So I'm slowly putting my FB back together, and I'm in the process of stripping down the carb and IM. I've removed the rat's nest, and have no interest in emissions controls, my goal is simplicity. I plan to do most of the Nikki stripping in the FAQ (note: all the pictures are gone from that DIY, but I have them saved. Mods, PM me if you want to reinstate them.)

I understand the coolant passages from the housings into the manifold can be blocked with 20mm plugs or quarters, but what about the rest of the shenanigans on the right side of the manifold? It's been so long since I pulled the motor I can't remember what went where, and what's important and what I can leave off.

Anyone have some diagrams or pictures on what I need to reinstall for a bare-bones manifold?

 

The freeze plug option works great, I highly recommend it.

Can't really help with your other questions though. I didn't strip my own carb, just got a Sterling instead. As for the vacuum lines, I run one from the oil fill tube to the base of the carb, and one to the vacuum advance system. That's it, just the two lines. Makes for a pretty clean looking engine bay once you get all of the BS outta there.

There's a bit of information on what else I stripped out of the engine bay, and where I relocated a couple of items to free up some space, in this thread here: https://www.rx7club.com/1st-gen-archive-71/other-finally-some-pics-441703/ Might be a trick or two in there that you can use.

Good luck man.






.

 

basically pull everything off and block the remaining holes with plates. done

although you still need the brake booster line of course

 

Thanks. Removing the BS is my goal with all this.

Right, naturally. But as far as all the coolant passages on the back, they don't serve any purpose I'm not seeing, do they? I'm not too concerned with cold weather operations (central Texas), and I want to keep it as simple as I can.

 

Hmm there is only one coolant passage on the manifolds ive seen, has two plugs in the manifold on the rear side. then there are just two flanges which can be blanked off with a plate.

From memory the purpose of the coolant passage is to warm the manifold to help in very cold conditions. i doubt it would be there to keep things cool. if you have extractors it would probably be a good idea to either heat wrap them or make up a heat shield from aluminium or stainless to keep the manifold cool. or do both.

 

When I ran Racing Beat's Holley intake I found the intake coolant passages are just as much about cooling as warm up in cold condtitions. One hot, windy summer day my Holley was vapor locking if I was driving with a tail wind. If I was driving into the wind I was okay. As soon as I had tail wind and little air flow under the hood she would vapor lock and die. You could also fry an egg on the intake. So I removed the frost plugs I had installed with the RB/Holley intake and went back to the Nikki intake. I would think twice before installing frost plugs in the intake coolant passages.

 

I don't see how hot coolant could cool the manifold. How hot does coolant run compared to ambient air temperatures?

The fact that the problem went away when you switched carbs does not (in my mind) conclusively point to a vapor lock issue. I think that vapor lock is kind of like a computer shop saying you had a virus (basically, they don't know what was wrong so they blamed it on the "mystery item" that nobody can argue against).

 

The coolant is used for de-icing. Because of the pressure drop in the boosters, carbs tend to ice sometimes if not heated. It's a drivability thing. It also ensures that all cars, whether in Alaska, Colorado, or Florida have relatively consistent carb setups, which made tuning and maintenance much easier on Mazda back when they had to warranty the cars.

The original reason that the old-schoolers would block them off was for racing. In stock classes (now spec 7, IT7, etc) you can be protested for having ported an engine to run in a stock class. When you're protested, you have to remove your carb and manifold so someone can put a lollipop in your runners and/or engine block to verify that they haven't been opened. In order to not dump coolant all over the pits whenever they were protested, drivers would block the coolant passages just to make it easier. Some series require it, but it's just handy if you're not worried about icing.

Besides, o-rings fail sometimes, and freeze plugs are easier than replacing that first set of o-rings that go bad.

Vapor lock is typically when you get heat soak in the fuel system / carb and your emulsion system takes a crap. Emulsion tubes actually bubble air through the fuel prior to delivery, so when the fuel itself boils all that metering goes to ****.

 

Functioning ACV = exhaust heating the manifold. You need coolant flowing to keep things coolish.

 

Unevolved, can you post the pictures from the how-to on stripping the nikki? I've been looking into doing it, but all of the threads that explain how to do it have the pictures removed.

 

Sure. This is mechanical secondaries, no emissions, no OMP.