Felix's How-To & How-Do-I
FAQ & Other Tech Goodies


Brake Miscellany

Normally you won't find stuff on this site that doesn't pertain primarily or exclusively to rotaries, but brakes are a seriously important subject, particularly to modified cars.

Brake fluid is hygroscopic., which means it absorbs moisture from the atmosphere. This takes time, but it reduces braking effectiveness and eventually results in deterioration of the brake (and clutch) hydraulic systems. Like oil, brake fluid should be periodically changed to minimize deterioration of brake parts and thereby braking effectiveness. Brake fluid replacement is done by a process called "bleeding".

The following was a clever method of brake bleeding posted on the newsgroup rec.autos.rotary by David Stephan

Subject:	Re: Bleeding brakes
Date:		Fri, 16 Apr 1999 22:03:48 +1000
From: 		David Stephan <dstephan0ozemail0com0au>

Here's a contraption I built to ease bleeding brakes:

1. One large Nescafe jar (or similar)
2. Drill two holes in the lid and epoxy two small tubes into it with about one
	inch on either side of the lid. The idea is to make the can/jar airtight
	(except the tubes)
3. Attach plastic tubing to each pipe (fish tank stuff works well)
4. Attach one pipe to the end of the bleed nipple on the brake caliper, also put
	a spanner/wrench on the nipple so you can open close the nipple easily.
5. Connect the other hose to a vacuum source on the engine.
6. Remove master cylinder filler cap and have brake fluid handy to top up. I
	suggest you put rags around the master cylinder to catch any small spills.
7. Start the engine and let it idle.
8. Open the bleed nipple and watch the brake fluid get sucked into the jar/can.
9. Watch the colour, the old discoloured stuff will turn to fresh looking brake
	fluid (whatever colour that happens to be).
10. Close the nipple. That's one wheel done.
11. Repeat for all wheels, remember to watch the master cylinder level and top up
	as appropriate.

This is by far the easiest way to bleed your brakes and does away with the
old "someone pump the pedal trick", which isn't that good IMO.

Make sure when you build the jar/can that the tubes are reasonably far apart
so that all the old brake fluid goes into the container and not back up into
the hose running to the vacuum line.  Also watch how full the container gets.

David Stephan
Note for those not familiar with bleeding: The first wheel to be bled should always be the one farthest from the master cylinder. To improve the bleeding process, first connect the device to the master cylinder reservior to remove the old fluid, and then refill with fresh fluid for a quicker and better bleed. Some reserviors aren't difficult to remove from the master cylinder. In those cases it may be easier to remove and clean it first before refilling. Just remember that brake fluid is a chemical that is hard on skin, and disastrous on paint.

How do I replace a 12A with a 13B?

This is not designed to be an exhaustive swap manual, as installations and cars aren't all alike. Because this is just an overview, the subects of intake selection, exhaust system, emission controls, and wiring are beyond its scope.

The dimensional differences between the 12A and 13B blocks are limited exclusively to their lengths. 13B rotors & rotor housings are 10 mm wider, so the engine is 20 mm longer. This is the only basic dimensional difference. Prior to the introduction of the 6-port engine configuration, in model year 1984 in the North American market, 12As and 13Bs shared side housings and front covers. As a consquence, all share the same transmission bolt pattern. Assuming you want to do the swap on an RX-7 that originally came with a 12A, here are the:

Parts to Definitely Replace or Modifydue to the 13B's longer length.

The GSL-SE has 20 mm longer mount perches, so installing an SE subframe is one solution for the length difference. Substituting a special front mount crosspiece for the original is the simplest and most elegant solution. You can buy one under part #11832 from Mazdatrix or Racing Beat. A cheaper, less sturdy option is to notch the mount holes 10mm each in your frame, forward, and in your old crosspiece, rearward. If using an engine made for model year '86 or newer, there is no mounting point for the crosspiece on the front cover, so one from an earlier engine must be substituted. The oil pan from an '84-5 13B is your only practical choice for installation into a 1st gen, but an oil pickup from any 1st gen engine will do. '84-up 13B rotor housings have injection oiling ports for better apex seal lubrication. In order to utilize the superior later oil injection system, a GSL-SE front cover and its quad-output oil metering pump are required. Otherwise, any '74-'85 front cover will do. If in good condition, your old radiator hoses can be reused with a slight trim. There remains plenty of fan to radiator clearance with the stock components. If the target car is an '83-5 model, the 12A OEM oil cooler should be replaced with the oil cooling system from a '79-'82 car, or from a GSL-SE. The water to oil cooler is of marginal capacity even for a 12A, and won't cool adequately with the bigger engine. The single row core '83-5 radiator is also inadquate, but can be recored to work just like an SE radiator or better. If substituting a carburetor on an '86-up engine, a distributor from an earlier car is required. The mechanical advance curve differs between 12A and 13B models. If using one from a 12A, its advance curve should be modified to match that of a 13B.

To put a 13B into an RX-3/Savanna, most of the above correlates. A crosspiece modification and an RX-4/Luce, RX-5/Cosmo or REPU oil pan are required. Radiator to fan clearance will be tight. To do the same with an RX-2/Capella, a custom oil pan will be required. A front mount subframe from an RX-3 will bolt right up under the RX-2 stabilizer bar, allowing use of a stock driveshaft with the longer 5-speeds from other rotaries.


How do I replace a 1st generation RX-7 13B with a 2nd generation RX-7 13B?

This is not designed to be an exhaustive swap manual, as installations and cars aren't all alike. Because this is just an overview, the subects of intake selection, exhaust system, emission controls, and wiring are beyond its scope. Also, a large portion of this topic is covered in the previous section and will not be duplicated here.

The simplest and lowest cost swap is to an NA block, starting with a GSL-SE, and keeping your first gen's original transmission, clutch, starter, intake and other accessories. Since the air ports in the block differ, they will have to be blocked off, and so you can forget about making the emission control system work as designed. If you don't have to pass an annual emissions test and you don't already have a header exhaust system, now is the time to add it, as it obviates any need to address the lack of air control function, and adds considerable power in the process. It also saves weight, as you will be leaving off the air pump. Use the flywheel that came with the engine, or take the opportunity to switch to a light flywheel, using the the counterweight designed for automatic transmisison models for the year of your new block. The effect of a lighter flywheel is quite noticeable in low and second gear acceleration, and makes the job of your transmission's synchros easier, extending their life.

Even if you plan to use a T2 engine, you can use your original transmission to keep cost down and simplify the process. Just keep in mind that your transmission doesn't have the load capacity designed for the higher output engine, and it can't be expected to last as long as if you converted to the heavier-duty T2 box. Making the converson to the heavier duty transmission requires a driveshaft with a bigger yoke. The transmission and therefore the required driveshaft lengths are the same. One thing that can make the swap a little easier is cannibalizing a pre-RX-7 Mazda rotary transmission, removing its bellhousing, which is designed for the same starter and clutch & flywheel diameters as RX-7 NAs, and installing that on the newer transmission - the T2 transmission is derived from the transmission used in RX-2s, RX-3s, RX-4s, Cosmos, and REPUs. That allows you to use the standard '83-'91 NA 225 mm clutch, as long as you choose the flywheel to match the engine block, or make the switch to a light flywheel, choosing the correct counterweight. Again, the turbo flywheel and clutch are heavier duty, larger diameter, and use different splines and starter, but you are also installing into a lighter car with shorter tires, so not all that capacity is certain to be needed. If sticking with the original transmission initially and running conservative boost, you may find you can go for quite some time before needing the heavier duty pieces, maybe indefinitely. If converting to the T2 transmission, you will need to adapt the shift mechanism from an '81-5 transmission to the T2 transmission to keep the shifter in the correct position in your console. This is a mere parts swap, but it does entail disassembling the rear of the trans to accomplish.


What parts do I need to replace an automatic with a 5-speed?

Cannibalize these if you can Get these new

Missing from the lists are the pressure plate and flywheel. A used pressure plate is typically acceptable. Only inspection of what's available will tell. To make the job as easy as possible, choose an aftermarket lightweight flywheel. It will bolt right up to the balance weight your torque converter flexplate is currently bolted to. Be sure to specify when shopping for one that you don't need the weight and thereby save its cost. A stock flywheel can be used, of course, but removing the balance weight is tough, and the light flywheel improves acceleration. The pressure plate fasteners are special. Be sure to get them with a used flywheel if that's your choice. Different ones will come with a new aftermarket flywheel.

If you have a 4-speed automatic, additional work may be required. The mount position on a 4-speed automatic is farther rearward than on a 5-speed. Your RX-7 may or may not have mount holes provided in the required location. If not, an adapter of some sort must be fabricated to move the transmission mount into the correct body location. One way to do this is is to find a square piece of steel plate 3/16" to 1/4" thick and appropriate in width to fit the transmission mount. Drill four holes in it, two to match the transmission, and two more rearward the difference in length between mount positions of the two transmissions. Measure your two transmissions carefully to determine the required distance apart. Affix the plate to the mount with bolts and nuts, then attach that assembly to the 5-speed. When bolting up the crossmember, space it down with washers the thickness of the plate, which will preserve the original driveshaft alignment and keep it from pushing the rear of the transmission upward in the tunnel.


Magic Potion

It isn't really magic, but on occasion, you might think so. The stuff is sold under at least three different names. Mercury and Mariner marine dealers call it "Power Tune". Evinrude and Johnson marine dealers call it "Engine Tuner". Some other marine dealers carry the same stuff under the name of "Marine Motor De-Carb", by ValvTect Petroleum Products. It is sold in the US in 13 oz. aerosol cans and in gallons. The can claims "recommended to maintain full power and efficiency".

What it is is a solvent that disolves or loosens carbon, varnish, and other engine deposits. It is water soluble, but also mixes with fuel. It is excellent used in conjuction with heat to free stuck bolts, which is only natural, as it is designed to prevent stuck piston rings when used as directed. It does a fine job of cleaning carburetor parts, particularly jets and other items made of brass, even with no added heat.

If some internal part of your engine is stuck or sticking, it's your easiest shot short of overhaul. It's also useful if your six-port valves are sticking or stuck.


Oil Problems

Leaky air-type oil cooler. This is usually a GSL-SE problem. Their coolers comonly develop cracks through the bosses that the lines connect to. Dave Disney explains a fix that's much less expensive than a new cooler.

Oily heater hose under the oil filter. This is a very bad thing. The oil reduces the strength of the hose, which can lead to overheating when the weakened hose breaks. When changing oil, the old filter should be pierced to allow drainback of the oil it contains prior to its removal. This reduces the mess when the filter is removed. If you wrap a rag around the filter base before unscrewing it, little or no oil should drip on the hose or other parts below. If you take this precaution and yet continually find oil on parts under the filter, the o-rings that seal the oil filter adapter and/or water-type oil cooler are likely responsible, but another possibility is that the dowel o-rings are leaking.

Puddling on top of the rotor housings is covered under o-rings in the FAQ. The problem is mostly cosmetic, not a reason in and of itself to overhaul an otherwise good engine.

Smoking from the tailpipe when you first start it or when you shift are covered in the FAQ. Continual smoking accompanied by high oil consumption is just the same problem at a more advanced stage.

Smoke from under the hood can be caused by a coolant leak. More commonly it happens when the oil injection lines become old and brittle and their connecting hoses deteriorate. A crack or complete break in one results in a reduced oil supply to your apex seals, as well as an external leak. Oil from an external leak can find its way onto the hot exhaust, thus creating smoke.

Foam is covered in the FAQ.

Dripping when removing engine. You drain the oil from the sump, then put the plug back in. That stops the drips, right? Well, not exactly. The front mounted oil coolers have two lines that must be disconnected unless you are pulling the cooler with the engine, and that's neither easy nor necessary. Be sure to use two wrenches to remove the long line from the oil cooler and the short line from the front of the engine. Once removed, and after removing the engine mount bracket, connect the long line back to the front of the engine, and connect the short line to the other oil cooler fitting. That keeps those parts from getting contaminated or dripping oil about while the engine's out.

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