1977 L82 Timing
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Heel & Toe
Joined: Aug 2009
Posts: 20
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1977 L82 Timing
I posted this question in the Info on Timing Sticky last week. Since I haven't heard anything, I thought I'd try here.
I have a 1977 L82 automatic that I think is stock (My father bought this car new in 1977, and except for a few years, it has been in our family). It is in mint condition with only about 50,000 miles.
After reading the Sticky on timng, I bought an advance timing light and hooked it up. I found that if I set the initial timing at 12 deg as called for in the underhood sticker, my "all in" mechanical advance is only about 28. That is, my distributor only provides about 15-16 degrees of mech advance. I cranked it up to 35 "all in" and now my initial is around 19. According to Lars' tech article, this doesn't seem excessive and is actullly pretty close to his ideal numbers. The car seems to run much better with more power and no pinging.
Here are my issues. First, with the factory springs and weights, my timing starts to advance at around 1100 and is all in by 1800! I tried using the gold (heavy) springs from the Mr. gasket kit 929 with the factory weights and center plate, but the results are about the same. I notice that the Mr Gasket weights are smaller and lighter than the factory weights. Any suggestions on spring/weight combinations that will get me closer to the 2500 rpm number?
Second, My vacuum advance (which seems to be full manifold) only adds about 10 degrees of advance. Assuming I can correct my first issue, can this engine benefit from 14-16 degrees of vacuum advance? If so, what part should I buy? Should I use one of the adjustable units?
If anyone has an L82 from this era I'd be interested if you have noticed similar numbers? Is there a place I can look up the factory timing specs for my car (other than just the 12 deg initial on the emissions sticker)?
I'd appreciate any insights. Otherwise, since the car seems to run well, I might just leave well enough alone.
Dan
I have a 1977 L82 automatic that I think is stock (My father bought this car new in 1977, and except for a few years, it has been in our family). It is in mint condition with only about 50,000 miles.
After reading the Sticky on timng, I bought an advance timing light and hooked it up. I found that if I set the initial timing at 12 deg as called for in the underhood sticker, my "all in" mechanical advance is only about 28. That is, my distributor only provides about 15-16 degrees of mech advance. I cranked it up to 35 "all in" and now my initial is around 19. According to Lars' tech article, this doesn't seem excessive and is actullly pretty close to his ideal numbers. The car seems to run much better with more power and no pinging.
Here are my issues. First, with the factory springs and weights, my timing starts to advance at around 1100 and is all in by 1800! I tried using the gold (heavy) springs from the Mr. gasket kit 929 with the factory weights and center plate, but the results are about the same. I notice that the Mr Gasket weights are smaller and lighter than the factory weights. Any suggestions on spring/weight combinations that will get me closer to the 2500 rpm number?
Second, My vacuum advance (which seems to be full manifold) only adds about 10 degrees of advance. Assuming I can correct my first issue, can this engine benefit from 14-16 degrees of vacuum advance? If so, what part should I buy? Should I use one of the adjustable units?
If anyone has an L82 from this era I'd be interested if you have noticed similar numbers? Is there a place I can look up the factory timing specs for my car (other than just the 12 deg initial on the emissions sticker)?
I'd appreciate any insights. Otherwise, since the car seems to run well, I might just leave well enough alone.
Dan
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Joined: Apr 2007
Posts: 184
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From: Atlas is shrugging KC, MO area
Have you tried the lighter weights w/ the stronger springs?
Not an expert on vacuum advance but I think much more than 10* would cause a little ping/knock upon sudden acceleration. But would defer to someone w/ experience on this.
I seem to remember that my '73 L-82 stock mech. advance wasn't all in 'til ~ 4,500 rpm. I put an aftermarket kit in and experimented w/ different combos 'til got all in by 2,500.
Not an expert on vacuum advance but I think much more than 10* would cause a little ping/knock upon sudden acceleration. But would defer to someone w/ experience on this.
I seem to remember that my '73 L-82 stock mech. advance wasn't all in 'til ~ 4,500 rpm. I put an aftermarket kit in and experimented w/ different combos 'til got all in by 2,500.
