I am extremely frustrated with trying to set the timing on my vette.
Specs:
-350 sb
-375 hp
-Mallory dist. with vac. advance
-750 Edelbrock Carb. with 1-1/2 turns out setting
-Idle at 800rpm
Just want to state I am very green in regards to setting timing and adjusting carb., but I am a quick learning and eager to learn. I have been reading a lot of articles on the net including Barry's and Lars for info.
Situation, I have adjusted the carb 1-1/2 turns out and it seems to run best with that setting. I plugged the vac. on the carb. and hooked up the timing light (sears adjustable timing light). I have tried every spring that came with the dist. (gold, silver & black) and the timing comes in all at 36* 2800rpm. with the silver spring and 3000 with the gold & black spring. But I don't really have any timing curve with any of the springs; 2800rpm I have 36* (total) at 2500rpm I have 34*, at 2000rpm I have 32*, at 1500rpm I have 30*, and at 1000rpm (around Idle) I have 28*. I have tried to retard the timing as much as possible and I still get the same curve. When I drive the car and give it mild to moderate throttle it knocks like hell. I also bought the mr. gasket springs and had the same results. I don't know if this matters but the distributer shaft seems to have a lot of side to side play, if you grab the shaft you can move it back and forth probably 1/4 inch; is that normal?
Sorry for the post and for my spelling. If you need more info please ask.
Thanks
Jake

 

1/4 inch play in Shaft thats a bit excessive I'd think you'ld be having cap & rotor clearance issues.
At Idle you've got 28* of advace with vacuum adv plugged??
Thats way too much at idle the weights shouldn't pull in any advance.
You sure you have the correct balancer and timing pointer on your engine?
You dont state if this is a new engine or if its been in the car awhile

 

It is a new crate motor that came with the balancer and pointer installed. I think the clearance with the rotor and cap are fine. It doesn't woggle side to side, I can turn the rotor a 1/4" back and forth. Like I said I am green and I want to learn how to tune the motor.

 

I was thinking that maybe the pointer was wrong, so I did test runs. I would turn the dist. a little then drive ect. But it didn't matter were the dist. location was it still would knock like hell, sometimes a little less with certain dist. locations..

 

I accually just measured the back and forth movement and it is 1/8".

 

Ok I see what you're saying on the movement -rotational movement-
Lets get back to basic timing.
Bring #1 cylinder to TDC of compression stroke then.Your pointer on the crank should be at "0*"
Drop Dist in its hole so the rotor tip is physically pointing to #1 cylinder,
Front left of engine.You may need to turn oil pump to align the slot with the shaft.
Tip: point slot in oil pump at the #1 cylinder before dropping dist in.
After dropping dist in mark on the outside of the Dist where pointer is aligned. You want this mark visible when the cap is installed.
Put cap on and make sure mark on dist is aligned with #1 on cap.
Timing is now set to 0* adv.
ensure firing order is correct 1 8 4 3 6 5 7 2 clockwise rotation.
Start your engine. It might not be too happy running there. twist dist counterclockwise a little till idle speed starts to increase. Now check your timing with the light.
With vacuum adv disconnected set timing to 10* advanced.
do all this then post back on how its running please

 

Lets not worry about curve(weights) yet. just want a good baseline tune to start with

 

Thanks for your help!
I did all the above except setting at 10* then start from there. Tomorrow I am going to take out the distributor and completely start over to make sure everything is right and start with setting my timing at 10* and go from there.