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10-01-2021, 09:14 AM | #1 |
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Join Date: Jun 2014
Posts: 5
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timing for a 5.5:1 head
what should the timing for a 5.5:1 head
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10-01-2021, 09:51 AM | #2 |
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Join Date: Mar 2021
Location: Camarillo, Ca
Posts: 167
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Re: timing for a 5.5:1 head
Why is it any different than stock timing? I can't se any reason for it to be.
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10-01-2021, 09:53 AM | #3 |
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Join Date: Apr 2018
Location: Mebane NC
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Re: timing for a 5.5:1 head
I haven't seen anyone post total timing for a 5.5, but for 7 they usually say about 22° and for 6 or 6.5 I've seen 25°, so maybe 27?
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10-01-2021, 09:58 AM | #4 |
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Join Date: Jan 2012
Location: Western North Carolina
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Re: timing for a 5.5:1 head
Manual or automatic advance?
I have the same head on my car. Bottom line is it depends. If it is too advanced you may ruin the rod bearings by pounding. There is a knee in the advance curve that is pretty close to the correct timing. When ascending a grade, start with the timing lever in about the center of the range. Then advance it one notch at a time. The engine will run better with each notch (pull stronger). You will reach a point where another notch will not improve the engine performance. Go back one notch. That is the knee in the curve. I will be a little conservative and go back two notches. When you get home, count the number of notches to full advanced so that you can go back to the knee setting. You can put a clamp of some kind at the knee setting as a stop. I do that on my car. Some owners will advance the timing beyond the knee if they are cruising down the highway with medium throttle at about 45 or 50 mph, but I think that is unnecessary for the higher compression heads and dangerous as, in my case, I will forget to put the timing back to the knee. Each notch is about 4 degrees advance. So you can figure out how many degrees of advance the knee is by counting the notches from the fully retarded position, assuming fully retarded is at zero advance. The knee may move to another position depending on if you are lugging the car at low rpm. In which case it is best to be conservative and retard the spark a little. When backing up the hill to back into my garage I will retard the spark as it makes the car a little more controllable at the lower rpm. If your hearing is good enough, mine isn't, you can hear knocking when the timing is too advanced. This is a dangerous condition for the engine and can ruin the rod bearings in short order.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 10-01-2021 at 02:31 PM. |
10-01-2021, 10:06 AM | #5 |
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Location: Western North Carolina
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Re: timing for a 5.5:1 head
The timing will change with different heads. The timing is advanced because it takes some finite amount of time for the fuel/air to burn. As the compression is increased and as the turbulence is increased the time it takes for the fuel/air to burn is shortened, so less advance is needed. The time for the fuel/air to burn is also changed depending on the fuel/air ratio. Plus, as the engine speed increases the turbulence is increased so less time is needed for the fuel/air to burn, but since the engine is running faster about the same timing advance can be used.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
10-01-2021, 12:55 PM | #6 |
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Re: timing for a 5.5:1 head
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10-01-2021, 03:52 PM | #7 |
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Join Date: May 2010
Location: VA
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Re: timing for a 5.5:1 head
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10-02-2021, 02:00 PM | #8 |
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Join Date: May 2010
Location: Between Seattle & Tacoma
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Re: timing for a 5.5:1 head
I run 22° on my 5.5 head but only at 50 plus. Play with your advance/ retard and you can feel where the engine is happy.
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10-02-2021, 04:51 PM | #9 |
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Join Date: May 2010
Location: Portland OR
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Re: timing for a 5.5:1 head
When you first set the timing, it should be the same as stock A if all the other parts are stock except the head. After that depends on where it runs best.
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10-02-2021, 11:07 PM | #10 |
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Join Date: Aug 2021
Location: alberta canada
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Re: timing for a 5.5:1 head
do you know why we advance or retard the timing?
we advance the timing so that detonation in the cylinder is at the most optimal piston location to produce the most efficient power. the slower the piston comes to the top of its compression stroke the more time the explosion has to happen in the combustion chamber before the piston gets there, so we can set the ignition timing to a more retarded position. the faster the piston comes to the top of the compression stroke the less time the maximum explosion has to happen before the piston gets there, so we have to advance the timing to make that explosion happen at the correct time. but/so there are lots of things that can change the speed of that explosion. air fuel mixtures, types of gas and gas additives, flow of gasses into the cylinder, the flooding of the cylinder with the air/fuel mixture and who knows wat-all else. so i would say yes you may have to adjust your spark differently for a different type of cylinder head but i think that is something you are going to have to experiment with and finds what works best on your engine. ou |
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