Owned FC's for 10yrs, going through my first rebuild: plastic thermostat neck cracked @ a track day, overheated. I think it will be straightforward. Originally posted in the Tech section but not much traffic

Motor is out of the car and I've been doing a ton of searching on the forum. A few questions:

-If everything looks good, OK to reuse all the hard parts? Replace the o-rings and re-assemble everything in the spot it came from. Motor is a low-stress S5 na with 10k on a Rotary Resurrection rebuild. Overheat was mild, champagne in the coolant but starts and runs, no warping or anything major is expected. A few threads (and Aaron) say OK.

- Main radiator hoses: are silicone worth the price? If so, is the $90 set from RB worth it over the $45 set from Evilbay?

- Minor coolant hoses for heater and TB: worth it to source silicone?

- Underdrive pulley: Car will see half a dozen track events a year. Used as a toy. Maybe 1000mi /yr. Worth it to get an underdrive pulley? Some sources say it cavitates over 4k. RB says do not use on dd cars.

- I plan to use Evans coolant. Special or mod radiator cap so it does not keep the system pressurized?

- While motor is out of car worth it to replace pilot and/or throwout bearing? Both seem fine.

I’ll have other questions as I go through it. Thanks for input! It's friggin HOT in the garage in TX! Thank the Good Lord for margaritas

 

i've always read to change out the pilot and throw out bearings when its out as to be safe its less money to do it now and know its good then to have to take the trans out and do that work you could have done while it was easier.

if you can find some silcone heater core hoses let me know. i'd like to get some as they resist oil. the original filter location tends to dump oil all over the regular rubber hoses which breaks them down. i didn't go for silcone radiator hoses with mine it was also a budget thing. i've never heard anything bad about them honestly. they seem to have longer life is my guess. pretty sure almost all the silcone radiator hoses are around $90. i've looked at samco, mazdatrix, and rb.

 

1. reuse of hard parts. as long as the parts are still good they are perfectly fine to reuse. obviously the better condition everything is in the better it will run and the more power you have. the shop manual has all the measurements and specs. there are a couple, for example the side seal clearance, where the factory tolerance is .002" to .010" many feel that .010" is way too loose, and that it should be more like .002-.004"

i've actually found that if you measure everything it becomes really obvious what you should replace

2. the stock rubber hoses last a really long time, and are cheap. i would go OEM over silicon, and then silicon over aftermarket rubber.

3. again i'd just use OEM, they fit, last a long time, etc.

4. i think for the kind of use your talking about you wouldn't have any problems with an underdrive. you might wanna think about an oil pan baffle plate too, actually.

5. evans doesn't work, we had a thread a while ago, and someone actually posted some actual information.

6. minimum you should lube the pilot bearing, and the t/o slides/pivots. if you're big bucks just change em (id buy these two over silicon hoses, for example), that way you don't have to pull the trans in the foreseeable future.

 

- I've decided to have Kevin @ Rotary Ressurection do the motor again - not worth the investment of time & specialty tools for me to tackle it.

- Evans: came across this thread, which has opinions on both sides. I will be further looking into it from across the interweb. https://www.rx7club.com/3rd-generati...oolant-945513/

-Suggestions where to source small parts, gaskets, etc? Mazmart still good? I plan to do it right, replace every crush washer etc.

 

Atkins, mazdatrix, pineapple racing, turblown are all good and I have very positive experiences with each.

Nothing wrong with using oem hoses. Save your money.

Check out these aluminum thermo necks.? Rotary13B1.com: Aluminum Thermostat Neck/Elbow 1989 -1992 RX-7

 

I have a pretty high opinion of the waterless coolant gig, Evans or otherwise. I changed to Evans when I couldn't find the leak causing my coolant to accumulate in the overflow tank. I pulled the inner seal off the rad cap and ran zero pressure with Evans. Now with the overflow merely acting as an expansion tank, the coolant stopped accumulating in the tank. Over a year later I found that the waterpump shaft seal was the source of my trouble. I remain an Evans cooling proponent.

I know for a fact Evans saved me from a rebuild on a hot summer freeway when one belt broke and took out all the other belts on the engine. I had to drive to the next exit and park. The engine never boiled and the VDO electric gauge read 325*. I cooled for a while, believing that the engine was toast. Drove about a half mile to an orielly's where I purchased all new belts. Installed them with borrowed tools and the help of a homeless guy. I drove the car away with no trouble. That was the summer of 2008. I've put several thousand miles on the car since then.

FWIW, although the Evans is in fact less efficient *at the same temperature*, the heat transfer increases with the delta T of the air and coolant. So if you were running 190* on a 105* day, that is a delta T of 85*. Run your Evans at 225* on a 105* day and your delta T is now 120*. That is a 41% increase in the delta T. The radiator WILL shed more heat at the elevated temp. It will make up for the difference in the heat transfer capacity. Don't want to run your car at 225*? That's because your engine is in danger at that temperature with conventional 50/50 mix of coolant. 225* is perfectly safe, even desirable with Evans coolant.

So you (may in some situations) have warmer coolant temps, almost no possiblity of boil-overs, no pressure on the hoses, less likelihood of hot-spot boiling. What's not to like about Evans? If it's too expensive, use 70% Sierra (propylene glycol) and 30% Prestone Extended Life (yellow). Now you have a poor man's version of Evans coolant.

 

Damn, you're the man. Anecdotes do not equal data, until there's a lot of anecdotes... and I keep hearing such anecdotes. My rebuild situation is due to a crack of the t-stat neck, then the conventional coolant all boiled out. Evans (or the poor man's) would have leaked but I suspect would not have allowed the engine to fail unless the level got below the level of the water jacket rings. Thanks a million.

 

Doesn't running hotter coolant reduce engine output?
I remember seeing it in the power block where they would run hotter coolant through an engine(v8) and the hotter the coolant, the more dramatic the horsepower loss. Kinda like cast iron vs aluminum heads... If this doesnt apply here then my bad... Just trying to learn

 

Quite likely, though I have seen no dyno data. Running 100% coolant would be in the interest of maximum engine longevity and protection, not maximum output. I'd gladly trade 3hp for a security blanket.

As part of the rebuild I plan to ceramic coat the header and wrap or heat sheild the IM as much as practical to reduce underhood and intake air temp.

FYI I received this from Racing Beat about wrapping/coating their headers:

"While there may be some benefits of wrapping or ceramic coating, this will likely vary from application-to-application and only thorough testing would reveal both the positive and negative aspects. With regards to the rotary application we do not recommend wrapping the header due to the extreme heat build-up and retention which results. You are correct; wrapping the external surface would likely encourage corrosion, as well as cause the metal to become brittle and fatigue, leading to likely cracking and failing.

You can certainly ceramic coat the header (both internally and externally), which will provide improved surface protection against corrosion. However, long-term effects on longevity or performance improvements are unknown"

 

i've heat wrapped and ceramic coated many rotary exhausts, i have not noticed any dramatic negative effects.

 

interesting - searching the forums found both good and bad feedback on wrap. Ceramic coat through HPC is $205 incl. return shipping, not bad, so I'll go that route.

Did it make a good difference in underhood temp?

 

if you don't want to wrap the header, a heat shield would also work, or you could wrap the intake...

 

Debating about a lightweight flywheel. Cost is around $400, I read the performance gain is pretty minor. Suggestions?

 

the flywheel is a minor difference in say RWHP, but it makes a huge difference in the way the car feels. so its personal preference. i think the stock fylwheels are way too heavy, and the RB steel flywheel is more like what should have been on the car from the factory.

 

i'd avoid an aluminum flywheel because anything below 10lbs becomes a bit of work to drive the car on the street and in traffic. 12-15lbs for the flywheel not including counterweight is about right for a little bit better acceleration and response compared to the stock 21lb flywheels which were aimed at correcting the lack of off the line torque from the rotary engine. the turbo flywheels can take off a foot if you're not careful...

 

I'm looking at the RB steel flywheel. They know what they are doing, and I trust their products.

The Mazdatrix website says "you will be able to accelerate faster. This is true to a much lesser degree on fuel injected engines than on carbureted engines" - which is giving me pause if it's worth the $400 to get the flywheel and counterweight.

 

if you're racing the car yes, if you're daily driving it 99% of the time no.

 

I have the Mazda Competition engine mounts. Thinking of a set of Derilin mounts
http://definedautoworks.com/prod8.html Cheap and pretty solid. My previous car had solid aluminum mounts, really didn't bother me even with the bridgeport shake.

Anyone have experience with Defined Auto Works? I had never come across them till a mention on the RX7 facebook page, a guy in Sweden having them build a motor. Rebuilds for $1600, and high-dollar headers and such.

 

Ordered the Atkins one piece 5/6 port inserts. The car had the Pineapple inserts, sliding around loose, and one pin was loose! poorly installed.

Also ordered an Intellitronics digital water temp gauge, the analog Autometer gauge has lousy resolution past 200F.
Small bits and pieces from Rock Auto: pilot and clutch release bearings (SKF please!) clutch alignment tool for like $2, new Goodyear upper and lower radiator hose for $3-5 each.

Looking to source Silicon for all small coolant and heater hoses. Around $3/ft from Evilbay vendors. These hoses are $20+ from Atkins/Mazdatrix. Just need to measure heater and BAC/etc coolant lines. Anyone know offhand what the sizes are?

 

I also am about to undertake my first rebuild and have a few questions before starting it myself. I had an overheating issue and am guessing i blew the coolant seals. Primarily wondering:
1. What special tools if any are required to do a rebuild?
2. Do the rotors need to be balanced?
3. Where can I find torque specifications?
4. Where in particular should I look for bad signs on the rotor housings etc. from the overheating?

Any help would be appreciated, I have been trying to sift through the pages on the forum to find this information and have had no luck.

Thanks

 

I had the same dilemma. There are some special tools: 54mm(?) socket & impact gun to remove the flywheel, engine stand adapter, precision dial calliper to measure tolerance, etc. I decided to have the pro (Rotary Resurrection) do it. My big concern is since I have no experience, I might miss something like out-of-spec housings or plates, etc. It takes an experienced eye to know what to look for and how to measure things. An issue with overheat is warping, and to check for warpage, special tools are needed as well. At the end of the day, I’d have spent around $500 on tools (estimate), plus $1000 for the Master Atkins kit, and ended up with a motor I would not be 100% confident in.

Kevin will do the rebuild for $1300 base price, he knows what he’s looking at. Add a couple hundred for shipping and the price is pretty similar. So it made sense to throw the pro some work and have a motor I can have 100% confidence in. Hope this helps, good luck!

Mazdatrix has some FAQ's FAQ's and How-to's
From my research Rotor balancing is not necessary unless you plan to spin past 8.5-9k routinely

 

1. you need the 2 1/8" socket for the flywheel, and some basic measuring tools.
2. no balancing needed unless you want to rev it higher, or are using mix and match parts.
3. the shop manual has a page in the back that lists all the clearances and torque specs. book is @ Foxed.ca
4. everywhere... there is a measurement for rotor housing warpage. although on a rotor housing usually they are pretty beat up on the apex seal sliding surface anyways

 

POWER STEERING

I really want to try a non-PS setup, but nervous to tear apart the stock (nice, tight) unit.

An option is a rebuilt rack from RockAuto for around $200. De-power that one the 'right' way and store the original if I ever want to go back to a stock setup.

Any other suggestions?

 

So Kevin has the motor apart and found a nice little break


other than that it all looks quite good.

The motor already has mild 5/6port job and made 158whp. He has offered to 1) complete the streetport as much as possible or 2)do a halfbridge

The car will keep stock ECU (and SAFC), vdi, etc. Halfbridge would be wasted and miserable without supporting mods, correct?

I am leaning toward doing the streetport for a little more oomph. Sound good?

 

Flywheel: went ahead and ordered the RB steel flywheel.

Replaced the clutch release bearing with a new SKF from rockauto. The old one feels smooth but was slightly noisy. I've had very good luck with SKF bearings (and it was only $35) so I hope this will be a good purchase.