Glazedham42

iTrader: (4)

Hey guys,

I'm trying to find a diagram or schematic of some kind that explains how the air control valve on the back of the 12A intake manifold works. I need to know what kind of air temperatures are experienced at the small rectangular port at the bottom of the center iron, the port that goes into the bottom of the intake manifold. Where does that rectangular port lead to? Does someone have a picture of a dissassembled engine that would show?

Is this setup explained in the factory service manual somewhere? I couldn't find a description of it anywhere.

Is there an old rotary book that would explain how the system works?

j9fd3s

iTrader: (3)

http://www.jimrothe.com/mazda/84_tra...raining_4a.pdf

temps are low there, because if there IS any flow, its air pump air to the exhaust port.

the ACV's basically all work the same, from 81-2003. the SA (and earlier) have a similar part, hardware wise, but the air pump air goes to different places.

DivinDriver

iTrader: (15)

Best explanation I've ever seen was in the 79 factory training manual on Sgt. Fox's site.

2nd best one, ironically, was in my 80 owner's manual.

Page 45 & onward of the 1981 Training Manual, same site, seems to geive a good schematic of what routes to where.

http://foxed.ca/rx7manual/manuals/19...ing_manual.pdf

Glazedham42

iTrader: (4)

I am planning to make a reusable intake manifold gasket out of 3/32" thick Teflon from McMaster Carr. I have drawn up the gasket in AutoCAD, and I'm going to have a local waterjet company cut the gasket out for me on their waterjet machine. I see two benefits from doing this. The first is that I would be able to reuse the gasket an unlimited number of times. The second is that the teflon would act as an insulator to help keep the intake manifold cool.

Also to keep the manifold cool I have blocked off both of the coolant ports in the engine with freeze plugs. Doing this also makes the intake manifold easier to remove. No more messing with coolant when you have to pull the manifold off. I have eliminated both of the holes for the coolant passages in my gasket design since they are no longer needed.

The reason for this thread is that I would also like to block off the ACV port in the engine if possible. However, I'm not sure what kind of temperature the gasket would encounter. I've heard of people using JB weld with mixed results. I'm not too keen about shoving a blob of epoxy down into the ACV port on my engine. If possible I'd like to block it off with my Teflon gasket.

Keep in mind that this engine is COMPLETELY stripped of all emissions equipment. With the air pump removed, and an ACV blockoff plate on the back of the intake manifold, what happens to the scenario then? What kind of temperatures do you think the gasket would see? The Teflon is rated to 500 F, but I would hate to melt it and have it run into the engine.

j9fd3s

iTrader: (3)

the stock paper gasket does just fine when you block of the ACV...

DivinDriver

iTrader: (15)

I don't think you'll have melting issues (just a WAG, no data) but I'm wondering if the teflon will have enough compliance to seal well.

I guess you'll find out for all of us!

DallasFC1

iTrader: (2)

If you have over 500F at the intake manifold, I would HATE to see your exhaust temps... I think you will be perfectly fine with the teflon except for one minor exception. Teflon does get soft at higher temperatures. It could very well deform and allow air to pass, or deform enough over time to tear loose. But straight up melting, I highly doubt it.

My $0.02

RX-7 Chris

iTrader: (19)

Just wondering. Why couldn't you use something time JB weld to fill the hole?

LizardFC

iTrader: (1)

I'm reviving this thread with some questions. I want to block off the port so I can freeze plug those pesky coolant passages, but my motor is currently in the car and running. So grinding away little bits of metal to properly quicksteel it up is out of the question.

Glazedham, did you ever try your teflon gasket idea?

Also, is it possible to just block it off at the manifold side by jb welding the port shut in the manifold?

DivinDriver

iTrader: (15)

You could, but that would bypass one of the few big advantages of doing it - - that you could remove your manifold without draining your block. If you plug the manifold side, you'll still dump your coolant every time you pull your manifold.

LizardFC

iTrader: (1)

I mean JB weld the square ACV port on the manifold. I'd still be putting the freeze plugs into the block.

74RX4

iTrader: (10)

That port is connected to the exhaust ports through channels inside the housings.

You can see how I block of the small hole in the rotor housings with JB Weld. I have blocked off the square hole under the center intake ports on installed engines. It takes several layers. The wet JB Weld sags down away from the port before it dries. It can't get inside the engine to hurt anything. It just drops down into the channel in the center housing shown in the last picture. I would think the Teflon would not be strong enough to hold tight against the exhaust pressure, resulting in a small exhaust leak.

LizardFC

iTrader: (1)

Thanks for the diagram and all the pics! I was wondering what that thing was and how exactly it works. I might give that method a shot. I'm just worried that the JB Weld wouldn't bond properly without the surface being cleaned and prepped. That was why I was wanting to plug it at the manifold, since I can clean and scuff up the surface.

Jeff20B

iTrader: (13)

I like to fill the ACV port in the engine with quicksteel. You clean the metal really well first, obviously. Then if there is any question as to whether it will hold over time, I also fill the ACV port in the manifold. Only then will I add brass freeze plugs in the coolant ports. I call it the cool manifold mod. Otherwise if you don't fill the ACV port but install freeze plugs only, you will have exhaust heat pulsing up into the manifold. Not good.

74RX4's mod is pretty good, but if your engine is together, filling the ACV port in the intermediate plate is all you can do and almost just a good. You still get some additional engine heating from exhaust but the manifold stays cooler than it would if you didn't block off anything, so it's better than nothing.

Hey 74RX4, I added some 14mm steel rod to my Cosmo housings. Really tapped them in there. Keeping that engine cool is a big priority as I don't have a lot of room for a radiator.

LizardFC

iTrader: (1)

Thanks Jeff. I'll be working on this today if I can get a hold of some freeze plugs. The only place online that has them in stock is rockauto, and their shipping prices are ridiculous. I'm gonna see if O'Reilly has any sitting around in the store.

LizardFC

iTrader: (1)

One O'Reilly store in town had TWO freeze plugs. I took ownership of them both and installed them yesterday with some RTV, and then installed my new modified manifold. The car fired right up and idled nice and smooth, but then it started smoking... a little... then a lot... then I saw it spit green out of the exhaust! So off with the manifold again. I'm just going to JB Weld the damn things shut!

Glazedham42

iTrader: (4)

So did you install the freeze plugs into the engine or into the intake manifold?

LizardFC

iTrader: (1)

Into the engine. It wasn't as easy as I thought... I had trouble getting them to go in straight. It's probably a lot easier with the engine out. One of them deformed quite a bit before I finally got it in right, so I figured that was my leak. But now that I've got the manifold off again, I can see that they were both leaking under pressure.

I also saw why they were leaking in the first place - whoever had the manifold off last didn't replace the o-rings at all. They just tried to fill in the groove with gobs of RTV.

LizardFC

iTrader: (1)

Update... filled in the holes with quicksteel and I think the leaking has stopped. Also blocked off the ACV port in the manifold. That stuff is amazing. I finally got to drive the car with the modded manifold and I can definitely tell the difference! Thread on that coming soon...

Glazedham42

iTrader: (4)

I finally got my gaskets cut out of teflon. I used the 3/32" electrical grade teflon from McMaster Carr. I gave my CAD files to the local water jet guy and he cut them out for me. I made two different gaskets for the intake manifold to engine interface. One of them is stock, the other one has no coolant or ACV ports. I am going to try using the teflon gasket to block off the ACV port. If it doesn't work then I'll just use the stock sized gasket as my backup and try something else. I also had them cut out a gasket for the carb base. This Rx-3 manifold is taller than the stock FB manifold. I can't use the black phenolic spacer with my air cleaner or the hood won't close. So I'm going to try this gasket and see if it gives the throttle butterflies enough room to open and close. This stuff is all kind of trial and error, so we'll see how it goes.

Jeff20B

iTrader: (13)

Wow, that manifold porting is worthy of a Sterling carb. Nice job on the new gaskets.

Did you decide against a PCV valve?

LizardFC

iTrader: (1)

Nice stuff!! Can't wait to see how this works. That RX-3 manifold is a beast! Is that stock or has it been ported? It looks like it was cast that way. Also, where did you get the AVC blockoff plate and gasket?

Glazedham42

iTrader: (4)

I'm going to be using a PCV valve and connecting it to the nipple that I left on the top engine side of the manifold. I removed the others, cut threads, and put in set screws for a cleaner appearance. I found out that the nipple is connected to that same hole that you put the heater hose fitting into. They all connect together and run to two small holes in the intake runners. So that nipple that I left, should pull vacuum just like the big heater hose location that you use does. I put a drain plug in where the heater hose fitting usually goes. If my idea doesn't work like I'm thinking, and I get lung mustard, then I'll just pull out the drain plug and hook it up like you recommended to me. Then it will work for sure.

I did some light porting, smoothing, and rounding on the top of the manifold where the carb sits. I didn't touch it anywhere else though. Just a good polishing and clear coat all over the outside. I did remove a bunch of the extraneous nipples, and fittings that I didn't need. I put set screws, or plugs into the holes after I threaded them. It gives a cleaner appearance, IMO.

I got the ACV blockoff plate from Mazdatrix. Racing Beat also sells it. I made the gasket for it out of Teflon. You could get some gasket paper and trace around the blockoff plate and then cut it out. My gasket is an exact copy of the blockoff plate, just made out of 3/32" teflon instead of steel.

I sent some pieces from my carb to Sterling around Christmas time for him to work on them. Hopefully I'll get them back soon. I know he's been REALLY busy lately, so I'm not getting my hopes up too much. But having a Sterling carb sitting on top of this ported/stripped Rx-3 manifold, with reusable insulating gaskets would make me shed a tear of joy. I've got a pretty sweet open element air filter setup to top off the whole thing. If I ever get the carb parts back from Sterling I can button up the carb and take some pictures of the whole shebang. It's going to be the highlight of the whole car I think. I've spent waayyyyyy too much time working on the manifold, carb, and air cleaner setup for this car. But it has been really fun and I've learned a lot. I'm really excited to drive it for the first time and see how it behaves.

LizardFC

iTrader: (1)

You did a really good job on the port work. I know what you mean about spending too much time on the carb/intake setup. I've been doing the same thing. It's gonna be fun when it's all finally together.

Glazedham42

iTrader: (4)

Thanks. I really don't have any flow data or measurements to prove that this is the ideal way to port the manifold. Just kinda going off of a gut feel really. I smoothed out all the sharp corners and just tried to sort of funnel everything down into the manifold runners. Is it the absolute best way to achieve maximum flow? Probably not, but I'm willing to bet that it's at least a little bit better than the stock Rx-3 configuration. Either way it was really fun.