Don't let a cracked rear iron get you down! How to change one without a rebuild! *pic
actually there's absolutely nothing wrong with it, if you say have an engine with less than 1000 miles on it and break a rear iron on the dyno, why tear it 100% back apart if you don't have to?
if it was a 100k mile motor, yes that is a hack as it should be resealed. but not in all cases are the seals due for replacement or carbon needing to be removed. this particular example, probably the latter but it is a "lemons car" after all and saving money is the game.
if it was a 100k mile motor, yes that is a hack as it should be resealed. but not in all cases are the seals due for replacement or carbon needing to be removed. this particular example, probably the latter but it is a "lemons car" after all and saving money is the game.
Last edited by RotaryEvolution; Aug 16, 2012 at 10:54 AM.
actually there's absolutely nothing wrong with it, if you say have an engine with less than 1000 miles on it and break a rear iron on the dyno, why tear it 100% back apart if you don't have to?
Well, maybe... but probably not.
I recently took my engine apart because it was seeping oil from the rear dowel area the last four races.
I naively thought it was a seeping o-ring because I had re-used some thinner than stock viton ones over and over the last 10 years or so and the engine was running fine.
It was a hairline crack at the rear upper dowel land.
3 cracked 3mm Mazda seals (rear), 2 cracked corner seals (rear), 3 slightly flattened apex seal springs (rear), 6 over clearanced sideseals (rear) and all 6 apex seals worn in the middle sides from the spark plug area of the housings expanding from the extreme heat of detonation which also gave me sparkplug hole cracks on both housings.
Engine ran fine and luckily everything had held together through some racing.
It takes some detonation to crack a rear iron (especially S5+) and that detonation is LIKELY to have affected other engine internals.
Well, maybe... but probably not.
I recently took my engine apart because it was seeping oil from the rear dowel area the last four races.
I naively thought it was a seeping o-ring because I had re-used some thinner than stock viton ones over and over the last 10 years or so and the engine was running fine.
It was a hairline crack at the rear upper dowel land.
3 cracked 3mm Mazda seals (rear), 2 cracked corner seals (rear), 3 slightly flattened apex seal springs (rear), 6 over clearanced sideseals (rear) and all 6 apex seals worn in the middle sides from the spark plug area of the housings expanding from the extreme heat of detonation which also gave me sparkplug hole cracks on both housings.
Engine ran fine and luckily everything had held together through some racing.
It takes some detonation to crack a rear iron (especially S5+) and that detonation is LIKELY to have affected other engine internals.
actually there's absolutely nothing wrong with it, if you say have an engine with less than 1000 miles on it and break a rear iron on the dyno, why tear it 100% back apart if you don't have to?
Well, maybe... but probably not.
I recently took my engine apart because it was seeping oil from the rear dowel area the last four races.
I naively thought it was a seeping o-ring because I had re-used some thinner than stock viton ones over and over the last 10 years or so and the engine was running fine.
It was a hairline crack at the rear upper dowel land.
3 cracked 3mm Mazda seals (rear), 2 cracked corner seals (rear), 3 slightly flattened apex seal springs (rear), 6 over clearanced sideseals (rear) and all 6 apex seals worn in the middle sides from the spark plug area of the housings expanding from the extreme heat of detonation which also gave me sparkplug hole cracks on both housings.
Engine ran fine and luckily everything had held together through some racing.
It takes some detonation to crack a rear iron (especially S5+) and that detonation is LIKELY to have affected other engine internals.
Well, maybe... but probably not.
I recently took my engine apart because it was seeping oil from the rear dowel area the last four races.
I naively thought it was a seeping o-ring because I had re-used some thinner than stock viton ones over and over the last 10 years or so and the engine was running fine.
It was a hairline crack at the rear upper dowel land.
3 cracked 3mm Mazda seals (rear), 2 cracked corner seals (rear), 3 slightly flattened apex seal springs (rear), 6 over clearanced sideseals (rear) and all 6 apex seals worn in the middle sides from the spark plug area of the housings expanding from the extreme heat of detonation which also gave me sparkplug hole cracks on both housings.
Engine ran fine and luckily everything had held together through some racing.
It takes some detonation to crack a rear iron (especially S5+) and that detonation is LIKELY to have affected other engine internals.
Race is this weekend so we'll post an update after 24 hours of hammering.
The turbo blew so we tore off the Intercooler and ran N/A while piecing together a replacement turbo.... we used my sock as an air filter. After this pic was taken we relocated the sock so that it wasn't secured to the 90* coupling; it was clamped directly to the throttle body. Worked great! No melting!
Interesting car. What makes the rear IRON Crack like that?
Is that a MR Fusion on the back? And why all the extra parts that dont really help with aerodynamics?
Is that a MR Fusion on the back? And why all the extra parts that dont really help with aerodynamics?
Last edited by rx7_FREAKKK; Sep 8, 2012 at 09:12 PM.
Junior Member
Joined: Nov 2008
Posts: 18
Likes: 2
From: Virginia Beach,VA
OK so our car was leaking oil out of the crack between the rear iron and rear housing. We figured that it was either a blown dowel o ring or cracked iron.
We only had one race on this motor and didn't want to rebuild it... luckily our lemon's team is nothing but geniuses. We wanted to share or success!
The first thing you're going to need to do is visit my favorite RX-7 parts store, the home depot. You'll need to get a few large turnbuckels (don't worry about the price you can return these when you're done).
If you've already used up all your bailing wire to hold your exhaust up, you're going to need some of that too. I think we had 14ga.
Remove the motor, don't bother taking anything off the front of it, just the manifolds.
The first turnbuckel will go on the top of the motor as so...
As you can see it's pulling the ear on the front iron to the rear housing.
This is where that bailing wire goes... wrapped around the water pump pipe and attaches the turnbuckel to the rear housing again.
Here we actually are useing the LIM to help hold the motor together, we removed it, then re-installed it with NO gasket but with washers under the bolts/studs except the ones in the rear iron. You can see a small gap between the motor and the LIM.
Now this is where it gets complicated... As you can see there is another turnbuckel that's been added here. It goes from a bolt on the rear iron to a wire, but where does THAT wire attach?
It goes around the front cover.....
Down the other side of the motor...
And to the spark plug on the other side, YAY!
That was an important around-the-word wire to hold the whole stack together.
Next we took off the oil pan to break the seal, and set it back on without the bolts that old the rear iorn.
Now it can come off!
Pretty sweet
You can't really see it here, but there is a tiny crack at that dowl pin hole
we've got a pretty sweet parts washing station.
We only had one race on this motor and didn't want to rebuild it... luckily our lemon's team is nothing but geniuses. We wanted to share or success!
The first thing you're going to need to do is visit my favorite RX-7 parts store, the home depot. You'll need to get a few large turnbuckels (don't worry about the price you can return these when you're done).
If you've already used up all your bailing wire to hold your exhaust up, you're going to need some of that too. I think we had 14ga.
Remove the motor, don't bother taking anything off the front of it, just the manifolds.
The first turnbuckel will go on the top of the motor as so...
As you can see it's pulling the ear on the front iron to the rear housing.
This is where that bailing wire goes... wrapped around the water pump pipe and attaches the turnbuckel to the rear housing again.
Here we actually are useing the LIM to help hold the motor together, we removed it, then re-installed it with NO gasket but with washers under the bolts/studs except the ones in the rear iron. You can see a small gap between the motor and the LIM.
Now this is where it gets complicated... As you can see there is another turnbuckel that's been added here. It goes from a bolt on the rear iron to a wire, but where does THAT wire attach?
It goes around the front cover.....
Down the other side of the motor...
And to the spark plug on the other side, YAY!
That was an important around-the-word wire to hold the whole stack together.
Next we took off the oil pan to break the seal, and set it back on without the bolts that old the rear iorn.
Now it can come off!
Pretty sweet
You can't really see it here, but there is a tiny crack at that dowl pin hole
we've got a pretty sweet parts washing station.
On newer seals this proably will not be a problem, but if you have 30k+ miles you really don't want to unseat the soft seals that you are not going to change.
Even on new seals you will have the problem of the sealing of the rotor housing "legs" at the bottom to the side housings.
If you release the tension and allow the stack to decompress you compromise this seal and it always seep oil here as the oil level is actually above the oil pan unless you keep your oil level at the bottom of the dipstick.
Even if you run your oil level low it will seep through capillary action from oil exposure when operating.
If you release the tension and allow the stack to decompress you compromise this seal and it always seep oil here as the oil level is actually above the oil pan unless you keep your oil level at the bottom of the dipstick.
Even if you run your oil level low it will seep through capillary action from oil exposure when operating.
Junior Member
Joined: Nov 2008
Posts: 18
Likes: 2
From: Virginia Beach,VA
Do you have a email that I can sen the pictures BC I can't unloaded from me iPhone to the website but you can due it without the wire and I have the pictures and the engine
Completed after and is running perfect without any problem.
Completed after and is running perfect without any problem.
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