[Project Car] 1986 Prelude "Lucy"

Looking under the car the first thing I noticed is the exhaust was hacksawed off before the catalytic converter. Not sure why that was done. The engine bay has an extra addon. After doing some research I determined it's a Travel Cruise OEM Replica Series Datsun cruise control device. Very interesting, but stupid. I wouldn't be surprised if it's the culprit for the performance issues. The installation job looks sketchy.

I tested the wiring to the pump and it does have voltage. I tested the pump itself by jumping 12V power to it and it does click a couple times, indicating that it works. Next I did a flow test, to verify that the pump isn't weak. I removed the fuel hose after the filter in the engine bay, then jumped the pump again and I do get fuel flowing out. (I also noted that the fuel filter is way way past its expiration date.) So the fuel pump is running but the engine doesn't run unless I give it starting fluid. That implies to me that the problem is with the carburetor. There isn't a mixture screw on this carb (thanks California) so I can't play with that. Maybe the valve in the carbs is stuck closed so no fuel is getting in the float bowl? I removed the air cleaner to inspect the carburetors and noticed there is this black gunk that looks like oil sludge. At this point I think the carbs are messed up, so the next step is to replace the carbs. I have a pair of webers ready to go so now is the perfect opportunity to use them.

Removed the carburetor and the intake manifold. It's not that hard until it comes to the bottom middle bolt on the intake manifold. The problem is the intake manifold is in the way of the intake manifold nut so it's hard to get a tool in that you can then move enough to loosen the bolt. I wanted to use a crowfoot wrench, which is an attachment for a ratchet. I have a crowfoot wrench set, but it doesn't have the 12mm adapter. 🔫 I doubt if the crowfoot would have worked anyway since there's a nipple for the PCV hose that is also in front of the nut, but it would have been nice to try. I tried using a wrench with a flexable head but turning it while keeping the head on the nut was too difficult. What worked for me is this: remove the air cleaner, remove the blowby chamber, remove the carb, remove the air cleaner support beam next to the black PCV box, unbolt the PCV box, remove the top hose on the box, then pop it out of the engine and pull it back. Take an offset 12mm wrench and remove the nut.

Lord have mercy may nobody have an intake manifold gasket leak on this car.

I finished bolting in the new carbs. Turned out to be a bit more difficult because the bolt holes were just a few millimeters off so I had to make them a bit bigger with a drill. The port for the brake booster is too long and it bumps into the engine, so I had to find an L-shaped adapter. The lever on the linkage for the throttle cable bumps into the engine so I'll have to move things around to a placement that works.

I plugged some of the nipples for coolant and rigged something for the temperature sensor attachment. I'm not happy with the setup yet. It's going to take some trial and error, plus me measuring things and buying hose adapters online, until I'm satisfied. One thing I hate is having to go to a hardware/autoparts store and trying to rig together some series of adapters in the hopes of making things fit. Some things you can only find online.

Ah ok. For timing as a start you should be ok at least to start with +10-15 deg (no vacuum advance). Once you get the carbs tuned you can advance little by little untill you get best results. Wonder how not having an exhaust connected could be affecting it though, bets to get that fixed first.

Those carbs are hardly a "bolt on mod" that we enjoy with modern cars, those bad boys require a lot of tune/test cycles to make run right (which is where the fun is!!). I had DCOE 40's on my car as well, ran well for the most part but we're a bit rich the the top end, never fixed that... You will want to pull and check the chokes, idle jets and main jets. If your timing is good maybe you are running lean. I would suggest buying a jet kit with assorted sizes to tune it up, and might as well go up to the max choke size while your at it (38mm) I think. The chokes and jets can easily be removed and checked with the carbs mounted, to the engine no worries.

Once you know your choke size, start with the idle jets, those jets run the engine up to about 3000rpm before the main jets take over. Tune the idle jets first for best idle and low rpm performance, then move to the mains.

Idle jets. 60/f9
Emulsion tubes f16
Main jets 135
Pump jets 40

Since I assume your motor is mostly stock you may need to be a bit smaller than that. Perhaps 50/f9 idles to get started? Running weber DCOE 40s, choke size 40mm (custom modified 36mm was biggest available) and size 6 Venturi.

That helps me out a great deal. The motor on Lucy is stock (and staying that way ) so I'm guessing the jet sizes will be different from what you have. On the site Weber jetting calculator they do recommend similar settings. I'm going to order those parts. The exhaust system is finally done (only took two months ) so once those jets arrive I can start tuning!