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Engine stall.

1256 Views 4 Replies 5 Participants Last post by  PA Camaro Guy
Hi I have a question and am looking for any ideas how to fix my problem. I have a rebuilt 355 in my 1968 Chevelle. It runs great, but when I am in neutral or park and put it into gear it will stall unless I really give it a lot of throttle. If I start it in gear it will go straight to a nice 1000 RPM idle. I am drawing vacuum directly from the manifold for the trans. and from the carb base plate for the vacuum advance. It has manual brakes. The engine has RPM intake, 650 double pumper carb, .488 lift 274 duration solid lifter cam, 9:1 compression, with World S/R torquer heads. The trans is a rebuilt TH400 with a 2200 stall converter. I assume this is a vacuum issue but not sure any ideas on how to fix this will be appreciated. Thanks Jay.
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Here is a theory. One thing that could be happening is the choice on the vac advance source. Carb baseplate means you're advanced at idle. So I assume you tuned the car with that condition present and you tuned it like most of us do... with the car not in gear. Once you kick it in drive now the TC is loading up and contributing drag to the engine. RPM's go down, and so does the vacuum reading on an engine that already makes very low vacuum given your cam. When the vac drops, now your advance falls off a bit. This acts to further push your idle RPMS down, and your fuel mix isn't calibrated to live at that level. Outcome: stall.

So you have some options. Move your vac advance to a tuned spark port above the baseplate so it's only active on throttle (and retune). Or try to adjust your idle mix for much lower idle RPMS. Have someone put the car in gear while you read the timing and see if you're getting a big swing.
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