j80leo Posted August 20, 2008 Share Posted August 20, 2008 Has anybody on here had a HKS headgasket which is 2mm or above or any different size over standard toyota gasket as my mate at work as got a sierra cosworth and he has told me that you can not increase the size of your headgasket to lower your compression or the engine will blow, your thoughts on this welcome:d Quote Link to comment Share on other sites More sharing options...
jim_supra Posted August 20, 2008 Share Posted August 20, 2008 That's a good one I doubt HKS would make a 2mm metal head gasket for a Supra if they caused engines to blow:D Also, a lot of the Na boys who are doing NA-T conversions fit thicker head gaskets to lower compression so they must be in trouble. Quote Link to comment Share on other sites More sharing options...
j80leo Posted August 20, 2008 Author Share Posted August 20, 2008 i told him that HKS do a 3mm headgasket he said its just a cheats way of lowering the compression? Quote Link to comment Share on other sites More sharing options...
rob wild Posted August 20, 2008 Share Posted August 20, 2008 HKS 2mm HG have been used many times on here and on SF and in 6 years of being on both i've not heard of any blowing. TBH Its not often you hear of supra engine blowing HG. Your mate is right in the sense that your 'cheating' but its the low cost option apposed to using pistons with a larger dish i.e. 17cc to 20cc etc. However by using a thicker HG you are removing the 'squish' factor from the engine. Quote Link to comment Share on other sites More sharing options...
j80leo Posted August 20, 2008 Author Share Posted August 20, 2008 HKS 2mm HG have been used many times on here and on SF and in 6 years of being on both i've not heard of any blowing. TBH Its not often you hear of supra engine blowing HG. Your mate is right in the sense that your 'cheating' but its the low cost option apposed to using pistons with a larger dish i.e. 17cc to 20cc etc. However by using a thicker HG you are removing the 'squish' factor from the engine. Thanks for the info rob;) Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted August 20, 2008 Share Posted August 20, 2008 A thicker headgasket will attract more detonation if this is to happen inside the cylinder, that's why it's a frowned upon practice in engine tuning generally. Quote Link to comment Share on other sites More sharing options...
Digsy Posted August 20, 2008 Share Posted August 20, 2008 Why's that then? Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted August 20, 2008 Share Posted August 20, 2008 When detonation occurs, it will attack the weakest place in the cylinder, that being the head gasket. The thicker the head gasket, the larger the weaker place is. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 20, 2008 Share Posted August 20, 2008 Using a thicker than stock head gasket reduces the squish Toyota designed in, which is to help stop det by moving the bulk of the charge from det prone areas, it's a far from ideal way to drop CR. That said modern thinking errs on a high compression ratio, very little turbine size induced back pressure, and good mapping at modest boost levels. WRC cars now run high N/A levels of CR and a lot of squish to give stunning off and on boost performance. It is tricky to get the balance right, but gives the best on road performance on pump fuel when you do achieve this. Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted August 20, 2008 Share Posted August 20, 2008 I thought I was right, but you explain it much better Chris Quote Link to comment Share on other sites More sharing options...
Digsy Posted August 20, 2008 Share Posted August 20, 2008 Ah, so when you said "will attract more det" you meant "will be more prone to damage from det" rather than actually causing it, or making the engine more prone to it. I can't say I've ever seen a head gasket damaged from detonation. That's usually piston crown and combustion chamber surfaces, and they can usually let go pretty damn quicky. If you had bad det I'd be surprised if the first thing to fail was the head gasket. I concur with Chris that squish lands are definataly making a comeback and geometric CR is going up. 12:1 on an NA isn't uncommon these days. Quote Link to comment Share on other sites More sharing options...
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