Hello all. I apologize in advance: I don't really know much about the mechanics of automobiles in general or my '86 Monte SS in particular, so please bear with me. My wife gave me the car as a Christmas surprise a couple of years ago and I love it. It had the original 305 in it, thus your average minivan could out-accelerate it, so I recently had a mechanic that I had at least some reason to rely on put a 'crate' 350 in it. He put 'headers' on it as well (his recommendation).
The car has auto trans, gear shift on the column, as it has a bench front seat; he says this is less common than buckets and auto trans shift on the floor. The upshot is that he says the shifter is bumping against the new headers, making it so that I'm not going to be able to shift into 1st or 2nd gear. Actually when I first got it back from him sometimes I wasn't able to shift into D at all! He says he's got it so I can get into D and OD, but not 1 or 2.
Does this sound plausible? Any other advice out there?
Also, since the new engine was put in, at low revs the power brakes seem to fail and I have to push very hard to get braking. He seems to be having some difficulty correcting this as well. Any comments?

 

With your shifter being on the column, the linkage may be right where the headers are running...Chances are, he put the long headers on and those can be right in the way. When I got my 84 it still had column shift but I took out the column shift linkage and put in a floor mounted, ZGate shifter. Now they do make smaller shifters than the ZGate. I DID have to modify my dash area where the radio used to be to get the ZGate in but I was building it to race and that was not an issue for me. I also had the bench seats at the time so it (the shifter) DID have to go a bit more forward than usual. Once I had the shifter cable attached to the transmission and adjusted, I had no issues whatsoever with any interference with my long headers. I go in to all gears just fine.
With your power brake issue. There is a brake booster (huge round thing) right behind the master cylinder on the drivers side firewall. There is a vacuum line that runs from that to the back of either the carburetor or intake (depending on how it was set up). Make sure that is present and hooked up and not kinked or bent. I need to replace my metal line on that set up myself as I bent a kink into it a few weeks ago and I am having the same power brake issue you are having. I have brakes but very little power brakes. I am not a huge person and I really have to push hard also. If there are no problems with your brake booster line, then it is a possibility that your brake booster is bad.
Hope this at least gives you some ideas.

 

Just another idea to help you out. For our older cars, the Chiltons manuals are wonderful and have great pics and wiring diagrams!! I use mine all the time and it is well worth the 30 bucks you pay for it!!
Here is also a link to TONS of info about our older Montes here on the forum
---->RWD Tech Guides '70-'88 - Monte Carlo Forum - Monte Carlo Enthusiast Forums

 

Thanks so much for the info! Definitely things to look for/think about. Funny about putting the shifter on the floor; I considered changing the trans to manual at the same time as the new motor, but the cost seemed too much 'sugar for a penny'; the shifter would have had to go on the floor for that, too. If I end up having to change the trans anyway, I might just go for the manual...

 

My transmission is still a 3 speed automatic. You do not have to change to a manual transmission. I just changed from column shift to floor shift.