BunnySlippers Posted January 5, 2009 Share Posted January 5, 2009 So I'm in the process of rebuilding an L28 (N42 block and head) That ran out of oil and cooked the #6 rod to the crank. I'm going to be picking up a crank, and rod + piston assembly from a junkyard soon. I'm wondering if it might be worth it to pick up a whole set of pistons and rods from an 81-83 while I'm there.. I'm looking for information on this piston swap. Would I have to run high octane? Is there re-tuning involved? etc, etc, etc. Basically I just want any and all info on this set up from people that have had experience with it. Thanks much. Quote Link to comment Share on other sites More sharing options...
naviathan Posted January 5, 2009 Share Posted January 5, 2009 Flattops on an N42 will net around a ~10.5:1 compression ratio using a stock head gasket. Although the stock EFI can probably handle this on high octane with a bit of tuning it would be very picky about fuel choices and probably ping bad in the upper end. Using 87 octane it'll blow out the head gasket around the number 5 and 6 pistons (I know this from experience). Grab up a 2mm head gasket (if you can find one) and the compression drops to ~9.5:1. You'll still require a retune and high octane, but it shouldn't be as picky or as prone to pinging in the upper rpm range. If you would like some fun (albeit reasonable) power to play with throw in a mild cam, 2mm head gasket, MegaSquirt and a header with those flattops. All in all you can get something fun to drive with a bit of kick and upgradeability for less than $1000 in parts. MS-II kit ~$250 (build it yourself and learn something) DIY Autotune Harness ~$70 Mild Cam ~$300 2mm Head Gasket ~$160 Pistons and Rods ~$100 Time spent learning and building your car ~$Priceless. Quote Link to comment Share on other sites More sharing options...
olie05 Posted January 5, 2009 Share Posted January 5, 2009 I have the same setup you are describing. I didn't really have to change much on the tune with the stock ECU just to get mine driving. I just ran 93 octane, and retarded the timing just a tad. Worked well for daily driving. That held me over until I got a mid sized cam, megasquirt, and advanced the timing. Now the engine is making some decent power. Quote Link to comment Share on other sites More sharing options...
BunnySlippers Posted January 6, 2009 Author Share Posted January 6, 2009 91 octane is the best I can get regularly here in Phoenix. I went and took a look in my storage unit today, which is full of Z31 parts, and got to thinking. Maybe I could just throw on a set of 3.0 injectors along with running 91.. I'm on a pretty severe budget to get the car going right now. Quote Link to comment Share on other sites More sharing options...
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