I've got a couple of questions I know you guys can help out with. First the background. I changed valve covers and intake manifold on my '79 350. Everything ran fine before. During the take apart phase, the distributer spun before I could mark it. We put it back together at TDC. It runs but is obviously not quite right. I've got a timing light. What's the best setting given my mods? The engine is a '79 350 with HEI distributer, Edelborck Torker, Holley 650 4bbl., headers and no exhaust. I want the most performance without having to worry about detonation or premium fuel. Thanks in "advance". And sorry if this question is a little "retarded". Get it? A little timing joke.
i have an earlier 350...i dont have the set up you do, but im running mine with a 12 degree advance.....hope that helps.
Cam is going to make a difference. A stock cam won't require as much total timing as say a bigger cam.
If'n you don't know what the curve and advance are in the dist, the best thing to do is put a timing tape on the harmonic balancer and then set for 38* @ max. advance by revving up steadily till you reach max advance and checking where you are on the tape. BUT, 1st either make or buy a piston stop to insert thru spark plug hole to find true TDC by adjusting the stop till it stops the piston just before it reachs the top when rotating BY HAND. Then mark that spot on your balancer where it in relation to the pointer. Now turn the crank backward all the way around till you bump the stop again. Halfway between this point and the mark you made is true TDC. Obviously you must make sure this is TDC on the compression stroke and not the exhaust stroke, or you'll be 180* out. Then you put the tape on with it's TDC mark dead on the TDC you have on the balancer. Now set the timing with your light to the aforementiond 38*. Dave On edit: forgot to mention disconnect vacuum advance and plug the line for this procedure, the reconnect after you finish.
Good explanation Handsome Dave. Check everything Dave just said to do. Once it's running correctly its time to make sure you have all the advance in you can stand an still have it start so you get best seat of the pants feel. Keep slightly advancing the timing until it pings when you floor it. Then back it off a touch. Shut the engine off - if it is able to restart without dragging the starter you are set. if the starter drags a little retard until it doesn't. Once it starts right and doesn't ping under accelration - you have it set. Then get the timing light back out and see what it is and record.
OK, so I couldn't get the timing light to work. So I did it by ear and feel. It runs like a scalded ****d ape now. I'm just not sure what the setting is for now. But thanks for the help.
Don't want to contradict my good friend Tudor, but setting the timing by "ear" can be dangerous! If the dist. has a "long" curve, the engine will feel and sound better at a timing setting that will be too high at an elevated rpm when the advance finally gets "all in". Then if you had too much initial advance to work with the final advance, you wind up with high speed detonation, which is hard to hear and a real engine killer. Make sure that you don't have over 38*-40* total advance when it's "all in". If it seems lazy, then get a kit and work on advance bushings and pins and springs to bring advance sooner for more initial advance. This will usually wake up a lazy engine. Back in the early-mid 70s when the 1st energy crunch hit, I was into 4 wheel drive stuff in the boonies. Lots of times you could find regular, but no premium out in the hinterlands. I hjad a Jeep p'up with a 283 SBC with 9.5:1 "power pack" heads which didn't like regular. So I did the reverse of what I'm telling you to do. I searchjed thru the manuals snd found the Chevy dist. with the longest and slowest curve available and then found that dist, IIRC, it was a 396 of some year and model. Anyhow, it could tolerate the 87 octane@ low speeds but when you started home on the hwy it brought the advance up enough to run good & get decent mileage, or at least as good as you could expect with a 4.10:1 gear. Spark advance has gotta be tailored to the use of the vehicle, it's gearing and weight, the engine specs, and the fuel octane. Just be sure to avoid high rpm detonation, cause it'll destroy an engine quicker'n a cat can lick his ***! Dav
Dave, I appreciate the advice. I'm going to confirm with a good timing light at the earliest possible time. I'll be down for at least another day due to a leak at the distributor seal. So, no driving in the meantime to worry about detonation. I'll be able to borrow a timing light from a neighbor tomorrow or Sunday to get it right. Thanks again.
Dave I did say go back and check it with the timing light when you get it where it feels good. I agree you won't want too much advance. Just like you said, spark advance has to be tailored to the use of a vehicle. Seat of the pants is better than somebody telling you set it at such and such a number. You'll never know if a little more makes it run better if you don't try it. You can feel high speed detonation too! I even offered to send him an hei advace curve kit in another thread
I really appreciate the offer, but I'm gonna leave it the way it is for now. And here's a little update. After setting the timing yesterday, I discovered an oil leak at the distributor. So I got a new seal and put it in today. This time, I was sure to mark everything well. It was literally a piece of cake and I had it apart and back together in the same place in 45 minutes. I put some silicone on the gasket and as soon as it cures, I'll start it up and see what happens. But it should be good to go. I've still got to get hold of a timing light so I can confirm the setting to make sure there's not too much advance. I've also got to change the oil cuz I got a little coolant in it when swapping the intake. I should definately be good to go and as good as new by this afternoon. I'll report back when all that's done. And I definately appreciate all the help and advice. You guys are the greatest. I love this place.
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