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Old 05-12-2011, 08:34 AM   #1
boltnut
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Default initial timing on 73 350

i am a little new to chevy so im still learning chevy ways....what initial timing should my 350 like before any mechanical or vacuum advance added ? 12 degrees ? 16 ? my pontiac motor liked almost 18 but it had aluminum heads. its a stock 190hp 350 with the next cam up...L48 or L82...something like that (the 330hp cam)

BTW what does all that "L" stuff mean ?
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Old 05-12-2011, 10:56 AM   #2
pws69
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Info on timing

http://forums.corvetteforum.com/c3-t...ky-thread.html

It is the 4th item down.....

Last edited by pws69; 05-12-2011 at 11:01 AM.
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Old 05-12-2011, 10:58 AM   #3
boltnut
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linky no worky !
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Old 05-12-2011, 11:01 AM   #4
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Works now
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Old 05-12-2011, 11:05 AM   #5
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"Depending on your year car, what motor you have, etc your initial timing will vary but for the sake of this procedure I’ll use the timing of my ’65 327/365hp motor. My ’78 L82 has completely different timing specs.
In this case the initial timing is suppose to be at 12. If your initial timing is different than what the manual calls for loosen the hold-down bolt on the distributor and rotate the distributor until you get the proper amount of initial timing. "

no mention of what the base timing should be for specific engines. i know i can probably look it up in a manual somewhere but i was curious wht others with the similar combo are using...
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Old 05-12-2011, 11:14 AM   #6
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Quote:
Originally Posted by boltnut View Post
"Depending on your year car, what motor you have, etc your initial timing will vary but for the sake of this procedure Ill use the timing of my 65 327/365hp motor. My 78 L82 has completely different timing specs.
In this case the initial timing is suppose to be at 12. If your initial timing is different than what the manual calls for loosen the hold-down bolt on the distributor and rotate the distributor until you get the proper amount of initial timing. "

no mention of what the base timing should be for specific engines. i know i can probably look it up in a manual somewhere but i was curious wht others with the similar combo are using...
That's because "Base Timing" is only to get you started - what you END UP WITH for "Base Timing" after setting everything up will be different (more advanced). You can start with whatever you like (i.e. 4 degrees), go through the process, then see what the "Base" is when you are done.
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Old 05-12-2011, 11:20 AM   #7
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what ? i always understood that you need to start with base timing, add your mechanical curve, then figure in the vacuum advance. need to know what to set the distributor up with for initial fire up. the number in degress the timing is at with the vacuum advance disconnected and no advance from the weights and centrifugal. it should be somewhere from 10-18 somewhere.
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Old 05-12-2011, 11:26 AM   #8
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Base timing for a stock engine will be shown on the tune up sticker under the hood. If that's missing, it'll be in the shop manual. If you have neither or have a modified engine and feel the need to experiment, follow the sticky already posted.
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Old 05-12-2011, 11:49 AM   #9
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you should always time it according to the emissions label under the hood
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Old 05-12-2011, 12:23 PM   #10
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Quote:
Originally Posted by SanDiegoPaul View Post
you should always time it according to the emissions label under the hood
Only if you have to worry about the fascist CA smog police.

Stock settings are based on stiff springs and smog considerations, I prefer performance settings.

Most small block Chevy's like 32-36 degrees of mechanical advance, all in by 3000 rpm for best performance. I run 36 which gives me about 18-20 at idle. Personally, I only care about the idle setting to make sure nothing has changed since I rarely drive at idle. In fact, not even then since it is easy to just rev the engine to 3000 rpm when checking timing.

My distributor is recurved for 16 degrees of mechanical advance all in by 3000 rpm. To set my timing:
1) Plug vacuum advance
2) Rev engine to 3000 rpm
3) Set timing at 36 BTDC double checking between my fully engraved balancer and my dial back light.
4) Let engine go back to idle (usually end up with 20 degrees or so).

I also have a vacuum can that adds about 16 degrees of advance for a total of 52 under light load which works well for fuel economy.
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Old 05-12-2011, 12:23 PM   #11
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Just a side note. Your car will actually let you know when the distributor is locked in the optimum position...just by driving it. Too advanced for the fuel you are using and it will knock under heavy load...such as lugging it in top gear up a hill. Too retarded and it will idle poorly and lack performance. You can always go back with a timing light and see what that initial number is...to satisfy your curiosity and for future reference. Factory numbers were very conservative because of warranty considerations, not to mention emissions.

Last edited by Faster Rat; 05-12-2011 at 12:25 PM.
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Old 05-12-2011, 12:28 PM   #12
Alan 71
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Hi bn,
The emissions sticker on my 71, 350 base engine, 4-speed, calls for 8 degrees advance. The emissions sticker on the cowl (AR) indicates engine needs to be warmed up, vacuum advance line plugged, and fuel cap off.
Regards,
Alan
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Old 05-12-2011, 12:44 PM   #13
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put her around 12 or 14 initial, 32-34 total. For those of us with bigger cams they like a little more initial timing around 16-18. my total timing in mine at the moment is 36 but she could use a couple more degress
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Old 05-12-2011, 12:51 PM   #14
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Right now I am at 12 base. Adding about 15 with the vac advance.....unknown springs in there. Idles at about 700.
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Old 05-12-2011, 01:58 PM   #15
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Right now I am at 12 base. Adding about 15 with the vac advance.....unknown springs in there. Idles at about 700.
Do yourself a favor and put a couple of rubber bands around the fly weights. Check your timing and rpm at idle with the vacuum plugged. Take the rubber bands off and see if anything changes. You do not want any centrifugal advance at idle...maybe start seeing it around 1100...and "all in" by 3000...but not really necessary for a stock engine driven on the street. I tried all the spring combos in the Mr. Gasket #928G re-curve kit. Had the fly weights coming out at idle and my timing mark jumping all around, so I ended up putting the original factory springs back in. Works fine now. How much total timing do you have? 34 should work fine for your engine. I'm running 36 in my slightly built BB, have run 38 and could probably get by with just a little more...but why take the chance? BTW...with the vacuum advance connected, your engine never sees the full centrifugal and vacuum advances at the same time (12+22+15=49) due to the loss of manifold vacuum as more air flows thru the intake. It is a crude system, but actually works quite well. Makes for an interesting looking graph of the engine operating envelope.
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Old 05-12-2011, 02:07 PM   #16
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you are right, i need to be sure my springs are not worn out. they were recently replaced by the previous owner though and they are stiffer than anything in those crappy MR GASKET kits....IMO those kits are junk.

what i am noticing is that the car seems to want more bypass air. it wont start with just a pump or two of the pedal. i actually have to hit the throttle a little to get more air flowing (or that is what it seems like). my timing mark on the balancer is rock steady but the tach in the dash jumps around a little. not sure what is going on there. also, i like to put a light on it and then crimp the vac advance hose to watch the change....my car took about one full minute to bleed off the vacuum can advance...not sure if that is normal or my can is going bad.
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Old 05-12-2011, 03:05 PM   #17
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I had good luck with the Mr Gasket springs. I used the ones discussed in the sticky and the timing is all in between 2300-2400 rpm which I feel is good. My stock ones were way too tight.
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Old 05-15-2011, 07:23 AM   #18
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Quote:
Originally Posted by boltnut View Post
you are right, i need to be sure my springs are not worn out. they were recently replaced by the previous owner though and they are stiffer than anything in those crappy MR GASKET kits....IMO those kits are junk.

what i am noticing is that the car seems to want more bypass air. it wont start with just a pump or two of the pedal. i actually have to hit the throttle a little to get more air flowing (or that is what it seems like). my timing mark on the balancer is rock steady but the tach in the dash jumps around a little. not sure what is going on there. also, i like to put a light on it and then crimp the vac advance hose to watch the change....my car took about one full minute to bleed off the vacuum can advance...not sure if that is normal or my can is going bad.
Can you measure, using a dial back timing light or a degree marked balancer, what your total maximum timing is and at what rpm? Heavy (stock) springs may not allow full advance until 4000 rpm or more. That is why lighter springs are use in the kits. You want to be all in at less than 3000 rpm.
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Old 05-15-2011, 10:14 AM   #19
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i am running a stock points dist. that has been converted so i am not sure how those springs are working. i am going to get a timing tape for the balancer and do it that way...
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Old 05-15-2011, 10:23 AM   #20
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If you have trouble getting it going when cold, your problem is likely the setup on your choke. Make sure carb and choke adjustments are set per the Chevrolet Chassis Service Manual. Then, work on your timing.
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Old 05-15-2011, 10:23 AM
 
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