Can someone guide me through the proper steps on setting the timing on my new engine ? I've never done this before and I'm sure to many its easy. Here is what I have to work with. Basic timing light, there is no adjustment knobs on it (old school) This is what I've done so far, I set it up on top dead center on the exhaust stroke #1 cyl. Then I rotated it passed 0 to 10* BTDC picked a spot on the dizzy to be #1 and stabbed the dizzy in. I also marked 14* on the balancer. OK, now what do I do ? and do I need to buy a vacuum gage ?
I may be wrong, but I believe you want it on the compression stroke. You could be 180* out. Other than that, it sounds like you should be close. On my intial start up, I pulled the coil wire and had my Wife crank the engine while I shot the timing light and adjusted the dizzy until it was where I wanted it. I figured the cranking would fill the carb also. Once set, I popped on the coil wire, cranked it again and it fired right up.
If you're not proficient in tuning.. a vacuum gauge is one of the best investments you can make. It'll pay for itself in mileage gains alone in a very short time. Possibly even the very first longer test drive since efficiency can be improved so substantially over "I set initial timing to 8* and ran the vac pot off the rec'd timed port". Try this on for size. Set initial to your current setting.. adjust mixture screws to achieve best idle vacuum and make note of that manifold vacuum reading. If you have the vacuum pot connected to a timed port?.. leave it there since it won't change any readings at idle anyways. Then.. adjust the initial timing to around 16-18* and run the vac advance pot off of a full manifold vacuum port. Readjust mixture screws to highest and most consistent manifold vacuum level and take note of the new readings. Higher is ALWAYS better as it shows more fuel is being burned and higher cylinder pressures are being produced to aid in power production. The caveat to this more aggressive type of tuneup is that you typically must NOT rev the engine up under power/load and you'll need to pull mechanical advance out for the same amount of initial that you added.. or the total advance number during higher rev's under load will go too high. High speed detonation kills cast pistons and head gaskets pretty fast so it's usually best to tune specific rpm ranges.. such as the idle to about 1,800rpm range that the initial controls before the centrifugal starts doing its thing to the timing curve. Basically.. heavy initial timing gives you significantly more off idle torque and response during heavy time limited throttle transitions(like quick full throttle jabs used for bunny hops) as the vac advance pot falls away and before the mechanical curve starts adding timing when you stay on the throttle for any longer period of time. When you get the initial and vac advance running anywhere in the ballpark it needs to be in.. you should have around 20* of initial and the vac advance supplementation should push it up to about 34-38 @ idle rpms. Then as you cruise down the highway and the mechanical has come in at least partially to add mechanical timing.. that advance number should be well into the 40's.. maybe even touching around 50* under part throttle lean cruise. You can verify that with a timing light if you know your highway cruise rpm and test timing at that rpm. Just be aware that when you start getting more aggressive with timing numbers that the carbs low speed bleed sizing may become inadequate(too large in size which leans the mixture out and forces you to adjust the mixture needle out too far) and lean surge or popping may result. Listen for light crackling sounds(kinda sounds like pop rocks crackling down under the carbs primary boosters).. although leaky throttle shafts can sound somewhat similar too.. or slight lean misses that can sometimes even be felt and slightly erratic vac guage fluctuations. At that point.. most people just back off the initial timing and/or adjust the vacuum pots contribution level with a 3/32 allen wrench to pull some timing back out. An easy test to see if the motor wants more fuel in the idle circuit.. if the mixture screws being adjusted to the point of almost falling out didn't tip you off.. is to just slip some very thin wires down into the low speed air bleeds orifices to displace the airs entry size. In severe cases of leanout.. you can also hear the engine and see the vac gauge become more steady state when you simply put you fingers over the air bleeds(they're located on the outside edges). At that point.. you need to start drilling idle feed restrictions9IFR0 out to make things right but I would not recommend getting that aggressive with the tune as it's easy to get lost in the woods without a compass. Sorry I started to ramble a bit there at the end. Going to be a very busy day and trying to do too many things already. lol Good luck with it all and go easy until you get an idea of what trends are.. and you will feel more comfortable as you go along and the motor responds.. or doesn't get any better.
Guess i just got lucky on mine. Advanced it to the point it didnt crank, then backed it off a hare. Runs great. Didnt have the luxury of a timimg light, so i found that solution somewhere online. When you do get it set though (whatever way you deem most appropriate) make a timing mark on the block and the dist. Will help if you ever have to pull it.
I started the engine last weekend. This is what I did, stabbed the dizzy in at 10* btdc on #1 compression stroke... Poured some fuel in the carb and it fired right up... This weekend I will put a timing light on it... I will pick up a vacuum gauge and learn how to use it... Do I set the timing with the vacuum hose unplugged ? I think I need to advance it to 14* but at what rpm ? also how do I check my total timing ? my light doesn't have the built in rpm gauge...
If you're running ported vacuum to the distributor, (vacuum sourced above the throttle blades) you can leave the hose connected. I don't use a vacuum gauge at all. I give it as much initial timing as the fuel I'm burning (octane) allows without pinging and don't worry about total timing.
best to set timing with it unplugged.. then measure it again with the hose connected back onto the full manifold vacuum source to see how much the vac advance diaphragm is adding into the mix. And a word of caution here too. NEVER.. and I mean NEVER just assume that you can add a bunch of initial timing and leave the mechanical sweeps contribution to "whatever it ends up being". You'll likely have a 16 or 18L reluctor notch which gets doubled for total degrees of mechanical advance sweep. With 15-20 degrees of initial timing being used(which I highly recommend).. you could very well end up with over 50* of ignition lead at full rpm. Not too good for power or durability in the long run. Basically.. pinging at low speed has MUCH less impact on piston crown and fire ring durability than high speed detonation does. Plus.. it's pretty tough to hear those hundreds of detonations occurring at 6,000 rpm which keep whittling away at metal until something pops. Heavy initial timing... Relatively quick AND reduced travel advance curve(mechanical sweep)... Reduced levels of full manifold sourced vac advance supplementation... = high idle vacuum levels.. improved throttle response.. wider power band.. AND increased efficiency.
Bottom line is you can do it the easy way or the complicated way. I've never lost a piston due to detonation. Seen a few stockers that crapped out due to the owner running low octane fuel and stock timing though with the stock cam
and when building a high performance engine.. there's also a right and a wrong way to do things. The bottom line I see many times is that no savvy builder or tuner that I know of would ever dream of jacking around with initial timing settings and not pull out some of the total number with a light. That would just be like tossing an unknown cam in with high ratio rockers without much concern for where you'll end up for PTV and geometry.
No.. I was just kidding. Some don't even check anything at all and there stuff ends up perfectly fine because of vast experience in.. "just run it". All the pro's do it that way too. :16suspect If you treat an engine like it's junk.. chances are high that it'll run like junk too. Like you.. I'm sure that the OP doesn't really care much how all his tuning turns out and will be happy enough that it starts and runs.
You'd be surprised at how many of those so called "experts" cut corners on things. And the end result is AOK. I've taken motors apart that were so trashed you'd never think they ever ran, but they did. I don't treat my motors like junk, they don't run like junk. That is your opinion you're inferring. It has no basis in fact. You have no idea as to what anyone else is capable of, despite your constant attacks and personal insults. Build your stuff the way you want to, but do not assume that your way is the only way because it's not. I could sit here and denigrate the way you do things but I do not. You should try it sometimes. I could go on, but I've got crude oil to haul to keep the east coast liberals in gasoline and happy. Buh Bye.
ouch.. the truth hurts coming off a barbed tongue. Ever watch a pro who's been doing it for years forego measuring and tuning when the engine's set up on a dyno?.. or a race car?.. or a rebuild shop? Errr.. I forgot.. dyno's and engine analyzers are useless tools that don't even come close to mimicking real driving environments anyways. All those silly race engine builders and auto tech's are just wasting their time and out money. For that matter.. you can just throw any old computer on any old car and let the self-learning feature figure it all out because timing and fuel curves makes no difference, eh? Try posting that drivel over on an engine builders forum and you'll be laughed off the site. "I'm so damned smart that I just tune everything by ear these days"! And for the record.. your opinions are no more fact or any less of an opinion than mine or anyone else's around here. Physic's can't be changed and they are what they are.
