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I've read the Best of Drivetrain section with the optimum spark thread and timing thread... But im just alittle lost.
If you line up the Harmonic balancer at 0 on the timing tab with the piston at TDC and the distributor rotor pointing directly at the #1 plug, then you are at 0* timing...
If you are looking at the engine do you turn the crank counter clock wise to 8* or so? with the mechanical advance that would be 16* advanced? I think i read that the mechanical advance was double what the number on the timing tab says... Bare with me cause i've read 3 or 4 different articles and its jumbling together...
That would mean the vacuum advance would have to be at 16* to get the 32* desired for most chevy's?
And when you first time your car you plug off the vacuum advance and hold the rpm at 3,000 are you just making sure the slot on the balance is lining up with the 8* mark every revolution?
And if you took the timing tape and snugged it around the balancer and hooked up the vacuum advance and put a white-out mark at the 32* point on the balancer and held the rpm past 2,000 then that new whiteout mark should hit the 8* mark on the timing tab?
Its unbelievable how difficult it is to understand a somewhat simple system!!!!!
im usually not to worried about initial timing all it does is allow the motor to start easier imo , what you want to do is rev the motor up to 3000 rpms with the vacuum advanced un plugged from the carb but plugged , then rev the motor up to 3000 rpms line up the " zero " on your dampner with the " zero " on your timing tab ...... i use a craftsman dial back timing light ( advancing nob ) i set the nob to whatever total timing i want ( 32 degrees for example ) when you rev the motor up line up the marks to give you 32 degrees of advance on your timing light ...... but this is only one part of timing there is also how quick your timing comes in , how much advance is in the distibuter to begin with , initial timing plus vacuum advance ,
remember when setting timing youll need to add your vacuum advanced in the equation too
Thanks Wolf, I'll check the vid out when i get home
And chevy, I'll check out the price of a dial back timer, my buddy was gonna let me use his but his is a chepo autozone special, I'd rather own my own anyways!
OK, I've seen a few different variations on how this is done, so please bare with me... Im trying to figure out if I've timed the car RIGHT!
When I started the car with the vacuum advance fully plugged off, and let it rev steady at 3,000rpm ... Put the timing light (with the dial back timer set to 0) and the notch on the balancer was setting around 30*... So I turned the distributor until the balancer notch lined up with 10* on the timing tab. Shut car off.
Hooked the vacuum back up and reved it to 3,000 rpm again, with the vacuum hooked up the notch on the balancer was around 30-32* advanced, so I then turned the Dial on the timing light to 32*, and the notch on the balancer lined up with the 10* mark on the timing tab... When I turned the dial on the timing light to 38* the notch on the balancer lined up close to the 0* mark on the timing tab.
Is this the correct way?
because on the video posted above it looks like they timed their car with the vacuum hooked up and used the dial to find out what the vacuum was pulling before they tried to find out the initial mechanical advance... this seemed wrong to me?
What should a chevy's timing be at idle with Vacuum Advance disconnected?
What should a chevy's timing be at 3,000rpm with vacuum advance disconnected?
What should a chevy's timing be at with the Vacuum advance hooked up?
I cant seem to find anything!!!
All i find is 8* initial + Centrifical advance + vacuum advance = total timing.
In the above post i think i messed up the timing... I set the 3,000 rpm mark at 10* advanced... But i didnt bother to let the car idle down to 900rpm and check the timing... I can do it tomarrow, but i want to find the answer before i fudge up again
I have read those, but they've never made since till now!!!
Lets see if I have this straight.
Lets ignore vacuum advance.
You set the initial timing (8,10,12) whichever runs best. You then rev the engine to 3,000 rpm, and check the timing to see if you have 32-36* advance. Thats pretty much it, because the vacuum advance really has no play at all, because if you get 32* advance and then add in that vacuum advance you get a overall total of 47* (if vacuum adds 15*)
If Im aiming for 34* total advance, and i know that the centrifugal advance is 24*, then i set the balancer notch at the 10* mark on the timing cover tab.
I think I understand now after 6 times of reading vacuum 101
Last edited by Richardlss; 4th-November-2009 at 12:26 AM..
[quote=Richardlss;1219693]OK the easier question(s) would be:
What should a chevy's timing be at idle with Vacuum Advance disconnected?
it all depends , there are a number of veriables
What should a chevy's timing be at 3,000rpm with vacuum advance plugged ?
normally between 30 - 38 degrees
What should a chevy's timing be at with the Vacuum advance hooked up?
this is not a good way to check timing ,as there will be little to no vacuum at 3000 rpms
I cant seem to find anything!!!
All i find is 8* initial + Centrifical advance + vacuum advance = total timing.
this is correct ^^^^^
In the above post i think i messed up the timing... I set the 3,000 rpm mark at 10* advanced... But i didnt bother to let the car idle down to 900rpm and check the timing... I can do it tomarrow, but i want to find the answer before i fudge up again [ QUOTE ]
Hey Chevy thanks for answering each question! I couldnt seem to find what i was looking for... i literally watched the MSD vid on timing 4 times, read the optimum spark 3 or 4 times, the timing by vacuum a few times and vacuum 101 more than i'd like to! but last night i found my answer that 30-38* of advance you want comes from the initial and centrifugal advance, nothing to do with vacuum advance
If your distributor has 20 - 25 degrees of centrifugal advance and it's all in by 3000 rpm then the answer to your first question is yes.
Once set at 10 degrees the initial advance should return to 10 degrees each time the engine returns to an idle (with the vacuum advance uhhooked).
Your centrifugal advance springs and weights determine what rpm the centrifugal advance starts (usually a little above idle) and the rpm it is all applied (3000 - 5000 rpm depending on the distributor). Check to see if your advance stops advancing at 3000, if it does, then you are okay checking total advance at that rpm. If it's a higher rpm (stock distributor) then you must check the total at that rpm.
The vacuum advance is used to advance the timing even more for better fuel mileage when you are cruising at a light throttle. With a light load on the engine it can, and will like, more advance. A vacuum advance will usually add 10 -15 degrees with the engine at cruising speed under a light load.
Allright done some more timing to it, but i couldnt get it dialed in just right... after numerious attempts i think its the centrifugal advance unit...
I set initial timing at 10*
rev to 3,000 rpm and the timing only hits 22* advance...
SO i took pictures of the weights and springs under the rotor, but camera's now dead and no power for it till the old lady gets back so i'll attempt to explain it:
The weights are attached to the bracket that holds the rotor in place, they are controlled by the springs...
Well when i move the bracket all the way over the weights dont "deploy" all the way... When i open the weights up all the way the bracket only turns half way... So im assuming the weights have been worn out... the question now is where to get new ones?
EDIT:
PHOTOS
This is with the bracket pushed all the way over:
And this is just pushing the weights all the way out... I was also pushing the bracket all the way over too... if i didnt that bracket would be about 1" further back..
To me it just seems like the weights arent able to pull the bracket all the way over?
Last edited by Richardlss; 4th-November-2009 at 07:05 PM..
www.jegs.com or www.summitracing.com has a spring kit that your looking for , it includes lighter springs & weights so your timing comes in even quicker , if your looking for stock parts try your local auto parts store and tell them you need springs & weighs for your distributer they should have them
do you know how much advance your distributer has in it ? ....... most hei's have around 16 to 20 degrees already in them , so if your set your " initial ''
(or idle timing ) at 10 degrees before tdc you should be around 30 degrees at 3000 , this is one reason i dont check timing at idle , what i do is set it at 3000 and then let it idle a see where its at , then if im happy with it i tighten down the distributer and recheck it to make sure it didnt move when i tightened it down
oh and all that rust on your springs and weights isnt good it will actually create spark scatter , you can spray it with some wd - 40 but try to wipe or dab the lube up some , with the rotor spining at 3,4,5,6, thousand rpms and it spraking it will create its own moisture , you can also drill a small hole in the cap so it vents some of the condensation out of the cap too
Last edited by chevyIIheavy; 5th-November-2009 at 01:55 AM..
all it does is allow the motor to start easier imo , what you want to do is rev the motor up to 3000 rpms with the vacuum advanced un plugged from the carb but plugged , then rev the motor up to 3000 rpms line up the " zero " on your dampner with the " zero " on your timing tab 
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