dladow Posted March 17, 2007 Share Posted March 17, 2007 I have been trying to figure out the compression ratio for various head chamber sizes on an L26 that I have in a parts car. I found a nice calculator at http://www.diamondracing.net/cocalc.htm and I had a hard time rounding up the data - in fact I never did find the Top Ring Down # which I used as a plug to solve for 8.8CR and I had to guess at the piston to deck clearance. I also guessed at the Head Gasket Bore diameter. Maybe someone can correct those figures, but I hope they are at least close. I haven't taken the engine apart yet. What it shows is that there is a .15 gain in compression for every one cc smaller size chamber. So going from a 47.7 cc chamber on the E88 head to, say, a 40cc chamber after unshrouding on a Maxima N47 head would give you 10.08CR. Pump gas on that should be doable. # of Cylinders - 6 Bore - 3.27 in. Stroke - 3.11 Rod Length- 5.08 Gasket Bore - 3.37 Comp. Gasket - .039 Block Deck Height - 8.18 Top Ring Down - .02 Chamber Volume cc - 40 Dome/Dish Volume - 0 Piston to Deck - 0.10 Dave Quote Link to comment Share on other sites More sharing options...
X64v Posted March 17, 2007 Share Posted March 17, 2007 http://www.ozdat.com/ozdatonline/enginedesign/ wonderful. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted March 17, 2007 Share Posted March 17, 2007 Thanks. I was just about to post the link myself.. Please let me reiterate if anyone has specs they want added, send them to me. Or even better, add them into the system yourself (See those `Add' links?), then press the `Export' button down the bottom and send me what it spits out. Cheers, Dave Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted March 20, 2007 Share Posted March 20, 2007 I caculated for my L26 with L24 flattops, stock L26/L28 cank and rods, 1.2mm felpro gasket, and my stock MN47 head (w/ "C" cam) I should have about 10.3:1. I was at 9.2:1 with all of the above with the stock E88 head and the flattops. Stock L26 pistons were dished by 7cc. Quote Link to comment Share on other sites More sharing options...
dladow Posted March 18, 2008 Author Share Posted March 18, 2008 I finally tore into my stock early production 260z engine and in searching for specs I ran across this old post of mine (how did a year go by so fast??). My L26 has flat top pistons, and a piston to deck clearance of -0.001 inch, so the pistons just slightly pop out of the block. I will be putting an MN 47 head on it with 42cc chambers, and a 1mm gasket, and I roughly calculate the compression ratio will be 10.1:1. Dave Quote Link to comment Share on other sites More sharing options...
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