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Timing for torque


davidmcw
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I had a BMW specialist adjust the valves and set the timing on my recently acquired 1976 2002. When I got the car back, it pulled smoothly to redline but seemed to have lost some low to mid range torque. What's the best timing for low to mid range power? Engine is de-smogged with an E12 head, Weber 38/38 downdraft carb on Cannon manifold, Tii mechanical advance distributor, Tii exhaust manifold with an Ansa Sport exhaust.

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A carb'd engine needs more advance than a FI engine because the fuel is not atomized as well. It's the fuel vapor that burns not the liquid drops.

A Tii mechanical advance distr does not have as much mechanical advance as the carb'd distr (forget the vac, I'm talking about the mechanical advance).

So if it was timed using the std distr specs, there is a loss of advance under power.

If you examine the distr advance curves in the shop manual, installing a Tii distr on a carb's engine is a shot in the foot, fancier is not always better even though there is a mystic about a Tii.

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A carb'd engine needs more advance than a FI engine because the fuel is not atomized as well. It's the fuel vapor that burns not the liquid drops.

A Tii mechanical advance distr does not have as much mechanical advance as the carb'd distr (forget the vac, I'm talking about the mechanical advance).

So if it was timed using the std distr specs, there is a loss of advance under power.

If you examine the distr advance curves in the shop manual, installing a Tii distr on a carb's engine is a shot in the foot, fancier is not always better even though there is a mystic about a Tii.

There are also advantages to a Tii distributor on a carb'd engine...especially if the engine is modded....

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I've found when you advance the timing you get torque, but it doesn't rev as high and if you retard the timing it revs to the moon, but it will not have as much torque and sometimes crunch when shifting into second and not start as quickly. Too much advance the shifter will feel tight and will also crunch gears and will sometimes pop out of second on deceleration. The mild mechanical advance on the Tii distrbuter might be an issue on a carbed car too. Good luck!

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I'm not an expert, but it sounds like your specialist timed it to stock specs...and you are not stock. So you need more advance. I have heard that you adjust your advance as much as you can until you get knock, then back off. Others may have more info. Nothing wrong with your setup, and actually its a good setup for your car.

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I'm not an expert, but it sounds like your specialist timed it to stock specs...and you are not stock. So you need more advance. I have heard that you adjust your advance as much as you can until you get knock, then back off. Others may have more info. Nothing wrong with your setup, and actually its a good setup for your car.

I've been looking for a definite spec. to set the timing. The fellow that was helping me with a new 4 speed install told me he sets the timing by "ear". I thought "that sounds kinda crazy". But now, after your comment it makes sense. Sounds like we have a similar engine setup, at least externally. Thanks for your input. We'll set the timing as you suggested.

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There is no spec for a tii dizzy on a downdraft carbed car, because it's

not the right distributor for the engine's needs.

Crud, it's not even very good on my race car with 11.5:1 compression,

100 octane fuel and a set of 45DCOE's. I want megajolt.

By ear isn't really the best way to time things, either. But ear and the

seat of the pants by someone who does it a lot is often pretty good.

On the dyno with a detonation counter is also a pretty good way.

And max advance before det really isn't related to max power,

unless you're compressed to the det threshhold of your fuel.

Which we're usually not.

36 degrees total advance at 4500+ seems to be a 'consensus baseline'

but the curve below that will vary.

Ignition science is really like rocket science over and over again.

Cheapest way to have fun would be to buy an 'advance' ignition light,

figure out what you have now, and start (carefully) playing with it.

Sometimes the best timing for your engine is what you like!

Do check the plugs after advancing it, though.

yup.

t

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A carb'd engine needs more advance than a FI engine because the fuel is not atomized as well. It's the fuel vapor that burns not the liquid drops.

A Tii mechanical advance distr does not have as much mechanical advance as the carb'd distr (forget the vac, I'm talking about the mechanical advance).

So if it was timed using the std distr specs, there is a loss of advance under power.

If you examine the distr advance curves in the shop manual, installing a Tii distr on a carb's engine is a shot in the foot, fancier is not always better even though there is a mystic about a Tii.

There are also advantages to a Tii distributor on a carb'd engine...especially if the engine is modded....

Please list with references.

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