Setting Timing w/o vacumn advance

[Guest]

Dear All,
Ok, my 6 should be running centrilfugal advance as I am not connected to the vacumn port on my distributor to advance the timing. (don't ask) Setting timing at idle, what is the optimum setting, what degree, and before or after top dead center, and which is which. Car was setup by mechanic and he screwed with my timing. I am bogging badly at or near 4K rpm under load.

Dr. Bill

 

[MDCanaday]

Dr Bill, when you change something like this the "book" is NFG to you. In my opinion you should tune the engine for the gas you plan to use by trial and error. At idle, advance the spark untill the engine starts to increase RPM, then, back off a little bit and road test. Under load (3rd gear slight incline) the motor should only ping slightly as full throttle is applied.Too much ping is bad but a little bit is near perfect as far as total advance, and fuel economy are concerned.
MD(mad dog)

 

[aeronca65t]

....or, here's an alternate suggestion.

Set the timing to 32 degrees *total* advance (at high RPM). What most people care about is timing at higher RPMs, when power is made. As long as car will start and idle OK, the low-speed timing isn't really that critical.

To do this, you have to mark your pully with a mark at 32 degrees (Before Top Dead Center). You can use the distances on your existing degree marks as a calibration method, to figure out the position of the added mark (I use bright nail polish to make the new mark stand out). Rev the engine to a fairly high RPM with timing lite hooked up....you'll need at least 4000 RPM to get the distributor weights to "max-out". This can be sort of hairy, with your engine screaming under no load....don't let it rev like this for more than a few seconds as you check the timing. I do this with my race-Spridget at 5500 RPM.

For reasons that are too long to go into, the "32 degree max" figure will work on most modern cars buring unleaded fuel. You can try it at 30 or 34 (to see if it's a bit better), but you really won't want to go much higher or lower than these numbers. I run the Sprite at 32 degrees even for racing. Once it's set, you can see where the timing mark is hitting at idle speed and use *that* number at idle in the future.

Setting the timing by listening for "knocking" or "pinging" ("pinking" to Brits) can be difficult, if you're car is a bit noisy....it's a good way if your car is nice and quiet. With the Sprite (and my 50 year-old ears) it's impossible.

By the way, disconnecting the vacuum line won't make any real difference for most people.....it changes the timing at middling-low RPMs to give greater torque, but has no affect on max-advance. You would only really miss it if you "drive like GrandMa".For perfomance applications, many people disable or remove the vacuum unit (mine's removed).

 

[Gary Pope]

I agree with aeronca on this one. You will find a lot of TR6 guys are setting the timing off the scale, I guess 32 degrees sounds about right, however this is the first time I have heard anyone put a number on it.

Suffice to say, setting the timing by the book will make your car feel gutless and sluggish when you hit the gas hard.

 

[Guest]

OK, guys, set the timing @32degrees btdc @ 4K rpm, give or take. No help. At 3500 rpm under load, it "boggs" really badly, and sounds as though it wants to backfire on deceleration, a burbling sound. Could it be that my roller rockers have gone out of adjustment. They were set at .012, cold. Should I have set them whilst hot, maybe closer to stock settings, .010?
All this happened when I had my rings replaced with some Deves rings. Stopped smoking. Engine is newish, head is new (TRF). Frustrating...
Never did this before, since engine was new, 8K ago. Where else to go?!

Dr. Bill

 

[aeronca65t]

Hmmmm...maybe rich or lean? (stuck float?).

Do you have the ZS carb? (if so, could be a torn diagphram).

If it has points, is this "points float" (old, worn points).

Do you have an EGR valve (and if so, is it leaking or stuck?)

Put the car in a dark area at night...start engine and "mist" water over it (with a plant sprayer)....and rev the engine. If it looks like "sparkly Xmas lights", you may have high RPM ignition crossfire.

 

[Bob Claffie]

Fageddabout the insignificant difference in the rocker adjustment, a FEW thousandths won't amount to diddlie squat. Agree with everyone else about max 32 degrees +/-. Aluminum (pistons) melts around 36 degrees. If you are going to continue NOT using the vacuum advance, once you determine max advance (32) you will find that your initial setting may have to be significantly higher than the "book" setting to compensate for the lack of VA. Bob

[ 06-27-2003: Message edited by: Bob Claffie ]</p>