FAQ and Tech Info
Whether you are a long term enthusiast or a new owner, there is a lot to learn and know about rotary cars. While it is impossible for me to teach you everything you need to know about your car and engine, I try to educate owners as much as possible while also saving myself the need to repeatedly explain pricing or information.
Please review the FAQ section and Technical info articles linked below, I think they will be very helpful.
Frequently Asked General & RX-7 Questions
No, I do not import or sell any jspec engines. I can only build from what you bring me.
No, I do not import or sell any jspec engines, and this engine was never sold in the US.
I do not currently sell rebuild seals or kits out the door, and only order what is needed for in house builds.
Frequently Asked RX8 Questions
This is a common mode of “failure” for rx8s with original engines over 80k miles. This is a result of compression in the engine dropping below a certain threshold where the PCM can no longer compensate and the symptoms appear. IT happens when warm but not cold because the rotary engine produces slightly more compression when cold than when hot. By “lost compression” mechanics actually may mean “has weak compression”. With this condition, nothing has catastrophically failed or broken. The internal seals and housing surfaces are worn and no longer sealing well. A rebuild is needed to resolve this problem. Generally this problem is fully rebuildable, however there is always the likelihood that your rotor housing chrome surfaces may be worn and not ideal for reuse.
You can continue to drive the car for a while this way, but the problem will continue to advance until the car is no longer reliable enough to drive and must be taken out of service. The problem can have other contributing factors such as a weak battery, starter, or ignition coils/spark plugs.
This is another common mode of “failure” for rx8s with original engines over 100k miles. This is a result of one or more failed coolant seals, which in a rotary engine is the equivalent of a head gasket. The function of these seals is to keep compression/combustion chambers and coolant passages separated. The coolant seals are basically large rubber bands, and when the rubber deteriorates the seal between passages is broken open, allowing coolant to get into the combustion chambers and flood the engine. This robs compression and wets the spark plug, making starting difficult. When you do get it started, the coolant in the chambers is burned off in the engine and exhaust in the form of steam. When the excess coolant is finally burned off, the plug begins to spark normally and the engine runs okay. Then compression pressure leaks into the cooling system and forces extra pressure in the hoses and radiator, causing coolant to be vented out of the bottle, sometimes causing them to burst and require replacement. The owner thinks the hose/radiator simply broke due to age, when in fact the extra cooling system pressure generated by the engine was the root cause. The problem usually accelerates quickly and will cause the engine to become unreliable and have to be taken out of service. The problem is usually 100% rebuildable with a standard seal set as long as the engine is not overheated too severely to melt or warp any components. The worst thing that you can do at that point is to park it as-is and let it sit for months until you decide to fix it. The puddled coolant inside the chambers will cause rust and damage the internal components of the block. This can greatly increase your rebuild costs as you must not only replace seals etc. but also the compromised major components. The proper storage procedure is to drain both the radiator and the engine block of coolant, then start the engine and run it for 30-60 seconds to blow all the coolant out of the chambers, then shut it off, then remove the bottom spark plugs from the block and inject a generous volume (several ounces per chamber) of thin oil into the holes while rotating the engine by hand or with starter bumps. This oil will coat the internals and prevent rust, while displacing any remaining water, and preserve the internals for later reuse.
This is the third major “mode of failure” for rx8 engines. Unlike the previous rx7 engines, the oiling system in the rx8 is not great and sometimes these engines do suffer bearing related failures. When this happens metal shavings are sent through the entire set of bearings/shaft and oiling system, and can do major damage. In general, bearings fail due to insufficient lubrication (aka oil starvation) allowing metal to metal contact of the shaft and bearings. Long oil change intervals can contribute to these failures since the rotary engine fuel dilutes/thins the oil over time, and also the heat generated by the rotary engine naturally breaks down the oil viscosity over time and reduces it’s ability to lubricate and protect. Finally, obstructions to the oil coolers, including bent cooling fin rows, can reduce their ability to control oil temperatures and promote heat exchange, and could possibly contribute to oil system failures.
Depending on what the failure was and how long the engine ran afterward, the damage can require a replacement eccentric shaft and full set of main/rotor bearings, all the way up to a basically 100% destroyed engine with no reusable components. On average, this is the most destructive mode of failure for this engine.
Also bear in mind that it is difficult to clean the oil pan once contaminated with bearing material, and also the oil cooler(s) and lines in the car will be contaminated with bearing material as well. It is a warranty requirement (and common sense) that the owner flush the oil cooler(s) and lines in the car prior to installing a rebuilt engine, otherwise metal shavings will be pumped right back into the rebuilt engine upon startup. Owners should budget the extra time and expense of cleaning the oil pan and flushing or replacing the oil coolers and lines as part of the rebuild job.
This is the last major, and least common “mode of failure” for rx8 engines. What they probably mean is that one chamber registers zero compression while the other shows relatively normal compression. This is when the apex seals (the major compression seals, similar to piston rings in a piston engine) wear down sufficiently that they shatter and fly around inside the combustion chamber. When this happens it damages all of the compression seals in that chamber as well as the rotor, rotor housing, and most likely both adjacent iron plate faces. Or, put another way, likely 4 of the 8 major components in your block have been destroyed. This will obviously add significant cost to the rebuild, as those components must be replaced, and each carries a used value of $200-400 or a new value or $500-700.
On average the original rx8 engines last to 80-100k miles. Some have issues before then at 60-70k. Some last longer to 120-140k. Most have problems in that range, though. Automatic models tend to fail at lower mileages because their owners never drive them hard enough at high rpm and carbon buildup causes internal seals to gum up and stick, further reducing compression. The same goes for babied manual models which do not get redlined daily. Much of the problem with this engine, as compared to earlier rotary engines, is that the chrome sealing surface on the rotor housings is thinner and tends to wear much faster, and also there is insufficient oil injection/lubrication for the apex seals so they wear out too soon. Finally mazda has recommended that owners run 5-20 or 5-30 motor oil in the engine which is actually insufficient and will cause main bearing and shaft wear.
First, used rotary engines are always a real crapshoot. Most of the ones you will find for the rx8 already have 50-80k miles on them and will be near the end of their life. Some may already have some of the issues you’re trying to resolve. The rx8 is a difficult remove/install job and it is likely that you’d be wasting time and money on another used engine unless you know it has good compression and fairly low mileage. Finally, rotary engines to not tolerate being left to sit for more than a few weeks or months without being started and revved up, or the seals will tend to stick and compression will be lost. In other words, a perfectly good engine can be ruined if it is not turned and started routinely. This is exactly what happens with junkyard engines, many sit untouched for months or years in the car or on a shelf until they are sold. What was a ‘good” engine when it was wrecked can be a weak or bad engine when you install it. Also most junkyards do not know about rotary engines and do not understand these facts. They will look at it as a “regular” car engine and they think that 80k is “low mileage” and so they will charge accordingly and expect real money for their unknown condition engine, usually around $1000-1500.
Second, there is not really such a thing as a “new” rotary engine. Mazda does not sell “new crate engines” like Chevy or Ford might. Despite what the parts counter man might tell you, they sell mazda remans which are remanufactured/rebuilt engines with a mix of new and used parts. IF these were in fact “all new” then why would mazda place a $1000 core charge on their purchase? They tear down previous recovered cores and reuse all major components possible, while replacing most seals….the same as most rebuilders would do. The difference is that they do not seem to be too particular in what components the reuse. They do not tend to give consideration to condition of the parts that go into one engine, so you might have two new components, two high mileage components, two mid mileage components, etc. all stacked together at random. There is of course the chance that you could get lucky and get a reman built with almost all new components (if the program was out of “reusable” used components at the time), but you have no way of knowing what you get or asking for one of the “good” ones. You just get whatever they send. They also tend to slather sealant all over everything, even in places that it should not necessarily be. This is a block with an oil pan, water pump, and flywheel, with all your old external accessories being transferred over from your original core, which you must then give back to them. Mazda retails these remans for $3300 plus $1000 core charge, not including fluids, remove/install labor, or other parts that your car may need. Dealers generally quote around $6000 installed for remans.
The only way that I’m aware of to get a truly “new” engine is to assemble one yourself out of all new parts purchased individually from mazda. You can use mazdatrix.com as a guide for the cost of internal parts, and pricing each seal, spring, and component for a rotary engine block, the cost would be around $5000-6000 for just the parts….not accounting for labor to assemble it and then install it. This is why no one builds “new” engines for this car like they might do for a mustang or Camaro.
So for many people who cannot find a “good” used engine or for those who want to restore the car to the best possible condition for their long term future ownership, a “private” rebuild with documented parts content is the best choice.
Those are difficult questions to answer, for a few reasons. One, the cars are not old enough to have worn out the original engine, had it replaced with a documented rebuild, and worn that one out too. Two, the engines that I (and most other private rebuilders) build usually go out the door and are never heard from again. It is human nature only to complain of a problem but not to commend a job well done, especially after a few months or years. Three, the cars are sold or wrecked more often than an average car, so one owner does not often keep them for the entire lifespan of one engine to know what that is.
A rebuild will never be as good as a new engine. The original engine was built with all brand new seals AND components, all with zero miles of wear and heat cycles. That engine made it 80-100k miles. A rebuild usually reuses all the major components, and simply replaces most wear seals/springs in those components. Those major components will still have 80-100k (or however many yours has) worth of mileage and wear. These major components usually cannot be repaired or restored to like-new or flat surfaces, so you must either accept their compromise of reuse as-is, or replace them with low mileage or new components at much greater expense. Due to the relatively low production numbers of this engine and the fact that mazda is the only manufacturer for it, the parts are extremely expensive, so most people balk at the cost of new parts, and choose to accept the compromise of reusing their original parts whenever possible. So we are placing new, perfectly flat compression seals against used, unflat sealing surfaces on the major components. This results in an engine that is not 100% of compression spec, but is better than the original in it’s deteriorated condition and can still offer several years of reliable service. My conservative estimate is that an average rebuild of such an original engine could last 50-70k miles before compression again drops too low to be reliable. Should the owner elect to replace the rotor housings (the primary sealing surface in the engine) with new ones, while reusing most other major components, you could expect to get the same mileage as (or possibly better than) the original engine, especially if you give the engine heightened maintenance and precautions to extend it’s life.
IF you want to make the engine as close to “like new” as possible, you will want to buy two very-low-mileage, or two new, rotor housings for use in your build
A: In order to compare different builds and options you basically have to have an exact list of what parts and services are going into each build. I post a list of standard parts and part brands that go into every build I do on my website and in an info document that I send via email with every inquiry. Most builders do not do that, at least not without being specifically asked, and sometimes not even then. If you know which new parts are being installed in a build then it is very easy to research the prices of those parts and do the math to decide how much labor a shop is making off of you on your build. Often you will find that shops advertise similar prices in order to be competitive but you will also find they are using more aftermarket/cheaper replacement parts/seals in the builds.
You also have to find out if the prices you are comparing include engine removal and install into your vehicle, a gasket kit for the installation of external accessories such as intake manifolds etc., and whether they are rebuilding *your* engine and giving it back to you or whether they are exchanging your original engine for one of their pre-built engines on the shelf and taking yours as a core exchange. All of these factors can affect price and so in order to form any kind of accurate comparison you NEED to have all of this information in front of you to figure out who is giving you the best value.
I do not usually have any pre-built engine blocks ready for outright sale or exchange. I stay very busy with existing customer jobs already brought to me, so it is usually not feasible to stop and pre-build a block for no-one in particular, and sit it on the shelf waiting for a buyer. That would also require that I obtain and purchase usable core components from which to assemble the block, which is not easy to do and places a larger burden on my strained schedule to search for and arrange shipment of these parts or core engines. If I have any pre-built engines on the shelf ready for sale, they will be posted in my ebay store at http://stores.ebay.com/rotaryresurrection
I suppose the true WCS would be if your core was totally destroyed inside and none of the 8 major components of the block were reusable. In that circumstance you would have no choice to rebuild, and would have to choose from these options:
Buy a used block to use as-is, or to use as a core to rebuild from.
Reassemble the damaged components of your block to use as a core to trade in for a mazda reman, and hope for the best.
Buy used replacement components individually from myself, other shops, or other sources on the internet and piece together a block.
Buy new replacement components individually from mazda (at great expense).
Very rarely would such a situation arise. Usually at least half of the existing core is reusable, if not most of it. You do not know what you have until you tear the core down and inspect it, however it is worth doing that rather than possibly abandoning several hundred dollars worth of reusable components as scrap because you do not want to fool with your original engine for whatever reason. You could at least tear it down and find out what is inside of it before making your decision.
The major concern with most rx8 engine rebuilds is the condition of the rotor housing chrome surface. This is the most important sealing surface in the engine, similar to a piston engine’s cylinder bore. Unlike a piston engine, this surface cannot usually be repaired or resurfaced adequately. Since all used housings will have some wear and other defects, some worse than others, it is always a compromise to reuse them, but this is done due to the high cost of replacements ($1500 for just those two parts, needed to build one engine). It is also difficult to find nice condition used replacements at the moment when you need them, so sometimes a choice between building a marginal engine with used worn housings, or spending an additional $1500 on new housings are the only available options.
Most builders including myself frown on "engines in a tupperware bin" that have already been disassembled. Usually the person that took it apart was not careful in doing so and may have lost or damaged small parts. Major components are also more suceptible to damage, rust etc. while apart in general. It places a burden on the builder to try and inventory what is present and what is not, find missing hardware and small parts, take extra time to inspect corners, edges, and faces of parts for handling/transport damage that would otherwise not have been a concern, etc. Also there are specific cleaning methods that work well on these parts, but differ from those you might use on engine parts for a piston engine. Often DIY cleaning attempts can actually damage or destroy rotary engine internals.
The bottom line is that I strongly recommend you do not tear down or attempt to clean your own engine if you expect me to work on it afterward. I may not necessarily refuse to take on such a job, but you should not expect any discount on my price if you do send it to me, and in fact you should be prepared for the possibility that you might have to pay a bit extra for additional parts or labor if some of your parts have been lost or damaged.
The ignition coils on these cars are very weak and should be considered a maintenance item replaced every 50k miles or less. If your car has original coils (or if you have no documentation of them being replaced recently) you definitely need to consider replacing them. This is especially true because dead coils can cause some cars to be diagnosed with bad engines that may not actually be dead.
There are aftermarket equivalents available at chain parts stores. These should work okay but are probably lower quality than the OEM mazda coils (which are themselves not very good obviously). It could still be worth using those if you get a good warranty with them. Mazda retails a set of 4) coils for around $250. Sometimes you will see “genuine mazda” coils being sold on the internet for much lower prices. Beware, these could be Chinese knockoffs which come in packaging that looks original, there is a discussion about this on rx8club.com. The best option is to get the coils through a legitimate mazda parts supplier or dealership. Finally, the end-all repair for the weak coil issue is to convert to GM LS2/truck coils which are often sold as a performance ignition conversion kit for around $450-500. These coils are better in both performance and longevity by a great deal, and they would probably outlast your car.
Another concern is the catalytic converter/midpipe in the exhaust. This is an emissions part. The cat tends to clog up or break at mileages over 100k, so it should always be checked while the engine is out. If it is found to be partially clogged or otherwise broken or damaged, it should either be gutted out or replaced with a new cat (very expensive). A clogged cat can cause engine damage due to excess backpressure and heat generated.
At this point both the radiator and the plastic coolant tank/reservoir are liabilities since both will rot and can leak coolant or burst and cost you an engine (be it an old engine or a new one). You also need to ensure the lower plastic undertray between the bottom edge of the bumper cover and the engine subframe is in place, which directs airflow through the radiator and is an important cooling system component.
Also the motor mounts on this car are sometimes an issue. Their purpose is to isolate engine vibration and stop from passing it into the chassis and interior where it can be felt and heard. With age and mileage, the rubber mounts harden and begin to pass the vibration into the car. IF you feel vibration or hear rattling at idle and want to resolve that issue you’ll want to replace your motor mounts. Sometimes they will even crack and break, and should be replaced then.
Obviously standard maintenance items like belts, hoses, clutch kit, etc. can be considered. Generally the water pump and thermostat hold up well on these engines are not a normal source of issues.
Also see the info below about the upgraded starter.
The coolant bottle has a level sensor in it that is bad. You must replace the entire bottle with a new one if you want to fix the issue and have it work normally with the protection of the light to alert you to a low coolant level. IF you want to take the easy way, you can simply unplug the sensor at the bottle and the light will never come on.
04-mid 05 manual models had an 11 tooth ‘slow” starter originally equipped. This worked fine when the engine was new and perfectly strong, but when it is internally worn and has weaker compression, the starter does not spin it sufficiently fast to start.
Some mid 05 and all 06 through 08 models got an upgraded 13 tooth “fast” starter that spins the engine faster during cranking and helps it start. This is the one that you want. Mazda also put out a TSB for the early models which were having issues, that the later upgraded starter could help. It is a direct swap for the original starter. The only way to be sure is to count the starter gear teeth. In most cases a starter that has a part number stick beginning with N3H1 will be the 11 tooth “slow” starter. The 13 tooth upgrade has a part number beginning with N3Z1. However there may also be late model factory 13 tooth starters with an N3H1 part number…so the number of teeth need to be verified. 09-11 models got an even faster 14 tooth starter that will work on the 04-08 manual models and is superior to the 13 tooth version.
A lot of these thoughts stem from the fact that I myself am also a builder who deals with customers, their budgets and expectations often, and I see some of the issues being brought to light here that I wish more owners/customers were educated about. The customer feels like the builder should have complete responsibility for every aspect of the build, yet there are some aspects that are not under the direct control of the builder. In reality the customer should share some of the responsibility for choosing what type of build and parts go into the engine based on some of the knowledge below, but unfortunately most buyers are not aware of any of these facts. They simply say "I bought a new engine and darnit, that thing should run better than it does. _____ builder sucks!" but in reality there is more to it than that.
First off...any rebuild from any shop in the $3000 or under price range WILL NOT have new rotor housings. That means it WILL have used rotor housings. Now as anyone who has ever tried to rebuild a renesis knows, used rotor housings are condition dependent and are also hard to find in any reusable condition, much less in great condition. All used housings will have some wear; some more than others, some in different areas, with different effects on compression and longevity. Think of used housings like used tires. There are a few defects that make a housing completely unusable, then there are new housings that are perfect, then there is a WIDE area in between of usable housings that are a judgement call as to whether or not they are suitable for a certain build, project, or owner. Finally, reusing rotor housings is ALWAYS a compromise in compression, longevity, and build quality, no matter who the builder is.
So with that said. If you bought a budget rebuilt block then I don't see how you can sit there and say you are expecting compression values anywhere approaching what would be in the dealer book for a new engine. Any educated builder or enthusiast will tell you that's simply not going to happen with a used housing build. And for $2100, how nice do you think the used housings in that build are going to be? Assuming you can get the builder to supply you with an accurate list of what new seals etc. go into the build, anyone can do simple math and add up the prices of all those seals...usually around $800-1000 depending on the builder and what brand of parts they are buying...and also start adding up the used cost/value of components to build that block from such as rotors, housings, irons, etc. and then add at least 400 bucks for the builder's labor. IF you do all of that you can quickly get an idea of the condition of the used components being put into the build. No one is going to work for free and so you have to do the math and see where the money is going and where it's being saved. So in this case we have to figure out that the builder is building with used housings with a very low value, and for that to be the case consistently that means the builder is using worn housings that are near the bottom of their service life. Once you arrive at that conclusion, it would be foolhardy to expect such an engine build to last anywhere near as long as the original nor to perform anywhere near what the original did in terms of passing/failing compression tests.
Now the non-engine-builders among you out there are going to read that and say "oh well if you can't pass the dealer compression test with the used housings being put into that build then they should never be used to begin with. a builder should only build an engine he knows will pass the dealer tests and be like it was when it was new in 2003". Okay, fine, who wants to line up to build all-new-parts blocks for 6 grand or more? Because that is the only way that's going to happen for you. Oh, I bet now some of you are backing off of that statement.
Yes reusing rotor housings is always a compromise but it's necessary for budget reasons. Not many owners are going to spend more than $4k for a rebuild with new rotor housings, which is really what's necessary if you expect to get anywhere near the original engine's lifespan or compression values. The whole car is not worth more than 4 or 5 grand so who wants to put that much into just the engine? Not many owners. So you have to figure out how to cut costs while still getting a decent result. The bottom line is the lower the cost, the more parts with wear on them that you have to reuse, and the weaker the result in terms of compression and longevity.
For the builder, the real skill lies in figuring out how far you can approach the borderline of worn parts reused for budget vs compression quality and longevity going forward for the owner. Every builder will have their own mindset here based on their customer base and their own experiences. For me I tend to err a little bit more on the side of caution and only reuse middle of the road parts that will provide at least 25k miles of normal use going forward. However that still doesnt mean that every used housing engine I build would pass a dealer compression test. In fact I've had to explain this concept a few times to customers of mine who equated a $2500 rebuild with a "new engine" and then were surprised their engine didnt have new compression numbers. I don't care if felix wankel himself stacks your block, if you don't give him all new or perfectly resurfaced components to do it with, you're not going to see strong compression values that pass dealer tests.
In my experience most rebuilds utilizing used rotor housings, used irons, etc. and mostly new oem compression seals/springs, will see 90-105psi of compression with an accurate test after break in, with the variation depending on the specific condition of the rotor housing surfaces used in that particular build. In fact a couple years ago I had a customer bring me an all original, well maintained rx8 with 72k miles for rebuild. The housings looked nice with light wear and were in above average condition. The iron housings had very light wear well within spec. All new oem rotor compression seals and springs were used in the rebuild. I recently did a comp test on that engine after 10k miles of break in and driving. The engine shows about 96psi on the front and 91psi in the rear. It starts cold or hot on the first 2 rotations, idles perfectly, makes good power, and runs like it should with no issues. On a dealer test those compression numbers are failing, a "bad engine" in their view. Does that mean the engine is bad? Heck no. In reality a used rotor housing rebuild isn't ever going to get a whole lot better than that.
IF you want more, you have to use new rotor housings in the rebuild. Right off the bat, a pair of new rotor housings is over $1400 even at most builders' cost. And you still have to pay for all the other seals and parts needed for a build, and the builder's labor. I would expect most new rotor housing rebuilds that utilize reused iron housings with mild/normal wear, to produce in the 105-115psi compression range. This is considered a middle of the road, acceptable but not great passing compression value but still not what the specs say a new hiroshima-assembled rotary from 2003 would have made. Finally, an engine built from new rotor housings, new or resurfaced iron housings with zero wear, and all new rotor compression seals, I would expect to see 115-125psi of compression. I have done a couple such builds and that is what they produced when tested.
Now, let's broach the subject of aftermarket apex seals. The bottom line is that in my experience aftermarket seals have nowhere near the long term longevity or sealing compression of oem apex seals. So you might ask, why do people make them and use them? Well one obvious answer is budget, a lot of these seals are half the cost of oem.
The other answer has a bit more psychology involved. Let's say your rotary engine blows up and you say "oh the apex seals failed. I don't think the apex seals should ever wear out or fail, so there must be something wrong with the stock seal design. there should be a better apex seal! let's make one". So you and your machinist select a random metal to design your seal out of. You size a few to fit the rotors and build a couple of test engines, which you run on the street and/or on the track for a few months or maybe a year or two. You take the test engine(s) apart and if those seals didn't catastrophically fail, you say "well dang man, my seals look like they work good, I'm gonna start selling them to other people. Down with stock apex seals!". That's essentially what happens with all these aftermarket seals. They get minimal testing and R&D before being released to market for you to be the long-term tester. They were produced based on the fallacy that because oem apex seals wear out or fail after 100k miles of use, those oem seals must be of poor design and should be replaced with something better. Yet in reality, the aftermarket seals rarely reach HALF of the lifespan of the oem seals before those engines fail or have to come apart for some reason. This is because they were only designed and tested in the short term. Sometimes they were only designed and tested for the race track under very specific circumstances which don't work out well in the long term on a street engine that needs good hot starting, idle, low rpm throttle response, and cranking compression. Maybe they are built to hold up to 28psi of boost and 10,000rpm of abuse on the track, but in order to do that, their material hardness properties had to be changed and now the rotor housing sealing surface that it rides against will get worn out much sooner than if stock seals were riding against the housing surface. Bear in mind that the seal and the housing surface were both designed to wear together, and when you drastically change the material properties of one, you will also upset that balance and change the longevity of the other. Mazda put decades and millions of dollars of R&D into designing their apex seals for maximum compression and longevity in stock form. Do you really think a random shop with one or a handful of dudes working on the project for a few grand investment are going to be able to improve on that tech? It's possible but unlikely.
This is further compounded by the fact that the average owner sees "racing seals" and decides they are going to be better suited for his naturally aspirated street driven rotary, even though in reality those seals are likely to perform worse in his engine than stock ones would have because he isn't using his engine for the specific "racing" that the aftermarket seal was developed for.
So looking again at the big picture, aftermarket seals were used in this build as a budget lowering tool and so it is not surprising that they a) don't make oem compression and b) don't last as long as oem. Now, again, you might look at this and say "well if the builder knows that ____ aftermarket seal won't last 100k miles like stock, then they shouldn't be building with that seal at all". Okay, well that means they will have to raise the price. And by the time you do everything you should do to produce an engine capable of lasting about as long as the original and making about as good of compression values that would pass a dealer test, guess what? Now your build is priced so high that nobody will buy it. As a builder you have to strike a balance and compromise between quality and budget.
In this case it looks like this builder fell a little short of that line, and maybe should have done better both with the initial build/parts selection and/or the warranty evaluation. But that also doesnt mean that I will side completely with the buyer here either, because as you can see above there are many considerations that the buyer should take into account going into the rebuild and with their expectations vs budget, and that doesn't seem to have happened here either.
YOU CAN NOT EXPECT A 2 OR 3 THOUSAND DOLLAR ROTARY REBUILD TO BE ANYWHERE LIKE NEW.