nategdizzle Posted January 8, 2007 Share Posted January 8, 2007 hey guys i was wondering if anyone had tried and had any luck by cc'ing a n42 head to lower the compression for use in a turbo setup. i saw a cc kit somewhere awhile back and wordered if i might be able to do it on my own being an amateur. any suggestions on some literature that might help me out would be great. thanks nathan Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 8, 2007 Share Posted January 8, 2007 It's really not that hard. You can buy an expensive kit with a burette and get precise results, but if you just want to improve on the factory's shoddy casting you can use a graduated cylinder (the taller and skinnier the better). I think I had a post or two here about the procedure, I know there is some good info on http://www.classiczcars.com about it. If you're really looking to lower the compression ratio there are better ways to do it, cc'ing the chambers is really intended to just even them out so that the compression ratio is the same on all cylinders. You can make some improvements to the chamber shape and take out some sharp ridges, etc, but really affecting compression ratio is better done with pistons or swapping heads in my opinion. Quote Link to comment Share on other sites More sharing options...
nategdizzle Posted January 8, 2007 Author Share Posted January 8, 2007 yeah mostly i want to get rid of the pits in the #6 chamber from where it must have wept through the gasket and sat for a long time before i got it. i have the bottom end together with dished pistons and new rings and arp hardware and dont plan on tearing it apart for as long as possible. I have this head ported and a new valve job on it and have a t3/t4 turbo and 24x 12fmic 3in dp microtech ecu a turbo cam..i am going to get 42lb injectors and run e85, 105octane, and also have a fuel map tuned for 91-93 oct 10% ethanol blend. i want to run as much boost as i can..as is i will be at 8.47cr and just want to lower it a little bit..how much can i lower the comp ratio by cc'ing, and how much boost can i run with good tuning on with that comp. ratio. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 8, 2007 Share Posted January 8, 2007 You can probably open up the chamber 2-3 cc resonably. More than that is going to be a real PITA. As far as what boost you can run, I'd say as much as possible without detonation. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 9, 2007 Share Posted January 9, 2007 A nice irrigation syringe works wonderfully for CC'ing heads. You can get a 50cc syringe out of the dunmpster at your local hospital..... Er, maybe not... Anyway, my dumpster proclivities aside, you can do a nice job with a syringe, the nice thing is you can read directly off the plunger no interpolation of the miniscus. Using a 1mm drill will give you an easily calculable hole in the plexiglass cover as well---just keep that in mind. You can inject an irrigation syringe through a 1mm hole, for a burette, you need something a bit larger to let it drop in. But polishing the head will net you little gains. Your best bet is to find pistons to lower the compression. I have run over 21 psi on stock JDM N42 head without issues, and that was a JDM N/A setup... Flow is more important than boost. Make an efficient pump, and boost drops, but horsepower goes up. Ask Jeff P about "boost goals"! LOL Quote Link to comment Share on other sites More sharing options...
dapiper Posted January 9, 2007 Share Posted January 9, 2007 I took 3.5 cc off my N42 an lowered CR to 8:1. Be careful when unshrouding valves to not undercut too much or the head may not seal well near the valves, although I had no problems with o-ring on block and head studs. Quote Link to comment Share on other sites More sharing options...
nategdizzle Posted January 9, 2007 Author Share Posted January 9, 2007 thanks for the tips guys they all sound like great ones..after a good cleaning up the needle i found in this alley behind the dumpster next to that dead guy the other night should be perfect..what do you guys use a die grinder or a dremel and what type of bits should i use? Quote Link to comment Share on other sites More sharing options...
nategdizzle Posted January 10, 2007 Author Share Posted January 10, 2007 also where would be the best places to take metal from to make the best quench area and flow Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 10, 2007 Share Posted January 10, 2007 Just work around the valves to unshroud them. Get the How to Modify book, it has pictures of where to remove the metal from. There is no quench pad in the N42 head, and you can't really improve that aspect by taking metal away, so don't worry about quench. Apparently you can get a bit more quench if you shave the crap out of the head, but then you'd be upping the compression ratio a lot, so that's a step back for you. Quote Link to comment Share on other sites More sharing options...
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