there are changes.... i put a washer above the gear to eleminate that play in vertical movement.There was a tiny spacer ,now it needed a rather tick one.For the rest distributor seems ok , had it completely open , cleaned en reassembled .Now the engine goes above 3000 rpms but runs strange , not "oiled" and at 4500 rpm i heard loud explosions exhaust.I also see that my stainless header tubes are discoloring very blue ... is that a lean condition ???

Is it possible that , lets assume, with the engine already lean ( rememberd some occasions when he wasn't so good in reving high ) that now with header tubes he need jetting larger ?
Another possibility :if  power valve was leaking  even with  much vacuum ,  now, new installed , not  ... again  a lean condition  for the main  system ?
I can be wrong but find driving that i could gain rev's with pumping  : fuel from the pumpers ???
Checked the jets and find primarys 66 and secondarys 76.Isn't 66 small ??? Find in a book that Holley double pumpers 600 come out factory with primarys 69... ??? I sure go get some sets on monday and try them out .Perhaps 76 for the primarys also ? Plugs are still very dry and center nose very light brown.So i think they may have some more fuel.

Whe are not finished but there is some improvement

Blue is very hot, but not necessarly lean.  Lean can backfire in the intake, rich usually backfires in the exhaust.  And usually as a result of misfire, or air getting into and mixing with the exhaust gasses.

Aftermarket carbs are usually set a bit on the rich side.  This is to not cause lean problems in the cylinder and create engine damage.  They don't want to pay those lawsuits.

When it backfires at 4500, was that under load, or a free rev?  ( should not free rev an engine that high)  You may want to look at total timing again.  With the shim/washer the total advance will be different.  Double check that first.  Then make sure the plugs were not damaged from the previous running problems.  I admit a light tan on the plugs is what you want.  So that may be right for fuel mixture.

backfires where under load.I checked timing again after shim .Tryed between 4° static and 12°. No much difference.The car "pulls" up to 3000 rpm and then goes higher but running "square".I think my mech advance is 24° as i see with 12° static reaching 36° reving with vac advance disconnected.( i have put a mark 36° on the damper )
Hope i'm right that the lines on the pointer are 2° increment ? Backfires are when i'm pushing the pedal total so opening the secondarys. 

for sure : the fires are in the exhausts , not carb.

Ken,
mayby i surch it toooo far but now i was thinking : CAN a faulty alternator generate a AC current in the cars circuit to interfere with ignition ????????? at a certain frequentie ???????? or is the DC battery always leveling that ??????????

Did the vibration damper slip, causing not being timed right?

Get number 1 cylinder to top dead center, then look at the timing mark, should be "O".

Denny

Hi Denny ,

ok, i check it but if you find 2° static with "timing light" and optimum vacuum at about 12° "timing light " isn't that the proof whe are in the right position ?

Oddly enough, if you have electronic ignition the answer is yes.  Weak diodes in the alternator that allow A/C current could affect the operation.  But not with points.  In new computer controlled cars it really reaks havoc.   Any thing over 0.5 volts A/C measured at the battery can be a problem for electronics.  It can also indicate a pending alternator failure.

Another thing to check.  If your secondaries on the carb are vacuum controlled, are they opening too soon?  That will make a backfire.  Open the throttle a bit more slowly and see what happens as speed picks up.  If they are opening too fast, the slower motion of your foot will override, and the car will wind up smoothly.  You can still go to wide open and see how it does after that point.

If the balance wheel slipped, the timing will equally off across the board.  Base will be wrong, and all will be equally wrong.  What you see on the light will look correct.  To check it, pull number one plug.  Turn the engine by hand until the distributor rotor is approaching number one cylinder.  Then watch in the cylinder or use a soft probe, such as a plastic straw, and turn the engine back and forth to find the peak top travel of number one piston, then look at the timing marks.  You should be at zero.  If you are off only a couple of degrees, then you are probably a bit off top dead center and it's okay.  If you are off more the 5 degrees look at the balancer very closely, it probably slipped.

Each line does represent 2 degrees.

I would also have to look back at valve adjustment.  If it's off you can lose your high rpm and get a backfire.  I seem to recall you have already done this, but I could be wrong.

kstyer38815.8003009259

thanx Ken, i do so tomorrow.The secondarys are mechanical operated , see they begin after +/- 1/2 open primarys.Already checked/bent the connecting rod very straight so they open as late as possible with the rods that where installed. Backfire is indeed when i push the pedal driving at 3000 rpms , so i assume opening the secondarys.What can be the reason ? Can they give to much fuel ? or just to litle ? and if vac drops at that point shouldn't be the power valve taking over ? It's a new one but i check that valve again and perhaps test-drive once without the check valve protection ?

see you
Norbert 

Yes, the power valve should kick in at that time.  I wonder if it is?  Might want to check the vacuum readings again, as see what it's doing.