View single post by Esprit2
 Posted: 11-23-2016 02:12 am
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
DonBurns wrote:
In the Des Hammill book he says that for Dellortos the average turns for the idle mixture screws from closed is from 3 to 5. That is incorrect, or too wide then?3 to 5 ?? Or 3.0 to 3.5? The Idle Mixture Screws don't function much beyond 4 turns out, so there would be nothing to gain by going out to 5 turns.

For Dellortos on production cars of the 70's (ie, Jensen-Healey), stretch the range to 3.75 turns out. European emissions specs forced the manufacturers to tune a bit lean. If you adjusted the mixture screws for better running without re-jetting, it would be necessary to go a little past the normal 3.5 max to compensate for the lean jetting.

If you do re-jet first, then target having the mixture screws end up 3.0-3.5 turns out.

DonBurns wrote:
I am curious to see if this fixes the overheating. A web search found opinions on both sides of the effect of leaving it out.It should. Without a thermostat, the radiator bypass circuit is open full time. Installing the thermostat closes the bypass once the engine is up to temp.

Most engines have a single cooling system circuit with a simple on-off thermostat. In a system like that, removing the T-stat does permit maximum cooling. The downside is that the engine often runs too cool.

The 907 has a dual circuit cooling system. The main loop out through the radiator and back, and another that bypasses the radiator and goes right back to the engine. In that case, the T-stat not only closes the main circuit, it opens the bypass circuit. Delete it, and the bypass is open full time. It only stands to reason that the engine will run hot with the radiator bypass open all the time.

Last edited on 11-23-2016 06:32 am by Esprit2