After looking at all the pistons and consulting with several experts it looks like #8 burned up do to running lean and detination. Unfortunately, this lean condition was not detected by the Wide Band O2 sensors. The wide band sensor is installed in the header collector and it measures an average across all four cylinders on the right side of the motor. For now I’m planning to leave the wide band installed for overall monitoring.
For tuning and to prevent this type of issue in the future we’re going to install EGT (Exhaust Gas Temperature) probes in all the header primaries. Then we can use the temperature reading to determine how the individual cylinders are performing and adjust them individually.
I dropped off the torque converter at PhD Converters this afternoon. Unfortunately, I arrived to late in the day for them to cut the converter open while I watched. The plan is to Cut, Clean and Weld the converter, but I won’t know if there is any damage until Monday morning.
The original block was inspected by Brian at Thomson Automotive , anyone need a boat anchor? Mike dropped off a good bare block. The new block will be zero decked, bored .010 or .015 over, new billet 4-bolt splayed mains will be installed and the block will be line honed.
We’re looking at new pistons from Diamond and JE. Hopefully, we can find some the will allow us to lower the compression ratio and have a little more material around between the dome and the top ring groove.
This motor came out of the Predator SS, more pics of the car at predator-racing.com
The original builder sold the car to another MISSL member, who killed the motor. The car is now owned by DonL, and was added as a stable-mate next to his DGGM 96 SS, which has run in SSHS for the last few years. I should mention that his wife is a saint for parking outside so two heavily modified Impala’s can occupy the garage.
Brief History of engine, Original Specs.
Original Engine built by Combination in 2005.
2-bolt main LT1 block, 0.040″ Over, hence 384.6 ci, which I’ll round to 385.. Zero-decked.
Billet splayed main caps on #2-3-4 mains.
ARP head and main studs
Eagle Forged crank, and H-Beam Rods
Custom JE Forged pistons – build sheet does not list the dish volume, I will have to cc a good piston to see what it is.
Ported Iron Heads
ATI Procharger running 9-16# of boost, depending on how much the belt was slipping.
I received the motor after it lost oil pressure. The motor was run for ~1 mile before it got shut down (Note to self: put a frickin HUGE oil pressure warning light on the dash so you notice it even when driving in busy traffic with screaming kids in the back seat..). Needless to say, motor came out.
Here’s why it lost oil pressure. Note the offset to the pump gear teeth. Not sure what the debris was, but it was hard enough to not get chewed through the pump, and small enough to get through the pickup screen.
Pump shaft was bent too.
Pulling main caps to see how FUBAR’d the bottom end was… not as bad as we thought it would be.
Minor embedded material in the #1 cap, I have seen much much worse.
#1 Main Journal
Hmmm….. not too bad.
#2 Main cap and bearing…..
Things got a little warm in there, note the bearing shrunk in. While it got hot, it DID not spin. Copper was showing on this one.
#5 looked the worst, but still looked decent, if the rod journals look good, this might not be too painful. New pump, polish the crank, new bearings and gaskets, … put it together……….. a strong example of why forged cranks are nice… kill bearings but the crank stays decent. Nice hard journals. A few hundred bucks and we are back in business
But what stuck the pump in the first place???? Time to pull the heads..
All 8 bores are scuffed, I’ll upload pics tonight maybe.
Hmmm, #8 piston looks a little funny..
Heavy detonation on the crown.
Top ring land was flared up near both sides of the broken away portion.