get it right.


Here you can see how tight it is between the carbs and the cable. With the pedal lever bent it’s a straight shot to the cable attachment.


The cable is 24” long, and will loop around over itself. The carbs connect to the throttle cable between them, right in the middle of the engine, and the lever pulls towards the engine, so there isn’t a way around having the cable loop over the cam covers.


The carbs use an obscure sized ball and socket joint to attach to the linkage, and I really didn’t want to cut the original linkage, so I took an original threaded socket joint and drilled/tapped two holes in it to make it accept a bare cable end. Not bad work considering I had a super cheap tap and my drill press is 108 years old. (I’m getting shorter screws soon)


This socket joint pops on to the carbs and will pull upwards and across. It’s a bit tight to this adjustment screw but I think it’s fine.



This setup will provide plenty of tip-in off of idle, but will stay pretty linear in the midrange. Pretty happy with how this is working so far. Still need to make a stop to prevent the gas pedal from returning too far.

 

Made a bunch of progress since my last update. Most importantly, it runs!

But back to where I left off- I finalized the throttle cable mounting. Both ends of the 24” throttle cable are held by brackets made out of 1/8” aluminum. Overkill, but the thickness allows me to round the edges and corners and make them look nice. Super happy with how they came out.



I riveted this small piece of steel to the throttle pedal to make the return stop. Super simple and works well.


I installed a new gas tank as the old one started leaking again. Super easy to replace, it comes out from the trunk.


I also finalized the mount for the fuel pressure regulator and pressure gauge. With the fuel lines hooked up and everything connected, it fired right up! Even with the carbs way out of sync, it sounded awesome.

https://youtu.be/aSIgL-1u_kY?si=72PUQ_iRafo5vnun

It ran really, really bad. I’ve been fiddling with it a ton, and it’s still far from there. Here’s where we’re at- it still idles like pretty rough, but on all four cylinders and consistently drops to the same RPM. It runs fantastic on the low speed jets, 1200-3500RPM. Once it transitions to the high speed jets, above 3500, it starves for fuel and pops. I know my jet sizes are close to perfect, if not perfect, as the guys on the forum helped me pick the right sizes.

I’m pretty sure that I have a fuel delivery issue. I replaced the stock mechanical fuel pump with a new one, which made the fuel starve a bit better, but not much. I don’t really want to put an electric fuel pump in it if I don’t have to.

I’ve still been driving it around, since the runs good on the low speed jets. Drivability increased significantly once I got the power brakes hooked back up. Needed an adapter for the vacuum line.


Haven’t put the hood back on it yet.


I still need to order air filters (they’re $350! ) and just make it run right in general. It’s getting there, slowly.

 

Just realized I haven't updated this thread in a couple months.

First of all, I was able to get the car to run consistently on the stock mechanical fuel pump, which was huge. I rebuilt it with a new diaphragm and cleaned out the intake screen really good, as it was pretty plugged with rust. Each of the carbs have a small screen, which I cleaned out when I rebuilt them, but they had gotten plugged up with gunk. I actually ended up replacing the entirety of the rubber hoses in the fuel system, and blew out the metal lines with compressed air. The final piece to the puzzle was actually removing the fuel filter, as it was seriously cutting down on flow and pressure. I'm not too worried about not having a filter, these cars didn't have one from the factory and literally every piece of my fuel system is new.

With my fuel delivery woes figured out, this thing fucking RIPS! The car has probably shaved off two seconds from 0-60, and makes consistent, linear power, all the way from 3000-6500RPM. I never realized how terrible the old setup was. Peak power used to be 3500RPM, and it would just fall on it's face above 4500. Normal acceleration would require at least 50% of the pedal's travel, and to maintain highway speed you'd need at least 75%. Now, acceleration is effortless. It's so obvious that the engine just breathes so much better than before, and the engine seems perfectly happy to rev or maintain high RPM, unlike before. Highway speeds requires 15% throttle at most, and there is SO much less vibration from the engine. I genuinely think I could do a 3hr roadtrip comfortably.

To give an idea of how much larger these carbs are, here's just one new carb barrel compared to the primary throttle butterfly on the old carb:


They were too big actually, and I had to swap out the 32mm venturis for 30mms, as it would bog below 2500rpm. 32mm is the right size for peak power at 6800rpm anyway, which is pretty much past my redline. Now you can punch it at 2000rpm and it won't bog.


I've still experienced my fair share of troubles getting it to be reliable. An idle jet gets plugged probably twice a week. I can't figure out where the gunk is coming from for the life of me. Not a big deal as it takes 2 minutes to unscrew the idle jet and stick a needle through it, but still annoying.

I also can't get it to idle on all four cylinders, at least some of the time. It idles super smooth and consistently on all four at about 1100RPM, which is a tad high, but sometimes the draw from the alternator is enough to get it to drop cylinder 4 and idle at 700ish. Nothing that I do to the idle mixture or air bleed screws have a significant effect on the idle, and I know for certain that those passages aren't plugged. Oh well.

I did a full interior/exterior/engine/undercarriage detail, which I've literally never done in my ownership. I'll be the first person to admit that this car is normally super dirty and gross, as I don't worry at all about it in the rain or dust.


The before/after on the wheels was crazy:



And I used the same Adam's Graphene wax that I use on the Tundra. Worked amazing as always!


Also changed the oil as it was full of fuel from flooding out the cylinders so many times. Tried out a Wix filter as the ones I ship from Italy aren't available anymore. Adjusted the clutch, handbrake, and topped off the gearbox oil at the same time.


Picked up a set of genuine 70s minilite wheels, which are 13s. Putting tires on them soon.


I’ve been driving and using the shit out of it. Really love this thing.