[PICS] - Cracked in half seal VS Non-camfered port job
 

Well, a few of you wanted to see this comparison. Not sure if it had much to do with the seal failure because I did have some pinging in the engine. However, it is all speculation.

For comparison read this thread on exhaust porting.
http://www.nopistons.com/forums/inde...pic=31895&st=0

This is an Atkins rebuild and one other on the forum said their exhaust port job didn't retain this stock feature. Which could have been a contributing factor to my failure.

http://img.photobucket.com/albums/v2...xhaustPort.jpg

I did just get off the phone with Josh at Atkins and said they have a different guy porting now and they do replace that stock feature...

James

Oh, this is a continuation of my previous thread.....

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/%5Bpics%5D-pulled-apart-my-blown-engine-56k-maybe-378432/

James

Awesome linked thread...learn something new every day. How many builders on this forum re-bevel their exhaust ports after opening them up?

I do. :)


-Ted

i do

all of them should

I do (not a builder except for my own car), because it's PROPER.

Anyone that ports the exhaust and doesn't rebevel it shouldn't be porting, even their own engine.

I'm glad Atkins has a new porter that does do it properly.

do you have to rebevel if you aren't porting the exhaust?

No...

When you port the exhaust you take away the factory 2mm bevel around the exhaust port leaving a sharp edge. So if you port the exhaust you have to add this back so the apex seal doesn't hit the edges of it. If you're not porting the exhaust then the factory 2mm bevel is still there.

ahhh ok thanks dDub. Just wondering for later on if I descided to take the rebuild plung myself ;)

Note that this is not really important on the leading (lower) edge of the port.. the seal just begins to expand outward as it hovers over the open port, and keep in mind that at a decent rate of speed (rpm) we're talking thousandths or ten-thousandths of a second, and the metal can only expand at a certain rate...so it's not like a rubber band or something. So anyway, the really important area to bevel is the closing half of the port...the sides and closing edge (top) need to gently nudge the seal back toward the rotor, which is what the bevel does. I usually give about a 1mm lip there and havent had any problems.

No problem.

But as long as you're in there doing a rebuild why not port it too? :D

I know I know, I would kick my own ass if I didn't port it while I was rebuilding it but me and die grinders are not very friendly :) Porting seems like something that a pro should do.

It's not as hard as you think, as long as you go slow and are careful. I was scared as hell when I did mine, but here I am with my break-in over and a ported motor and all I can think about is opening it back up to go slightly larger on the front/rear plates and much larger on the intermediate plate :)

That's the same story I got. Well, it was more like "I had someone else doing all the motor work because I didn't have enough time"

how long ago did you get the motor done?? i think mine was ordered prolly 1.5 years ago.

thats cool! Do you have any pics of your port job?

I would say about 2 years ago. It does irritate me slightly to know that their porter was not in the know when he was doing his work.......

Oh well...this is now..time to get over it

James

oh, yeah, i'm well past all that now, i didn't even bother sending it back, i just rebuilt it the way i wanted and it's been fine since.

here is a theory that sounds like it jives with the picture posted for this thread.

softer apex seals without a beveled exhaust port will 'chip' when they contact the exhaust port with no bevel because it is striking the port as it heads upward. those 'chips' out of the apex seal may not be large to start with but without the contact to the rotor housing to cool the seal it is being blowtorched by the combustion process and more and more metal is taken away as the engine is run especially at higher RPMs where the temps are hotter and more static compression is being built.

so, yes, always bevel your intake/exhaust ports.

Since some us in the begining wondered why the seal failed lenghtwise....this might add some more to it...
http://www.atkinsrotary.com/index.php?pag=40-9

James

Sounds like they are trying to blame something else other than themselves...

It could be they are blaming the EFFECT rather than the CAUSE...

Think about it.
The apex seal is slamming into the sharp edges of the exhaust port.
This causes the apex seal to "wobble" in the apex seal groove in the rotor.
...causing the apex seal groove tolerance to widen over time.

duh


-Ted

so they are telling you that because they did shitty ports before and your motor failed over time because of this, they still will not do anything about it, not even offer you a huge discount on replacement parts?

I never tried to get anything from them.....

Maybe I should....

At this point I don't care.

James

I can totally understand what you mean, I wasn't asking if you went after them... but rather that they didn't impose compensation on your! know what I mean? Maybe I am being unclear? If I am just let me know I will try to explain what I mean in better terms.

Nah, your fine.... when I initally called them I assumed it was compeltly detnoations fault. Then, after reading more posts I realized it was ONE of the reasons the engine failed so soon.

James