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Brief history. Car has 106k miles, daily driver. It was cammed by the previous owner. I bought at 37k and had the Comp Cams fail, taking out the lifters at 58k. I pulled the motor, replaced with a RCR specd Lunati cam, BTR dual springs, trunion kit, new oil pump, cleaned the motor and pan. Pistons and valves were great at this time. I hadn't raced the car since the rebuild, just driven to work. Even sold the nitrous kit since I wasn't using it.
About 3-4 months ago, it started to have a strange intermittent click in the valve train. Turned out to be 2 broken inner springs. I changed the springs with BTR duals, changed valve seals and cleaned the metal debris from the valve area, hoping the cam was fine.
The lifters have since started ticking, so I pulled the driver's side head this weekend. Figured the cam and lifters were damaged from metal shavings. The plan was to change the lifters, cam, oil pump and timing chain, clean the pan and reassemble.
However piston #1 looks to have some damage or burning at the locating dimple with a lack of carbon buildup around it, like it was a hot spot causing denotation. The car had also been pinging on highway acceleration the past few weeks. The head and valves look normal, no cracks or pitting there. Only the piston looks to have a small amount of damage.
Question- should I change the piston? Should I have the injectors tested? The scratching in the carbon on cyl #1 was from me. The cylinders have coolant in them from removing the head, no oil and plugs looked normal, no oil.
Full mods- stock internals, heads milled 0.040, cam, springs, stock valves. Car had nitrous but I hadn't used since the last rebuild.
You need to find the cause before you damage the piston worse, most likely a clogged-dirty injector. You really can't say if the piston is damaged unless you pull it out and inspect it. Looks like it was very hot and may have cracked a ring. But it maybe be fine, tough call. Its surprising how quick these pistons get damaged on the top edge like that, the ring will get so hot it expands enough the break the piston. Pull it or toss the dice.
Finished removing the pass side head and that side is totally normal, just typical carbon buildup on the Pistons. Valves are good, plugs were good, although cyl 2 could use a deg or so less timing based on the mark on the spark plug ground.
Yeah, maybe I will pull cyl 1 just to check the rings. If good, just slap it back in.
05-28-2018, 07:56 AM
G8 GT piston damaged? 
