Allright I have a pretty big cam "I dont know the size because the guy that i bought it from didnt know either?" Anyways, if i wanted to set my timing, what would be the best possible way? One guy told me that i couldnt use a timing light because of the cam. Another guy told me that i needed a timing light to get the presice timing :confused: Im so confused, should i use a timing light or should i time it by ear? thanks

 

Hey,

There is a pretty good article on Timing in the tech section. Also, for user opinions, do a search for timing.

I think you'll find enough information to make one's head spin. :crazy:

 

thanks :D

 

You'll need the timing light so you can reference what the timing is at. I'd start at the factory settings and move up or down by 2 degree increments(start by going up or more advanced) you'll "road time" it to get the performance/drivability you want and use the timing light to precisely adjust your changes and to get the final acceptable setting, then write it down so next time you'll have that as reference. Usually I just keep adding advance until I start getting "pinging"(pre-ignition) then back it down 2 degrees or so. Hope that helps.
Scott

 

Set it at total as that's what will give the best power and economy. If you just add or subtract from initial you're as likely to wind up with more or less total than is optimum. If you don't have an adjustable timing light you can still set your total. Measure the circumference of the balancer, divide that figure by 10, put a mark on the balancer that distance from the TDC mark (on the driver's side if the TDC mark is facing up). With the vacuum advance disconnected and plugged, and the timing light hooked up, rev the engine until the marks stop moving, align the new mark on the balancer with the 0 mark on the tab and you will be at 36º total. Make note of your idle timing and you can use that figure for future adjustments. Because many distributors don't reach full mechanical advance until over 4,000 rpm, it's important to rev it until you're sure that it's through advancing. 36º isn't necessarily the optimum total for all engines but it should be close to for most and will be a good place to start.

 

DR -
I think the timing articles the guys are referencing are the ones I wrote and posted up on the tech site. But here are a few things for you to consider (do let me know if you need the article - drop me an e-mail and I'll mail it out to you V8FastCars@msn.com)

First, you do need to use a light. Regardless of the cam you run, you still want to set your engine up for TOTAL timing. Total timing is the maximum amount of timing that the distributor will give you at elevated rpm with the vac advance disconnected. As rpm comes up, the centrifugal advance dials in more timing. You want this total maximum timing at elevated rpm to be around 36 degrees. Once you go past this point, most cars will start loosing peak power, although every car is a bit different. But 36 is the best all-around starting point I have found - regardless of how big of a cam you have. If you have fast-burn cylinder heads, you need to limit this total advance to about 32-34 degrees. To set this, you need an adjustable timing light (available from Sears for about $69 - a bargain - go buy yourself one for Father's Day).

Once you have the maximum total timing set at 36, you can drop the car back down to idle. Check the timing and note where the idle timing - or "initial" timing - is at. It could be anywhere from 6 to 16 degrees. Now, with the vacuum advance disconnected and the car at idle, start turning the distributor back and forth slowly until the best QUALITY idle (which is not necessarily FASTEST idle) is obtained. You may need to re-adjust idle mixture screws and idle speed while you're playing with this. Once you find the sweet spot where the best quality idle is obtained, put the timing light back in the crank and see where the "initial" timing is. It may be quite a bit more or less than what it was once you had the timing set up for TOTAL timing. The difference in the settings is the amount that you want to change your centrifugal advance curve by. For example: if you ended up with 8 degrees initial advance with 36 total, and you find you get best idle quality with the initial timing at 24, you need to shorten your centrifugal advance curve by 16 degrees (8 distributor degrees). Resetting the timing to 36 with the shortened curve will then give you 24 degrees initial. These numbers are only used as an example, and will not be indicative of your actual numbers...

You can also play with ported vacuum vs. manifold vacuum to your vacuum advance in order to get the best idle quality out of the car. But don't be alarmed if you find that a bumpy cam needs a LOT of initial timing - this is quite common. But if it does, make sure you shorten your advance curve such that you don't end up with too much total advance - this will kill your top-end power, and possibly produce detonation at high rpm with associated engine damage.

 

Lars, I think this is the first time that I've seen anything about shortening the advance curve. How is this accomplished? Thanks, Craig :chevy