Custom Carb Spacers

[Oiluj]

When I upgraded my brakes, I switched to a 280ZX master brake cylinder with the bleed nipples on the engine side. When removing the air cleaner, the forward bleed nipple keeps scratching the paint on my air cleaner cover.

My solution is to move the carbs inward 0.35" by machining down the carb spacers. (see attached pic of original spacer next to thinner spacer.). This should provide adequate clearance for the air cleaner.

This week I'll do a gasket drawing and use the laser at work to cut some new gaskets. (Yes, it's a cool toy...).

* If you try this, be aware that machining phenolic can create toxic dust, so use a vacuum to carry-away the fines generated during the milling operation.

I'll let you know how it turns out!

[Oiluj]

Attached is a pic of the gaskets I cut using the X-Y laser at work.

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On the left is a pic of a cut sheet before removing the gaskets. The dark gasket was the original Nissan gasket. On the right is my thinner phenolic carb spacer block.

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I left 1/8” inch uncut sections in the periphery of each gasket, and two on the inside diameter because I didn’t know if the material would curl when cutting. Turns out it wasn’t necessary. The separate gaskets were removed from the sheet using an X-Acto knife to cut the six, 1/8” long uncut areas. Difference in color is just different gasket stock.

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I used a 75 watt laser, with a 0.005” dia beam. I quickly found it only took 4 watts of laser power to cleanly cut the 0.040” thick gasket material. The sheet on the left has burn marks on edges of the cuts because I started with 12 watts of laser power.

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Plan to install the carbs this Friday. My only concern is that the thinner phenolic carb spacer lock may be more prone to cracking during installation or over time. Guess I’ll find out!

[Bruce Palmer]

Would have been a whole lot easier to gring the nipple off that bleeder screw. You can bench bleed the MC on the workbench thus never having to touch the bleed screws on the car.

With thinner insulators watch for possible interference between the now longer studs and the back side of the carb bodies.

[Oiluj]

Bruce,

Thanks for the post. I really appreciate someone with your experience replying to my post. Shows what a great site this is!

Grinding-off the bleeder nipple was the first thing I tried, but it's still a pretty tight fit.

In fact, I put some internal threads, (4-40), in the forward nipple and threaded the outside of a thin wall tube with some tygon tubing to use as a bleeding tool. Works pretty well.

Before starting on this tack, I measured the length of the studs and clearance before I cut the insulator down, so it "shouldn't" interfere. We shall see if measured correctly...

The gaskets are available and inexpensive, but cutting on the laser was more of a fun, "just cause I have the tool available", excerise. I'm very happy with the result.

BTW, I have a set of spare carbs I'm thinking of sending you to be rebuilt later this Spring. Some jobs are better left to the pros... I need to clean them up a bit first and wait for my annual bonus in early April. (Assuming there's anything left, as my wife already has plans for a portion of it).

Again, thanks for the input!

[Oiluj]

The thinner spacers give me plenty of room for the air cleaner. The gaskets I made worked great as well.

Turns out Bruce was right and I did need to shorten the studs a bit. Not a problem, as 8x1.25 x 50 mm studs are readily available. Plan to order a new set to pack into a plastic bag with my original spacers.

Still need to tune the carbs and plan to do that this coming Friday.

[Inf]

Beautiful engine bay