How do you establish initial timing? My best buddy, back in Michigan, does it by ear. My bro in law says to slowly advance until it kicks back on start, then back off a couple degrees. I've confirmed the timing mark on the damper is right. Now...
Initial timing
- Thread starter skinny mike
- Start date
Island Girl
Well-Known Member
That's a bit much for a SBC . . . around 10 - 14 is pretty average.
The real thing to watch for is your max/overall timing, which would be your initial and mechanical combined.
32 to 34 overall is generally max before you start risking damage.
Depending on your distributor, and what adjustments it provides for advance rate and advance travel limits, you may need to set timing based on overall advance, and then let the initial be what it comes out to be.
Aftermarket distro's usually have several springs that allow you to set the advance rate and threshold, and several travel stops that let you set how much they can advance.
If you don't have that kind of control over your advance curve, set it at 32 to 34 at about 3000 rpm, (or wherever it stops advancing as rpm increases) and you're done.
JetMech727
Active Member
Same here. W/36-38 total.
Indycars
Well-Known Member
If we are going to split hairs, we would need to know what combustion chamber shape is involved and maybe do some testing with the particular engine combination? The main point is don't get into detonation because that will cause damage to the engine. I'm really talking about total ignition timing.
Guy
Member
I pulled the timing tab off yesterday trying to bend it a little so I can see the mark on the pulley, it's so big covers the pulley, I have looked online but it's hard to tell how wide they are , at first I advanced it till it ran good and left it but then friend from the northeast telling me not to go to around 18 will cause damage . Hoping today is cloudy and I can see the mark on it I did marked the pulley with whiteout , it seems no matter how it's set running good starts like a champ , running cool around 180, I will keep in touch
Guy
Member
Island girl 10-14 is normal but we aren't talking normal with cam and lifters
Island Girl
Well-Known Member
That's what makes these cars so much fun . . . .
It's all from the horsepower to weight ratio increase as you drop the overall weight.
My caution on running 18 degrees initial was based on not knowing what distributor you have, and if you have a way to control how much mechanical advance it adds.
If it's a relatively stock advance curve setup, and the distro adds 22 to 24 degrees, then your total is up there around 40, which is almost guaranteed to produce detonation and other damage, especially with older cast iron heads with their older technology combustion chambers and poor cooling, as opposed to newer aluminum offerings.
And for what it's worth, cam choice has little input into what timing to run, compared to other variables like rod length to stroke ratio, combustion chamber shape, and air flow efficiency.
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Island Girl
Well-Known Member
Guy
Member
With the whiteout I can see the timing line now running at 16 , but I also purchased a vacuum gage and it is running low like 5hg but I don't know what I am idling at no RPM gage but it's as low as the car will run if I idle it up a little goes to 18 in the green on the gage , while in garage figured I am going to do a lifter adjustment while running only one cylinder was too tight , so at this time waiting for the storms to go away and take a run
Well...I see different settings but, how do you DETERMINE initial timing. I understand if it ain't right it can cause overheating ( too low) or knock ( too high). How does one Determine the right setting?
Hey, Mike . . . check this out: how to time a sb chevy - Bing video
Guy
Member
409T i had to retard it was turning over slow and not acting right
Island Girl
Well-Known Member
Whether stock or modified isn't going to make a lot of difference if it's an automotive V8 running on pump gas, as far as timing goes.
If the centrifugal advance is working properly, and the vacuum advance is working, then setting you max timing at ~32 to 34 and then accepting whatever that makes the initial should be fine.
Unless you have an aftermarket distributor that lets you customize your curve, you can't set initial and max independently of each other. . . . and it's excessive max timing that can do the most damage in the least amount of time thru detonation.
If initial ends up at ~10 to 12, (which it should with a stock type distributor) then a working vacuum advance is going to advance it considerably at idle and no-to-light load conditions so it runs fine and accelerates briskly, but remains easy to turn over and start.
If you don't have a working vacuum advance system and you're trying to split the difference by setting the initial artificially high, you'll have nothing but problems.
I could not disagree more. I never run vacuum advance on my hot rods, and know many who do not as well. Blanket statements like that, when presented to those who are trying to learn can be very misleading and maybe even detrimental.
