My 1883cc Porsche 356 912 Blog

Chronology of a hot-rod street Porsche 356/912 1600 to 1883cc conversion based on LN Engineering's Nickies big bore kit.

Monday, June 26, 2006

Fine Tuning

Up to 3000 mi. After the drive to and from Hershey I realized that I need to properly tune the engine. I purchased an LM-1 wideband o2 sensor along with their rpm converter and tailpipe sniffer. With this equipment, I can drive the car and the data logger collect information on rpms and corresponding air fuel ratio. I came to find that at wide open throttle I was running around 8.5:1 - it's a miracle the engine didn't wash away with the amount of gas I was dumping in. I was also idling very lean, so I changed the idle jets out for 55s. I put in a set of 180 air correctors and put back in the 150 mains. I was still in the 9.5:1 AFR and still had the bog from 3000-4000, but at least it was running cooler. By cooler, I noticed that even though I could get the heads up to say 385F, when the load was removed, the heads would cool down faster, against my prior thought that by throwing more fuel I was helping things. I then swapped in a set of 140 mains and presto, it now runs perfect. No bog, no hesitation. I also backed the timing to 28 degrees max advance, which is now my preferred timing. After all this tuning, I checked the valve clearance and it was still at .008" on both the intakes and exhaust. All is good. Now just to drive.

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