Triple Weber Install

[rocketdog]

I always wanted to put triple Webers with braided SS fuel lines on my late 260Z (11/74) (original owner). I have been running ’72 SU’s since the early 80’s which eliminated the dreaded vapor lock of the flat tops. Mike W’s posts provide an excellent, detailed description, problem solving and great drawings with even part numbers spelled out. His posts inspired me to do it now. Fortunately when I bought them MSA had a sale on the Webers for $1495. (Interestingly MSA’s old blue catalogue from years ago had them listed for $2000!)

The Webers are 40 DCOE 151 with Main jet 130mm; Air corrector Jet 170; Emulsion tube F11; Idle jet 55 F9. The package came with Cannon intake and throttle linkage to fit to stock Z throttle, some basic rubber fuel hose and a few hose clamps. The first thing I had to do is swap the throttle levers to the correct side. The kit came with additional throttle levers which I later ended up using to connect the return springs. When buying the kit MSA didn’t even suggest new manifold gasket and studs and the fat washers, which they should have. I had a “well, duh” moment when I started ripping the old stuff out and ordered them.

Manifolds: Taking off old studs went easily. I sprayed them with PB Blaster several times over two days and using the double nut technique and once broken loose they were finger loosened. One problem I had was that the exhaust header (the original 6 to 2 Twice Pipes from the late 70’s) hit the lower steering assembly so I had to loosen much of the rubber knuckle joint bolts to give the header room to slide off the studs.

Once everything is off I cleaned the whole area of 35 years of crud. Acetone works great for a lot of it. The new intake manifold is sleeker than the OEM and old dirt will show. I installed the carburetor mounting studs on the intake manifold using Loctite. One minor but significant item not mentioned in the directions is that the studs MUST protrude 1 ¼ inches from the intake surface otherwise there is not enough thread to mount the carbs with their spring washers. I had to redo all the studs after everything was installed…much easier on the bench. Test fitting the intake there were some minor points that hit the exhaust manifold and had to be ground off.

Prior to spraying the copper gasket cement I masked off everything with blue painters tape and newspaper. VERY IMPORTANT…this stuff is just like spray paint and goes EVERYWHERE. Once on it ain’t coming off. The manifolds went on easily. Be sure to torque them per spec.

Heat Shield: I had a heat shield fabbed from aluminum: 21" x 6" with a 3/4" lip in the back bent at 120 degrees so the shield drops down from the carbs at a 30 degree angle. I drilled out one hole for each carb to mount and cut out sections for the other 3 mounting studs. Don't need 6 nuts holding on a piece of aluminum. Had to do a little hand cutting with tin snips and wire cutters to get it to fit under the carbs. Used Mike W's idea of the shield, a washer, spring washer and nut. With the shield angled down a bit I could fairly easily reach the washers and nuts by feel and tighten with a ratchet extension.

Installed the throttle linkage per their spec. Had to move where my stock linkage bolts to the firewall over about 1 1/2" so it is now a fairly straight shot to the carb linkage. Figure fewer angles the better.

Fuel system: I wanted to use the OEM mechanical fuel pump with the stock electrical pump at the tank. The specs for the mechanical pump should be enough both in PSI and volume. I didn’t want to have to wire in a new electrical pump and emergency shut off. I purchased most of the 3/8” SS braided hose and Earl fittings from anplumbing.com. Everything is sized to a 6AN. Be prepared for sticker shock as many of the end fittings run from $8 to $21 each! The Magna Fuel Log I got from Summit as well as the fuel pressure gauge. Before ordering I drew out a diagram of what goes where and then made up a parts list…and checked it many times. The fittings are a classy red and blue aluminum and very high quality.

Cutting and installing the SS lines was very easy. Follow the tutorial video on the AN website which uses a sharp chisel and 5# sledge to cut the line. I got a 2 ½” wide chisel from Ace and sharpened it very sharp. Since I didn’t have block of aluminum for a cutting block I used an 8”x8” chunk of wood column I had and stood it on end on the concrete floor. Put the chisel on your mark; whack it a couple of times with the sledge and it cuts slicker than frog snot! Using a vise per the video to hold the fitting and a tiny screw driver to push errant SS fibers in is quick. Screwing on male fitting was easy. Each fitting end probably took only 5 minutes or so. Earls also has a connection for fitting to the 5/16” hard line fuel lines. Works exactly like your standard compression fittings in some of your house plumbing. Cutting the hard lines was tough because of tight space. You want a very straight section for the fitting to work. I used my tiny copper cutter which took a long time. I used a tiny round file to deburr the inside of the tube.

I fabbed a piece of sheet steel to bolt the fuel log above the intake manifold. Since I decided to use the fuel return line I installed the pressure gauge on the fire wall and ran the return into the stock hard line. Finding the right fittings to replace the stock in and out nipples on the fuel pump was tough. Since it was Japanese I assumed it was metric. After many attempts I finally got a 1/8” NPT thread to 6AN to work, though it was tight and I had to remove the pump from the engine work carefully to get it to thread. Perhaps there is a “metric” NPT…anyway no leaks.

Fire ‘em up! After adjusting the throttle linkage for equal action on each carb and assure pedal hits bottom right before full throttle, I set the idle and mixture screws to initial settings per spec. After cranking a bit to get fuel flowing the babies fired up. Lots of fine tuning, balancing followed to get them basically tuned. The initial drive was awesome for throttle response and power. Definitely feels 30% increase in power/torque. The usual hesitation spots at 1800 and 2700 rpm as others experienced and eventually worked out. I don’t have an oxygen sensor so tuning is by balance gauge, sound and seat of pants. After a bit more tweaking I took it for a longer drive. At 70 mph when you punch it, you can feel the pull. Before returning home I tried a full throttle through the gears. At high rev third the engine started stalling out and worse in forth. No power so limped along the side of the highway for a bit and then it started running well again. Fuel starvation.

I never could get the fuel pressure gauge to register at all. I wondered if the fuel pump was worn out or perhaps the return line was too open (OEM had a restriction in the line). I assumed the pressure regulator would help manage the flow. I bought some more fittings from Earls and moved the pressure dial to right before the fuel log and plugged the fuel return at the log. Gauge now showed 4 ½ to 5 psi so fuel pump is putting out okay. I wanted pressure at 3+ psi to keep the Webers happy. Keeping the dial at the fuel log I reconnected the return line and was now only getting 2 psi at the carbs. No wonder fuel starvation. I tightened the pressure regulator screw in as far as I could and the PSI finally rose to 3psi. I retried the hard acceleration again and absolutely no problems, even after three consecutive runs.

Living at 4000 feet one would think I need leaner jets, but currently I’m about 90% there with tuning. I richened the idle mixture screws less than ¼ turn and seemed to get rid of the 1800 rpm lag. Viewing the progression holes I am pretty much right on where the throttle plates should be. I’ve added a third return spring as idle wants to return only to about 1500 rather than the 8-900 I tuned it for. I need a better source for springs as choices around here are slim.

Distributor: I wanted to have the mechanical advance option so purchased a Mallory Unilite from Summit. I wired it per directions using the stock ballast. I have a new Pretronics coil. No spark. After pouring through FSM and wiring diagrams, I ran a thread here and on Zcar.com looking for advice which I did get, but nothing worked. Calling MSA tech we tried a test which appeared to show the dizzy was defective. I returned it to Summit and got my money back. Reinstalling the OEM, she fired right up. That’s where I am now.

Observations:

A fun project. Webers are so adjustable that adds to the mystery and solutions. If going the SS braided hose for the bling be prepared to spend some $$. My final cost was around $500. I’m still puzzled about the fuel pressure regulator. A Summit regulator at $80 it’s pricey for what little if anything I’m getting out of it. I need to call Summit to see if it is working properly. When the dial is at the fuel log there’s 3 psi, but put it on the regulator it shows 0. I’ve driven in traffic in some hot weather (95) and the aluminum shield appears to be working. No vapor lock problems. The carbs are hot to touch, but apparently not too hot. I thought I would need to add the thermal blanket. The engine fires up quickly even when cold. With the SU’s and full choke I had to crank a while. The sound through the Dynomax Super Turbo muffler is awesome, much deeper than with SU’s.

[d240zx2]

Nice write-up.

[Jeff G 78]

Thanks for posting. It looks great and I'm sure it sounds even better. I had triple Webers once and they sounded fantastic. I'd like to have them on a Z again someday.

[rocketdog]

Jeff,

I lived in Pinckney, MI and worked in Ann Arbor from 1980 till 1993. Kept the Z garaged in winter to protect it from the salt. In 1972-1974 I lived in Port Huron and had a new '72 240, that lime-yellow. The salt ate it up and when I got transferred to San Francisco I traded it in for the new 260. The dealer didn't want the rust-infused Z on his lot....didn't get much $$ for it. Baby poo rust color on yellow. They still racing at Waterford Hills? Used to love going to those.

Gary

[Jeff G 78]

Gary,

We just missed each other. I moved from Ohio to Michigan in 1994. They do still race at Waterford, but I prefer Grattan and GingerMan. The neighbors around Waterford complain too much about noise and it makes it very strict as to when they car run and for how long. I always wonder why people move in next to a race track and then complain about it. The track was there long before the houses. I did do a test day last summer at Waterford.

One of my Z cars came from Greg Clark (is that right???) just North of Phoenix. He used to have a whole fleet of Z's for sale. I ended up selling it and then it traded hands one more time. It now belongs to another forum member "Lazeum" and resides in Paris. I'm always amazed at the journey cars take. I have bought cars from many different states and moved them around.

[Zedyone_kenobi]

Great write up!

I just went through the same thing as you did. A wideband O2 is God send, and the instant you have about 150 bucks laying around, get one.

I recommend you adjust your floats on your MSA webers. Mine, are exactly the same as yours, and I also had to readjust my studs on the intake side so I could get a nut on them to mount the carbs. Good job putting that in the write up.

I went down to a 160 Air corrector which helped eliminate a large part of my flat spot. Then I found all my floats were too low, and that was the biggest change in how the car ran. I have all flat spots 95% gone now. I have to actively try to make the car falter a bit. I think the F11 E tube is a good one. I think the 55F9 progression jet is probably a bit too much but it is okay for now.

I really think I want to go down to a smaller main jet and a smaller Air corrector. But for now, I am happy. I have not tried to dial in the accelerator pump yet, as I think most of the tuning is with the jets, and air correctors. But look at your float levels. They will make your car even happier. They are critical to how the main jets and air correctors work.

Most of all, great looking engine! My throttle linkage bar from MSA was bent and I could not use it!

[LeonV]

Makes me want to go to AN plumbing on my triples!

I'll second the float comment, I finally set mine using Keith's optical gauge this weekend. Front carb was 2mm low, middle was perfect, and rear was 1mm off. I set them correctly, and although the difference in float height was relatively small, the effect it has on driveability is huge. The vacuum signal in the main ciruit is just strong enough to lift the fuel up into the venturi by only a few millimeters so float height is critical.

[rocketdog]

I just got Keith's optical gauge and measured all carbs twice. They are all way low: the front and middle are 3mm-4mm low and the rear is 3mm low. My tomorrow's project will be futzing with the floats to get them where they should be. It'll be interesting to see any performance change.

[rocketdog]

Got the floats all dialed in...fairly easy and quick job....if you have Keith's optical gauge. Took my first drive. YEE HAH! All the stumble at 1800 and 2700 rpm are gone. Who'd a thunk a simple thing as float level could make such a significant difference in driveablilty. Even in 4th you step on the gas at just below 1800 and the engine just smoothly picks up speed...same at 2700. No need to run at a lower gear just to keep higher revs and avoid those "spots". Much of the literature I've read does not put much emphasis on float level as it should. I think fokks tend to fiddle too much with jet sizes trying to solve the problem when a simple float adjustment does the trick.

[Jeff G 78]

Congrats on the fix!