502 blowby
03-28-2016 | 06:05 AM
#22
Registered
Joined: Nov 2005
Posts: 4,554
Likes: 3
From: Fredericksburg, Va
I've wondered why nobody makes a totally adjustable ignition, or why I've never heard of it. In the Harley world you run 2 programmable, different curves and switch between based on an adjustable vacuum switch. It also allows to advance or retard one of the cylinders and withhold spark for X revs on startup.
Seems like a doable deal for 8 cylinders also.
Seems like a doable deal for 8 cylinders also.
03-29-2016 | 04:41 PM
#23
Thread Starter
Registered
Joined: Aug 2003
Posts: 477
Likes: 1
From: Catawba Island, Ohio
Oddly enough #7 came out with rings in tact and no real signs of detonation. Only thing of interest was the position of the rings.. they came out in the same position... too close?
Back of Piston:
Back of Piston:
03-29-2016 | 08:00 PM
#25
Thread Starter
Registered
Joined: Aug 2003
Posts: 477
Likes: 1
From: Catawba Island, Ohio
Initial thought was rings moved and then caused the sudden crankcase pressure increase.
Remaining cylinders looked the same. Except #8. Top ring was siezed into the groove. Blocks heading to machine shop tomorrow for home and re-deck for MLS gaskets and heads for a refresh.
Remaining cylinders looked the same. Except #8. Top ring was siezed into the groove. Blocks heading to machine shop tomorrow for home and re-deck for MLS gaskets and heads for a refresh.
03-30-2016 | 04:50 PM
#27
Registered
Joined: Nov 2001
Posts: 3,393
Likes: 6
From: IBX
Check the ends of the compression rings on #7 to see if they were butting (shiny). Also when you measured the bore of #7 what did you get for an actual clearance with #7 piston and did you note any egg shape?
03-30-2016 | 05:09 PM
#28
Registered
Joined: Nov 2004
Posts: 14,177
Likes: 3,731
From: On A Dirt Floor
Or maybe you jotted down #8 and #7 wrong at one time.....I would believe the stuck ring in #8 would cause the compression loss if everything else checks out...wgich it sounds like you are doing now. ie: measuring things since the stuck rings is the only smoking gun found so far.
03-30-2016 | 07:23 PM
#29
Registered
Joined: Dec 2015
Posts: 96
Likes: 1
From: Conklin NY
Did anyone check those cylinders for out of round? There also looks like excessive scuffing on that #7 skirt. Anything more than 0 out of round is unacceptable and could have an effect on ring seal
Last edited by Pol83x; 03-30-2016 at 07:27 PM.
03-30-2016 | 08:33 PM
#30
Registered
Joined: May 2012
Posts: 1,465
Likes: 9
The back side of that piston looks like you had to much timing/detonation.
