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Forum namePerformance/Engine
Topic subjectThe number one piston.
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=135756
135756, The number one piston.
Posted by 99eclipse420a, Jan-11-12 07:12 PM
I was having some misfire issues and so I did a compression test. I had 160psi across the board untile number one with a small 30psi. I removed the head expecting some sort of valve issue only to find the piston was sitting g uneven in the bore. It is lower on the transmission side below the deck and proper height on the timing side. Hopefully, you all will see this in the pictures.



135757, RE: The number one piston.
Posted by CODE4, Jan-11-12 07:31 PM
Drop the oil pan, and have a look underneath.

Time for a rebuild.
135758, RE: The number one piston.
Posted by 99eclipse420a, Jan-11-12 07:35 PM
That is my plan I will be taking pictures of all that I find. Luckily, I found a good engine at pullapart for temporary use.
135760, RE: The number one piston.
Posted by DarkOne, Jan-12-12 06:54 AM
Yeah, i'd say that's a damaged piston and an ovaled cylinder.
135761, RE: The number one piston.
Posted by 99eclipse420a, Jan-12-12 07:53 AM
Yes I agree with that. Also, the machinist honed the block at a 25 degree instead of 45. I believe he just treated it like a v8 instead of a inline 4.
135762, RE: The number one piston.
Posted by 420agreenvilleSC, Jan-12-12 07:56 AM
high comp time :)
135763, RE: The number one piston.
Posted by 99eclipse420a, Jan-12-12 08:03 AM
Mikey, I am not running anything to support that.
135766, RE: The number one piston.
Posted by 420agreenvilleSC, Jan-12-12 09:20 AM
FINE! :D FYI, i ovaled my cylinder(s) once too.. sucked, but thankfully i had a spare block that had standard bore measurements.

if you do infact do a rebuild, don't tell the machinist anything about the engine's history (or that you think a cylinder is oval), let him tell you what he finds first

worse case? if oval, you'll need to overbore and get new pistons :(
best case? hone and reinstall w/ new rings :)

update this thread with your findings.. i'm curious

good luck!
135773, RE: The number one piston.
Posted by Slo2g, Jan-12-12 08:18 PM
Supporting mods for a high compression piston is an ECU! :P The stocker will run them!
135777, RE: The number one piston.
Posted by Dstach, Jan-13-12 12:05 AM
was the motor rebuild before? IIRC from the factort doesn't have std stamped on them. same with bearings. Could it be improperly put together?
135780, RE: The number one piston.
Posted by 99eclipse420a, Jan-13-12 06:36 AM
The engine is a rebuild with only 2000 miles on it.
135824, RE: The number one piston.
Posted by 99eclipse420a, Jan-18-12 07:19 PM
I removed it from the bore and lets see if the pictures give away what I see.



135825, RE: The number one piston.
Posted by CODE4, Jan-18-12 07:21 PM
Nice curve.
135826, RE: The number one piston.
Posted by 99eclipse420a, Jan-18-12 07:27 PM
Yes Dave it is. I was shocked.
135827, RE: The number one piston.
Posted by Slo2g, Jan-18-12 07:30 PM
Just what I was gonna say Dave :P sucks but now you know!
135828, RE: The number one piston.
Posted by 99eclipse420a, Jan-18-12 07:35 PM
The funny thing is it never knocked, just misfired at low rpm.
135829, RE: The number one piston.
Posted by JoshDSM, Jan-18-12 08:13 PM
Was the motor Na or boosted?
135832, RE: The number one piston.
Posted by 99eclipse420a, Jan-19-12 04:44 AM
It is NA with only bolt ons.