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Help with New Carb and Timing Posted by BradW [Email]  (#3273) [Profile/Gallery]
(more from BradW) on Fri, 10 Jul 2026 20:45:37
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We just swapped our 30 y,o. Weber 32/36 DFV, which had served well but was leaking like a sieve, for a new Weber knock off 32/36 DGEV by Thundermingo (we're saving our new, spanish built Weber for the new engine we're building).
Here's the issue: I can't get the engine to idle under 1500RPM without dying. It is crazy rev happy and will go past redline in a heartbeat :-o but down low it's grumpy and under load (in gear). The idle circuit does still work (turning the idle mixture in and out makes a difference), and I've plugged the PVC valve in the 3rd runner just to eliminate that possibility.
Idle timing with the vacuum advance disconnected and plugged shows 6 degrees BTDC idling at 1500. With the vacuum line connected the total advance is 20 degrees BTDC (which is OK by Jack Ashcraft's book).
The cold idle also runs about 1500-1600 RPMs. The carb does go on and off the fast idle cam with the appropriate cold/hot condition.
I checked the spec on the jets and while they overlap with what Ashcraft recommends for the V4 pretty closely. Thundermingo main idle jet is a 60 vs. 50, pump jet 60 vs. 50 on the Ashcraft schedule. And the accelerator pump is visually putting out a good squirt.
Also checked the spark (condenser, points, coil), and we're getting a nice blue spark at the plugs (via tester).
Any ideas on what to check next?
1973 SAAB Sonett III, 70,000 miles, parked for 30 years, only upgrade has been to the dual carb and manifold. Otherwise totally stock. When we brought it back from the dead with the NOS (but also 30 years old) DFV, new fuel pump and filter, all new brakes and brake cylinders, we've driven it 10,000 miles in a year so it's been running well until the DFV retired.
->Posting last edited on Sun, 12 Jul 2026 10:34:20.
, Fri, 10 Jul 2026 20:45:37 <-- Viewing This Message, Mon, 20 Jul 2026 07:46:04
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