First off, sorry if this has been covered before guys. I've done about all the searching I can handle in the last few weeks, trying to find out whats going on inside my motor from descriptions of posts on this board.

Anyways, suppose that I my 305 main bearings or rod bearings are going out. Lets just say they are toast. So I'm looking to put in a 350 since I will have to pull the motor anyhow. Ok no biggie.

Now my first question is, will the 350 have the same outer dimensions, like will the headers and y-pipe bolt right up with no mods from the 305 setup?

Secondly, can I keep all my cc stuff (distributor and carb)? Before someone says right off the bat "oh my gosh, you need to get rid of it if your swapping anyways" well, I cant afford it. "But its only gonna cost maybe a little more for what benefit your gonna get" Well, I cant afford it guys. I cant afford doing this. I'm broke as a joke, actually I owe money. I might be taking a small loan just to cover getting the car running again. Plus I just spent money getting the O2 sensor bung in the headers, new O2 sensor, new Ignition coil, cap, rotor, and the carb is now fully rebuilt, so yes I'm keeping the computer stuff. Am I gonna have any ill side effects on the 350, ie is the computer gonna behave differently with the 350?

Another thing is, I plan on using the heads I ported and polished w/ valve job. I realize I'm gonna get a high CR, can anyone give me a ballpark figure at what I'm lookin at, CR-wise? I know people do it, but am I gonna have a problem with predetonation? Dumb question, but they are newer style heads ('87 up) any problems there?

And I swapped a cam into the 305 also. Its a Comp Cam CS 270H-R10 (.500 lift I and E, duration 215 I and E, love sep. 110*), yes, its a roller cam. Will there be any problem with using that in a non-roller block, can I just swap the roller lifters and pushrods righ to the 350, or will it require special roller lifters to adapt? Also, does this cam sound mediacre for a 350 setup?

And one last thing, will leaving the knock sensor unhooked have any bad results since (I dont think) a later model 350 block has a place for a knock sensor? Not quite sure what effect that would give the computer.

I'm trying to get an idea of what I'm looking at before I go ahead with it, weighing possibilities. I dont think that the 305 will be worth putting the money into even though its got comparatively low miles (80,000). Hell I dont know why a bearing would go out in the first place, motor's never been ripped or treated harshly. Never. Anyways, my original goal was to get the 305 into the 260hp +/- range, but hell if I'm gonna end up pulling the motor for bearings, may as well crap out a few hundred extra and do a swap.

Anything else I should know about?

Thanks guys.
-Ben

 

1:the 350 and the 305 are identical in all dimensions except the bore of the cylinders.

2:all the computer stuff will swap right on to the 350 with no problem, you may need to do some tweeking to the carb settings because of the bigger displacement, see the tech articles for directions.

3:the heads and intake should bolt right up to the 350, yes it will raise the compression some but I don't believe enough to worry about.

4: provided the 350 is a factory roller block, the cam and lifters will swap right in,if it is a non-roller block you will need to get some retrofit roller lifters for it along with some different pushrods. that cam should make good power in the 350, it is a little bit small but not to bad.

5: you cannot leave the knock sensor unhooked, it will give you computer problems. the 350 block should have the proper holes you need for all your sensors, they may have plugs in them when you get it but they are easy to unscrew.

the only other thing to watch is the rear main seals, the 87 will have a one piece seal and depending on the year of the 350 it could be a two piece. try to get a one piece seal 350 block,they are more reliable and you won't have to change your flexplate/flywheel.

 

Factory roller blocks & cams use a retention plate for the cam. As far as I know, there isn't any way to hold a factory roller type cam in place in a non-roller block.