tried searching, couldnt get answers

i have an 83 bird with the LG4 and TH200.

my friend has a 75 vette which he just put a 383 into and i was looking to buy the 350 that came out of it, rebuild it and swap it out with my 305.

my question is: how different is the motor from the 305 i have now and how difficult would it be to swap out the 305 for the 350. how well do the 305 and 350 parts interchange? can the TH200 bolt to the 350 and handle the hp and torque?

any suggestions?

thanks guys.

 

the blocks are the same externally, the only issue you may have is the lack of accessory bolt holes in the heads, some older heads do not have all of them. im not sure of the hp/tq rating of this 75 vette 350, i dont think its enough to toast the trans, but get a second opinion

 

what about any sensors? like coolant temp, etc? will they all go on the same way? my 305 is a computer controlled carb and the vette 350 isnt. any differences in the distributor, control module, etc? what about the computer controlled torque converter lockup? what would i have to do if i took the computer out?

problem?

p.s. i know its a lot of questions at once but i've never done anything like this before and i really cant afford to screw it up.

 

A '75 Vette 350 has about the same power as 3rd gen LG4's. Slightly more torque, that's about it.

The engine should only be considered for its shortblock. The heads are large chamber garbage (FWIW, the '75 heads have the necessary accessory holes). The cam is a paper weight. Rebuild the shortblock and put your LG4 heads on it, and with a decent cam, you'll have a decent package.

The '75 block will have the dipstick on the driver's side. No 3rd gen V8's had the dipstick on the driver's side, and they didn't worry about that when they designed the 3rd gen exhaust manifolds - hence, routing problems. All solved by putting on headers, but a challenge if you stick with the stock (soda straw sized) factory 3rd gen manifolds. You should never consider putting a 350 in a 3rd gen with LG4 exhaust, anyway.

All sensors will transfer. Use all of the LG4 stuff (sensors, intake manifold, carb, distributor, etc.). Don't bother with the Vette stuff. Don't take the computer out.

The TH200C isn't that strong. They can be improved, but stock with a healthy 350 ahead of it, don't plan on it lasting that long.

 

Five7kid, worth mentioning, if you plan to bore the 350, or even if you dont, your carb will need tuning or you'll run too lean. I have this same transplant, except my firebird is an 87, with a 75 vette motor, and 69 heads. All sensors transfer over, my accessories also transfered over. I have some maching done, so i needed to shim some stuff, with washers and what not, to get everything to line up.

I used to have an aftermarket tunnel ram setup, but it was downgraded to a EGR intake manifold, with a q-jet on top, probably from an LG4. Mine is a 355, but it is still very fuel starved.

You may or may not have this prob, but i highly recommend tuning your carb. As for ignition, stick with the LG4 stuff, its HEI is superior to the 1975 setup, unless your freind had upgraded to HEI and is giving you the setup.

Its a very simple swap.

 

Actually 75 corvette came with HEI ignition, it was the first year they swtiched from points to HEI.

 

The '83 HEI is computer controlled. It will work fine with the 350.

My '86 LG4 set-up was fine with a 350 under it. Of course, I'm at 5800' elevation.

 

Youre right, i didnt realize that. Which makes it that much easier.

 

Doesn't really matter if you're using the computer controlled set-up. You won't be using the '75 distributor in that case.

 

good to know everything should work. will the dipstick on the drivers side cause any interference (besides the exhaust) and what kind of dipstick should i get?

any tips/ tricks you guys have if i DO decide to do the swap?

p.s. everyone on here (incl. the whole board) has been such a help

 

The only dipstick problem is hitting stock exhaust manifolds. What you should get is headers - solves 2 problems with one stone.

What kind of tips/tricks do you think you still need?

 

idk anything else that could help the swap go easier or quicker. i only ask b/c i've never done anything else like this before. i guess i just dont want to get in over my head or run into anything unsuspected.

 

My dipstick isnt a problem. Doesnt interfere with exhaust or anything. Only prob is, last guy didnt seal it to the block, so sometimes when i pull it out, the shaft comes with it.

Got headers installed today (shorties), havent seen my car yet, but no problems reported about the dipstick. Power steering pump bracket had to be modified, but other than that its all good.


As for anyother tips and tricks, were giving you alot more info (just lookin out for you) than you would think you need. Its basically, unbolt/unplug old motor, pull out, drop in new one, bolt up, plug in, and go. Very simple swap.

 

hey guys i dont mean to be annoying but....

i work @ a local parts store and i looked up motor mounts and realized the Firebird motor mounts are different from the Corvette motor mounts, but they mount in the same location.

do i need to change out the motor mounts and if so how easy is it?

 

You need to take the mount halves off of the 305 and put them on the 350. They are all steel, no rubber.

Whether you change the chassis mounts is up to you. I would highly recommend getting poly inserts while you have the engine out. The stock rubber inserts tend to sag over time.