Adjustable timing light
Thread Starter
Instructor
Joined: Feb 2003
Posts: 176
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From: jacksonville florida
Adjustable timing light
I finally bought an adjustable timing light,I found that my total advance was 41 degrees, all in by 2500 rpm,The car starts fine and runs very well,I don't hear any ping and I only use texaco 93 octane,Is this too much advance? :confused:
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Adjustable timing light (hauk)
By the fact that you say it is not pinging I'd say the timing is ok.. You want as much advance as possible without pinging for the best performance and economy. Many advance curves will work. Different blends of fuel will respond differently as well.
Le Mans Master
Joined: Feb 1999
Posts: 6,807
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From: Hoosier
Cruise-In III Veteran
Re: Adjustable timing light (hauk)
If that reading is the mechanical advance with the vacuum plugged, then yes. For the typical small block it is. Most run about 36 degrees at around 2700-2800 rpm.
Double check your light is at zero when you retard the timing at idle to zero.
You can get an effect they call reverse torque. That's where the burn starts too soon and the piston has to overcome some combustion on the upstroke.
[Modified by biltogo, 5:48 PM 6/24/2003]
Double check your light is at zero when you retard the timing at idle to zero.
You can get an effect they call reverse torque. That's where the burn starts too soon and the piston has to overcome some combustion on the upstroke.
[Modified by biltogo, 5:48 PM 6/24/2003]
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Re: Adjustable timing light (hauk)
41º is probably too much for best peak power. As Biltogo posted, there's a point where lighting the cylinder too soon saps power by creating more downward force on a piston that's trying to rise. In that scenario, the power produced by the pistons that are on a downward power stroke have to use some of it's energy to compensate. End result is less power overall. Because the additional timing results in more advance before total is achieved, the engne might feel stronger in the low end but is actually making less power at mid and high rpm.
You didn't state your compression ratio. If it's a low ratio like in `71 and later stock engines, your shouldn't need 93 octane. If you do have a stock cr, you shouldn't have any pinging unless yourtimng is way past optimum.
You didn't state your compression ratio. If it's a low ratio like in `71 and later stock engines, your shouldn't need 93 octane. If you do have a stock cr, you shouldn't have any pinging unless yourtimng is way past optimum.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Adjustable timing light (hauk)
hauk -
41 total mechanical is too much timing whether it's pinging or not. The low-compression engines will not ping on high-octane fuel even when the timing is WAY off, so don't use the "pinging-method" for setting up total timing - best torque and power is achieved at 36-38 degrees on almost all GM V8s.
On the timing issue: You didn't state whether the 41 degrees was with the vac advance hooked up or disconnected. Be sure to check total timing with the vac disconnected. With the vac hooked up and pulled in, total combined timing (full advanced centrifugal and the vac advance fully pulled in) should be in the 48-52 range. So if your 41 degrees total is with the vac hooked up, you're not running enough timing. Be sure to check it correctly and set it up right.
You also didn't state what year car you have or the type of distributor you're running. If you have a point-style distributor that's producing too much total timing with correct initial timing, chances are good that your advance stop bushing is missing. A good check-out is in order.
Tag me back with any questions on this. A correct timing curve with correct total timing is key to optimum performance on these cars.
41 total mechanical is too much timing whether it's pinging or not. The low-compression engines will not ping on high-octane fuel even when the timing is WAY off, so don't use the "pinging-method" for setting up total timing - best torque and power is achieved at 36-38 degrees on almost all GM V8s.
On the timing issue: You didn't state whether the 41 degrees was with the vac advance hooked up or disconnected. Be sure to check total timing with the vac disconnected. With the vac hooked up and pulled in, total combined timing (full advanced centrifugal and the vac advance fully pulled in) should be in the 48-52 range. So if your 41 degrees total is with the vac hooked up, you're not running enough timing. Be sure to check it correctly and set it up right.
You also didn't state what year car you have or the type of distributor you're running. If you have a point-style distributor that's producing too much total timing with correct initial timing, chances are good that your advance stop bushing is missing. A good check-out is in order.
Tag me back with any questions on this. A correct timing curve with correct total timing is key to optimum performance on these cars.
Thread Starter
Instructor
Joined: Feb 2003
Posts: 176
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From: jacksonville florida
Re: Adjustable timing light (lars)
Lars: Thanks for the information,I just sent you an IM. Heck I didn't know what an adjustable timing light was untill I bought a Corvette and started reading this forum,My thanks to all you Vette heads for keeping me on the straight path. :flag
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Adjustable timing light (hauk)
Hauk - listen to Lars and go to the tech section and printout the paper he did on total timing. Then you should have a better ideas of setting it. I would also check the light against TDC at zero. Make sure you right over the timing mark and not at the side or your can get a parallex error with your eyes. Either way 41 is too much and in a hot climate like yours - detoniation city!
What distributor are you running? Unless someone has modfyied it (ground out the pivot point foir the advance, or it is a MSD with changeable bushings and the smallest that will allow a large advance is installed, 41 degrees is hard to get on on mechanical only. Be safe - read Lars article and check it out.
What distributor are you running? Unless someone has modfyied it (ground out the pivot point foir the advance, or it is a MSD with changeable bushings and the smallest that will allow a large advance is installed, 41 degrees is hard to get on on mechanical only. Be safe - read Lars article and check it out.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Adjustable timing light (bigvette1)
Hi big!
Good to see you're still kicking around! Thanks for the plug for my articles... In talking to hauk, his timing check was done with the vac advance hooked up, so he's actually not running enough timing. He's going to yank his vac hose off and get that total mechanical advance set up at 36 degrees and then re-check with vac connected to see what the combined total is. He's getting some good use out of that new adjustable light he just bought...
Good to see you're still kicking around! Thanks for the plug for my articles... In talking to hauk, his timing check was done with the vac advance hooked up, so he's actually not running enough timing. He's going to yank his vac hose off and get that total mechanical advance set up at 36 degrees and then re-check with vac connected to see what the combined total is. He's getting some good use out of that new adjustable light he just bought...
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Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Adjustable timing light (bigvette1)
Bob -
I agree with big - The Sears adjustable light is a great bargain at $69. It's very accurate, and I've been unable to destroy mine in all the tuning tours I've taken across the country and with all the times I've stuck it into the fan blades of running cars. The San Antonio guys even tried to help me break my light by dropping it on the floor a couple of times, but they failed to damage it.
I agree with big - The Sears adjustable light is a great bargain at $69. It's very accurate, and I've been unable to destroy mine in all the tuning tours I've taken across the country and with all the times I've stuck it into the fan blades of running cars. The San Antonio guys even tried to help me break my light by dropping it on the floor a couple of times, but they failed to damage it.
Drifting
Joined: Aug 2000
Posts: 1,758
Likes: 4
From: Medford, Or
Re: Adjustable timing light (lars)
Bob -
I agree with big - The Sears adjustable light is a great bargain at $69. It's very accurate, and I've been unable to destroy mine in all the tuning tours I've taken across the country and with all the times I've stuck it into the fan blades of running cars. The San Antonio guys even tried to help me break my light by dropping it on the floor a couple of times, but they failed to damage it.
I agree with big - The Sears adjustable light is a great bargain at $69. It's very accurate, and I've been unable to destroy mine in all the tuning tours I've taken across the country and with all the times I've stuck it into the fan blades of running cars. The San Antonio guys even tried to help me break my light by dropping it on the floor a couple of times, but they failed to damage it.
Dan
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Adjustable timing light (lars)
bil -
That's pretty cool. I'd like to see you get that setup through airport security.
That's pretty cool. I'd like to see you get that setup through airport security.
Is that an electronic tach? How much was it and did you just hook it to your tach output on ignition box while the dash is still connected to tach drive distributor? That looks like a great idea and I'd like to try it.
Le Mans Master
Joined: Feb 1999
Posts: 6,807
Likes: 0
From: Hoosier
Cruise-In III Veteran
Re: Adjustable timing light (tshort)
Is that an electronic tach? How much was it and did you just hook it to your tach output on ignition box while the dash is still connected to tach drive distributor? That looks like a great idea and I'd like to try it.
Burning Brakes
Joined: Jun 2002
Posts: 792
Likes: 2
From: Norcross GA
Re: Adjustable timing light (lars)
Is this the unit that is being talking about? http://www.sears.com/sr/product/deta...=null&bidsite=
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Adjustable timing light (biltogo)
Here's what I did to make it easy on myself. The Sears light works a-ok with an MSD.
