My engine was really getting on my nerves

[carmangary]

I have a 260 Olds. I was having these weird problems where it would stumble a bit when I touched the pedal. I figured it was either dirty carb, vacuum leak, or timing problem. So today, I rebuilt the carb to rule that out. In the process, I checked my intake bolts and noticed they were a little loose so I retorqued them. Once I got the carb back on it was possibly a little better but I was still not happy. So, out of a hunch, I ripped off the SAVM and short circuited. Things improved but I still had a stumble at one point. For the heck of it, I decided to reconnect my EGR valve that I disconnected awhile back since it was giving me problems. Then I realized that I left the EGR port unplugged when I removed the SAVM. Now, I have the EGR hooked up, SAVM bypassed and its running like a champ. It actually accelerates now. I almost made the tires squeal while flooring it and going around a corner. I think I finally have the 260 running as good as it gets. Yippee ki yay mother ****er!

 

[carmangary]

This morning while it was nice and cool I took out the car to see how yesterdays changes work out on a cold engine. It went back to harsh upshifting and slight power loss when touching the throttle. I knew the power loss was because due to the EGR valve being hooked back up again so I went back and plugged it. As soon as I did that the power loss went away and the transmission started shifting a whole lot better.

Just recently I learned that someone had swapped a TH350 into my car and took out the original 200. I didn't realize it until recently that the 350 uses vacuum for shifting. What was happening was that the EGR was opening and lowering vacuum and screwing with the transmission shifting.

I'd like to be able to use the EGR valve. Do I need a different EGR valve or do I need a new transmission vacuum modulator or do I need both? Since my 260 engine and th350 transmission is an oddball combination, I don't think the parts books or stores know what I should actually be using. Can anyone help? For now I will just leave the EGR valve disconnected.

 

[FE3X CLONE]

The 260/TH-350 isn't an odd combination. My brother's '81 had a 260/TH-350C stock. You may try looking up an '81 Cutlass Supreme for your parts.

 

[Bonnewagon]

They cannot share a vacuum source. The transmission uses a dedicated fitting at the rear of the carb base so it gets full manifold vacuum. The EGR needs ported vacuum so it must go to a dedicated ported vacuum fitting on the front of the carb. Use a vauum gauge to verify what type of vacuum you get at each fitting.