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Mod | | | Forums66 Topics128,021 Posts1,055,355 Members48,420 | | Most Online14,466 Apr 26th, 2026 | | AD Chevy Trucks Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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on the Internet for over 30 years! and not clogged down with Ads! Again, thanks! | | | | Joined: May 2008 Posts: 49 Wrench Fetcher | | Wrench Fetcher Joined: May 2008 Posts: 49 | I am just now getting around to checking out this near worn out, completely stock 1972 350 that is in my 55 2nd. The engine cranks and runs great but it leaks and smokes some. I am concerned about the timing. Initial is 15 degrees, Mechanical runs up to 36 degrees, and with the vacuum advance, total of 50 degrees. Now I know this sounds too high, but it runs good. Is there serious harm from these settings? It does not ping. Should initial be lowered to 10 degrees? Any opinions would be appreciated.
Thanks, Hugh | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Sounds like it is just right. If it doesn't kick back when starting & doen't ping i'd leave it alone. If it was an engine in real good shape with stock cam I'd say 36 is a little high, more like 34, but you know the timing chain is stretched makeing the cam timing slow. They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Feb 2004 Posts: 29,746 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,746 | Sounds good to me. We run the race engines at 37 degrees at 2500 RPM, initial and centrifugal, with no vacuum advance. 50 degrees total advance is just a bit high, but not enough to get concerned about, as most of the vacuum advance goes away as soon as a little load goes on the engine, uphill, passing, etc. It's mostly a light-throttle cruise thing for better gas mileage. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | 6-8 deg BTDC with vac hose plugged at dist. end
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn | | | | | Joined: May 2008 Posts: 49 Wrench Fetcher | | Wrench Fetcher Joined: May 2008 Posts: 49 | Thanks for the input. I will just leave it as it is. Who knows how long it has been that way.
Thanks, Hugh
| | | | | Joined: Sep 2008 Posts: 137 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2008 Posts: 137 | I have always read that you advance until it pings on acceleration and then back it off a hair until it goes away. Sounds like that's about where you're at. I'd leave it. | | | | | Joined: Jan 2000 Posts: 2,074 'Bolter | | 'Bolter Joined: Jan 2000 Posts: 2,074 | Hook up a vacuum gauge, and adjust timing for highest vacuum, then back timing off just a bit. | | | | | Joined: Jun 2009 Posts: 2,201 Shop Shark | | Shop Shark Joined: Jun 2009 Posts: 2,201 | Jim; If you have a timing light available, how much is "just a bit"?
EDIT: Let me rephrase that to "if I have a timing light" I'm not asking you to measure it, just looking for an estimate of how many degrees.
Last edited by FriedGreenTmater; 08/27/2010 10:01 PM.
| | | | | Joined: Apr 2010 Posts: 283 Shop Shark | | Shop Shark Joined: Apr 2010 Posts: 283 | From my experience, with stock cam and advance characteristics if the static timing is advanced more than 4 deg from factory spec you may get more pep at light load acceleration, slight milage improvement, less smooth idle, less power and rpm at high throttle opening/max revs. I would limit the extra static advance to 4-6 deg.Most of these engines used 4 deg static so it sounds like you are advanced by 11.Back it up to original specs and try it you may be pleasantly surprised.
Bob Taylor
| | | | | Joined: Sep 2008 Posts: 137 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2008 Posts: 137 | Back off 2-5 degrees is what I do | | | | | Joined: Feb 2004 Posts: 29,746 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,746 | On a series of chassis dyno tests of the family race car back in the mid-1950's, we found that once maximum HP was reached by advancing the timing, one degree more timing killed as much power as retarding the timing 4 to 5 degrees. If you're unsure of where the max power point is, less is always preferred to more advance! We've observed the same basic trend on alcohol-fueled flathead Ford engines, NASCAR-specification small block Chevvies, Big-block Chrysler tractor pull engines, and various bone-stock street machines. Too much timing advance destroys horsepower and engine parts! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
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