[rockhoundcow528]

Check this one out guys. 429 out of a F700. Bought the truck, it actually ran fine, but had a ton of blowby. Compression test showed #5 and #6 were dead. Any thoughts what would cause this? Strangely enough, no debris in the oil pan.

 

[The Mad Porter]

Detonation likely aggravated by oil contamination of the intake charge.
If the piston tops are mottled like an orange or eroded that is more evidence.





Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

 

[rockhoundcow528]

You may be right. There was a substantial amount of oil sitting in the intake galley pan.

 

[The Mad Porter]

You may be right. There was a substantial amount of oil sitting in the intake galley pan.

Oil in the valley pan is normal.
By contamination of the intake charge I mean oil getting past rings and into the chamber where it kills fuel octane.







Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

 

[rockhoundcow528]

Got ya. I believe someone was in this engine once before. Every bolt I touched was pretty loose. I am puzzled that there wasn't any debris in the oil pan from that much carnage. Thanks for the pointer Mad Porter!

 

[boss 9 howard]

howdy: The lack of aluminum in the pan is from the piston vaporizing.Aluminum goes to vapor under exhaust temps.I have observed plating in the headers from demolished motors.Also chunks of valves,rings,even pieces of head.

 

[PSIG]

2nd ring seizure. Ring ends butt when hot and seize in the bore, breaking out the lands. Caused by improperly-gapped rings, or excessive heat (including detonation), or some of both. The OP may have found it (or at least the chunks in the pan) and buckled it back together to sell, as those aluminum chunks and ring bits would not migrate anywhere that they would be vaporized. Oddly, bore ring seizures may or may not leave damage or scoring in the bores, but something visible is usually left behind.

While they may have been oddballs the assembler missed, a check of the other ring gaps may give clues. Check the rods for straightness and cracks. If it's been running a while this way, the bearings may show some clues also. Some inspections and forensics on tear-downs helps to find unknown issues. Good luck!

 

[JimL]

Check the oil pump for scoring, too. The oil filter may have remnants inside.