69 Riviera 430, on hard acceleration was getting backfire through carb. Timing was set at factory's Setting of 0 TDC, I advanced timing to 8 TDC, no more backfiring car runs really strong. My question is am I doing any harm to my engine running at 8 TDC. Thank you Jerry
You have to verify the maximum mechanical advance that your distributor is putting out. Read Larry’s first post in his Power Timing thread in the FAQ section of the forum
I assume you mean BTDC. Before TDC.... Is vacuum advance working? Did you set timing with vac adv plugged? Up to 1970 0 or 2.5 was spec but they ran vacuum to full vacuum port to get nice idle and low end power. With 8 deg you will have too much total....
If your timing chain and gears are original or old enough you just compensated for chain stretch by adding in that advance of 8 degrees.
Jerry, your question is exactly why I wrote the power timing thread many moons ago http://v8buick.com/index.php?threads/power-timing-your-buick-v8.63475/ Initial timing really tells you nothing. The only time you are at the initial setting is when you sitting at a traffic light. As soon as the engine goes above idle speed, timing is added by the mechanical and vacuum advance mechanisms inside the distributor. The stock timing for a 69 Riviera 430 is 0* (TDC). That distributor has 30-34* of mechanical advance. Here's the thing though, that ONLY applies if you have the original part number 1111335 distributor. The distributors over the years differ inside with the amount of mechanical advance. Some have less. Unless you have owned the car from new, and you know it's history, you may have a different distributor with less mechanical advance. The common mistake guys make is to adjust the timing to what the book says even when parts have been changed. What you need to do is set the maximum amount of advance (initial + mechanical) to 30-34* like Buick engineers intended. The linked thread will show you how to do that. Also check to make sure your vacuum advance is hooked up and actually working. Many canisters go bad.
Thanks all for the reply backs, I have installed a MSD Pro-Billet Distributor part # 8552 The distributor come with 5 different advance stop bushings. It comes with with a Blue (21 degree ) bushing already installed. The other ones in the kit are,Red=28 Silver=25, Green=23, Purple=19, Black=18 I kept the one already installed on the Dist the blue one =21 degrees. I also installed a MSD Blaster coil. So with idle timing set at 8 degrees and MSD Dist at 21 degrees will I harm my engine.
Put the 18 degree bushing in, and time it at 14 degrees initial advance, thats the best bang for your buck. You want as much initial as possible without harming your engine. 32 degrees of total timing is safe.
That's fine. 30-34* is what the engine wants for best power. Right now, you have 8 +21= 29. You can go to 12* initial. That will give you 12 +21 =33*. Do you have the vacuum advance hooked up?
Good, Just make sure to set the initial at as low an RPM as possible. Depending on the springs used, there can be some mechanical advance in at idle speed which will make your setting of the initial inaccurate.
https://www.holley.com/products/ignition/distributors/buick/parts/8517 Think they have changed things up in the past few years. The 8552 is a ready to run distributor, no box needed.
Larry, you mentioned the stock timing for the 69 is at 0* TDC / distributor has 30-34* of mechanical advance in it. When factory stock (dwell at 30* and premium gas) does this mean you can set initial anywhere from 0* to 4* degrees without detonation? Thanks
You ALWAYS set dwell, then set timing. Dwell changes timing, timing does not change dwell. The stock 69 distributor specs say maximum mechanical advance is 30-34*@ 4600 RPM. Manufacturing tolerances of the day mean that it could be anywhere in that range. That's why I advise guys to set the maximum advance they want to run. Then, the initial advance ends up where it HAS TO BE depending on what maximum you set, and the actual amount of mechanical advance in YOUR PARTICULAR distributor. To do that, you must be ABSOLUTELY sure that ALL your mechanical advance is in WHEN you set your maximum advance. Use the lightest springs you can, and raise the RPM enough so that you are sure. When checking your initial, use the heaviest springs, and lower the RPM as much as you can to be certain that the weights are FULLY retracted and there is NO mechanical advance in. That is how you power time YOUR distributor, NOT the one described in the specifications.
Larry, i am not interested in power timing at the moment. As i said, ALL STOCK. Is it okay to turn the distributor initial from 0* TDC to 4* BTDC. Just from a factory point of view. Setting Dwell at 30* and initial at 4* BTDC (instead of 0* TDC) would that be just fine?
