DarrylD's Mazda RX-7 Restoration Project Journal

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Darryl's 1985 RX-7 Restoration Project Journal

Last Updated on July 12, 2017


PROJECT JOURNAL ENTRIES (IN CHRONOLOGICAL ORDER)


Entry: 10/8/14 - Hey, somebody put rice in my sauerkraut! What's a Japanese car doing in my garage? Well, what can I say, I'm a sucker for survivor cars and this RX-7 came into my sights with only 43,000 miles on it at my buddy, Peter Leinberger's consignment car sales at Cottage Lake Motors (now out of business). The the original owner hardly drove it, let it sit and then was surprised it wouldn't run right and was tired of trying to find somebody to fix it every time she went to have the emissions tested to get license plate tabs every two years. The mid-80s were the point in automotive technology that carburetors gave way to fuel injection simply because they couldn't come up with enough vacuum and electrically operated work-arounds to make them meet federally-mandated emission control requirements. Throw in the fact the RX-7 uses a Wankel rotary engine with oil injection and you have an especially difficult problem to solve with emissions. The car was local, purchased at University Mazda in Seattle and spent its life in nearby Bothell. Repair receipts show that the the first 40,000 miles were put on it prior to 1992 and then it sat, and sat, and sat. A new fuel tank and carburetor were installed in 2003 and then it sat again for a decade. Notice the EPA estimated city mileage is 17 MPG and that's optimistic! There is only one major cosmetic flaw, a wrinkle in the passenger door up by the hinges, it didn't mar the paint and it's only visible when you look closely, however the body is not flawless and I will have to address that bodywork at some point.

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One look at my RX-7's engine compartment and it was clear why the internet bulletinboards dedicated to the car referred to the snarl of hoses and wires on the top of the engine as the "rats nest". A browse of the .pdf file copies of the factory manuals showed the poor engineers at Mazda had pushed the design to its limits with so many subsystems on the intake to accommodate every possible situation, hot starts, altitude change, sub-zero atmosphere, literally dozens any one of which caused a problem 30 years later when it failed to work as designed. Luckily after 25 years on the road, a motor vehicle is exempt from any further emission testing in Washington State so I gutted the car of all my RX-7's emission related parts and installed a hot "Racing Beat" Holley carburetor intake and catalytic converter free exhaust system.

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Everything above the white stick on the floor is the factory intake and exhaust that was on the stock RX-7 and everything below it is the Racing Beat intake and exhaust system featuring a specially modified and jetted Holley 4-barrel carburetor designed specifically for a stock "12A" model engine with unmodified ports. There are actually three separate catalytic converters on the stock exhaust system, any of which can get clogged and really make performance suffer. At ony 43,000 miles, the exhaust components were like new and the fasteners virtually rust-free allowing easy disassembly.

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The 1100 cc Wankel rotary engine without any intake or exhaust components is a pretty compact and lightweight piece rated at about 100 horsepower in stock configuration. Notice also that the engine lies behind the front strut towers, making it a "mid-engine" configuration where the weight is balanced 49% rear axle and 51% front axle, much like the Porsche 914.

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The Holley 4-barrel carburetor and two-pipe header system of the Racing Beat kit really simplify the engine compartment. Eventually the huge wiring harness will need to be unwrapped and all the emissions-related wires removed so only the wires to the engine oil level warning light and alternator light remain, much like pruning an oak tree back to a sapling.

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The bottom side of the car is super sanitary too, the connecting pipe between the "pre-silencer" (catalytic converter delete) and the muffler was an original piece that I simply sandblasted and repainted using high-temperature silver exhaust paint so it matched all the other new components. New rubber exhaust hangers were installed where necessary too so the whole system installs using stock mounting points and brackets.

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Racing Beat recommended replacing the stock fuel pump with a Mallory 4070M fuel pump that provides 6 psi fuel pressure for the Holley 4-barrel carburetor. I installed 3 captive "rivet" nuts into the frame channel just ahead of the axle and behind the stock fuel pump location (under the shield), retaining the stock "pre-filter" ahead of the fuel pump, there is another filter in the engine compartment which is also stock and in the factory location. I had a very hard time getting the 5/16" NPT threaded fuel line nipple connectors to seal and after a second seepage using NAPA teflon sealant, had to resort to using a varnish-type hard set sealant of the type used in aircraft and boating applications.

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Removing the emissions control air pump and belt required installing a small lawn mower belt (part number 3L220) between the main crank pulley and the pulley on the waterpump so it has two belts and won't slip.

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With the high-performance air cleaner installed on the Holley and the rest of the engine compartment cleaned and detailed the business-end under the hood is looking fresh and new. Once the wiring harness modifications are complete, the whole thing will take on more of a '70s muscle-car look instead of the "there's an engine under there somewhere" look of '80s cars. The first 500 miles on the car since the modifications have been amazing, clearly much more horsepower, Racing Beat claims 140-150 horsepower on their dyno tests and it's clearly way better than how I got the car, which ran fine until it got hot then the idle went up to about 3000 RPM, probably due to a stuck servo or plugged port on the carburetor. Now it's just a matter of fine tuning the Holley 4-barrel, which when compared to twin carburetors on a Porsche engine, is a piece of cake.

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The burgundy vinyl on the door panels had faded over time to have a bit of an orange tint and didn't match the leather insert anymore, so I used the same SEM burgundy aerosol interior dye product I've used on my Porsche projects and freshened it up with a very light coat. The before and after photos show that it's a perfect match and looks fantastic!

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I'm a rather large guy, 6'5" and 240 pounds so this car is a tight fit. I finally gave into the rub on my thigh when I tried to clutch and turn at the same time and repurposed an old MOMO steering wheel I had in my Porsche 914 for over 20 years before upgrading it to a MOMO Prototypo more fitting for the car. I've got to admit, it's perfect for the RX-7 and now if I can find a MAZDA horn button, it would be perfect.

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After a little detailing of the metallic black paint and redying faded vinyl areas of the interior, the car is immaculate, a burgundy-colored leather interior GSL optioned car that was just too pretty to pass up, especially at the price of $3000! The Racing Beat parts, with a Mallory 6-PSI fuel pump came to just less than $2000, so for $5000, I have a fun little hot rod rice burner that's an absolute blast to drive. I think we're at the ragged edge of what's going to be collectible in the future years because when computers started running the engine management systems, spare parts ran dry and junkyards are brimming with road-worthy examples that nobody wants the hassle of finding parts for. Thank goodness for after-market companies like Racing Beat and lax emission laws in a state that accommodates car enthusiasts. More details will follow...


Entry: 12/3/14 - So after close to putting 1000 miles on the Holley conversion, it was time to permanently remove the abandoned emission control system's wires in the engine compartment. The way I approached the problem was to fist carefully unwrap the wiring harness starting from the end and working back towards the firewall. When all the wires were exposed, only 8 wires are still in use and 14 required amputation. I carefully pulled the wires out of the engine compartment and soldered any that needed to be shortened or "pruned" from branched-off circuits so everything was the same length. The unused wires were amputated about 2" from the firewall and the ends sealed using liquid tape. Once the liquid tape dried I reassembled the 8 used wires into a wire "loom" tube which matched the OEM wiring and taped the amputated wires into a stump, hid them in a short length of wiring "loom" tube and hid the end under the windshield washer bottle.

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The result is a super sanitary and completely visible engine block with only a slim, OEM-style wiring harness "branch" going across the engine, holding the vacuum line to the distibutor away from the block with a wire tie around it and the fuel line. No more "rats nest" and complete access to the carburetor and ignition systems. I've also upgraded to a little hotter (heat code 7) iridium-tipped NGK spark plugs in my first effort to address a flat spot in the carburetor at about 3500 RPM. I really get a big kick out of driving my little "rice burner" because of the kick in accelleration that happens about 5000 RPM, it feels like the turbo boost kicking in, then a buzzer that sounds like a car horn honking goes off in my ear, reminding me that I've hit 7500 RPM and I really should shift! I have also started the practice of running a 100:1 mixture of 2-stroke oil in the fuel as a little extra lubrication for the apex seals as recommended by several Mazda rotary motor experts on the internet forums I read. I think I have achieved a very sustainable vintage car configuration and look forward to enjoying this car for many miles and years into the future.

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Entry: 1/21/15 - I purchased a new stereo with amber setting to match the gauges with a mounting kit that fit into the factory mounts. I also purchased the wiring adapter kit that allowed me to wire up the new stereo using the existing factory plugs so no wires were cut. This provides for the option of putting the original factory stereo into the car if I or some future owner should desire, for now I really enjoy playing CDs and using the USB port to plug in my cell phone and use apps like Ulysse Speedometer.

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Entry: 4/23/16 - I thought it would be handy to see what the fuel pressure is when troubleshooting problems so I added a liquid-filled fuel pressure gauge.

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Entry: 5/23/17 - The windshield trim on the right side of the car was dented so I purchased a new one and attempted to install it. Of course, I cracked the perfect factory original windshield so I had to have it replaced with a Pittsburg Glass Works (p.k.a. PPG) replacement by my local Speedy Glass in Bothell, who used the new trim piece when they reinstalled everything. Now it's a beautiful new windshield and flawless trim. Speedy Glass did an awesome job to remove and reinstall the original trim without messing anything up.

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Entry: 5/30/17 - So after driving the car almost 2000 miles with the Racing Beat Holley conversion and enduring a flat spot around 3500 RPM, I finally came to the conclusion that the secondary circuit wasn't opening early enough. I got on the phone with Racing Beat's technical support and found out that the short yellow spring is the one that is used in the conversion kit. A spring kit from Holley (ordered via Summit Racing) included the next "softer" white spring and a they also offered a "quick change" system to allow the springs to be changed in the secondary circuit vacuum canister very quickly. I used an old RW DVD container to create a "Darryl-proof" cover so I wouldn't accidently drop anything down the open 4-barrel while I had it apart. Sure enough, the lighter spring allowed the secondaries to open earlier and cured all the flat spot problems. Now the car drives very smoothly and any problems I encounter with flat spots are really just an idiosyncrasy of rotary engines and easily avoided by adapting a driving style that doesn't lug the engine, especially coming out of corners. I simply downshift and accelerate a little more aggressively than I would with a piston engine. I'm getting a little over 16 MPG in city driving with the Holley conversion so the performance improvements haven't come at the cost of fuel efficiency, unfortunately that's still pretty low by today's standards and when considering the more expensive ethanol-free fuel and 2-stroke oil additive, kind of an inefficient, gross polluting car to drive.

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Entry: 6/1/17 - After a year of watching eBay, the extremely rare MOMO horn button with the Mazda trademark came up and I quickly snatched (a.k.a. "Buy It Now") it from a guy in Australia!

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Entry: 7/12/17 - The one major cosmetic flaw with the car since day one was a wrinkle in the passenger door from something falling over against it. It was behind the hinge plate so the dent removal guy couldn't fix it. I finally took it to Fenders & Fins, Inc. bodyshop here in Woodinville and had them do their magic. For $1,184.15 (with tax) I got the door dent fixed, the metallic black paint blended and clear coated over the door and front fender and the red pinstripe reapplied. I'm really impressed with the work that Jon Carson and his crew did on this job and pleased to have such a talented bodyshop just down the hill from me!

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