katman Posted February 28, 2007 Share Posted February 28, 2007 To clear the combustion chamber. Because of the valve size and placement the combuston chamber on L heads is often outside the dimensions of the bore in the fore/aft sense. For example, a stock factory L24 gasket measures about 3.515 inch in the fore/aft direction but only 3.335 inch perpendicular. These dimensions can vary by +/- .050 thou or so depending on the gasket and brand. For example, our ITS engines used a custom solid copper gasket with an odd shaped hole to minimize the volume. SCCA tech inspectors routinely measure the long and short dimensions of the oval and then average the dimensions to calculate a circular area that they multiply by the gasket thickness to get the gasket volume as one of the inputs to their compression ratio calculation. In our case I we couldn't get repeatability close enough from stock gaskets to keep my blood pressure down during ARRC teardowns, so I designed one that minimized the clearance around the bore and/or combustion chamber. The dimension minimized by our +.040 L24 bore was 3.329 (included +.020 for tolerance), and the dimension minimized by the combustion chamber of an E88 (early rare E31 combustion chambered E88 mind you) was 3.509. Quote Link to comment Share on other sites More sharing options...
eec564 Posted February 28, 2007 Share Posted February 28, 2007 Ahh okay, very good to know. Thank you. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted March 4, 2007 Share Posted March 4, 2007 I've been running the HKS 2mm gasket (2x 0.5mm layers and 3x 0.33mm layers) with one thick and one thin layer removed for years now, no problemo. So I'm at 1.17mm. This gasket is a relative bargain considering it allows you to tailor h.g. thickness to your needs. You could use two thin layers to make a 0.67mm gasket. Quote Link to comment Share on other sites More sharing options...
Careless Posted March 4, 2007 Share Posted March 4, 2007 i think the best thing to do is call the company, and basically act like a bitch. it's the best thing to do, if they won't own up to the fact. and if no one there can be held responsible, ask them to talk to someone who could be held responsible, or someone who has the power to correct the situation, by means other than a repurchase, or reshipping the item. if that doesn't work, a letter to the Nissan Motorsports head, or the buyer at the website you bought the gasket from is always good measure. your engine will be built and assembled by the time anything happens, but you might just get a couple of free gaskets out of it in the future. my boss did this recently with Apple computers and they ended up sending him a new laptop. yah, it took a while, but if a company is content on sending a 2500 dollar laptop to someone who brought in a laptop worth about 800 dollars (even 1 day after the warranty expired), I'm sure Nissan could do something about it. Quote Link to comment Share on other sites More sharing options...
Careless Posted March 4, 2007 Share Posted March 4, 2007 To clear the combustion chamber. Because of the valve size and placement the combuston chamber on L heads is often outside the dimensions of the bore in the fore/aft sense. For example, a stock factory L24 gasket measures about 3.515 inch in the fore/aft direction but only 3.335 inch perpendicular. These dimensions can vary by +/- .050 thou or so depending on the gasket and brand. For example, our ITS engines used a custom solid copper gasket with an odd shaped hole to minimize the volume. SCCA tech inspectors routinely measure the long and short dimensions of the oval and then average the dimensions to calculate a circular area that they multiply by the gasket thickness to get the gasket volume as one of the inputs to their compression ratio calculation. In our case I we couldn't get repeatability close enough from stock gaskets to keep my blood pressure down during ARRC teardowns, so I designed one that minimized the clearance around the bore and/or combustion chamber. The dimension minimized by our +.040 L24 bore was 3.329 (included +.020 for tolerance), and the dimension minimized by the combustion chamber of an E88 (early rare E31 combustion chambered E88 mind you) was 3.509. if the combustion chamber is out of round, wouldn't that make it difficult to bore properly? or would it not be the same once bored to be round? Quote Link to comment Share on other sites More sharing options...
katman Posted March 5, 2007 Share Posted March 5, 2007 We don't bore combustion chambers. Cylinders yes. Heads, no. Quote Link to comment Share on other sites More sharing options...
savageskaterkid Posted March 25, 2007 Share Posted March 25, 2007 Any body have any thoughts, comments, or have used the MSA 2mm gasket, and have taken some layers off? I bought it and I'm awaiting the motor to get back from the machine shop, and would like to know of anyone running one of these on an L28et with a few layers missing Quote Link to comment Share on other sites More sharing options...
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