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View Full Version : help 350 to 305 swap


Lucas
10-25-2007, 09:24 PM
i have a 305 engine and a th 400
problem is the torque converter wont bolt up to the
305 12.5" flex plate. Can i put the 350 13.5" flexplate on the 305 as long as the starter bendix lines up.
will i have issues with the 350 flex plate on the 305...


basically i have a 305 car motor and a th400/208 set up i want to work......This shitbox has to be ready for KOTP

kootenaycat
10-25-2007, 10:11 PM
Been a while since I did this swap. When I swapped a 305 into my old truck (was a 350), I just used the starter and flexplate from the 305, but I had a TH350. I can't see a problem using the bigger flexplate and starter to match. 400SB (and big blocks) is the only one with external balancing issues.

Kinslayer
10-25-2007, 10:39 PM
Bellhousing is different, so is the starter.

C-10ss
10-25-2007, 10:46 PM
i done a 305 to a 350 swap in my old 72 i had , i just swaped the flex plate off the 305 to the 350 and no problems

ottoman
10-25-2007, 11:19 PM
Bellhousing is different, so is the starter.

this sounds like something a flockin newbie would say. :dontknow: just swap the shit over and your good to go. they sre the same on the outside just different inside. 305 & 350 have the same stroke just different bore so balance of the flexplate should be the same and if there is a small difference you nver know when your given it the beats anyway [cheers]

Kinslayer
10-26-2007, 12:09 AM
this sounds like something a flockin newbie would say. :dontknow: just swap the shit over and your good to go. they sre the same on the outside just different inside. 305 & 350 have the same stroke just different bore so balance of the flexplate should be the same and if there is a small difference you nver know when your given it the beats anyway [cheers]

Yeah so? It's TRUE. Well it was in my case. I mean, the starter is dependant on the bellhousing used, and maybe the holes line up with the 305 housing. I've only swapped one way after all (the right way, I may add, 305 TO a 350..)..but I used all the 350 stuff as well and ditched the small starter and shit.

And I am a newbie so fackoff

Lucas
10-26-2007, 12:19 PM
thx ottoman i think it will work fine

KOTP here i come

kootenaycat
10-26-2007, 11:38 PM
Yeah so? It's TRUE. Well it was in my case. I mean, the starter is dependant on the bellhousing used, and maybe the holes line up with the 305 housing. I've only swapped one way after all (the right way, I may add, 305 TO a 350..)..but I used all the 350 stuff as well and ditched the small starter and shit.

And I am a newbie so fackoff

Last time I checked, Chevy starters bolt to the block, not the bellhousing or trans like a Ford. The lower torque shield is even cut out for the nose cone.

And all (most?) Chevy (SB and BB) use the same bellhousing layout, can interchange a SB of any sort to a BB, just can't use Pontiac, Olds, Buick, etc.

Lucas
10-27-2007, 12:08 AM
put the starter on today ,we will see if it works when i go to fire it up.
now the next problem is i want to run the fuel pump on the motor cause i think the tbi pump in the tank will be too much psi for the carb to handle.
could i just unhook the fuel pump in the tank and conect the lines to the block mounted pump or do i have to remove/bypass the one in the tank


tryin to get this shitbox ready for KOTP and down to the wire.thx for the help

Kinslayer
10-27-2007, 12:38 AM
Last time I checked, Chevy starters bolt to the block, not the bellhousing or trans like a Ford. The lower torque shield is even cut out for the nose cone.

And all (most?) Chevy (SB and BB) use the same bellhousing layout, can interchange a SB of any sort to a BB, just can't use Pontiac, Olds, Buick, etc.

yeah I guess you are right, it does bolt to the block, but they are not all the same, there are at least two different types that I know of, the more common 'large' starter which is in pretty much everything, and the smaller one that was in my 305.


put the starter on today ,we will see if it works when i go to fire it up.
now the next problem is i want to run the fuel pump on the motor cause i think the tbi pump in the tank will be too much psi for the carb to handle.
could i just unhook the fuel pump in the tank and conect the lines to the block mounted pump or do i have to remove/bypass the one in the tank


tryin to get this shitbox ready for KOTP and down to the wire.thx for the help

Well you probably wont have the same issue I did then, mine wouldn't even come close to fitting.

Growly Gorilla
10-27-2007, 08:00 AM
You can either run a pressure regulator on the tbi pump at the carb(hafta make sure you have a return line) or run lines from the mechanical pump. Make sure if you use the mechanical pump you fully disable the electric pump,remove the fuse and relay,unplug the wiring from the frame infront of the tank and block the lines off.

godtool
10-27-2007, 08:10 AM
My 1981 Jimmy has a th350, however the inspection cover bolts on with six bolts, either with 1/2" or 9/16 heads, I can't remember offhand. It is not that thin tin cover that is held on with a couple of screws. I also have two struts that bolt onto the bottom of the inspection cover and bolt to the two motor mount's. When I put a 400SB in my Jimmy, I had to reuse my 305 starter since the starter is made to match with the 6 bolt inspection cover for the th350. The larger starter will not fit on using the bolt on inspection cover. The nose cones are different. My smaller starter spun that 400 no problem. As for flex plates I know I have 6 of them lying in my shop as of today. I remember the diameter of the flex plate and how it bolts onto the crankshaft was an issue but easy to solve.

When I had my 400SB, the truck it came out of had at tH400 that had the thin tin inspection cover held on with screws and a larger starter.

Lucas
10-27-2007, 07:22 PM
it runs!!!!!

the 350 starter worked,the 305 is absolutly gutless but will work

i unhooked the pump and used the same lines and ran the mechanical pump through the electric pump .works fine


will the 305 have more power with or without exaust?
open headers is just so easy

Kinslayer
10-27-2007, 07:58 PM
it runs!!!!!

the 350 starter worked,the 305 is absolutly gutless but will work

i unhooked the pump and used the same lines and ran the mechanical pump through the electric pump .works fine


will the 305 have more power with or without exaust?
open headers is just so easy

I think it would probably have less power - not enough back pressure...but it depends on the condition of your current exhaust I would suspect.

godtool
10-28-2007, 07:23 AM
With 4:10 gears a 305 is not bad anymore in 2wd. I bought those cheap $19 flowraptors from Lordco for mu dual exhaust. They burn out fast but do the job still. Eventhough now burnt out they are still quieter then cherry bombs. Go cherry bombs. I had good sound and good power for my Y piped 305 back in 2003. I hear they sound better if you put them on backwards!! Never tried though. I have 2 used ones I'll put on my 305 soon but may wait till I put my 454 in. Go flowmaster (40's) if you can afford it. I hear the 40's sound good if combined with headers. Get quick disconnects for your headers... my Dad made his own back in the 70's on his Bronco!

ottoman
10-29-2007, 12:39 AM
if your going on a trailer then i would say screw the exhaust and call her done so she can get her beats LOL