Correct Combustion? Your Thoughts
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,093
Likes: 7,619
From: Poolville
Right, The higher octane can handle higher combustion pressure and temps before preignition occurs.. unlike 87 fuel but you really need at least 98 octane to really make any difference.. 106 and 110 is better but you really need the higher compression for a better burn..
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,093
Likes: 7,619
From: Poolville
Would be interesting to see the entire ignition curve throughout the rpm range..
Grand HDF Member
Joined: Sep 2022
Posts: 4,420
Likes: 3,824
From: Florida
But I would concentrate on 4000-6500. Sure I like it to have street manners.. and it does, but I’d compromise for the 4 to 6.5
Last edited by Rains2much; Apr 9, 2026 at 11:28 AM.
Thread Starter
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Club Member
Joined: Jan 2007
Posts: 3,554
Likes: 1,932
From: NE Florida
Apologies to @BigMike didn't mean to go of the road..
I'm going to advance the timing by 2 marks because it took a lot of retarding to get the dot in the hole when I timed it. I had to guess at the rpms when setting it. I'm also going to test the VOES as well as replace its vacuum line. Then run the new plugs when it's hot and read them. I have my weekly ride on Wednesday so I'm trying to get everything done by then so I can put 150 miles on it with the new plugs. I really appreciate everyone's help on this!
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Grand HDF Member
Joined: Apr 2007
Posts: 3,725
Likes: 3,070
From: Brighton, MI
No worries, good reading.
I'm going to advance the timing by 2 marks because it took a lot of retarding to get the dot in the hole when I timed it. I had to guess at the rpms when setting it. I'm also going to test the VOES as well as replace its vacuum line. Then run the new plugs when it's hot and read them. I have my weekly ride on Wednesday so I'm trying to get everything done by then so I can put 150 miles on it with the new plugs. I really appreciate everyone's help on this!
I'm going to advance the timing by 2 marks because it took a lot of retarding to get the dot in the hole when I timed it. I had to guess at the rpms when setting it. I'm also going to test the VOES as well as replace its vacuum line. Then run the new plugs when it's hot and read them. I have my weekly ride on Wednesday so I'm trying to get everything done by then so I can put 150 miles on it with the new plugs. I really appreciate everyone's help on this!
The VOES is still just a simple on and off switch (it's just turned on and off by vacuum) and should not be running any real ohms when "on" or in technical terms: when in the closed position. (a switch in the closed position is "on", an open switch is "off"). I don't recall how many volts goes through to trigger/operate the voes switch, but it's milliamps for the signal. So resistance at the switch contacts is a bad thing.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,093
Likes: 7,619
From: Poolville
When you test the VOES, don't just check for "on" or "off" when applying vacuum. Use an ohmmeter to check resistance. My old VOES switch worked "sometimes" and it really lead me down some troubleshooting loops and dead ends. Until I checked the resistance. Ran about 100 to 120 ohms...not good. Replacement checked at 0 ohms.
The VOES is still just a simple on and off switch (it's just turned on and off by vacuum) and should not be running any real ohms when "on" or in technical terms: when in the closed position. (a switch in the closed position is "on", an open switch is "off"). I don't recall how many volts goes through to trigger/operate the voes switch, but it's milliamps for the signal. So resistance at the switch contacts is a bad thing.
The VOES is still just a simple on and off switch (it's just turned on and off by vacuum) and should not be running any real ohms when "on" or in technical terms: when in the closed position. (a switch in the closed position is "on", an open switch is "off"). I don't recall how many volts goes through to trigger/operate the voes switch, but it's milliamps for the signal. So resistance at the switch contacts is a bad thing.