‘66 stumbles under throttle load
Race Director
Joined: Jan 2003
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From: Central Arkansas
Good point Larry. I was assuming he already had some replacement springs in his distributor - it’s probably a rare distributor that doesn’t after a handful of owners over 50 years. But assumptions can trip you up sometimes.
Thread Starter
Racer
Joined: Dec 2013
Posts: 418
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From: Ct
I did not replace the springs when I had the distributer out the past few weeks and have not in the 3yrs I’ve owned it.
Possibly it was done when the car had a full frame off restoration which was some 12yrs ago and maybe 2500mi, roughly.
Race Director
Joined: Jan 2003
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From: Central Arkansas
I don’t think you will need to go that high. Standing beside a howling engine, bent over it with a timing light at any thing near 5,000 will not be pleasant to say the least and probably not the best thing for the engine with no load. I would just rev it until the timing advance stalls and go a few hundred more revs and if it stays stabilizes then stop. That should be good but it’s best to look inside the distributor and make sure it doesn’t have any stiff, large wire dia, springs in it. If so, I would replace it with a softer one. Too bad the days of local speed shops and mechanic shops with a Sun distributor machine are long gone.
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Joined: Apr 2005
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From: Bowling Green, Kentucky
I don’t think you will need to go that high. Standing beside a howling engine, bent over it with a timing light at any thing near 5,000 will not be pleasant to say the least and probably not the best thing for the engine with no load. I would just rev it until the timing advance stalls and go a few hundred more revs and if it stays stabilizes then stop. That should be good but it’s best to look inside the distributor and make sure it doesn’t have any stiff, large wire dia, springs in it. If so, I would replace it with a softer one. Too bad the days of local speed shops and mechanic shops with a Sun distributor machine are long gone.
2. Double check fan for any cracks or tears. Do a trial run to 4000 and then do a check at 4000. If needed do a trial run at 4500, and then do the check at the same speed. Make certain that engine sounds solid at each speed. Have a helper in the car on the gas.
I used my wife and new goggles when I did this for my own car. Wife is fearless on the gas, and would instantly give me the RPM I requested.
She used the car tach to set the RPM.Unless you use two hands to communicate your desired RPM, you should stay below redline.
Larry
EDIT: Another way to get the same result (maximum centrifugal advance) is to actually remove your old springs and install a set of new light springs for the testing. That will give you your max mechanical advance.....at much lower engine RPM. Subtract initial advance to get the maximum centrifugal advance built into the distributor (which will not change regardless of the springs used).
Last edited by Powershift; Mar 24, 2022 at 09:18 AM.
Race Director
Joined: Apr 2005
Posts: 11,281
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From: Bowling Green, Kentucky
I did 4000 RPM with wife on the gas. I thought I was in a Hurricane (common here in Louisiana).
I truly recommend anyone try and stay below 4000 RPM.........especially when engine is free reving.
Larry
I truly recommend anyone try and stay below 4000 RPM.........especially when engine is free reving.
Larry
1967 Pedal Car Champion
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I can't begin to imagine this experience -- with sure death spinning 6 feet in front of you:
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Thread Starter
Racer
Joined: Dec 2013
Posts: 418
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From: Ct
I went back and checked my timing and I’m glad I did.
The advance was still coming in above 3600 and settled down around 4000rpm. I now have 35 btdc read from the dial timing light next to the “0” mark at 4000rpm, car warmed up obviously, vacuum plugged and idle was set and dwell set at 30.
This results in 15 degrees at idle, vacuum plugged.
The motor runs very strong and sounds great.
I have a second set of 1Q66 shielded wires coming from Zip. IF, that’s a big “IF”, they test ok on the ohms meter and IF the crimps look ok this time I may install those and the chrome shield around the distributer to button up the project.
I very much appreciate the advice and education with this project.
The advance was still coming in above 3600 and settled down around 4000rpm. I now have 35 btdc read from the dial timing light next to the “0” mark at 4000rpm, car warmed up obviously, vacuum plugged and idle was set and dwell set at 30.
This results in 15 degrees at idle, vacuum plugged.
The motor runs very strong and sounds great.
I have a second set of 1Q66 shielded wires coming from Zip. IF, that’s a big “IF”, they test ok on the ohms meter and IF the crimps look ok this time I may install those and the chrome shield around the distributer to button up the project.
I very much appreciate the advice and education with this project.
Race Director
Joined: Jan 2003
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From: Central Arkansas
I think you would benefit from some lighter springs, especially with a 4 speed. My own opinion I don’t like real fast curves like all in by 15 - 1800 rpm because I like stable timing at idle without the weights swinging in and out as the idle fluctuates. But all in by 25 - 2800 rpm makes sense to me, a little higher yet for an automatic unless it has a loose converter.
Race Director
Joined: Apr 2005
Posts: 11,281
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From: Bowling Green, Kentucky
I think you would benefit from some lighter springs, especially with a 4 speed. My own opinion I don’t like real fast curves like all in by 15 - 1800 rpm because I like stable timing at idle without the weights swinging in and out as the idle fluctuates. But all in by 25 - 2800 rpm makes sense to me, a little higher yet for an automatic unless it has a loose converter.
Agree. But if you also run vacuum advance, you then want your vac can to be optimized to the new centrifugal curve..........so that you don't have too much advance and experience detonation.
Back in the day, when we recurved the distributors for a quick curve for extra horsepower, we DISCONNECTED the vac advance and ran without it. The reason is above. Today, I am a bit wiser, and realize that you can have both............but you also need to think it thru and then get the correct vac can for your "revised" distributor.
The centrifugal advance for my 67 327/350 HP car does not stop advancing until 5000 RPM.......and has 40 degrees of total mechanical advance at this point. The factory vacuum can is the #236. It provides 16 degrees of additional advance, and doesn't begin to cut back on this vacuum advance until around 7 inches of vacuum. So if I quicken up the centrifugal advance as suggested, I really need a vacuum can that will begin to shed the vacuum advance much earlier than 7 " vacuum to avoid part throttle detonation.
Not a hard problem to solve, but one that does need a good solution.
Larry
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I have seen a bad arc like you are describing mess up the brass floats in a Holley. Basically it melts the solder that bonds the two halves of the float together. The float then is able to take on gasoline. The float no longer shut the Incoming fuel off at the correct level because it’s buoyant. The engine then runs really rich.