Ok, I've searched and read and can't find this one.
Just put my 350 into my sons 78 malibu replacing the 305. Its running except for a little fast(by ear) idles fine untill its put into gear TH350, the engine dies. My mechanic brother and a customer both say vacume leak. I've plugged all lines & ports and connected a vacuum gage to the PCV hole and have no inducation of vacuum, maybe just a hint of pressure when reved. Have taken off his Qjet(ran fine on the 305) and replaced it with my holley and get the same thing. The engine has fewer than 200 miles on a rebuild. Has corvett cam , stealth manifold and home done port job. Been so long since I ran it in my now project car can'nt remember if it ran that way for me. Before I pull the intake I am looking for ideas to track down the vacuum leak or other possibilities?

You've eliminated the carb. This problem has been discussed before, though it's been a while. You may not want to hear this, but quite often, this problem has been transmission related, particularly the torque converter. You did make sure the torque converter was installed correctly I hope. There should have been clearance between the converter and flexplate, and you should have been able to turn the torque converter very easily by hand after the engine was bolted in. If the torque converter was not installed correctly in the transmission prior to installing the engine, the most likely result would be a pump failure rather than loading the engine when in gear, but we do need to insure correct installation of the converter regardless.
If you know for a fact the converter is installed correctly, all you can do is double check your timing and fuel delivery. Make sure the fuel pump is supplying sufficient fuel wo whichever carb is on the engine, about 4 - 7 psi on a gage installed on the line from the pump.

[This message has been edited by Randy Mosier (edited 09-18-2002).]

I had this same issue with my 350/TH350 setup...one day it was running fine the next it would not stay running once I put it in gear. Turned out the transmission vacuum modulator came disconnected and it was losing the vacuum through there, once I connected it and used a small hose clamp to keep it in place, problem was solved. Of course I found this after checking the entire motor for vacuum leaks. Most of the times it's the simple things that drive you nuts!
Good luck!

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Bob C.
70 Malibu
N.E. Chevelle & El Camino Assoc. #085
rcroatti@adelphia.net
Bob's 1970 Chevelle Malibu (http://www.chevelles.com/showroom/Bob701.jpg)

you mentioned carb replacements, if you are putting the 305 QJ on this manifold it will probably leak without the proper gasket,same thing with the holley. if they don't seal correctly you will have that problem. use grease or something on both sides of the gasket and bolt it up then remove and see if it is sealing. JIMK

Had the same problem with my '70. Had a 307 and was forced to set idle at 1300-1500RPM. This was due to a 500RPM drop when put into gear. Pulled my hair out changing carbs, pluggin off every vacuum port, spraying carb cleaned everywhere checking fo a vacuum leak. Even through the oil fill in the valve cover in case bottom of intake was cracked. Checked vacuum reading, compression, etc.
Should have used the KISS method. http://www.chevelles.com/forum/redface.gif I said let's see. Engine idles great and runs great but stalls when put into gear.
I put in a 350 engine, reused the same trans as is, but had to change the TORQUE CONVERTER.....all problems gone.
Hope this helps.

Rob
member #519