Good evening everyone! I have a few questions about timing a Chevy 350. This motor has already had its "base" timing and has been drove as a daily driver. I put a new carb on it and did some ignition work to it and it's backfiring through the exhaust pretty bad and that usually means the timing is out of wack. Question 1: I know there are many videos on this, but I'm a little confused about the timing marks on the harmonic balancer. I don't have a tab or any marks on my balancer, so how do I go about making my own set? Question 2: I've seen in videos where guys have fancy timing lights and they set the light to for example 8° and it shows on the 8° mark on the timing tab. My question is: Do you set the gun how ever many degrees of timing you want and then rotate the distributor until it lines up with the set number of degrees you have on the gun with the mark on the timing tab? Thanks, Tex
No marks at all? that's fun...how about posting a picture so we can see what you have? but yeah, you can make your own timing pointer and put a line on the damper, and then you'll have timing marks. Figuring out where to put the mark, that's fun....because you want it to line up when the #1 piston is at Top Dead Center. Make a piston stop, and carefully rotate the engine around until it touches the stop, mark the damper, then turn back around the other way until it touches again, and mark the damper again. the TDC line would be exactly between the two marks. The way a dial timing light works, is you set the light to 8 degrees, then when the timing mark lines up at Zero degrees (TDC), that means it is really advanced 8 degrees.
First your going to have to find top dead center. Once you find that you should be close to 0° on timing. Top dead center is the number 1 piston at the very top/end of its stoke. The "fancy" timing light works as such: if your timing is set at 8° on the motor and your timing light is set at zero, your light will show 8° of timing on the engine marks. Now as you turn the dial on the timing light to 8° the marks on the engine will show 0°. As now your showing the amount of timing on the light instead of the engine. The reason for these lights is for checking total timing at higher rpm`s. A lot of engine timing marks stop around 12°, not enough when your trying to read 36° or so of total timing. So you rev your motor to 2500 rpm, turn the dial on the light until the timing marks line up 0° and read the timing light dial, now this is your total timing.
That clears up a lot, thank you! I may have more questions once I get deeper into it. Yes, I can get a picture of it in the morning. It's dark outside and it's in a shed with no electricity, so it'll have to wait until the sun rises.
What squirrel said. I am amazed at how many SBC’s I’ve messed with lately have incorrect timing marks and or pointer position. The only way to check is by finding TDC and going from there.
Finding TDC or verifying that it's correctly marked is important, but it's so basic it's overlooked. Causes a lot of confusion and head scratching.
So where does rotating the distributor come in? I want to keep my timing around 8° because this is just a street cruiser not a racer.
That's not the way to look at it, when you set the timing at the distributor, that's just one part of it. The total timing is what you're really interested in. The initial number isn't really critical, but where it tops out is. That's why it has to be checked out with a timing light and spooling the RPMs up to 3000 or so. Make sure it's done advancing all the way. It doesn't matter if you're racing or not, the ignition timing should be set to spec or it will run hot, probably overheat, wastes gas and mileage and won't run for shit. Adjust the distributor wherever it needs to fall to reach 34° or 36° BTDC with the vacuum advance disconnected and plugged. Test drive it and check for ping under hard acceleration. Basically any engine runs best with as much timing as it will stand short of any ping or detonation at all times under all conditions. Then re-connect vacuum advance, and check for part throttle ping under cruise acceleration. Vacuum cans are adjustable, start at max and back off as required.
There's a mark, it's probably full of gunk but there's a mark. There may not be a pointer but that balancer has a mark
Ok, so I think I'm beginning to understand how timing works. If I do find a mark on the balancer what do I do after that?
I’m Generaly more concerned with total timing being close to 34-36 by 2800 or soRPM’s than the initial being at 4-8. And go from there.
Keep in mind, the mark may appear where you don't necessarily expect it to be, depending on the era of the engine. Chevrolet used three different locations over the years. There are aftermarket tabs for all three. TDC never moved, nor did anything else, except for both the tab and the groove in the dampener. As long as the tab and the damper groove match each other, it's 6-of-one or a half-dozen of the other. If you are not seeing the groove on the damper, try looking at the near-top. Lots of people forget to look there. Any chance you know what year the engine is? If not, how about the code that is on the pad in front of the passenger side head?
Thanks gimpy, saved me some work. @Tex Flick The 350 came out in 1967 so it's anybodys guess who's had their fingers in your engine. Not knowing the history (you or us), as gimpy showed you could have any number of mismatched parts. The best way to get a reasonably definative answer is to get some photos submitted so we can get a better handle on what your working with such as the timing cover/pointer, harmonic balancer, etc. Many times people will just rotate the distributor until it runs reasonably well and call it good. The engine code and some photos are what we need to start. Does your timing tab look like the above photo or like mine below, which is a 67 engine (327).
There is an exception to the diagram that I posted. Vans, as far back as 1980, that I have seen, have the tab/mark near the top, as elsewhere would be impossible to access.
The Jalopy Journal
