Core Values
 

No, this is not a religious or political rant. :)

I'm trying to get a feel for the value of a 20B short block with a blown apex seal on one rotor. Any ideas?

maybe $1000-1500?

i would say about $1500 too, and if you find one, or have one for sale, let me know, its EXACTLY what i'm looking for.

I think it's a little higher. Maybe $2,000- $2,500. Reason being is the core is still highly valuable blown or not. Most people open them up for rebuild anyways.

I sold a blown core to a buddy for $500. I think $1000-$1500 is apropriate.

-Destin

I liked t-von's answer best, but that's just self-interest. ;)

Thanks for the feedback, all.

if you have a blown core, pm me, im looking for one...

I thought that I might purchase a Jspec motor, but that deal fell through. I'll just re-build the one that I have.

George

I bought my 20B with one blown rotor for $2500. It was a c series though, so I went for it.

George, it finally went down? Any idea what it was?

Reese

In part, it was operator problems. I heard a noise while accelerating (passing six cars on a two-lane road), but the noise sounded like it was coming from the transmission, not the engine. In retrospect, I should have suspected pre-detonation and backed off, but I was thinking too hard about what could cause that kind of noise in a transmission.

As for why it went lean, I don't know. Perhaps I'll find out during the post-mortem. If not, I'll turn the car over to Ray at PFS and ask him to test it thoroughly (once it's back together) to make sure that it's running right throughout the rpm range.

10 bucks says the center rotor is what blew. That's the rotor that runs the leanest because of it's center location (getting heat from both sides of the engine) and the LIM has better air flow into the center rotor due to no bends in the secondary port runner.

The Post Mortem
 

Please send me your ten bucks ASAP, as I need it for the re-build. ;)

Seriously, here's what Kevin found:

"As suspected, you blew apex seals...on the front rotor. That housing is
toast, it has a big long deep gouge in it, and is not useable for any
purpose other than a paperweight. The rotor is also damaged and will
need replacement. FYI the breakage was not due to
wear, as the apex seals had very little wear on them...it was a
forcible break, i.e. detonation of some sort. <snip>

Everything else in the engine looks great including the other 2
rotorhousings...they have no significant wear at all."

I'm just posting this as a bit of potentially useful information. The motor had approximately 65,000 miles on it. The conclusion I would draw is that the 25 ml./gal. of pre-mix was quite sufficient. The other, obvious conclusion is that if you can control the nut behind the wheel, the motor would probably last well over 100,000 miles.

WOW I'm really starting to believe in the stock seals again. You would think that at your hp levels the seals would be more worn than they were. Too think that it could have lasted over 100,000 miles and at that power level with the old 3 piece seals just blows my mind. I mean think about it, hardly no one on this forum has had a modified rotary last this long with the kind of power you were putting down reliably. Sure more displacement helps with the larger 20b but, it just goes to show how durable the rotary actually is with all factory equipment in place. Your detonation in the front rotor could easily be a slightly clogged injector. Get those bad boys cleaned and flow tested.

With all due modesty (and I'm due quite a bit), that 100K estimate is only my opinion. I wouldn't urge anybody to bank on it. FWIW, I'm switching to the 2-piece seals based on Kevin's recommendation, as well as yours.

As for "modified", my 20B was internally stock. All the mods were to engine management and boost control. It's a tribute to Mazda's engineering that the motor worked so well and so long beyond its specs.

I agree with you that the injectors are suspect. And it would make me feel ever so much better, if the blow-up wasn't my fault. Then, I could stop the daily self-flagellation. ;)