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High Hc (Hydrocarbon) On Solex Phh


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Hi Guys!
I have problem with my stroker engine. On low RPM I've really to much HC. It's more than 3000 ppm on idle.

Engine is after rebuilt, this is spec:

Pistons: 89,9 from M30B35

Head: E12

Rods: 135 mm

CR: 9,5:1

Camshaft - regrind 290, measured on engine:

Intlet open - 37
Intlet close - 90
Outlet open - 90
Outlet close - 35

Dizzy: JFUR4

Carb: Solex 40 PHH from original 2002Ti

Exhaust: header from TEP and original mufflers


I've double check the valve timing, block is lowered about 2,5 mm, head also 2 mm, so I've to delay timing 6 degrees. Valve gaps are set to 0,2 mm. When gaps were 0,3 HC was lower. Carbs are balanced, ignition is ok, engine is strong and pulling really good, but exhaust gas is very intensive. When I put gas analyzer carbs are tunable, CO is 3,5.

He have also lot of air (O) on exhaust gas.


I don't have any waccum leaks, idle is 1200 rpm. Spark plugs, ignition wires, ignition timing is ok.


Any ideas?












And short film, sorry for poor quality:



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How much time is on the engine? HC will be very high until the rings are fully seated. With that much off the block and head you would need to ADVANCE the cam not retard it. What ignition advance do you have at idle? Retarding the timing will help lower HC. I,would guess 12-15 deg BTDC at idle would be a good place to start, and you will want 34-36 deg BTDC at full advance ( it should be all in by 3500 rpm) I agree float level will make a difference. How tight are the throttle shafts in the carbs? PHH Solex carbs are notorious for worn throttle shafts and raw air leaks through them.

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Yeah, I have to check my notes what I've done with cam: adwanced it or retarted it.

Engine have already less than 2000 miles.

Advance was set 25 deg BTDC at 2000 RPM.

Throttle shaft is tight, to be correct there is 0,15 mm play.

I'll try to set timing again, and we will see.


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Be careful not to assume that your distributor has the correct advance curve. Springs break, weights stick, things wear out and sometimes they don't do what you expect them to do. Using the "factory" method of setting timing only works if the distributor is doing EXACTLY what it is supposed to be doing because it relies on the distributor being at a very specific point in the advance curve at a very specific engine speed. If the springs are weak and all of the advance is in by 2000 rpm and you set it at the ball you will be 10 deg retarded at the higher engine speeds. If the weights are stuck and the advance is not comming in like it should you could be easily 10 deg advanced at idle. There should be roughly 20 deg of centrifical advance in the distributor, if you have 15 deg at idle you should have 35 deg at full advance.

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OK. It's done.

I've checked my notes, and my cam is advanced 6 deg.

I've set advance at 15 deg BTDC at idle and right now is much better. HC dropped below 3000, but the exhaust gas are almost odorless.

On this setting engine on low rpm is running poor, I have to change it little bit.

I have to see what advance is on high rpm.

Thank You Preyupy for good advice.

Can You confirm, that Bosch dizzy 009 from VW bug have the same curve advance like BMW 2002 ti/tii? Or is this a myth?

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