I was meaning to datalog and tune the upper RPM part of the VE table on Megasquirt and thus i was giving her a good flogging. She ran great, pulled hard until 6500 RPM and after about 45 minutes or so, i headed back home. All of a sudden, she died on the middle of the road. Starting wasn't doing anything. Good thing it was midnight so she didn't cause any traffic. I waited until she cooled off and tried the starter again. She woke up reluctantly and limping. I couldn't get my foot of the gas or she would die again. It was a very loud ride back home.
Successfully made it home, i opened her bonnet and oil was splattered all over the engine. Started her again and there was massive blow-by from the dipstick tube. Yikes.. In the morning i tried changing her spark plugs but the limping was still there. Desperately checked the injectors and they were great. This can only mean one thing: major compression lost, which equals major cash to be spent.
The next day, the engine was opened ( i sure didn't waste any time, did i?) and this was found:
The other three slugs weren't so much different. Broken ring-land is a good sign of massive predetonation, which surprises me a lot. Sure my spark map isn't what you'd call moderate but i won't say it's piston-melting as well.
I wasn't hearing any pinging and my AFR readings were good, about 12.5-13.0 on the high RPMs. I can't say she's a quiet car anyway, with all the rattles and noise she makes, i might've missed those predetonations.
The newfound blow-by wasn't her first. She was already suffering minor blow-by since her first high RPM run a few weeks ago with a much milder spark map, advance was only 22 degrees max. So i'm indecisive on whether the spark map killed the engine. It might also be crappy rebuild by the first workshop or bad fuel quality.
Anyway, this mishap has forced me to fast forward the project schedule.. by a lot! I was planning on putting the 4A-GZE forgies next year but i guess now would be the best time to do it. My only regret would be that the bores were scratched so that new cylinder liners are needed. I was already .50 overbore when the first rebuild was done and with the same diameter that my 4A-GZE pistons have, cylinder relining is inevitable.
Right now i'm waiting for the machine shop to finish the relining and hopefully by next week, she'll be back on the road again with lower compression and a turbo sitting on the exhaust this time.
During my time to gather parts for the second rebuild, i compared the head gasket between my smallport with AE92 4A-FE one. This would help to confirm that putting a 4A-GE head to 4A-FE block won't be a straight easy work. Some of the coolant and oil lines were blocked, judging from the gasket comparison. 4A-FE's gasket is the bottom one.
By the way, here's a good discussion on what happened to my engine on toymods forum.
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