140 engine stumbles when cruising

[Frank DuVal]

My main recommendation has always been an upgrade to a relatively simple, stable and reliable FAST XR-700 optical-trigger breakerless system.

[RBohl]

As someone had predicted, the problem with my '65 140 engine was a too-small main jet in one of the primary carburetors. The fellow that rebuilt my engine didn't match the primaries (one was 1965 vintage, the other just older), and the carb rebuilder installed a drilled 0.046" jet in the old carb, the other ('1965) primary had a reworked jet of questionable size. The old carb was replaced with one of the proper vintage. Once all the units had 0.052" jets the stumbling stopped and the engine had more observable power. Thanks to all for your kind and helpful suggestions.

[66vairguy]

As someone had predicted, the problem with my '65 140 engine was a too-small main jet in one of the primary carburetors. The fellow that rebuilt my engine didn't match the primaries (one was 1965 vintage, the other just older), and the carb rebuilder installed a drilled 0.046" jet in the old carb, the other ('1965) primary had a reworked jet of questionable size. The old carb was replaced with one of the proper vintage. Once all the units had 0.052" jets the stumbling stopped and the engine had more observable power. Thanks to all for your kind and helpful suggestions.

Glad you found the issue. Drilling out a jet is a NO-NO. Sad you got stuck with such a carburetor mess, but not that uncommon. I once got a bargain on a box of used Corvair carburetors and about half were such a mess they went into the recycle bin.

I know Brad is very defensive about Pertronix products, but in spite of all the Pertronix advertising hype, the real world use feedback has shown the Ignitor II and Flamethrower coils are more problematic versus other ignition options.

Many defend points, and they are fine, but they require more maintenance and today the quality is not good. For the non-turbo engine, the FAST XR-700 and stock coil and ballast work well, as does the Pertronix original Ignitor and stock coil and ballast.

Good luck with the car.