Timing

[lukecp]

What is the best to set my timing at? It is a '72 P/U with a 350, automatic, and a 204/214 degree duration cam. We just played around with the timing, and with the vaccum advance removed and plugged, it is right at the 0 on the mark. With the advance hooked up, it jumps to about 4 at idle. Is this a OK setting, or should i move it more to the advance side?

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Lucas

"Another proud owner of one of the coolest trucks ever built"

drop_shift@hotmail.com

My Daily-Driver: '72 Chevy LWB Custom/10. Rebuilt 350, roughly 300 HP thanks to a mild cam, Edelbrock intake and carb, headers, and 40 seires Flowmaster mufflers. Ochre with a white top. Plans as of now include a bigger cam, lower gears, and lots of body work.

[misfits]

just keep playing with it until you find where it runs best.

[Gordo]

I would advance it a little (counter-clock-wise) every day until you here a pinging noise under normal driving conditions then back off until it stops. Advance is good,,,spark knock is bad. With the vac disconnected and plugged, I would start at 8-10 degrees and go from there. A lot depends also on the octane in your gasoline,,make this adjustment with your normal/every day gas purchase.

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

[MikeB]

Your vacuum advance should make at least a 10 degree difference at idle, unless you are connected to a "ported" vacuum fitting on the carb. Another possibilty is your distributor has adjustable vacuum advance which is set too tight. Is there an allen screw in the vacuum line nipple on the advance canister? If so, play with it a little. With the vacuum line plugged, you need about 8-10 degrees mechanical advance at idle, and 30-35 degrees total at 2000-2500 rpm. You should have 40-45 degrees total (including vacuum advance) at your cruise rpm to get good fuel economy. You can check total advance with a "setback" timing liight or by using timing tape on your balancer. Unfortunately, your stock distributor probably has less total advance that doesn't "come in" as quickly. It's probably something like 25 degrees mechanical that doesn't fully come in until 3000 rpm. You can change this with a $10 weight and spring kit.

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MikeB
69 C-10 Fleetside, mild 383, Dart Iron Eagle 180cc heads, Crane Energizer 266 cam and 1.6 roller rockers, Edelbrock Performer manifold and 600cfm carb, HEI w/ MSD components, 1986 front spindles/disc brakes, Vintage Air in-dash.

[Longhorn Man]

Good info you are recieving here...one thing to remember, as a rule of thumb, the bigger the cam, the more timing your motor will want.
I would start as said before, but not count on keeping it there.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

[LT-102]

I was wonderinng if going to a higher octane fuel will prevennt spark knock and allow more timing advance?

[Scott Menzies]

Yes going with a higher octane fuel will reduce chances of detonation. A high octane fuel will burn more evenly (start combustion in one place in chamber as opposed to multiple mini burns.)

[Longhorn Man]

However, using higher than needed octain is not only waisted money, but will reduce power out put.
The octain number refers to the resistance to ignition. On some vehicles (my old lady's S-10 Blazer for example) if you put 93 octain in it, it will actually run worse than if you run the 87 octain.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

[lukecp]

Don't worry, im cheap and only run 87 octane in it. With 8.5:1 compression, i don't really see the point in spending the extra cash. I went to O'reilley's and bought a cheap timing light of my own to put on it. I moved it up to 6 degrees advance, and it runs alot better. I may go screw with it some more later. This is a dumb question, but every little mark on the timing pointer is 2 degrees, right?

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Lucas

"Another proud owner of one of the coolest trucks ever built"

drop_shift@hotmail.com

My Daily-Driver: '72 Chevy LWB Custom/10. Rebuilt 350, roughly 300 HP thanks to a mild cam, Edelbrock intake and carb, headers, and 40 seires Flowmaster mufflers. Ochre with a white top. Plans as of now include a bigger cam, lower gears, and lots of body work.

[69 longhorn]

Yes, every mark shouldbe 2 degrees. I think that you should be able to run that initial timing from 8-12 degrees(just go 2 degrees at a time, & check for spark rattle). To get the most out of it, you may have to recurve. I use a Crane adjustable advance can,set for 10 degrees of vac timing,& plugged to full man vac source @ the carb(limit the pull to .110 on the plunger),& use the springs to give full mech advance @ 2800-3000 on a street truck. You can set the curve faster for racing,but the idle will be erratic if the advance is opening @ idle speed(too weak of springs). Good luck.......69 longhorn.

[MightyFine69]

I have a 1969 K20 4x4 with a 350 and the original points distributor, and a quadrajet. When I set my timing I plug the vacuum line that goes to the distributor. I run the timing at 0 degrees. (manual tranny, went with what book says) When I hook up the vacuum hose again, the timing doesn't change. Using the vacuum port next to the pcv port on front of carb. Any thoughts as to why it doesn't change?

[MikeB]

MightyFine69 -- Disconnect that vacuum hose at the carburetor. You should be able to suck on it and feel resistance. If you can actually suck air, the diaphragm in the canister is leaking.

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MikeB
69 C-10 Fleetside, mild 383, Dart Iron Eagle 180cc heads, Crane Energizer 266 cam and 1.6 roller rockers, Edelbrock Performer manifold and 600cfm carb, HEI w/ MSD components, 1986 front spindles/disc brakes, Vintage Air in-dash.

[Brewski*]

The manual on my KE2500 says 4 degrees for the manual and 8 degrees for automatic. I set my manual at 8 and it runs much much better than at 4.
Also take into consideration the altitude where you live, and advance 1 degree for every thousand feet of elevation~!

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Red Rocket: Stock 1971 GMC KE2500, LWB, Custom Camper, 4x4, 350 V8, 4 bbl, 4 speed http://www.brewski.freehomepage.com/index.html

[Custom 68]

This may be a weird question but I have a Carter AFB carb with 2 vac lines on front one has zero vac at idle and goes up as I rev the motor and the other has vac til I rev then it goes to zero? Is this normal and which do I hook the vac advance to?
Thanks
Dave

[Gordo]

For a stock to mild engine, I use the ported vac (0 at idle) for economy.

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

[bigjimzlll]

if you use the unported vacuum it will give you more advance at idle...this can help your idle quality if you have a cam with some overlap to it..also IMO it gives you quicker throttle response off the line

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67 lwb fleetside...first hotrod in 25 years...283..186 bowl ported heads..270h comp cam 600 1405...stealth intake..HEI..th350 with 2500 rpm stall..4:10 POSI
god I love to go fast