Need some help diagnosing what may be one or two unrelated issues on my '67 Dodge. It's got a stock 318 with closed-chamber heads at ~9:1 compression, a vintage low-rise dual-plane intake that is 318-specific (correct small intake runners) intake, and I'm running an aftermarket small-cap vacuum advance distributor firing an HEI and a 570 Holley Street Avenger. I'm fighting a hesitation off-idle when you punch, and also a bad RPM drop at idle when using the power steering. These might be related, or might be two separate issues? The truck is a stick-shift, so I've got it tuned to idle about 750 RPM. 10° initial advance, about another 12° at idle from the vacuum can since it's hooked up to manifold vacuum. I think the carb is on the edge of being too big because I had to completely close the rear idle screws and it's only got the fronts open ~3/4 turn (when I tried to adjust it as a 4-corner idle, all the screws were open less than 1/2 turn all around). The transfer slots are not uncovered more than .020"-.040" in the primaries and the secondaries are completely closed at idle.
The hesitation is something I've worked through before with accelerator pump changes. If you roll into the throttle the truck is completely fine, but if you punch it (either from a dead stop or even while cruising 60+ MPH) it coughs and hesitates badly for a second or so before taking off. The hesitation is worse when it's cold, so my inclination is not enough accelerator pump shot, but before I go that route I wanted to make sure it isn't tied to my other problem. I'm still running the original #31 squirter and red cam in the accelerator pump BTW.
The truck has an aftermarket P/S setup which provides some significant drag at idle when maneuvering into a parking space. For instance, and it'll drop the idle by 200+ RPM, even more on a surface like hot sticky asphalt, and can occasionally stall the truck. Is it possible my idle RPM drop and my stumble off idle are actually the same issue, or at least related to some extent? Obviously the squirter can't help my dead idle P/S performance, but at the same time I don't want to go chasing the squirter tuning only to find out later that it was some other issue causing both problems? I've never tuned a carb with P/S before, and it's messing with my head since it's not a consistent load and it can be very abrupt. Some reading has suggested that maybe I'm relying too much on the vacuum advance for idle and that's why it's dropping out under the P/S load, but since I'm not giving it any throttle when steering. The vacuum stays about the same when the idle drops (I can't verify what the timing is doing without a second set of hands, but if the vacuum isn't dropping the timing should be the same as well). Is this an application where ported-vacuum would be better? I suspect both my idle stability issue, my hesitation, and the fact that my idle screws are so far in might all be related somehow?
Also the engine makes 21 inHg of vacuum at idle so I moved up to a 10.5 power valve, but it ran the same with the original 6.5, so I don't think that's causing my issue? Not sure what to chase first at this point.
The hesitation is something I've worked through before with accelerator pump changes. If you roll into the throttle the truck is completely fine, but if you punch it (either from a dead stop or even while cruising 60+ MPH) it coughs and hesitates badly for a second or so before taking off. The hesitation is worse when it's cold, so my inclination is not enough accelerator pump shot, but before I go that route I wanted to make sure it isn't tied to my other problem. I'm still running the original #31 squirter and red cam in the accelerator pump BTW.
The truck has an aftermarket P/S setup which provides some significant drag at idle when maneuvering into a parking space. For instance, and it'll drop the idle by 200+ RPM, even more on a surface like hot sticky asphalt, and can occasionally stall the truck. Is it possible my idle RPM drop and my stumble off idle are actually the same issue, or at least related to some extent? Obviously the squirter can't help my dead idle P/S performance, but at the same time I don't want to go chasing the squirter tuning only to find out later that it was some other issue causing both problems? I've never tuned a carb with P/S before, and it's messing with my head since it's not a consistent load and it can be very abrupt. Some reading has suggested that maybe I'm relying too much on the vacuum advance for idle and that's why it's dropping out under the P/S load, but since I'm not giving it any throttle when steering. The vacuum stays about the same when the idle drops (I can't verify what the timing is doing without a second set of hands, but if the vacuum isn't dropping the timing should be the same as well). Is this an application where ported-vacuum would be better? I suspect both my idle stability issue, my hesitation, and the fact that my idle screws are so far in might all be related somehow?
Also the engine makes 21 inHg of vacuum at idle so I moved up to a 10.5 power valve, but it ran the same with the original 6.5, so I don't think that's causing my issue? Not sure what to chase first at this point.
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