1993 Mazda Rx7 - Rotary Engine Rebuild - Part 4

Intro - Part 1 - Part 2 - Part 3 - Part 4 - Parts List - Final

It has been a while since my last post due to a touch of procrastination...then the holidays ended up creeping in on us. In this posting I am going to go over some engine rebuild notes as well as some of the reliability mods I had installed in hopes to prevent the issue which prompted this rebuild in the first place.

First off, a lot of the links I had provided in my previous rebuild postings are to websites/videos that really helped me so I suggest you check those out. Below I am also including additional links to specific videos/procedures which I had used during my rebuild.

1. Installing heavy duty water seals
A lot of people use gasket sealant around the outside of the motor housing water jacket. I however, opted not to gum up the entire motor with sealant as it is completely unnecessary. If you take your time cleaning your housings and verifying that they are within spec, you can simply follow the process in the instructional video above and you will be good to go.

2. Eccentric shaft thermal bypass valve modification
This simple mod bypasses the eccentric shaft thermal valve so it allows more oil to reach the rotors sooner rather than waiting for the engine to heat up. At the same time, if this valve fails it will prevent your rotors from being cooled properly and can lead to seal failure. Definitely a mod worth doing while you have the engine apart.

3. How to set end clearance on rotor side seals

4. Installing rotor bearings (similar to main bearings)

On to the parts! Below I am going to review the main components I had selected for the rebuild along with the upgrades/reliability mods I had installed as well. I am going to skip over all of the typical gaskets/seals I had replaced however I will be posting a complete list of parts with part numbers soon.

Heavy Duty Water seals:
My choice for replacement water seals were from Pineapple Racing - http://www.pineappleracing.com/hdwatersealsfdrews5re.aspx - They claim that the seals are reusable and that they have been building race engines with these seals for quite some time without any issues. Check the site out for more info as they provide a few other key rebuild seals within the kit also. Note: I just realized that my kit did NOT come with the 18 tension bolt washers as stated in the description so make sure to double check your parts if you order this kit!

Thermostat w/ gasket:
Good time to replace this guy! Can be found at www.rx7.com - I am glad I remembered to crack the thermostat housing open because my thermostat was completely warped and the gasket was falling apart.

Apex seals:
I purchased from Mazda dealership but they can be found at mazdatrix.com - The apex seals that I had removed from the motor after 90k miles still would have been usable if they had not been rusted into the rotors. Because of this, I ordered the stock replacement Mazda 2mm 13B steel apex seals (2 piece) to ensure I had the same quality and best compression for my motor.

Rotor bearings/ Main bearings:
I purchased from Mazda dealership but they can be found at mazdatrix.com.

Front side iron housing:
Needed because the original iron housing was cracked which caused my coolant loss and water seal blow out as seen in "Part 3" of my Rx-7 rebuild posts.

Koyo Radiator with N-FLO & OBX Silicone Radiator Hose Kit:
Ordered from http://www.sparktecmotorsports.com/ - All aluminum aftermarket radiator which I believe is twice as thick as the stock radiator and installs perfectly in the stock position without any modifications. I must say I am very happy with this purchase.
Below is a photo of the stock radiator.
As you can see, one of the fan blades broke off of the electric fan motor and flattened many of the fins on the radiator, preventing proper airflow. I am guessing this probably is one of the factors to the initial overheating issue.

Below is the new Koyo radiator with repaired stock electric fan assembly and new silicone hoses. I found a great deal on a used stock radiator fan assembly on ebay for $80 which included 2 good motors. Now I have a spare for backup!
Note: After the car reached normal operating temps, I had driven around on multiple occasions under medium-heavy boost (Apex-i is dialed in @ 13PSI) and I am seeing steady 179F-180F temps while driving on my aftermarket temp gauge. (installed next to the thermostat housing)

Aftermarket motor mounts:
Ordered the" 2 Himni Polyurethane Motor Mounts - STREET/RACE Mazda RX-7 93-00" from himni-racing.com - The installation required some modification to the stock brackets however the install was very easy. The price is not bad either when compared to stock replacements. Note: Once you get a majority of the old rubber off of your brackets, I recommend using a bench grinder with a 6" wire wheel to remove any excess rubber. The wire wheel makes this a breeze.

Silicone Vacuum hose kit:
Ordered from http://www.hosetechniques.com/ - I purchased this kit to replace ALL of the vacuum lines on the car since most of them were getting brittle due to heat. The kit is nice but it includes much more than what you really need to replace all of your vacuum lines. You probably can save some cash by purchasing solely what you need.
Before and after photos ...
If anyone out there has the motor apart and is unsure whether or not to replace these vacuum lines, do it! It is well worth it to get all of those brittle lines removed and it is extremely simple to do. Just take your time and replace the hoses one at a time and you will have the peace of mind that any small vacuum leaks will have been fixed. My only caution is to be careful when removing the lines from the vacuum solenoids, I actually cracked a nipple off one of them because I was in a hurry. Luckily, I was able to epoxy it back on without an issue.

Aftermarket Aluminum Air Separation Tank (AST):
Ordered from http://www.rx7.com/ - Bolts into stock location perfectly and the aluminum design resolves issue with the stock, plastic AST cracking due to excessive heat.

Oil pan brace:
Ordered from banzai-racing.com - I used to have a seemingly non-stop drip of oil coming from the bottom of my motor around the oil pan, which is typical for this car (especially with 93K miles). Some people have reported success with this type of oil pan brace which allows you to tighten everything down uniformly so the pan does not twist/bend. Accompanied with "Permatex's Ultra Black Maximum Oil Resistance RTV Silicone gasket maker", I have not seen any drips yet. **Crossing fingers**

This oil pan brace kit comes with all required hardware (studs/nuts) however I purchased the "Himni SS Oil Pan Nut & Bolt Kit" from himni-racing.com since it includes stainless steel bolts.

Here is an image of the oil pan w/ brace bolted onto the motor using the Himni stainless bolt kit. You will also notice the Himni poly motor mounts installed as well.

Here are a few other things I had done while the engine was apart and out of the car.

Polished intake manifold:
Hand sanded and polished upper intake manifold to improve overall appearance of engine bay. Below are a couple photos after the hand sanding and polishing.
Note: You will need a dust mask for this and I recommend some latex-type gloves as well, you do not want to be breathing this stuff in. I started off with a heavy-medium grit sandpaper to remove any large imperfections, then repeated the process with medium, fine, very fine, then lastly I wet sanded the surface as smooth as possible. The more scratches, dimples and chips you are able to sand out of the surface, the better it will look after polishing. Then I used some white aluminum oxide compound with a buffing attachment on my air die grinder and buffed the entire surface to get ready for final polishing. Lastly, I put on a new buffing pad with some red rouge and polished the surface to a high gloss finish.

Exhaust manifold cleanup:
I cleaned up the exhaust manifold with my bench grinder, retapped one of the turbocharger bolt holes due to a broken stud and replaced the nuts with new copper nuts to make disassembly easier in the future.

Painted shortblock housing:
Decided to take some time and paint the shortblock housing. This will give it a clean finish and assist in keeping oil and dirt from sticking to the surface.

That just about completes the main rebuild part overview. My next posting will include my complete list of parts ordered for my rebuild as well as some info on trouble I ran into after the car was back together. If you have any questions regarding the rebuild process or are looking for recommendations, please feel free to contact me and I will reply as soon as I am able.


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