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4.3l To 350 Swap

jdwcobra93

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jdwcobra93 New Member

jdwcobra93

Posted
Posted

Hi,

 

I have a 1995 GMC Sierra with a 4.3l. I just found a 1972 350 motor and 350 transmission. I am trying to find out if this will be a simple swap or will I have to do any mods as far as mounting goes. Will my existing transmission bolt up to this motor? I plan on using the carburetor and ignition from the 1972 motor. Thanks!!!!

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
Hi,

 

I have a 1995 GMC Sierra with a 4.3l. I just found a 1972 350 motor and 350 transmission. I am trying to find out if this will be a simple swap or will I have to do any mods as far as mounting goes. Will my existing transmission bolt up to this motor? I plan on using the carburetor and ignition from the 1972 motor. Thanks!!!!

As far as I know, the trans you have should bolt right up, and the 350 should just drop right in. I really doubt the 4.3L Torque converter would mate to the 350 flywheel, and I am almost 100% sure the 4.3L starter wont fit.

 

The T/H 350 Trans is a stronger trans than the 4L60E you have on your 4.3 though.

 

I'm sure it wont be as simple a swap as it should be, but for the old complexity meter rating I would rate it a 6 - 6.5 out of 10.

Badass69 Senior Enthusiast

Badass69

Posted
Posted

Transmission, starter and so forth are bolt ons. Unless your 350 has a different flexplate than the 4.3 V6 does of course. You have 2 ring gear sizes, being 153 tooth and 168 tooth. Even if they are different all that affects is the starter.

 

Accesories should bolt up, most of the holes present on the late model blocks were there from the past as well.

 

The thing to remember is a 4.3 is nothing more than a 350 missing 2 cylinders.

 

Motor mounts are different so you need to buy the correct ones for a V8 in your case.

 

Then there is the potential to need a heavier rad, you need a V8 trucks fan shroud and so on.

 

It's not a terrible swap really. Honestly if you want to keep the TBI versus going to a carb all you need is a V8's distributor and intake manifold, injectors and prom to run it. Your choice however.

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
Transmission, starter and so forth are bolt ons. Unless your 350 has a different flexplate than the 4.3 V6 does of course. You have 2 ring gear sizes, being 153 tooth and 168 tooth. Even if they are different all that affects is the starter.

 

Accesories should bolt up, most of the holes present on the late model blocks were there from the past as well.

 

The thing to remember is a 4.3 is nothing more than a 350 missing 2 cylinders.

 

Motor mounts are different so you need to buy the correct ones for a V8 in your case.

 

Then there is the potential to need a heavier rad, you need a V8 trucks fan shroud and so on.

 

It's not a terrible swap really. Honestly if you want to keep the TBI versus going to a carb all you need is a V8's distributor and intake manifold, injectors and prom to run it. Your choice however.

Yeah the engine should mount in exactly the same place if I'm not mistaken...minus the actual mounts like you said.

As for the fan shroud, I wouldn't even bother...we put an electric fan in my buddies K5 blazer out of a Ford Taurus, with a temp switch. It pulls way more air than anything on the market that's relatively affordable...(3000CFM per fan and there is enough area to fit 2 on a Full size Chevy rad)

Badass69 Senior Enthusiast

Badass69

Posted
Posted
Transmission, starter and so forth are bolt ons. Unless your 350 has a different flexplate than the 4.3 V6 does of course. You have 2 ring gear sizes, being 153 tooth and 168 tooth. Even if they are different all that affects is the starter.

 

Accesories should bolt up, most of the holes present on the late model blocks were there from the past as well.

 

The thing to remember is a 4.3 is nothing more than a 350 missing 2 cylinders.

 

Motor mounts are different so you need to buy the correct ones for a V8 in your case.

 

Then there is the potential to need a heavier rad, you need a V8 trucks fan shroud and so on.

 

It's not a terrible swap really. Honestly if you want to keep the TBI versus going to a carb all you need is a V8's distributor and intake manifold, injectors and prom to run it. Your choice however.

Yeah the engine should mount in exactly the same place if I'm not mistaken...minus the actual mounts like you said.

As for the fan shroud, I wouldn't even bother...we put an electric fan in my buddies K5 blazer out of a Ford Taurus, with a temp switch. It pulls way more air than anything on the market that's relatively affordable...(3000CFM per fan and there is enough area to fit 2 on a Full size Chevy rad)

 

 

Just suggesting if he wanted to use a mechanical fan. I need to do that swap on my 96 pickup...... I like the dual fan setup on my 96 9C1 Caprice and may just use one of those.

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
Transmission, starter and so forth are bolt ons. Unless your 350 has a different flexplate than the 4.3 V6 does of course. You have 2 ring gear sizes, being 153 tooth and 168 tooth. Even if they are different all that affects is the starter.

 

Accesories should bolt up, most of the holes present on the late model blocks were there from the past as well.

 

The thing to remember is a 4.3 is nothing more than a 350 missing 2 cylinders.

 

Motor mounts are different so you need to buy the correct ones for a V8 in your case.

 

Then there is the potential to need a heavier rad, you need a V8 trucks fan shroud and so on.

 

It's not a terrible swap really. Honestly if you want to keep the TBI versus going to a carb all you need is a V8's distributor and intake manifold, injectors and prom to run it. Your choice however.

Yeah the engine should mount in exactly the same place if I'm not mistaken...minus the actual mounts like you said.

As for the fan shroud, I wouldn't even bother...we put an electric fan in my buddies K5 blazer out of a Ford Taurus, with a temp switch. It pulls way more air than anything on the market that's relatively affordable...(3000CFM per fan and there is enough area to fit 2 on a Full size Chevy rad)

 

 

Just suggesting if he wanted to use a mechanical fan. I need to do that swap on my 96 pickup...... I like the dual fan setup on my 96 9C1 Caprice and may just use one of those.

 

Yeah those are fairly high too...cant remember the CFM though...we did look at them when looking for a fan.

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