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Please, don't kill me immediately, but read to the end.
I just openend my engine for a rebuild. When I bought the car 5 months ago, I got a receipt for a rebuild 5000 miles ago in the UK. The compression results where low (58 to 80 psi) so I decided to open it up. By the way, I can't recommend rebuilds by SVA Imports..
What I found was at least one much to short side seal (minimum of 1mm play, maybe even more), busted bearings (rear rotor and main bearing, see https://www.rx7club.com/3rd-generati...heavy-1099266/) and not perfect rotor housings. I say not perfect, because its my first rotary and I have no clue whats good and whats not. If you need it, I will upload detailed pictures of the housings. What I can say is, that there are grooves in rotor turning direction, but not noticeable with the fingernails, only slightly with the finger. To my eye and feel, they are acceptebale at least.
The apex seals. They look not really good, but the meassurements look not bad at all:
- height of the seals from 7.685mm to 7.795mm (Standard or new is 8mm, minimum is 6.5mm)
- clearance between seals and rotor around 0.09mm, lowest is 0.08mm, highest 0.10mm. Maximum is 0.15mm, standard between 0.051mm and 0.101mm.
I will say at this point, that I'm on a budget. Thats mainly because I lost my job a few days ago, secondly because I don't like to spend money thats not absolutely necessary. That said, I don't want to blow the engine after 2000 miles either. My short goal is to run the engine on the track with around 300hp at max for the next few months or longer on stock twins, and maybe get a spare engine to rebuild slowly and with time for going single turbo and 350-400hp. If its absolutely necessary to get new apex seals, I will do it.
Here are the pictures of the apex seals:
*somethings not working with the upload, keeps telling me the image must not exeed 10MB, but its only 7.8MB. Tell me if you need the pictures compellent, I will try to upload them otherwise if needed.*
The car ran pretty good. Idle was a little rough and vacuum was a little low (around -6psi when idling), other than that there were no problems and the car was running strong.
I used a self made compression tester (Removed the valve from a standard tester and filmed the needle with low speed).
The side seals were all pretty bad, not the right angle, to short and so on. I will meassure the clearances today.
I would absolutely NOT reuse the apex seals. Loose side seal clearancing will definitely affect compression. Mazda spec is .0020-.0059" or .05-.15mm. 1mm is HUGE! You are over 7 times the max clearance. I clearance most motors to .0020". For really high hp .0030-.0040". I would check the ENTIRE build. It should also be made public who did this kind of work so others don't have the same experience.
I don't entirely understand your post. When I said 1mm or more I meant one sideseal had that clearance. Of course they will all NOT be reused. And as I said, the rebuild was done by SVA Imports in the UK.
Your engine is open and in pieces. Do not use ANY old seals. Entirely not worth it. If you are wanting something that you don't have to cross your fingers every time you turn the key, then replace the seals. Just.......replace the seals.
And before te next guy comments let me just speak for him too.......replace the seals.
I don't entirely understand your post. When I said 1mm or more I meant one sideseal had that clearance. Of course they will all NOT be reused. And as I said, the rebuild was done by SVA Imports in the UK.
According to the FSM, the apex seals are in spec.
I was stating what the side seal clearancing should be. Even 1 side seal at 1mm clearance will cause problems. I personally would not reuse any seals, even if they measure in spec. Can't account for heat cycling and other damage from a poor build. Springs too.
Used apex seals that are within spec should not be a problem. Of course it would advise against anything on the lower end of that spectrum. Sure new would be better. But let's face it rebuilds can be expensive especially with all new hard and soft seals. And if you're on a budget there is nothing wrong with reusing parts that are still with in spec. All Mazda rebuild are set around the user reusing seals which is why they set a strict criteria to determine whether a part is still usable. I for one personally do not reuse seals in my rebuilds but did for a client a couple years back that was on a very low budget I used nothing but used parts in his build (no warranty obviously) all within spec. Zero problems. And he does zero maintenance. I honestly don't know how the engine is still alive.
Used apex seals that are within spec should not be a problem. Of course it would advise against anything on the lower end of that spectrum. Sure new would be better. But let's face it rebuilds can be expensive especially with all new hard and soft seals. And if you're on a budget there is nothing wrong with reusing parts that are still with in spec. All Mazda rebuild are set around the user reusing seals which is why they set a strict criteria to determine whether a part is still usable. I for one personally do not reuse seals in my rebuilds but did for a client a couple years back that was on a very low budget I used nothing but used parts in his build (no warranty obviously) all within spec. Zero problems. And he does zero maintenance. I honestly don't know how the engine is still alive.
He must be cheating.......crossing toes and fingers.
Lmao..... Must be I wouldn't be surprised if he's riding around with 2qts of oil in the pan. He's one of them self admitting keys in the ignition gas in the tank types. And gas in the tank only on E.
just my 2 cents. i opened my motor while it was still running well not a single problem but could not trust the odometer reading. my apex seals where fine and still had plenty life in them, i still used new seals because why not pt brand new in. peace of mind
like stated above dont reuse the apex seals apex seals even if you are on a budget do some research and decide which seals are best for your application . and good luck
imo its ok to reuse hard seals if they are in spec, at a minimum always replace the soft seals. my current engine blew a coolant seal last december.. tore it down, replaced only the soft seals, didnt clean ****, bolted it back together and its been running like a top ever since
imo its ok to reuse hard seals if they are in spec, at a minimum always replace the soft seals. my current engine blew a coolant seal last december.. tore it down, replaced only the soft seals, didnt clean ****, bolted it back together and its been running like a top ever since
Exactly. It's more important to put the money in places where it's really needed (cleaning the fuel injectors to prevent lean conditions is an example). If those apex seals aren't bowed, I would put them right back in since there well within spec. Fact is most aftermarket apex seals should last 50,000 miles. That engine has 5k. You do the math. Just because you opened that engine doesn't mean the apex seals are gonna take a **** after reassembly. If they go, something else caused them to fail.
Exactly. It's more important to put the money in places where it's really needed (cleaning the fuel injectors to prevent lean conditions is an example). If those apex seals aren't bowed, I would put them right back in since there well within spec. Fact is most aftermarket apex seals should last 50,000 miles. That engine has 5k. You do the math. Just because you opened that engine doesn't mean the apex seals are gonna take a **** after reassembly. If they go, something else caused them to fail.
Definitely a good point on the injectors. He opened a motor up that had 5k miles on it. He got really low compression numbers. Replace those seals. Within spec or not, you will always doubt yourself when you drive it. I know I would. I'm all about putting money where it counts, but if I have an engine torn down I'm replacing seals. Maybe part of it is because I don't trust myself to know all the things to check for when going through one of these motors. If you are not confident, which you aren't because you are asking people on the forum, then replace them.
I have the clearance of the side seals on the front rotor now:
0,20mm - 0,40mm - 0,18mm on the stationary gear side
0,07mm - 0,075mm - 0,22mm on the other side
They might be on the spec side (Max. is 0,40mm), but just looking at some of them tells me they are definitley part of my compression problem at least.
If you're going to to all the work to rebuild the engine, I would strongly recommend replacing all the seals. That is, unless you know for certain that the engine was recently rebuilt. At the very least you should replace the springs.
OTOH, simply cleaning everything and replacing whatever is out of spec might be enough... but you don't want to have to pull the engine again, do you?
those seals are not Mazda seals. Mazda has the triangular corner piece closer to the edge to minimize gas leakage.
if that was my engine i'd bin those seals for the following reasons.
1. if they aren't Mazda, what are they? this is the last place you want mystery.
2. you plan on running track days. you're going to be harder on the seals than if it was a street car.. and you know this now, when it is apart.
if you do decide to reuse those, you need to check the end clearances, as those seals leak more than the OE seals when they adjust for length
you also need to check the bow on them as well, the seal wear surfaces are not flat.
Who says he can't find another job within a week or two? No need to **** on the guys future plans just because he's down and out right atm.
Well I tend err on the side of caution as I wouldn't even consider spending money on a hobby unless I was employed. Because like most people if I ran out of money before I becamee gainfully employed, the first to go would be the toys. I really wouldn't like that.
And it is not kicking a guy while he is down, unemployment is a temporary situation. Sometimes we all need to be told that the path we are currently on may not be the best one.
To the O.P.:
I firmly believe in doing it right and doing it once. I would agree to just buy new seals as you plan to track the car in the near future.
I meassured the clearances of the side seals on the other rotor (rear) today:
0,40 - 0,05 - 0,55 on the stationary gear side
0,45 - 0,35 - 0,15 on the other side
I'm pretty sure now, that the side seal clearances are the reason for the low compression. I'm not too sure, if I really want to reuse the apex seals though.
Here are some pictures of the housings:
Front rotor housing:
Rear rotor housing:
I think, they look not too good, and in the pictures its worse than in reality. BUT when I go over the surfaces with my fingernails, I feel nearly no grooves at all. With the fingertip you can tell its not supersmooth.
Is there a way to meassure this?
There is one thing I haven't mentioned yet that makes me think I have to use the old apex seals: All Apex seals have a small bulge that sticks out on the outer edge of the long piece. I can't tell if that comes from a groove in the housings that was already there, so that there is no wear and the seal has its original size there or if it is a kind of damage. Either way, there has to be a groove in the housing NOW, so if I use new seals on the worn housings, I would say there has to be a gap between the flat seal and the groove in the housing, so compression would be lost.
Oh, and one more, pretty important, question if I reuse the apex seals: How do I make 1 piece seals out of these 2 piece seals for installation? Glue? Which one?
04-21-16, 05:08 PM
