While you're in there...

[jimlam56]

OK folks, my 2004 MM has 86k on it. Second owner since 17k in 2005.
Recently I noticed a rough idle and high speed missing. Replaced coil packs, plugs and fuel filter with OEM, cleaned MAF and TB.
Checked compression all 120 but one which is 80.
Thinking compression ring because no smoke.
As you know replacing a ring requires the whole front of the engine to be taken out. What else should be done, or should I yank the engine and rebuild the whole thing?
Any comments are appreciated.
Thanks,
Jim

[a_d_a_m]

120 seems awfully low. It's been several years since I did a compression test but my numbers were much higher than that except for on my bad cylinder.


Edit: found my compression test results from August 2012 in my post history. Passenger side readings were consistent in the 230-240 range. Driver's side front to back was 230, 180ish, 180ish, zero (cylinder #8).

[O's Fan Rich]

OK folks, my 2004 MM has 86k on it. Second owner since 17k in 2005.
Recently I noticed a rough idle and high speed missing. Replaced coil packs, plugs and fuel filter with OEM, cleaned MAF and TB.
Checked compression all 120 but one which is 80.
Thinking compression ring because no smoke.
As you know replacing a ring requires the whole front of the engine to be taken out. What else should be done, or should I yank the engine and rebuild the whole thing?
Any comments are appreciated.
Thanks,
Jim

Sell it.... :D
C'mon, Jim.. time for a 10 second build!!!

[Spectragod]

This should help............

http://www.modularmotorsportsracing.c om/cart/index.php?main_page=index&cPath=65_67

[jimlam56]

This should help............

http://www.modularmotorsportsracing.c om/cart/index.php?main_page=index&cPath=65_67

OK, good start.
Really not interested in S/C only because of the money, but wouldn't mind a solid N/A motor with 400+/- hp and good low end torque.

[Spectragod]

OK, good start.

Really not interested in S/C only because of the money, but wouldn't mind a solid N/A motor with 400+/- hp and good low end torque.



Then you'll need to start with a coyote 5.0.

[MOTOWN]

Then you'll need to start with a coyote 5.0.

I hear them things are the bees knees!:banana:

[chief455]

OK folks, my 2004 MM has 86k on it. Second owner since 17k in 2005.
Recently I noticed a rough idle and high speed missing. Replaced coil packs, plugs and fuel filter with OEM, cleaned MAF and TB.
Checked compression all 120 but one which is 80.
Thinking compression ring because no smoke.
As you know replacing a ring requires the whole front of the engine to be taken out. What else should be done, or should I yank the engine and rebuild the whole thing?
Any comments are appreciated.
Thanks,
Jim
I'd test further before blaming the rings. Could be valve seating related.

[lifespeed]

Checked compression all 120 but one which is 80.
Thinking compression ring because no smoke.
As you know replacing a ring requires the whole front of the engine to be taken out. What else should be done, or should I yank the engine and rebuild the whole thing?

Do a leakdown test on the weak cylinder and listen for where the air is leaking out to diagnose. Most internal engine problems related to compression warrant a full rebuild, the exception being a single valve problem.