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 Posted: 12-16-2017 06:21 pm
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 319
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chrisl wrote:
I've acquired a set of Strombergs and am refurbishing them to fit on my GT. It currently has Dellortos on it and runs fine other than the stutter on flooring it but IIt's interesting to see how different people view and/or fix the same problems. I have 3 907 engines, and fixed all the carb issues by converting to Dellortos.

If your Dellortos have an off-idle hesitation, or don't otherwise run smoothly, then they are not properly set-up and tuned. If the Strombergs aren't set-up & tuned any better, then they will give you problems as well.

... a lot of the pipework on the Strombergs is missing so I am working through what goes where. The shop manual is no help; and I see from your post above a lot of the vacuum lines aren't really necessary anyway.
As far as removing vacuum lines goes, follow Answerman's simplified schematic. However, it's also important to defeat the devices those lines feed, rather than just disconnecting the hoses & plugging the ports.

The Bypass Valves allow intake flow to continue around the closed throttle butterflies during closed-throttle over-run. The strong manifold vacuum that would otherwise result would produce a strong spike in oxides of nitrogen. The Bypass Valves prevent that.

The Vacuum Switch (aka Vacuum Delay Valve) controls how long the Bypass Valves stay open after the throttles close. The Delay Valve and two Bypass Valves are all part of the same function. If you delete one, delete them all.

In addition to disconnecting the hoses, also blank-off the Bypass Valves. Remove each valve, replace the gasket with one that is hand-cut and solid (no center holes and passages for vacuum), and re-install the valves. The 'solid' gasket blanks off the valve, making it little more than decorative.

Separate, and not vacuum related...
If the Thermal Compensator is suspect or not working, then don't bother fixing or replacing it. Simply adjust the plunger in all that way such that it can never unseat/ open the port. The Thermal Compensator is a 'seasonal' thing, providing a slightly richer mixture during the warm-up cylcle in cold weather. Most 907 powered cars get put in storage and aren't driven during 'real' Winter. If that's the case for you, then restoring the Thermal Compensator is a waste of effort.

Regards,
Tim Engel

Last edited on 12-18-2017 05:07 pm by Esprit2