scaredspitless Posted April 27, 2008 Report Share Posted April 27, 2008 Hey, I have an L20b with flat tops, an A87 open head and a L16 cam. I have just purchased and rebuilt some Webber Dcoe 40's. I would like to get some figures for the main jetting and emulsions. i have the Idle circiut figured out but took it for a burn thru the parkade and it crackles & farts like crazywhen letting off the throttle. It seems pretty slow & boggy to get going. Does anyone out there have any info for this set up. PS: i searched jetting and webber first 10.5-1 compression (approx), 135 main Jets, 45f9 idles, F11 emulsion, 180 air jet, 32 main choke,3.5 Aux choke. I threaded & blocked starter circuit. Float is at 7.5 & 15 droop. Timing is about 12 deg. Everything has been immaculately done. i have followed tones of online info. ??????????????????????????????????????????????????????????????????????????? Quote Link to comment
bonvo Posted April 27, 2008 Report Share Posted April 27, 2008 i know for a fact that the stock l20b cam is better then the l16 that could be part of the problem Quote Link to comment
datzenmike Posted April 27, 2008 Report Share Posted April 27, 2008 An L20B (stock bore) A-87 open head (stock un-milled) flat top pistons (L28?) crushed gasket thickness of 1.2mm, will have a compression of 9.94 and a swept cylinder volume volume of 488cc or 1,952cc for the motor. This is the total air volume drawn into the motor for every 2 RPMs. Unless you have an L16 SSS cam you are much better off with a stock L20B cam. They are virtually the same lift and duration as the true SSS cam. The A-87 head has somewhat smallish intake ports, an advantage at lower speeds as it has higher velocity air flow. That's a lot of carb and I don't doubt it is slow and boggy off the start. You may be able to tune some of it away but this is the price you pay for better top end power. Turning the idle up slightly may help with the exhaust crackle or maybe a turbo muffler with some baffles in it, not a straight through can. Quote Link to comment
scaredspitless Posted April 27, 2008 Author Report Share Posted April 27, 2008 Thanks guys, Mike, I spoke to you a few months ago about trying to find a head. Thanks again. I do plan on finding a new cam, I haven't planned for that yet. I don't know much about this one. The previous owner called it a 210 ??? Do you have any ideas ? I used to have a single Webber 45 on it before and it ran fine. Quote Link to comment
fiveNdime Posted April 27, 2008 Report Share Posted April 27, 2008 I don't mess with SU's for this reason. I take it to someone cause I would just make it worse. Quote Link to comment
scaredspitless Posted April 27, 2008 Author Report Share Posted April 27, 2008 Yeah, I'm on the list to take it in to Specialty Engineering, but they have a 3 week wait. It's like sand in your shorts having to sit & wait. I would like to get as much done a I can, I'd like to think I can get it close... Quote Link to comment
datzenmike Posted April 27, 2008 Report Share Posted April 27, 2008 Which head do you have on it, a 210 or an A-87? Look just above the block on the head just below the #1 spark plug. The 210 head was an L13/L16 head with even smaller ports and valves. Avoid.! Maybe switch back to a known runner carb if you don't get that one sorted out. My mistake you mean the cam. Don't know the 210. The stock L20B cam has 248 degrees duration and 0.413 lift. Quote Link to comment
scaredspitless Posted April 27, 2008 Author Report Share Posted April 27, 2008 Hey mike, Um, It's not an A87. It is a U67! OOOps. It has been shaved a small amount. The Original I had on the car was an A87 P-nut The compression was way High! I think in the range of 12:1. That's when you & I spoke. Quote Link to comment
phatdave Posted April 27, 2008 Report Share Posted April 27, 2008 http://www.nismoparts.com/cart/?pn=m-11041-v9182 Quote Link to comment
datzenmike Posted April 27, 2008 Report Share Posted April 27, 2008 Hey mike, Um, It's not an A87. It is a U67! OOOps. It has been shaved a small amount. The Original I had on the car was an A87 P-nut The compression was way High! I think in the range of 12:1. That's when you & I spoke. Doesn't change much really. The intake ports are much bigger. If this head was milled say 1mm (0.039") you would have 10.98 cr. Quote Link to comment
bonvo Posted April 28, 2008 Report Share Posted April 28, 2008 not to thread jack but what about a all stock l20b after a rebuild and the head surfesed? it will have the stock pistons just new rings bearings and im gonna have the head done Quote Link to comment
DISLEXICDIME Posted April 28, 2008 Report Share Posted April 28, 2008 is the u67 head a open chamber Quote Link to comment
banzai510(hainz) Posted May 7, 2008 Report Share Posted May 7, 2008 I seen a Nismo 44mm kit installed on a stock L16 and it worked. The faster the better it worked. yes they bog on such a small motor if opened up to fast. YOu have some other proplem. junk carbs, jetting totally off(most should get it running) or something totally off(floats sank) timming off. Distributor? Cam timming? Coil getting Hot or mismatched. Ballast resisitor if using points Quote Link to comment
scaredspitless Posted May 9, 2008 Author Report Share Posted May 9, 2008 yeah timing was off a bit. Quote Link to comment
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