Timing using an Adjustable Timing Light on a 350 engine
07-03-2014, 11:52 PM
#1
Burning Brakes
Thread Starter
Timing using an Adjustable Timing Light on a 350 engine
There has always been a lot of how to perform this on this forum and I am sure it has been posted in the past. Since I am in the midst of doing this to my 1977 Small Block 350 with the original Q-Jet Carb I figured I would share some stuff that was shared with me recently.
First off is always adjust your timing before you adjust your carb why because the Vacuum in the Manifold changes after you adjust your timing and will affect your carburetor. The carburetor adjustments will never affect your timing on the engine.
Commercially Rebuilt Quadra Jets are not always your best bet because each Rochester is built for different years and different model cars so I have read. Sometimes they have inexperienced Techs rebuilding the carb and it is not always meant for your year or application of engine.
When I tore down my Q-Jet Carb the Secondary tubes had fallen out of there holes after 37 years this is very common and they have to be pounded back in with a light weight plastic or rubber mallet. You will also see on these older cars that someone has removed the limiters on the air mixture screws. This is most of the time a good thing because as the car ages the limiters on the adjustment needles need to be removed so you can adjust the carburetor for the best to a leaner mixture especially since on pre 1975 cars they could still run leaded fuels. Todays fuels have 10% or more Ethanol in the mix. Alcohol burns at a lower temp and combustion ratio than Gasoline does and burns different so getting the correct mixture on the carb is very different these days.
This also brings up another issue make sure your car rebuild kit is meant to meet the new standards of Ethanol fuels.
When I rebuilt mine the Accelerator plunger fell apart when I removed it the new ones are Blue or Red depending on the manufacture of the kit. Mine was Blue.
Now we will get into the Timing after I explained some other stuff.
When Timing an early model Engine it is best to have one of the newer timing lights which are either Digital or Manually adjustable. In my readings since I got back into Muscle cars of the past it is best to adjust your timing at Between 2500 to 2800 RPMs with the vacuum advance to the distributor disconnected and Plugged so you do not loose any vacuum. In days of old we did it at premium Idle Settings but in the new world with racing history and performance behind it the experts say 2500 to 2800 RPMs this way you time the engine at it's running speed. Makes perfect sense to me
Adjust your timing light either Digital or Manual to 36 Degrees Advanced then pulse the timing light on the timing marks and make the adjustment at 0 Degrees. How does this make sense Yup you have used your timing light to make the adjustment for you and you need the 0 to match on the Harmonic balancer and Timing arm
You cannot perform this with a really old timing light and it must be either digitally adjustable or manually adjustable.
I am only really posting this with those that have HEI Ignitions systems the Points Style take another approach and it deals with the springs here is what I have read on those
Remove your distributor cap and rotor. If you have a points-style distributor with the stock, factory, heavy springs in place, remove one of the springs. Disconnect the vacuum advance by simply pulling the hose off the vacuum advance control unit on the distributor – there is no need to plug the hose, as the vacuum leak will have no effect on timing. Install the rotor and cap. Loosen the distributor hold-down clamp bolt just enough so that the distributor can by turned, yet leave it snug enough that the distributor will hold its position.
Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this.
If you’re using a non-adjustable light, perform the same process, but align your new 36-degree mark with “0” mark on the timing tab.
Now I want you to know this is non of my information and have to contribute everything I have learned to an expert Lars Grimsrud and just reposting information he has already provided. I like to credit those I have learned from and I hope he respects it.
First off is always adjust your timing before you adjust your carb why because the Vacuum in the Manifold changes after you adjust your timing and will affect your carburetor. The carburetor adjustments will never affect your timing on the engine.
Commercially Rebuilt Quadra Jets are not always your best bet because each Rochester is built for different years and different model cars so I have read. Sometimes they have inexperienced Techs rebuilding the carb and it is not always meant for your year or application of engine.
When I tore down my Q-Jet Carb the Secondary tubes had fallen out of there holes after 37 years this is very common and they have to be pounded back in with a light weight plastic or rubber mallet. You will also see on these older cars that someone has removed the limiters on the air mixture screws. This is most of the time a good thing because as the car ages the limiters on the adjustment needles need to be removed so you can adjust the carburetor for the best to a leaner mixture especially since on pre 1975 cars they could still run leaded fuels. Todays fuels have 10% or more Ethanol in the mix. Alcohol burns at a lower temp and combustion ratio than Gasoline does and burns different so getting the correct mixture on the carb is very different these days.
This also brings up another issue make sure your car rebuild kit is meant to meet the new standards of Ethanol fuels.
When I rebuilt mine the Accelerator plunger fell apart when I removed it the new ones are Blue or Red depending on the manufacture of the kit. Mine was Blue.
Now we will get into the Timing after I explained some other stuff.
When Timing an early model Engine it is best to have one of the newer timing lights which are either Digital or Manually adjustable. In my readings since I got back into Muscle cars of the past it is best to adjust your timing at Between 2500 to 2800 RPMs with the vacuum advance to the distributor disconnected and Plugged so you do not loose any vacuum. In days of old we did it at premium Idle Settings but in the new world with racing history and performance behind it the experts say 2500 to 2800 RPMs this way you time the engine at it's running speed. Makes perfect sense to me
Adjust your timing light either Digital or Manual to 36 Degrees Advanced then pulse the timing light on the timing marks and make the adjustment at 0 Degrees. How does this make sense Yup you have used your timing light to make the adjustment for you and you need the 0 to match on the Harmonic balancer and Timing arm
You cannot perform this with a really old timing light and it must be either digitally adjustable or manually adjustable.
I am only really posting this with those that have HEI Ignitions systems the Points Style take another approach and it deals with the springs here is what I have read on those
Remove your distributor cap and rotor. If you have a points-style distributor with the stock, factory, heavy springs in place, remove one of the springs. Disconnect the vacuum advance by simply pulling the hose off the vacuum advance control unit on the distributor – there is no need to plug the hose, as the vacuum leak will have no effect on timing. Install the rotor and cap. Loosen the distributor hold-down clamp bolt just enough so that the distributor can by turned, yet leave it snug enough that the distributor will hold its position.
Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this.
If you’re using a non-adjustable light, perform the same process, but align your new 36-degree mark with “0” mark on the timing tab.
Now I want you to know this is non of my information and have to contribute everything I have learned to an expert Lars Grimsrud and just reposting information he has already provided. I like to credit those I have learned from and I hope he respects it.
Last edited by MakoJoe; 07-03-2014 at 11:56 PM.
07-04-2014, 12:13 AM
#2
Burning Brakes
Thread Starter
The only other thing I forgot to add on this Post is KEEP your fuel tanks full on older Cars that have Ethanol in the Fuel. Why Ethanol Attracts Moisture and Moisture Causes RUST in older fuel tanks that are not lined like they are these days. Newer cars have a lined Fuel tank and Older cars do not to prevent rust. There is a product from Stabil that will prohibit rust in the tank called Stabil 360 good stuff and I also like to plug in a good product. I am lame sometimes after a long Drive or Car show and will just park my car without refilling the tank but most of the time I filer it up to the brim on my way home. I use additives all the time in my 37 year old engine and hope they help.
When I park it for the winter for 5 months this fuel system gets a complete put to bed treatment. I use marvel mystery oil to lube all the gaskets, Stabil Fuel Treatment and an Ethanol Treatment like Stabil 360 than park it for 5 to 6 months. Engine always fires up in the spring I know I have protected it.
When I park it for the winter for 5 months this fuel system gets a complete put to bed treatment. I use marvel mystery oil to lube all the gaskets, Stabil Fuel Treatment and an Ethanol Treatment like Stabil 360 than park it for 5 to 6 months. Engine always fires up in the spring I know I have protected it.
Last edited by MakoJoe; 07-04-2014 at 12:24 AM.