Timing Question...

[Don]

My engine builder is recommending me to lock out the distributor's advance timing to 0° and setting the initial advance at 36° instead of using an advance curve.

Pros:
Better throttle response at low rpm will make for good launching.
High hp engines need more initial timing to be happy.
Engine will run cooler and cleaner.

Cons:
Can be hard on the starter, especially if it is not a mini high torque starter.
Low throttle highway cruising may use more fuel.
Better throttle response at low rpm could make the car jumpy.

Just got done reading an interesting article on this topic:
Where should I set the timing on my performance engine? (http://www.badasscars.com/index.cfm/page/ptype=product/product_id=76/category_id=13/mode=prod/prd76.htm)


What are your thoughts? I am not very educated on this subject.

[wallace18]

Personally I would not suggest that at all. I always set timing at idle close to manuf. specs and then set the total advance to what the engine builder suggests. I my case that is me, about 32-35 total. I would research this topic thoroughly before you ruin your engine.

[skullandbones]

I didn't see anything that radical about the article. He is advocating under 36 degrees total advance. He talks about bringing the timing in sooner so that makes sense for a better launch (2000 rpms or less) and says he like a basic timing of 10 to 14 degrees. So I think they are just saying to adjust the timing of the timing. That is adjust the time at which your total timing comes in. He also used the word "lockout" which I think could be confusing. It doesn't sound to me that he is locking the timing down to 36 degrees all the time. That sounds dangerous and something that would make for a very unfriendly engine for drivability on the road. This must not be an EFI conversation!

WEK.

[tkrupinski]

I used an MSD dist with the lock out for the vac adv. Set the timing at 8deg and used the 28deg bushing and netted me 35 deg on the timing light. It is all in at 3300rpm. This is a 410 stroker. We like the power so the gas mileage does not matter to us.

[Tocoti]

As the engine rpm increases, there is a shorter time for fuel burn so a slight increase in timing with the increase in rpm is needed because the fuel still burns at the same rate. If you increase the timing at low rpms it will be burning way before it should be burning causing a front and heat and "ping" from the opposing front .

[Don]

Based on what you guys are saying I am thinking of the physics involved here. Hypothetically, 91 octane fuel burns at a constant rate. In the image below, the burn graph is not displayed as a function of time but rather in degrees, at a particular rpm. The graph will widen considerable at high rpm, because the burn rate is constant while the crank speed is variable.
http://i573.photobucket.com/albums/ss172/donandcarlynn/2014%20May/fuelburn.jpg

As the engine increases in rpm the time it takes for the crank to move 10° or 36° shortens.

I made a graph here to see how many seconds it takes for the crank to move in 10, 20, 30, and 36° increments.
http://i573.photobucket.com/albums/ss172/donandcarlynn/2014%20May/Timing.png

If I arbitrarily say fuel will burn in .0020 secs, then I am safe to say that if my initial timing is only 10° then I will not be burning through the fuel before reaching TDC. However if I have the initial timing at 36° then I will burn through the fuel by the time I reach 26° BTDC, causing detonation. As the article I sited states, this is usually not an issue for race engines as they live above 3000rpm all the time. I would imagine putting a load on the crank will only exasperate the issue.

Anyway, I think I have made my decision to set my initial at 16° and advance it with 20°. Thanks for helping me think through this. Feel free to correct me if I made a mistake. :)