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Username Post: Timing Adjustment for GM 305 engine        (Topic#209542)
Silverado90 
Contributor
Posts: 101

Loc: Tarsus / Turkey
Reg: 10-22-04
02-13-09 03:47 AM - Post#1629015    

hi everyone,
as the title says i have couple questions about timing. I have a GM 305 engine(1979) in my CJ, i found this info on the net;

Basically, your 305 initial timing (timing you're going to see with the timing light) will be between 8-10 degrees BTDC (before top dead center). you'll want to loosen your distributor to the point you can move it with resistance, but not to the point it's really loose. You need to disconnect the vacuum line from the vacuum canister( if your distributor has one ) on the distributor and plug the line, connect the timing light to the number one plug wire (1st wire on the driver's side) make sure it's not near any exhaust or it'll burn the timing light wire, or melt the plastic. Start the truck and point the light at the timing tab. You'll notice one side of the tab will either have an A or B, or it'll be marked ATDC or BTDC on either end of the timing tab. You'll need to make sure the timing mark on the damper is on the number 8 or 10 on the BTDC side of the timing tab, and not the ATDC side. Once you get it where you want it, tighten the distributor taking care that it doesn't move on you, then recheck your timing to ensure it didn't move. Shut the truck down reconnect the vacuum line(if you had one to disconnect) and you should be good to go. Rotating the distributor housing counter clockwise will advance the timing (which is what you want) depending on where your timing is at to start with and rotating it clockwise will retard the timing.

I understood this very well. now i got a "Craftsman Timing Light Model 21023".since my english is not good enough i couldnt understand some things on the owners manual.
first of all ,what is the purpose of the knob whish is located at the back of the timing light.there are numbers till 60 from 0.

i started the timing light,knob is pointing zero,i couldnt see the timing mark,as i turn the knob to the right,when the knob hit 55-56 i saw the timing mark on the engine.
what does that mean?

shortly what is the knob for ?? and am i doing something wrong??
if you explain it with simple words i will really appriciate it.

thank you
1961 Chevrolet Apache 10 -all stock but needs rebuilding,
1990 Chevrolet K1500-305 V8,700R4,LT255/75R16 BFGs All Terrains


Edited by Silverado90 on 02-13-09 03:48 AM. Reason for edit: No reason given.

 
Phazer 
Valued Contributor
Posts: 3004
Phazer
Loc: Armpit of the Universe
Reg: 10-10-03
02-13-09 06:45 AM - Post#1629079    
    In response to Silverado90

Sometimes you have to disconnect the vacume line to the distributor.

The knob on the timing light helps you check the timing if the timing mark is beyond the tab or for checking total advance.

The knob doesn't actually change the timing. Through electronic trickery, it moves/changes when the timing light flashes. Let's say for arguments sake that you want TOTAL timing at 3000 rpm to be 32*. You set the knob at 32* and start the engine and rev it to 3000 rpm. The mark should be at the 0, (zero), setting on the tab. If it's not, loosen the dist nut just enough that you can rotate the dist with a little force and recheck.

Your situation will be something in the 8-10* range. Set your knob at what the sticker/book calls for and the indicator ought to be at zero when it's properly set at the specified rpm.

But like I said, it's important to see if the vacume hose needs to be disconnected.
My "To Do List" for this weekend:
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Silverado90 
Contributor
Posts: 101

Loc: Tarsus / Turkey
Reg: 10-22-04
02-14-09 04:40 AM - Post#1629671    
    In response to Phazer

i am sorry i still didnt understand what to do with the knob .
1961 Chevrolet Apache 10 -all stock but needs rebuilding,
1990 Chevrolet K1500-305 V8,700R4,LT255/75R16 BFGs All Terrains


 
Phazer 
Valued Contributor
Posts: 3004
Phazer
Loc: Armpit of the Universe
Reg: 10-10-03
02-14-09 06:45 AM - Post#1629697    
    In response to Silverado90

Just put it on "0" and adjust as specified.
My "To Do List" for this weekend:
Nothing but womens names...
and drugs....

92 Bravada
96 Sunfire
00 Impala
05 Stratus
90 Wrangler
77 Cub Lo-boy
87 Intruder VS700
95 Intruder VS1400


 
Silverado90 
Contributor
Posts: 101

Loc: Tarsus / Turkey
Reg: 10-22-04
02-14-09 02:39 PM - Post#1629901    
    In response to Phazer

okay ,thank you very much Phazer ,and again i am sorry about my english i am trying to improve it.
1961 Chevrolet Apache 10 -all stock but needs rebuilding,
1990 Chevrolet K1500-305 V8,700R4,LT255/75R16 BFGs All Terrains


 
Silverado90 
Contributor
Posts: 101

Loc: Tarsus / Turkey
Reg: 10-22-04
02-23-09 10:44 AM - Post#1636599    
    In response to Silverado90

well today i set my timing to 8-10 degrees.result is not good.runs like crap.acceleration is very bad. now setted to off scale.acceleration is ok but nowt very good. did i do something wrong??
1961 Chevrolet Apache 10 -all stock but needs rebuilding,
1990 Chevrolet K1500-305 V8,700R4,LT255/75R16 BFGs All Terrains


 
Phazer 
Valued Contributor
Posts: 3004
Phazer
Loc: Armpit of the Universe
Reg: 10-10-03
02-23-09 12:33 PM - Post#1636688    
    In response to Silverado90

Did you set it BTDC or ATDC, (before,(advanced), after,(retarded))?

I'm pretty sure it needs to be BTDC.

Set it to "0" and see if it improves. If it does, adjust it to the "other" side of "0" from what you were.

The timing tab should look something like below, maybe not as many numbers:

8-6-4-2-0-2-4-6-8

If you set it at "0" and then rev the engine while watching the timing mark, it should advance, (move) when reved up. You want to adjust it to that side or that direction of "0" at idle.
My "To Do List" for this weekend:
Nothing but womens names...
and drugs....

92 Bravada
96 Sunfire
00 Impala
05 Stratus
90 Wrangler
77 Cub Lo-boy
87 Intruder VS700
95 Intruder VS1400


 
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