Trash

Not pull the max RPM it did in the past, or well short of rated WOT rpm with reasonable load and prop.

Trash

Usually the intake valves tulip because of the larger diameter.

I had the exhaust seat come clean out of the head for the #1 cylinder to consume. After that it spread the cheer to 2 other cylinders on the opposite bank in about .3 seconds. Outcome was complete failure of exhaust seat, crunched #1 piston, broke all three rings, bent all three ring lands, bent wrist pin, breached hole in head near spark plug, drained water from breach into cylinder, spit pieces of broken valve seat upstream through the intake valve (when it opened) up through the runner into the plenum and #2 and #4 cylinder then ate pieces of #1's valve seat. In addition the pieces embedded themselves into the piston top.

The carnage was righteous.

jfried

So a little more information after speaking to mechanic in person.

Compression test on all 8 cylinders -- good between 180 and 190, on all, except #2 which had zero compression.

Leakdown test revealed air rushing out the intake, and nothing out of the crankcase, so they are pulling the head next week to see what's going on.

ezstriper

instead of looking like a "T" looks like a "Y" and sometimes big pieces leave !!!

jfried

So, an update:

Intake valve in #2 cylinder was bent, causing the loss of compression. Upon pulling the head, they discovered that many of the valves are sticky, so have recommended that both head be rebuilt, which is the route that I'm going with.

I guess the question now is, do i have them just replace whatever parts are broken? or does it make sense to do upgrades at this point in time?

Baja Rooster

iTrader: (1)

Budget wise, if you upgrade the entire heads you'd buy bare castings and have to have a machine shop put in all brand new parts anyways. The piston that bent the valve is fine? If this is an OEM motor why would the valves be sticky? I'm no expert and curious myself.

jfried

Yes -- the piston was apparently fine... saw it yesterday and didn't look problematic to me. They claim some bad gas and detonation has caused all of the sticky valves.

What is the typical head upgrades for these motors?

mike tkach

iTrader: (3)

i would sure like to know how bad gas caused sticking valves.i would ask them to explain that theory.

SB

iTrader: (1)

Overheating the valves. More common the center exhaust ports of SBC's as they are right next to each other.

mike tkach

iTrader: (3)

i have seen tuliped valves from to little timing and seen my fair share of detonated junk but never seen one stick a valve from it but i guess if the stem to guide clearance was to tight it could happen.