Lost Compression in cyl 7&8 Mystery Solved!

[Crackerjack17]

Hows the build coming along? Lets see some pics!

Done! All back together and running great! About 400 miles on it so far. I cranked it over with the injectors disconnected, got oil pressure, plugged them in and bam it started right up. For now setup is exactly what I had before but with 10:1 compression. I've made several pulls and sent files to tuner, logs look awesome. Zero knock, adding timing everywhere. The lightened flywheel is nice, revs a touch quicker. Gotta watch spinning the tires. The thing revs to over 7500 instantly. Feels like it pulls a touch harder than the old motor. But old motor could have been hurt for a whIle and "soft" since it was down on compression.

Now I need to install my fore fuel system, switch to E85, pulley it down and break this mt82 so I can justify either an magnum xl or auto swap.

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[SoCalTim]

Home built..... love it.

 

[Crackerjack17]

Home built..... love it.

Thanks. And yeah, if your reasonably mechanically inclined, meticulous and triple check everything, it's not that bad. Assembling it is straightforward. Obviously, I didn't assemble the shortblock, because I figured I'd leave that up to people that do it all the time and have the equipment.

I've been meaning to pull the rings off the broken pistons, put them in the old block and see what the factory gaps are. Maybe tonight after work.

 

[HISSMAN]

I dig the color matched 5.0 emblem. That looks a lot better than I would imagine that it would. It looks embossed.

 

[kcc0521]

I vote for the auto swap.

 

[Andrewg]

Awesome thread. Thanks for taking the time to document the build. Also running the P1SC stage 2 beefcake special and just got a CEL a few weeks ago. Got the results of my compression test back today and looks like cylinder #8 has the same issue as you had. All cylinders around 215-225 apart from #8 which was 130. Leakdown showed air coming from the PCV valves and oil filler hole so guessing my heads are ok and valves are still sealing and the car runs fine albeit only making a max of 8psi of boost instead of 10-11 like it used to. Looks like i'll be going the same route as you with a built shortblock.

 

[18 Smoke]

That's exactly what I'm doing! I am enjoying putting this together. But, I'm mad at myself :headbonk::frusty: now for not going ahead and getting it sleeved. Oh well, next one. Lol

Look at this motor porn. Cams are back in, timing chains on and ready to install front cover.

Boing!!!

 

[Peedystablo82]

Just broke my ringlands most likely and I'm on e85 full-time .Smh. So that definitely does not eliminate the issue

 

[SolarFlare]

Sorry to hear peedy. Were you doing a pull? How much power?

 

[Peedystablo82]

I'm making 806 to the wheels with the Paxton supercharger, 3.33 pulley and e85. I was doing a third gear wot pull for a data log and when I got up to about 7200 RPM, it felt like it did not want to go anymore and then when I pulled over at a gas station that has stopped my car was cutting off and I can see smoke and oil coming from the driver side tube going into my intake and into my supercharger and out of my blow off valve .

 

[SolarFlare]

Good to know. Going stock replacement or some form of built motor?

 

[Peedystablo82]

Built as best as I can . Or buy a built.

 

[Peedystablo82]

Yeah I might as well get whatever I can built on it while it's out because it would be pointless to fix the problem and it happened again in six months or a year.

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