willxs 0 Posted January 5, 2007 i think the head for an engine im planning on rebuilding maybe slightly warped. question is, is it reuseable with just a skim? or am i going to have to source another one? Cheers, will Share this post Link to post Share on other sites
Richie-Van-GTi 72 2 Cars Posted January 5, 2007 best option is take it to a machine shop and have them check it, they wont skim it if its beyond use. Share this post Link to post Share on other sites
willxs 0 Posted January 5, 2007 ok. thanx for the quick reply Share this post Link to post Share on other sites
ALEX 98 1 Cars Posted January 8, 2007 (edited) You can Skim upto 2mm off the standard XU 8valve head apparently. Though I wouldn't take that much off as You will get pre ignition issues, unless your fitting a programmable ECU. Edited January 8, 2007 by ALEX Share this post Link to post Share on other sites
willxs 0 Posted January 8, 2007 its an S16 head. just stripping it down at the moment then will take it to a machine shop (along with the block for a skim) and see what they say. then its off for a clean Share this post Link to post Share on other sites
butpug 0 Posted January 10, 2007 Though I wouldn't take that much off as You will get pre ignition issues, unless your fitting a programmable ECU. How would a programmable ECU prevent detonation due to high comp. ratio? Wouldn't you would have to lower the compression ratio?! Share this post Link to post Share on other sites
ALEX 98 1 Cars Posted January 10, 2007 (edited) How would a programmable ECU prevent detonation due to high comp. ratio? Wouldn't you would have to lower the compression ratio?! The ignition advance on the standard set up is controlled by the Dizzy. This is a crappy linear advance as it is controlled with bob weights on springs inside the dizzy. In time these springs get stiff/relax messing up the timing on older engines causing Detonation/pre-ignition. Also if you were to take a large chunk off the head i.e. 2mm the standard advance would be too much. You could retard the timing to compensate but then that’s a compromise on power. If you were to fit a programmable ECU you could replace the dizzy fit coil packs and set up the ignition to what best suits the engine. Learnt all that from PPC magazine, It's a good read . Edited January 10, 2007 by ALEX Share this post Link to post Share on other sites
Mikey S 29 1 Cars Posted January 10, 2007 put a straight edge on it (i usually use a metal ruler) and measure with feeler gauges. im unsure what the max warp is but you can usually find out in the haynes manual. Share this post Link to post Share on other sites
Guest BrainFluid Posted January 11, 2007 They will preform a leak test on the head at the shop , correct me if I'm wrong but I'm 90% sure the head will need the valves in to do this. Mine did anyway he said just to leave them in. Share this post Link to post Share on other sites
Guest BrainFluid Posted January 11, 2007 If you were to fit a programmable ECU you could replace the dizzy fit coil packs and set up the ignition to what best suits the engine. Sure but with too high a comp ratio would it not be the case of the ECU igniting the squish before it self detonated. Good to avoid but not really what best suits the engine. Hypothectically speaking of course. Share this post Link to post Share on other sites
butpug 0 Posted January 11, 2007 2mm sounds like a hell of a lot to me, but then I'm not used to dealing with those kind of details. I suppose it depends on standard comp ratio and bore size, which will be different for different engines. If we were to take 2mm off some of the heads we deal with at work youd end up with no valve seats! Share this post Link to post Share on other sites
B1ack_Mi16 67 Posted January 11, 2007 2mm sounds like a hell of a lot to me, but then I'm not used to dealing with those kind of details. I suppose it depends on standard comp ratio and bore size, which will be different for different engines. If we were to take 2mm off some of the heads we deal with at work youd end up with no valve seats! I've heard it's normal to try to bend the head straight if it's heavily warped. Then you skim it afterwards to make it 100% straight on head-gasket mating face. Only skimming it would make the camshaft bearing bores still beeing out of alignment. Share this post Link to post Share on other sites
butpug 0 Posted January 11, 2007 (edited) Never really thought of that. Jeez it starts to sound quite messy! Edited January 11, 2007 by butpug Share this post Link to post Share on other sites
ALEX 98 1 Cars Posted January 15, 2007 (edited) Sure but with too high a comp ratio would it not be the case of the ECU igniting the squish before it self detonated. Good to avoid but not really what best suits the engine. Hypothectically speaking of course. Covered topics that might be useful here link link2 2mm skim is possible and the engine can tuned to avoid pinking. But if you use the standard ignition and fuling map then I imagine it will pink like buggery. Edited January 15, 2007 by ALEX Share this post Link to post Share on other sites
