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Old 11-09-2010, 05:01 PM   #1
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Default what's the base timing for a 1st gen 350 sbc?

i'm trying to get my new small block running. i've asked some friends of mine and heard a couple different degrees advance for the initial timing. i've heard anything from 7 to 10 degrees.

i just wanted to get ya'lls opinion on here.
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Old 11-09-2010, 11:51 PM   #2
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For a stock SBC, I'd do at least 10 btdc. For any aftermarket cam (even a mild one) though, I'd do more like 15-18. Just remember to watch your total timing and, if needed, reduce the mechanical advance when you boost the base timing. I have the Gen 1 SBC in my Nova set at 15 base + 21 mech. for a total of 36, plus an additional 10 vacuum advance at cruise. Engine has a mild 268 cam and low compression on old style GM heads. I had zero ping with those settings all summer, so I'll probably try a degree or two more next year.

Ideal total advance will be dependant on your individual setup, but with early style heads, 36-38 should be good. Maybe 32-34 with a vortec style head.
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Old 11-10-2010, 12:12 AM   #3
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how to set the base timing? can it be set when putting the balancer BTDC before starting the engine? a friend of mine put it ATDC few degree's then start the engine and play with the distributor and i have a feeling this is the wrong way
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Old 11-10-2010, 06:43 AM   #4
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When I am putting a distributor in, I like to set the balancer at 20* BTDC and put the distributor in so the rotor is lined up with #1 plug. This way, you should have plenty of advance to get the motor to fire up right away. After that, use a timing light and twist the distributor to get it right.

Listen to RPM...his timing advice is right on. Way too many guys out there trying to run performance cams with 8-10* initial. Then they wonder why they get crappy gas mileage and the car keeps overheating. I run 20* initial, 16* mechanical and enough vacuum advance to have 52* at idle. 10.8:1 compression and no ping on 92 gas.
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Old 11-10-2010, 06:57 PM   #5
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on my setup i have the dart iron eagle 230cc heads. my compression is 9.4:1. so its pretty low. i have a hydraulic roller cam. the duration at .50 is 244 int/ 252 exht on a 110 lsa.

so do you think i should run 15* initial or more?

yesterday i started at 10* degrees and the engine would not even hold an idle.
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Old 11-10-2010, 07:50 PM   #6
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how to set the base timing? can it be set when putting the balancer BTDC before starting the engine? a friend of mine put it ATDC few degree's then start the engine and play with the distributor and i have a feeling this is the wrong way
i'm surprised it even ran if the spark plug fired after it went down. was there alot of detination?
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Old 11-10-2010, 08:51 PM   #7
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i'm surprised it even ran if the spark plug fired after it went down. was there alot of detination?
not a single ping but thats how my friend do it in everycar I told him before about setting base timing but he insist he do it that way so should I set the timing again?
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Old 11-10-2010, 09:15 PM   #8
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on my setup i have the dart iron eagle 230cc heads. my compression is 9.4:1. so its pretty low. i have a hydraulic roller cam. the duration at .50 is 244 int/ 252 exht on a 110 lsa.

so do you think i should run 15* initial or more?
Definitely 15+ with a cam like that. I have a mild Comp 268 cam, and I'm at 15 base with great idle/low rpm driveability and throttle response....MUCH better than when it used to be at 10. For a cam your size, I'd say 16-18 at least. Once you start getting past 18, the starter might struggle a bit when trying to start the engine warm. Even at 18, you might have some slow cranking if your starter/electrical system isn't up to par. Again, just make sure that as you bring your base timing up, you're not going too far with the total advance. You could probably get by with 38 total with that comp ratio and those heads, but every application will vary a bit. Start at 36 total, to be safe. Then raise it slowly. Some go as high as 40 without ping.

You'll probably also benefit from running full manifold vacuum advance, so you can get the most timing possibile at idle. I run ported vac advance, because my advance unit isn't providing full advance at my idle vacuum, so timing at idle would be unstable if I ran manifold vacuum. One day I may change the vac advance unit, but for now with a cam as mild as mine, the engine runs great with just 15 initial advance at idle. Depending on what distributor/vac advance unit you have, you may also have to change the vac advance unit to one that provides full advance at about 2" of vacuum below your idle vacuum, for a stable idle.
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Old 11-11-2010, 08:28 AM   #9
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That is a huge set of heads, big cam and really low compression. This engine will most likely want the timing locked out at 38* or so and then use vacuum advance to add another 15* for idle and low speed. I would start by limiting the mechanical to 10* and add 25* intial along with vacuum advance.
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Old 11-11-2010, 04:47 PM   #10
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this is my first time putting something like this together. i'm not too familiar with with what the vacuum advance is. or how it works. my distributor has a small vacuum port on the side so i put a vacuum hose connecting it and a vacuum port on the carburater. but thats about as far as i know what to do. how do i adjust the vacuum on the distributor?
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Old 11-11-2010, 10:23 PM   #11
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how do i adjust the vacuum on the distributor?
some distributors has adjustable vacuum not all of them my Mallory HEI has adjustable one I adjust it with small Allenkey
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Old 11-15-2010, 05:49 PM   #12
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alright. i set the the timing at about 15* advance. i fired her up and she held an idle. but then after a while the rpm's started climbing.

why would this be?
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Old 11-15-2010, 08:12 PM   #13
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this afternoon i set the timing at 16* advanced and it wouldn't even fire over.

i'm so confused!
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Old 11-22-2010, 08:10 PM   #14
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do any of ya'll have some more ideas??
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Old 11-23-2010, 06:40 AM   #15
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Are you getting spark? Fuel? If yes to both, then maybe your balancer marks are wrong or moved. Try turning the distibutor counter-clockwise as you crank (that will advance it some) and see if it fires over.

What distributor are you running?
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Old 11-23-2010, 06:47 PM   #16
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i'm running a custom billet hei distributor from Davis unified Ignition. and i know i'm getting spark and fuel. i've pulled a plug and checked. my fuel pressure reads 6.5 psi.

and i thought it wasn't a good idea to move the distributor while its cranking? i thought it was bad for it
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Old 11-24-2010, 06:33 AM   #17
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You can move the distributer while cranking. You don't need to turn it more than a few degrees. Also, make sure the plugs aren't covered in carbon. Lastly, check that the distributer is getting a full 12 volts while you are cranking. If the battery is a little weak and the distributer isn't getting 12 volts minimum, you will have problems getting it to fire over.
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Old 11-24-2010, 03:05 PM   #18
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ok. thanks man. i'm going to get me a volt meter and check it. i didn't think about it not getting enough volts to the distributor.

and i've pulled the #1 spark plug. it was a little black like it was running rich. but there wasn't a big layer of carbon or anything. i'll go ahead and pull all the plugs and check them.

i'm about to check it here in a little bit and we'll see what happens.
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Old 11-24-2010, 10:39 PM   #19
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I have a question of my own. My set up is kind of similar to the OP's all but the cam. Mine is 235/235 and 285/285 on a 108 LSA. I have my timing set at 14* at idle and 34* total. I'm using an MSD Streetfire HEI and the vac is not hooked up. What would happen if I hook up the vac port to the carb?
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Old 11-29-2010, 11:29 AM   #20
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If you hook up the vacuum advance...it will run better! Try it and see how it goes. It should idle better and drive nicer in traffic. You should also get better gas mileage, run cooler and the plugs will last longer. It probably wont impact your top end charge at the dragstrip.
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Old 11-29-2010, 11:29 AM
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230cc, 350, advance, base, big, block, cam, chevy, engine, gas, heads, large, milage, run, sbc, time, timing, vacuum


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