rkhanso

My son's new/used '81 RX-7. We're putting the exhaust and intake manifolds back on...the previous owner had it tore apart because he said the gaskets were leaking. He didn't finish the work and sold us the car.

I'm wondering what this part is. I've searched the shop manual I downloaded (but for a '80 RX-7 since I couldn't find one for the '81). I looked in the engine and the emissions sections and didn't see the part in there. But, I coulda missed it. I tried searching the forum (and Internet) but am probably using the wrong words and not getting the results I hoped for.

It looks like it could be some sort of vacuum switch or something. There are the 2 lines that go up to the carb area.

I'm hoping it's not needed 'cause we have one of those Racing Beat intake manifolds and a Holley carb on it. I'm guessing there's nowhere for the hoses to hook up anyway. All of those solenoids and vacuum lines have been removed from the top of the engine, too (seen in the lower picture).

Spannerhead

iTrader: (1)

That's your metering oil pump or MOP. Injects a bit of engine oil into the intake to lubricate the apex seals. Absolutely necessary unless you're going to run premix.

erick31876

iTrader: (8)

if its a real racing beat holley carb it will have a fitting on it on the primary float bowl to hook them hoses up to, if not you can somehow run a rubber hose from them into the top of the carb.all you will need is a piece of hose and a vacuum tee.that is your oil metering pump

rkhanso

I can't say if it's a real Racing Beat Holley carb or not. There is a vacuum port on the primary float bowl (see picture). But, it was capped off. (bottom picture, top right circle)

There are just 2 other vacuum ports on the carb. A large one on the secondary side (which is capped) and a smaller one at a 45 degree angle on the primary side (which is also capped).

There is a rod off the pump, but it seems frozen and it's not connected to anything at the top. It's just stuck in a bracket so it doesn't rattle.

It sounds odd that it connects to the port on the side of the primary bowl. You're saying that the Holley can take this oil in and mix it with the fuel? I'd think this would plug something up in the carb. It reminds me of the oil injection on my Johnson Outboard motor that failed and cost me the $ for a rebuild on it.

Is there a way to test this pump to make sure it's working? I really hook those 2 tubes up to the carb primary float bowl port? Would running pre-mixed be better?

I know, the carb is pretty nasty looking (and missing some parts - choke plate/shaft, choke cable clamp). I'm going to try to get the engine running and see what else it needs before I rebuild the carb.

plentymoon

I feel sorry for that motor not to be rude. I hope you and your son have fun learning about rotaries they are a great engine and over all fun cars.

BeenJaminJames

That rod coming from the OMP goes to the throttle linkage. If it's a true racing beat prepped holley, it should have a place on the linkage to attach it. The omp regulates oil supply in relation to rpm and throttle position. Rotaries require oil to lubricate the apex seals. Running the engine without either a functioning OMP or running premix, will destroy the engine in very short order. You can make a block off plate, remove the OMP, and premix the fuel if you want. In most cases it's best to just hook the OMP up correctly, as it's entirely mechanical on these cars and not usually a reliability concern. The benefits of the omp are that you don't have to measure out the premix every time you stop for gas. The downside is that it's using engine oil, so you still have to pop the hood and pull the dipstick every time you fuel up. I prefer to keep the omp on mine, as I check fluids at every fuel stop anyway, and it saves having to mentally judge how much oil to put in the tank. Removes human error from the equation, as every once in a while you're bound to mix too much and drive around looking like a tool, blowing blue clouds everywhere you go and fouling your plugs. Not to mention that you never really are sure how often you misjudge in the other direction and put too little, causing irreprable damage to the chrome-lined housings. For a street car, letting the OMP do the work makes life easier and offers peace of mind.

That said, alot of guys running aggressively driven track cars prefer to premix, as it allows you to mix more oil and the smoke and plug fouling is less of an issue with a track-only car

rkhanso

Thanks for the very helpful information. I'll contact Racing Beat today to see if they can email me their installation instructions. I'll also know what to search on this forum and The Google now that I know the correct terms.

Thanks a lot.

Cookboy

iTrader: (10)

I would suggest a stock intake. They can be found, and will solve several problems.

wankel=awesome

Nobody noticed the backwards choke adjustment screw?

Also, those float bowl plugs look like they've never been removed. Who did you buy this carb from?

rkhanso

I just came back from the carburetor shop. The guy said the choke adjustment screw is supposed to be in backwards like that. It so it doesn't wear off the cam or whatever it is.

The carb came with the car. The car was not running when we bought it.

rkhanso

Had it running today. Pretty bad, but running. Smokey for a while. Needs a lot of work yet, but at least it has a heartbeat.

DivinDriver

iTrader: (15)

Your "missing stuff" in the first post isn't actually missing anything.

That flat flange on the mid-plate is where an EGR valve would go on a smog-built engine. Yours is not machined with the required gas passages, so it never had or needed an EGR valve.

Essentially, means it wasn't a California engine.

swbtm

iTrader: (2)

Can't see the pics now and not much time on break. I'll take a pic and post it of my setup tonight. I have a 465 holley with a simple mod to get the carb to be much more happy overall.

swbtm

iTrader: (2)

Jeeze do I have to clean...




When I got my car it had the OMP/MOP line collected into one line and fed into the primary float bowl. I don't know about you, but I did not like the idea of having oil floating through all the venturis and other small passages in the carb.

Mr rx-7 tt had a great suggestion to routes the lines directly to the intake below the carb.

I had a spare nikki hanging around so I pulled off two nipples and found a drill size that would make a press fit hole for them. Drilled two holes through the side of the racing beat intake. Pressed the two nipples, then found some hydraulic hose with an ID that fit both the nipple and the OD of the OMP lines. I also shortened the effective length of the linkage between the OMP and the throttle linkage by exaggerating the bends in the rod. I think this shortened the rod by around 0.25"-0.5" I would have to measure to check. This is another option to add a little more oil instead of premix. This was to protect a fresh rebuild and a nice street port.

That vacuum port in the primary metering block goes to the distributor vacuum advance, if you plan on using it. I run it with no issues, street only no track autocross yet.

rkhanso

Thanks swbtm. That helps a lot.

I don't really like the idea of the oil going into the carb, but can see a point of it connecting to the carb bowl where it may dissolve into the fuel and be more effective than just running down the intake and dripping into the engine. But that's just how my mind pictures it - and it really may be no difference in the end. I'm not a physicist to understand how that all works.

Thanks for that bottom picture. It'll help me fabricate a bracket to put on the carb for mounting a rod down to the OMP. Though, I'm not 100% sure our pump is working yet. We haven't had the car running long enough to pump the oil up the hoses. I guess I'll try and fill them from the top tonight to help it along - when I set the ignition timing and try to adjust the carb.

I put the trailing vacuum diaphragm hose up to the vacuum port at the bottom of the carb...the port that comes out at a 45 degree angle. I thought that would be a more accurate/better vacuum for the distributor. The Racing Beat instructions say to not connect the leading vacuum diaphragm hose.

My son't throttle cable mount is missing on the carb. I rigged something that sort-of works, but is really ugly. Could you take a picture of the other side of the carb and post it? I'm thinking I need to connect that cable to the carb better.

Still have a lot of work to do before it's road-safe.

swbtm

iTrader: (2)

Here you go.



About oil dripping into the intake... yes it smokes a little more than a properly vaporized oil. Although, in my mind, as long as I keep the revs up often enough and open the secondaries to get the flow past those nipples often to clean any residual oil out. It seems to be happy. Just gives me another excuse to pull 4k to 7k rpm more often. Also, once the oil gets into the compression cycle it is going to be distributed reasonably well for my purposes.

rkhanso

Thanks for the pictures swbtm. They'll help out a lot.

Now, I'm trying to adjust the ignition timing. I can't find the marks on the pulley and wonder if it's the correct pulley (yes, I see there's 1 bolt missing).

I rotated the engine by hand and didn't see any obvious marks - though the pulley is pretty dirty/rusty.

Does this look like the correct pulley?





Link to video of the pulley being rotated:
https://dl.dropboxusercontent.com/u/...180633_664.mp4

mazdaverx713b

iTrader: (91)

That's the correct pulley. There should be two notches in the pulley. One notch is painted with orange paint and the other with yellow paint. Set the timing using the orange mark. This is the leading timing mark. This indicates top dead center. If the paint is gone, look for the notches.