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Index > @ the Pickup Bed (General Topics) > Thread: think i coughed up an apex seal on my REPU
Thread: think i coughed up an apex seal on my REPU [' This thread is 2 pages long: (1) 2 ']
Elysian


Revvin Up
Posts: 60
posted February 29, 2004 12:28 PM

think i coughed up an apex seal on my REPU

i went to pass someone who was going slow on the highway, dropped it down a gear... clank... pop pop pop out the exhaust... the truck feels like its running on half power now... i'm going to be pulling the motor out soon and tearing it down, i have a set of seals i can throw in, and get gasket set from atkins, and replace any seals that need it... we'll see when i get it apart i guess...

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Elysian


Revvin Up
Posts: 60
posted February 29, 2004 03:56 PM

its official, its the rear rotor, almost no compression

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Klaus43


Rotorhead
Posts: 1259
posted February 29, 2004 04:44 PM

Harsh!

Of course, now we're all curious just how bad it wasted your housing, etc. ... and why.

       
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Jeff20B


Moderator
Posts: 661
posted February 29, 2004 05:38 PM

Ouch! At least REPUs are super-easy to work on. I can pull an engine from mine rather quickly. I also once spent 5 minutes and lowered the engine into its home and had all the bolts finger tight in the tranny and front cover motor mount plate thing.

Have fun. I know I always do. :)

Oh, before I forget, let us know if it's a genuine R5 13B. If so, you've got a very cool engine in there. Don't spend more than $150-200 on a gasket set and soft seals (Mazdatrix gasket set that I use http://www.mazdatrix.com/getprice.asp?partnum=99-100D-3565). GSL-SE rotor housings would be a great upgrade too if you do need new housings (kinda spendy though). Heh I'm still using some old rotor housings that are missing a little chrome in mine. One was reusable and the other was questionable. We towed Tom's rotary powered baja yesterday with the not-fully-broken-in-yet engine, and it did as well as I was expecting (with streetports and low RPM so you can guess how it did). Actually, the engine overheated right after it got broken-in the first time, and all I changed were the rotor housings, so only the apex seals needed breaking in to the other set of housings. Yeah, it did pretty well.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Elysian


Revvin Up
Posts: 60
posted February 29, 2004 08:29 PM

thx for the link jeff, i'm going to have to talk to the guys at work this week to see about getting the time to do this... i plan on having this truck running again by the end of the week if all goes well...

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Elysian


Revvin Up
Posts: 60
posted February 29, 2004 08:31 PM

now will that gasket set work on my 13B? it says for a 74-75 REPU, but my motor is definately not 74-75

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Jeff20B


Moderator
Posts: 661
posted March 01, 2004 12:27 AM
Edited By: Jeff20B on 1 Mar 2004 00:39

It's what I got for my '81-'83 Jspec 13B. It has the same rotor housings as yours (three aluminum things around the spark plugs), and the intake ports are the same. We have the same engines. It should work for you as well as it worked for me. Of course you can get a second opinion before you spend any money.

Here is a pic. The one on the left ought to look familer.


____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Elysian


Revvin Up
Posts: 60
posted March 01, 2004 05:45 AM

mine doesn't say rick on it;)

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Jeff20B


Moderator
Posts: 661
posted March 01, 2004 08:42 AM

LOL yeah, he used to own the white REPU. :)
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Elysian


Revvin Up
Posts: 60
posted March 01, 2004 08:53 AM

jeff if i need a new rear housing u wouldn't have any i could buy would u? i'm planning on getting the motor pulled out tomorrow and hopefully apart wednesday, ordered the gasket set today, got it shipped 3 day air

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Elysian


Revvin Up
Posts: 60
posted March 01, 2004 09:03 AM

btw jeff check ur pm's on the club

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Jeff20B


Moderator
Posts: 661
posted March 01, 2004 11:03 AM

I have one '76 rotor housing that is missing a lot of chrome. I was going to use it on my single rotor 13B project. My other JDM ones (with Rick on them) are overheated and had no bevel in the exhaust port which caused apex seal bouncing (Rick ported them heh). The bevel could easily be performed, but the crushing damage has already been done.

Ken might have a set of rotor housings. I'm not sure if you'd want to buy them from him though.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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dhood


Hauling
Posts: 134
posted March 01, 2004 07:34 PM

Curious how you measured the compression. Since my 77 went lame like one rotor not working, I tried to measure the compression with a std gauge and but can't tell for sure how to read it.

       
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Elysian


Revvin Up
Posts: 60
posted March 01, 2004 08:05 PM

quote:
Curious how you measured the compression. Since my 77 went lame like one rotor not working, I tried to measure the compression with a std gauge and but can't tell for sure how to read it.


the standard hand near the plug holes test... easy to tell which rotor is good and bad if its apex seals... if its a side seal u'd hear uneven pulses on one rotor(found that one out when my mechanic checked out my 88 TII)

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Jeff20B


Moderator
Posts: 661
posted March 02, 2004 12:11 PM

You could remove the Schrader valve? Sorry, that's all I know since I've always just listened for uneven pulses.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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admin


Administrator
Posts: 446
posted March 02, 2004 12:16 PM


This is from:
http://www.rx7turboturbo.com/robrobinette/compression.htm


A compression test will give you a good idea of the health of your engine. It will indicate whether you have a broken apex seal or a blown side seal.

I just figured for $20 for my pressure tester, I got what I paid for. :) It really wasn’t meant to be an accurate compression tester. Remove the schrader valve from the compression gauge. That’s what holds the pressure reading. You can also just hold the relief valve down during the test so you can watch the needle bounce for each rotor face.
Procedure for a 3rd gen is (page C-11 RX-7 Workshop Manual:

1. Warm up engine to operating temperature, then allow it to cool for 10 minutes while you get the plugs out.

2. Remove the front and rear trailing (upper) spark plugs while the engine cools.

3. Disconnect the circuit opening relay, and the igniter connector. The CAS and EGI fuse are both unplugged so that no gas nor spark will occur during the test.

4. With both spark plugs out, fully depress the accelerator pedal to the floor, and motor the engine for 5-10 seconds. You should watch for 3 bounces of the needle (once for each rotor face). Specifications vary depending on the brand of shop manual. I’ve gone by 7.0 kgf/cm2 or 100 psi minimum @ 250 rpm as stated in my 93 RX-7 Workshop Manual. Other references say 6.0 kgf/cm2. Yes, you can compensate for higher cranking rpm during the test. There's a chart in the Workshop Manual.
More On Compression Tests

Several earlier posts have referred to a compression test for the rotary engine. Is this test conducted pretty much same as on a piston engine car? Which spark plug hole to use? or does it make any difference?

You can use the top spark plug hole (easiest to get to and there is no difference between top of bottom values). You need a special rotary compression tester allowing you to measure the difference between the 3 rotors. The test should be done on a warm engine and you should get above 200 rpm from the starter motor. (you should remove a spark plug from the second rotor to reach the 200 rpm (no counter-pressure). You have to floor the throttle while testing and don’t forget to disconnect the ignition (I had cars starting to run on one rotor while testing :-)) Cold compression tests mean NOTHING. I have seen differences of 5 Kg between hot and cold. If you don’t have a special rotary tester available, some hints:

You can use a normal tester but you will not see the difference between the chambers. I have never tried this and some guys are not very confident in this method [I've tried it and it works ok], Mazdatrix e.g. says you can as well hold a finger on the spark plug to measure compression with a piston tester.

I know of some others that have drilled a small hole through a normal spark plug. They turn this in and listen to the whistle. The higher sound you get the better. You can also hear the difference in the chambers. (peep peep - whoosh is no good)

What compression would generally indicate a healthy engine, or weak one needing rebuild? Any other diagnosis tips would be appreciated.

All compression above 7 kgf/cm2, 100 psi is good (no rebuild needed). Anything below 5.5 is likely to break down when driving the car home. You should not see differences of more than 1 kg between chambers and 1.5 between rotors for a good engine. Unless it has been partially rebuilt, where you can have strange values like 9 front and 6 rear.


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rotarydave


Hauling
Posts: 108
posted March 02, 2004 05:13 PM

be careful when replacing that damaged rotor housing not all the housings have the spark plugs in the same exact place and i know that many of the J-spec parts are different than the US ones, the engine kit should work with no problems however check your intake manifold and the gasket from the kit, I can not remember which years/motors had and did not have them but some did not have a heat riser on the center cast iron and some did, i made a huge mistake by doing an engine job and not paying attention until i fired it up the first time, believe me it got my attention quick. the advice given on the GSL-SE housings is very sound they are a great housing i use them in all of my 13b 4 port rebuilds, yes it adds $$ to the project but will cost less in the long run with longevity. One thing i do know you can not mix and match the 74 housings with any other housings the timing is very different.

Last and not least if you use NEW apex seals stay away from the cheap seals from Rotaryaviation esp if using USED housings. They are too hard and do not seem to seat right also they seem to be scraping away the chrome plating. This is coming from some of my Drag Racing buddies.

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Elysian


Revvin Up
Posts: 60
posted March 02, 2004 06:20 PM

quote:
be careful when replacing that damaged rotor housing not all the housings have the spark plugs in the same exact place and i know that many of the J-spec parts are different than the US ones, the engine kit should work with no problems however check your intake manifold and the gasket from the kit, I can not remember which years/motors had and did not have them but some did not have a heat riser on the center cast iron and some did, i made a huge mistake by doing an engine job and not paying attention until i fired it up the first time, believe me it got my attention quick. the advice given on the GSL-SE housings is very sound they are a great housing i use them in all of my 13b 4 port rebuilds, yes it adds $$ to the project but will cost less in the long run with longevity. One thing i do know you can not mix and match the 74 housings with any other housings the timing is very different.

Last and not least if you use NEW apex seals stay away from the cheap seals from Rotaryaviation esp if using USED housings. They are too hard and do not seem to seat right also they seem to be scraping away the chrome plating. This is coming from some of my Drag Racing buddies.


atkins might have the housing i need, if i were to replace it with one of the same type... so i might be getting the 76-78 jdm housing from them... we'll find out... if i'm lucky i don't need it, but thats incredibly lucky if i don't lol

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rotarydave


Hauling
Posts: 108
posted March 02, 2004 08:33 PM

r u in wa? i am working 4 them

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Jeff20B


Moderator
Posts: 661
posted March 02, 2004 10:04 PM

Are you Dave G?
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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