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cc estimate for L20b


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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.

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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.

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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.

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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.

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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.

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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

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