datzenmike Posted September 8, 2017 Report Share Posted September 8, 2017 I'm using Imgur but have been waiting to see where the chips fall. Recently have been using it more and more.... holy shit, fast and simple Quote Link to comment
Stoffregen Motorsports Posted September 8, 2017 Report Share Posted September 8, 2017 It takes me eight clicks to get one image copied and pasted from PB to any forum. Really quite a joke. Quote Link to comment
datzenmike Posted September 8, 2017 Report Share Posted September 8, 2017 ...and 80 seconds to get into PB, then wait and wait and fail to load, and wait and load image and go and try to find it in your album. I can go to Imgur, then find an image in my computer, load and copy it and post it in Ratsun in less than a minute.. 1 Quote Link to comment
KamakSun Posted September 8, 2017 Author Report Share Posted September 8, 2017 https://i.imgur.com/rICEyZb.jpg Quote Link to comment
KamakSun Posted September 8, 2017 Author Report Share Posted September 8, 2017 Please let me know if this worked. If it worked, what's the apx compression? 1 Quote Link to comment
Stoffregen Motorsports Posted September 8, 2017 Report Share Posted September 8, 2017 I see a link, but no image. Quote Link to comment
Stoffregen Motorsports Posted September 8, 2017 Report Share Posted September 8, 2017 ...and 80 seconds to get into PB, then wait and wait and fail to load, and wait and load image and go and try to find it in your album. I can go to Imgur, then find an image in my computer, load and copy it and post it in Ratsun in less than a minute.. Really? Imagur is that easy? You can upload from your PC directly to a forum? Sounds like you know your PB. That's exactly what happens, every time. Quote Link to comment
datzenmike Posted September 8, 2017 Report Share Posted September 8, 2017 ...and 80 seconds to get into PB, then wait and wait and fail to load, and wait and load image and go and try to find it in your album. I can go to Imgur, then find an image in my computer, load and copy it and post it in Ratsun in less than a minute.. Not so fast. :lol: I can go there, find an image in my computer that I want, load it (into imgur) copy it and post in Ratsun. (make that 80 seconds fro sure) I'd say it's working. The A87 has 33.75mm intake ports so not quite as large as the U67's at just under 35mm. The intake valves are almost 42mm and the exhaust valves are 33mm or 35mm. I'm guessing the 33mm were on the heads used on the L18 and the 35mm were for use on the L20B. I've never seen an A87 on a stock L20B but I hear it was only the very early ones. If that's the case the '74 610 may be the one. After 40+ years one could have been swapped on to any L20B. Quote Link to comment
datzenmike Posted September 9, 2017 Report Share Posted September 9, 2017 Can't work out the compression without knowing the volume of the piston dome, the piston pin height and the volume of the closed chamber head. Often they have been previously milled down. A stock L20B with a closed chamber head would be... 8.9 Above with flattop pistons........................................... 10.68 anything with a dome will be much higher. Quote Link to comment
KamakSun Posted September 9, 2017 Author Report Share Posted September 9, 2017 I'm just screwing up all around, reverse dome aka dished. Quote Link to comment
datzenmike Posted September 9, 2017 Report Share Posted September 9, 2017 It's ok. Are these stock L20B then? A 1mm overbore only just tops 9 to 1 Quote Link to comment
KamakSun Posted September 9, 2017 Author Report Share Posted September 9, 2017 I have no idea of the engines origin. The current head is the rare one that has no significance to it, u60. I think you told me it is the same as a u67 Quote Link to comment
datzenmike Posted September 9, 2017 Report Share Posted September 9, 2017 So L20B and closed chamber head. Well compression will be about 8.9.The advantage of a closed chamber head will not be fully utilized as the pistons are dished. You do have the compression. The tighter you squeeze the fuel and air the faster it burns, the stronger the explosion and the more energy that can be put to work moving a piston. You are simply making more efficient use of your fuel. For an engine with 8.4 compression (a stock L20B) increasing it upwards one point will generally get you about 4% more hp. The next point is a little less than 4%, the next point a little less and so on. This is because you are getting closer and closer to the ideal efficiency. Going from 8.4 to 8.9 is worth about 2-3 hp. Quote Link to comment
hang_510 Posted September 14, 2017 Report Share Posted September 14, 2017 The machinist said that not a lot of gains are to be had unless the head is ported, valves and springs changed and a hotter cam installed. Is this correct? Additionally, he wants me to switch to headers and this board told me to keep the cast manifold. He is correct.The board is correct. I had 4-2-1 header and like the cast manifold better. Quote Link to comment
Three B's Racing Posted September 14, 2017 Report Share Posted September 14, 2017 9:1 compression will work great. Put your money into head work, cam, valves, lubrication and remember, your engine is nothing but a air pump, the better it breathes the more output you get. Quote Link to comment
Crashtd420 Posted September 14, 2017 Report Share Posted September 14, 2017 So L20B and closed chamber head. Well compression will be about 8.9.The advantage of a closed chamber head will not be fully utilized as the pistons are dished. (Quote) With the engines that came with a closed chamber or peanut head did they come factory with flat top piston? I see a bunch of motor builds with dished pistons and a peanut head... even coming from engine builders.... Why would that combo be chosen if flat top pistons are the better choice with a closed chamber head? Quote Link to comment
datzenmike Posted September 14, 2017 Report Share Posted September 14, 2017 The whole point of a closed chamber head is to induce swirl and turbulence of the air and fuel. This homogenizes the mixture (no rich or lean spots) and cools the combustion chamber piston top valves and spark plug reducing hot spots that can auto ignite the mixture. This is why (all things equal) a closed chamber head is more detonation resistant that an open chamber head with the same compression. To get the swirl/turbulence, a combustion chamber must be smaller than the bore below it. This means that when a flattop piston is at the top of it's travel there are areas where it is up against the head surface, being separated only by the head gasket thickness. (about 1.2mm or less than 0.050") As the piston approaches TDC the air caught in this area is violently pinched out into the combustion chamber. The area where the piston and the head almost touch is also called the quench area. As you can see having a dished piston negates most of this pinch effect. People who build with them either don't know better, don't have the resources to get flattops or it doesn't matter as higher compression is all that they want. There may be a few closed chamber heads around but likely these came here on import engines in the '80s. The '70s was all about lowering compression and emissions. I find it exceedingly unlikely that Nissan randomly sent some engines with higher compressions than advertised. What pistons the import engines used with them, I don't know but the L16SSS and L18SSS used in the 510 coupes were flattops. 1 Quote Link to comment
Crashtd420 Posted September 14, 2017 Report Share Posted September 14, 2017 Knowledge is key.... Got lucky when I assembled my L16 with the w53 head.. I wasn't paying attention just buying parts not understanding how everything interacted.... In the end it all worked out, barely.. Higher compression than what I wanted, but was able to utilize the head to its fullest.... Proper planning definately helps.... 1 Quote Link to comment
Stoffregen Motorsports Posted September 14, 2017 Report Share Posted September 14, 2017 I've run 12:1 on the street in a long rod L 2200 (my street car for many years) and it ran on pump gas. It also had a big cam which used up all that cylinder pressure. 10:1 is ideal for the street, but if you go over, it's not the end of the world. 1 Quote Link to comment
distributorguy Posted September 14, 2017 Report Share Posted September 14, 2017 The spare race motor I built was 12.5:1, and I plan on eventually assembling our parts truck, possibly using that as a street motor. It was quite tame and controllable with a set of SU carbs on it. Knowledge IS key! 1 Quote Link to comment
Crashtd420 Posted September 14, 2017 Report Share Posted September 14, 2017 When you say pump gas what octane? I'm at 10.7:1... mild cam, initial timing at 14.... running 93 in the tank? Was definately fun on the street... 1 Quote Link to comment
Stoffregen Motorsports Posted September 14, 2017 Report Share Posted September 14, 2017 Pump gas here in CA at that time was around 92 octane. When I say big cam, I mean it was big. It idled like a big block Chevy. Quote Link to comment
Crashtd420 Posted September 14, 2017 Report Share Posted September 14, 2017 Well since 87/89/93 are my choices.... I'll stick with 93.... I can hunt for stations and maybe get 91/92, but I'll just be wasting gas to do it.... Quote Link to comment
racerx Posted September 14, 2017 Report Share Posted September 14, 2017 So after reading peoples input, its not worth it unless you will race it. Could this be the reason why peeps say fuck it and install a KA motor? Quote Link to comment
Crashtd420 Posted September 14, 2017 Report Share Posted September 14, 2017 Probably.... I'll say this.. with the money I put into my L16 I could have done a motor swap and bought a spare motor.... and I still wanna spend more and have the head ported and what ever they do with the flow bench... But I'm that fool that likes the matching chassis and motor #.... Was it worth it probably not, do I love the motor i built and what I've accomplished.... hell ya... The biggest thing I learned was proper planning before I bought things, what intended to build was not what I ended up with.. Quote Link to comment
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