Home » Public Forums » GMCnet » spark advance control for stock distributor
| spark advance control for stock distributor [message #276258] |
Mon, 20 April 2015 06:56  |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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When I started pulling my 3000 lb towd I had to back of the timing 2-3 degrees to stop the bad pinging on inclines. When I run without the toad I notice a great loss of power, so much it feels like the toad is still back there. I'm running the Mallory unilite module in the stock distributor for a 74. Is there a dependable aftermarket distributor with easily adjustable timing or something with knock sensor available or both that others have gone to. Yes I run 93 octane, I have to with all the mods the PO made. Any ideals, as usual, will be greatly appreciated. Thanks Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: spark advance control for stock distributor [message #276272 is a reply to message #276258] |
Mon, 20 April 2015 08:33  |
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wally
Messages: 643
Registered: August 2004
Location: Omaha Nebraska
Karma: 5
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skip2 wrote on Mon, 20 April 2015 06:56When I started pulling my 3000 lb towd I had to back of the timing 2-3 degrees to stop the bad pinging on inclines. When I run without the toad I notice a great loss of power, so much it feels like the toad is still back there. I'm running the Mallory unilite module in the stock distributor for a 74. Is there a dependable aftermarket distributor with easily adjustable timing or something with knock sensor available or both that others have gone to. Yes I run 93 octane, I have to with all the mods the PO made. Any ideals, as usual, will be greatly appreciated. Thanks Skip Hartline
We ran an MSD variable timing control that works with an HEI distributor and an MSD knock alert. Jim K has them.
http://www.appliedgmc.com/prod.itml/icOid/552
http://www.appliedgmc.com/prod.itml/icOid/551
I've since changed to J&S safeguard with individual cylinder retard - all automatic.
http://www.appliedgmc.com/prod.itml/icOid/1154
HTH
Wally Anderson
Omaha NE
75 Glenbrook
[Updated on: Mon, 20 April 2015 08:38] Report message to a moderator |
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| Re: spark advance control for stock distributor [message #276283 is a reply to message #276258] |
Mon, 20 April 2015 09:34 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Skip:
Timing curves need changing when engine modifications are made. The Vacuum advance senses and adjusts for changing load conditions.
You might want to try a different Vacuum advance Pot, or check that yours is working properly. You can also get adjustable pots to tune or dial in a better timing strategy. The Delco units have numbers like 614-XX where the XX is the additional advance the unit offers.
Most adjustable pots adjust the vacuum levels that advance is applied but Crane adjustable Pot also has adjustable total advance.
Having a proper vacuum advance system will allow the timing advance to be higher at low load conditions and lower at high load conditions.
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: spark advance control for stock distributor [message #276319 is a reply to message #276258] |
Mon, 20 April 2015 17:10 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Re: your post and my post together:
[quote]installed a Patterson Q-jet and Double Trouble woke up! I then installed a Patterson distributor and it got insomia!
Regards,
Rob M.[\quote]
He he he
To music now:
"I could have danced all night
I could have danced all night
and still have asked for more"
Hopefully someone remembers that song. 
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
[Updated on: Mon, 20 April 2015 17:17] Report message to a moderator |
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| Re: spark advance control for stock distributor [message #276327 is a reply to message #276258] |
Mon, 20 April 2015 19:15 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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Senior Member |
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Thanks for the suggestions, Ive been looking for an excuse to pull the distributor out and replace it's oozing
oring.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: spark advance control for stock distributor [message #276354 is a reply to message #276258] |
Tue, 21 April 2015 06:37 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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New question for the brain trust, when hooking vacuum line up on an edelbrock modified engine is the ported or manifold vacuum desired. I been checking on hotrod forums and they swing both ways on this thought.
Skip
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: spark advance control for stock distributor [message #276371 is a reply to message #276354] |
Tue, 21 April 2015 10:25 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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I like the response and driveability I get from manifold vacuum on all of my engines...some tweaking may be required on the idle speed and base timing to get the setup right, and when it is right, I usually get the most fuel mileage and power that I can achieve from the components. Results depend on the way the distributor is set up inside and other factors, and many people have great results using ported vacuum with their particular combination of parts. Try it both ways and see what works best for your setup. At least it's easy to mess with when the engine is right there at your feet. Just take the necessary tools and parts and head down the road, pull off and make a change, (just one thing at a time) and keep going till you get what you want.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] spark advance control for stock distributor [message #276373 is a reply to message #276371] |
Tue, 21 April 2015 10:42 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Throttle response and driveability are a couple of pieces of the tune up
triad. The third component is like an ugly step sister. Emissions. Some
places have very strict regulations in this area. Some not so stringent.
Conforming to these regs usually clamps down on optimum performance. One of
those is ported vacuum to the distributor vacuum advance device. I guess we
all need to breathe, so, kinda got to learn to live with the devil we know
best. On later coaches in California, you have to do it like it came from
the factory or risk not passing emissions tests and having your license
plates not renewed. Just the way of today's world.
Jim Hupy
Salem, Oregon
78 GMC ROYALE 403. (still with carb and all the vacuum lines and equipment
it came equipped with, except for headers and a few internal goodies. )
On Apr 21, 2015 8:26 AM, "Terry" wrote:
> I like the response and driveability I get from manifold vacuum on all of
> my engines...some tweaking may be required on the idle speed and base timing
> to get the setup right, and when it is right, I usually get the most fuel
> mileage and power that I can achieve from the components. Results depend on
> the way the distributor is set up inside and other factors, and many
> people have great results using ported vacuum with their particular
> combination
> of parts. Try it both ways and see what works best for your setup. At
> least it's easy to mess with when the engine is right there at your feet.
> Just
> take the necessary tools and parts and head down the road, pull off and
> make a change, (just one thing at a time) and keep going till you get what
> you
> want.
> --
> Terry Kelpien
> ASE Master Technician
> 73 Glacier 260
> Smithfield, Va.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: spark advance control for stock distributor [message #276375 is a reply to message #276258] |
Tue, 21 April 2015 10:50 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Skip:
Ported vacuum advance is still a throw back from 70s emissions strategies that are used in the stock GMCs were driving. You've already screwed that up with the engine modifications in your coach.(probably runs way better now) Th ported vacuum retarted advance at idle to decrease emmisions but added heat to everything. The Vacuum temperature switch allowed full manifold vacuum to be applied to the distributor when engine temps got higher to compensate for the problem. (Vacuum tree on the front of the engine) I would suggest manifold vacuum.
Im going to post a copy of someone else's timing description in a new post to help explain in more detail. I'll call it ENGINE TIMING
Best regards .
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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