Knocking under slight load.

[rgafitanu@gmail.com]

Hello all,
230SL engine, 051 distributor, adjusted to 8BTDC at idle and 35 at 3000 rpm. Split linkage test gives me slightly rich at idle and higher rpm. I am using premium gas. In the 1500-2800 rpm the engine knocks if I push the throttle to keep up on an incline, it won't slow down but it will knock. The advance increases gradually with rpm from 8 to 35 BTDC so it's not an abrupt change. The only thing that I haven't try is AFR measurement, I feel the mixture is (too) lean in the mid range.
Anybody has any idea?

Radu

[Benz Dr.]

Remove the vacuum cell on your distributor and turn out the pull rod one full turn to achieve 38 degrees of advance.

 You could be lean. Do a split linkage test at the same RPM range as where you're having problems.

[rgafitanu@gmail.com]

I can get to 38 @ 3000 the normal way, I just felt it runs better at 35. Were you suggesting to turn the pull rod for that?

[Benz Dr.]

Mechanical advance is pretty much fixed and can't be changed but the vacuum portion can. Turning the rod out will increase vacuum movement and turning it in will decrease.  I generally set to about 38 degrees which should work well.

[rgafitanu@gmail.com]

Anybody would lend their AFR gauge? Of course I will pay for shipping and gift card to local microbrewery.

[rgafitanu@gmail.com]

Split linkage @ 2000 rpm still shows rich. However 750 rpm idle 6 BTDC with vacuum and 11 BTDC without vacuum. I'm lost.

[Benz Dr.]

Set it up with vacuum. Without is just for testing.  You are only getting 5 degrees of advance with vacuum when you should have about 10. At 2,000 RPM, you should have about 28 degrees of advance.  Check at 3,000 RPM where all your advance systems should be full or 38 degrees.