Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - locked out timing or timing curve?
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Old 07-06-2011, 08:34 PM
z-adamson z-adamson is offline
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Originally Posted by oldbogie
The 20 degree retard leaves only 15 degrees out of 35. The amount of advance is sensitive to RPM, throttle position and load on the crankshaft. while 15 degrees might be fine for idle it will be insufficient in the mid RPM range where most street vehicles spend most of their time.
With the timing locked and the start retard activated anything above 800rpm will be more like 35* or whatever the timing is set at. So the mid RPM range will be 35*. So as I understand it, 20* retard with locked timing shouldent be too much unless I am missing something.

Originally Posted by oldbogie
But I'm pulling straws here as I really don't understand what it is you're trying to do. For the engine you described and the use of the vehicle locked out timing just doesn't make sense. So what's really going on?
I have a project that basically fits this description...

"low stall, low gear combo such as 1500-4500 powerband, th350 auto w/ 2krpm stall, 29" tires and 4.56:1 gears"

...and my ignition system + distributor (MSD) are set up to allow me to lock the timing and use a start retard. Although it can also use centrifugal advance w/ vacuum. I was contemplating wether to lock it out or not and as such I am trying to understand when to use locked timing and when not to. When locked timing can be made to work well and when it wont work well no matter what. This isn't something I have played around with before nor have I researched it much.

It is a heavier vehicle (~4200lbs) and I won't be flying down the freeway at 70mph so I don't mind the low gears. I am content with 50-55mph in the slow lane. Plus with the heavy vehicle weight and low stall the gears help reduce the load on the crankshaft....another reason for the low gearing.
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