Maybe someone can explain this to me. My 327 chevy has a slightly longer duration than a mild cam. I Think I should be running about 16 to 18 degrees btdc. The marker on the timing chain cover goes up to about 10 degrees btdc. Now, I can guess at 16 to 18 and that has worked reasonably well. How can I tell more accurately. Do they make tapes that go around harmonic balancers or is it a guessing game? Thanks
Mr. Gasket makes timing tape. Different diameter dampers take different tape. Or you can measure your timing tab and mark your damper from there. If your gonna run a lot of initial timing, you'll need to take some out of the centrifgal advance in the distributer to get your total right. Larry T
A good timing light does it for you, I set my light to a degree I want and read zero on dampner. If you like to mark your dampner just use a degree wheel and scribe your desired marks you want. A little hard to do in a car but on the dyno and in some marine applications I prefer to time off the flywheel.
Get a timing light that has a programmable advance. You dial in your initial, then line up the timing mark to 0 BTDC.
i have a timing light with a dial on it. instead of using the numbers on the timing chain cover you use the dial on the light. when the mark on the balancer or crank hub hits the zero on the timing chain cover, what ever reads on the timing light dial is what your timing actually is. these lights are only a little more then a regular light but come in handy if your marker only goes to ten or if you have to make your own timing marks.
The curve kits will both limit total centrifugal and speed it up... There are tapes for all sizes of SBC balancers, which will usually disappear pretty quickly in use. Free accurate measurement: Find an eighth grader who is taking plane geometry. Beat him up and run away with his protracter and compass. Use the compass to draw a circle the diameter of your balancer on a sheet of cardboard. Draw another circle a couple of inches bigger around that, putting the compass into the same center. Use the protractor to mark in as many degrees as you wish from center out to edge of outer circle. Cut out inner circle, slide outer circle over your balancer...you can split the circle for ease here. Put zero at TDC, mark off your degrees, sharpy, whiteout, chisel or file...
my reply is to use a Snap On dialback timing gun, worth the money and keeps flashing to 7,500RPM one of the few tools you need from Snappy also set your #1 TDC witha positive stop i turned crank both ways and marked dampner on each end of the stop and measured to center the two marks and cut the new place with a hacksaw and filled line with yellow junkyard marker, shows up then it is very common when building engines from parts on SBC to be off from 3/4 in to slightly over a inch always think about total timing advance, I run 40 deg on stockers and about 38 degrees on 12.5 CR engines others advice may varry from these and street engines may run about 10 degrees over that of they are stock
First I would use A top dead center device to find TDC. This screws into spark plug hole rotate engine (by hand slowly) until piston contacts the stop. Mark this on the dampiner rotate the eng the other direction to the stop. Mark on the balancer. Now take a tape measure and split the distance this mark should be 0* on your balancer. If it is not purchase an adjustable timing marker. Set your TDC mark on your balancer. Now get an adjustable timing light It allowes you set your timing light to your initial adavance to what is desired.IE:10* advance on your timing light it will indicate 0*on your timing light. Then raise rpms and see total advance.
Thanks for the information to all of you. I guess a programmable light is the way I need to go. That will make the third light for me! My timing cover is original. I do need to address my mechanical advance. I think I will find someone with a distributor testing stand. Can you use that to determine the correct mechanical advance.
Just use the light to read initital, then rev it to 3500 or so and see what the total advance is. Then subtract the difference to see how much mechanical advance your distributor is providing.
...unless you're running an MSD box or something like it. Digital and dialback timing lights get confused by the MSD box and won't work right. Turns out the first line of the instructions for the MSD box says not to use those timing lights. I have an MSD digital 6 plus box, and my snap-on digital dialback was all over the place with it. Pulled out my 30 year old craftsman light, and it works great.
Maybe I'm wrong here but if its an 8" balancer cant you take 8 X 3.1415(PI)=25.132 divided by 360=.0698 x16=1.1169" so 1.11inches from the TDC mark should be real close to 16*
I used to use one of these (Snap On), until I checked it against a degreed balancer. Lots of difference in readings. In all fairness, I was checking total advance and not initial. Larry T
No offense to anyone above, and if you have good luck with a dialback light, that's cool...but I have NEVER found one that was accurate. As Larry notes...if you check them, they are always off, to a greater or lesser extent. At a rough guess I've tested 10 or more, Snap-On, Sun, Craftsman. Doesn't really make a difference which ignition is being used, although as patman mentioned, multiple-spark units will completely throw them off. As they say, your mileage may vary.
Easy deal, with the engine off bump engine to 10 btdc then put a mark on the balancer at 2 btdc. Now fire it up and set timing to the mark you made and now you have 18* of timing.
Yep, simplest, easiest, cheapest way to do it right here. And just to clarify, the mark you made on the damper is 8° BTDC, so you need to time it with the new damper mark lining up with the 10° BTDC mark on the timing tab, 8° + 10° means a total of 18° BTDC
one of the car mags had a how to on changing the curve and limiting the mechanical advance, you used different weights and springs and welded up one of the slots, i dont recall what mag, maybe 30 years ago it was?
I have been messing around trying to "dial in" my engine as well. I'm running a large cam that is only providing me with a vac of 11. I'm also running a matic, every small tweak of the carb can affect some aspect of the total performance. Almost every engine is going to need just a slightly different tweak to get the best performance out of it. I suggest using your timing as a bench mark and keeping a log of performance, adjust make a pass, on a manual trans car this should be fairly straight forward as you won't have to consider adjusting the vac modulator. Best thing to do is put your ears on and go make some passes, log and adjust.
If your just interested in your base timing, use the vacuum gauge. More advance = more vacuum. Then drive and turn back to stop the pinging. I would not use the timing light until you verify tdc is actually tdc. If you are tuning for all out performance, then total timing is the way to go. And again, as mentioned, flog it and take notes, and change it some more!
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