Gas Mileage???
@rmchrgr I think you understood me wrong.. I meant 10 deg @ idle...and 25 deg. advance on top...so 35 deg. all in.. at 4000 rpm.. ( yes I know the curve is slow..but the enginge pulls very very strong .. sadly the vacuum canister... only works well under WOT and off the line. The 50-60 mph ratteling is still there.... ( Made some test runs today )
OK, gotcha. That sounds about right but... your initial is still low. 10 degrees is not much, that's factory spec. and does not allow for much 'performance'. I didn't see what your engine combo was but if it's stock, then OK but if it's modified in any way then you want more initial. Even a stock 318 2bbl can benefit from more initial.
But, the caveat here is that you need to limit the mechanical advance. This will segue into my next reply, see below.
I know now...that the engine doesn´t want more than 25 deg of advance @ 2400 /2500 rpm....
Is that normal ??
Greetings Juergen
I think what's happening here is that since your advance curve is slow to come in, it's probably still advancing at anything under 4,000 rpm. Add in vacuum advance and you have too much timing for that low of an an RPM. Vacuum advance comes in with a high vacuum situation like cruise so yeah, it's gonna ping.
If you're wanting to get this sorted out, you have to get into the distributor. You need to change the advance weight springs to get the curve to come in quicker, so likely a lighter spring than what you have now. The advance curve should be 'all in' by 2,500-3,000 rpm. Just to make sure - when you set the timing, you have the vacuum advance disconnected and plugged, right?
If you decide to try more initial timing, you will need to figure out how much centrifugal advance is in the distributor. You have to measure the slots in the plate under the pickup.
Here's a chart to show how much advance the plate gives. Multiply the number X2 to get the amount of advance. Most of the 'stock' type distributors I've taken apart usually have 13 degrees and up (13 x 2 = 26). If you want less, you have to weld/epoxy the slots to get the advance to stop.
Or, get the FBO limiter plate which also comes with springs.
So you can see what happens if you have a lot of centrifugal advance, you can't run a lot of initial or you start to go beyond the normal 34-36 range.
degrees / slot size
6.............. .340
7................355
8................375
9................390
10...............405
11.5 ...........420
12...............435
13...............445
14...............460
15...............475
16...............490
17...............505
18...............520
