502 blowby
03-28-2016, 06:05 AM
#22
Registered
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
Registered
Thread Starter
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
Registered
Thread Starter
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.
03-29-2016, 08:47 PM
#26
Registered
Join Date: Sep 2014
Posts: 108
Likes: 0
Received 0 Likes
on
0 Posts
But #8 had 145LBS on compression test, is the blowby due to the rings that were lined up? Just trying to sort it out in my mind. No real signs of detonation, at least on the top ring lands. Help me out guys.
03-30-2016, 04:50 PM
#27
Registered
Join Date: Nov 2001
Location: Pennsylvania
Posts: 3,385
Likes: 0
Received 0 Likes
on
0 Posts
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
iTrader: (1)
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
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
The back side of that piston looks like you had to much timing/detonation.
