1962 GMC 478M V6 Swap

[Rezzato]

I thought i might post this swap as it is pretty unique. I have a 1962 GMC 1000 that had a 305 V6 in it. It got me interested in these V6 engines and I discovered there were many more offered in various displacements. I wanted a larger V6, so i found a 478 Magnum on craigslist that I am getting ready to put in. The block will bolt right in but changes need to be made with the flywheel and bellhousing.

The 478 comes with a heavy duty truck bell housing that houses a massive flywheel, clutch, and pressure plate. This bellhousing is too large to fit into my 1962 GMC 1000 and I will need to replace it with the light duty bellhousing found on the original 305.

Unfortunately the 478's flywheel will not fit in the light duty bellhousing and needs to be replaced. The problem is that the 478 is externally balanced using its flywheel as a ballancer. This flywheel also has an eight mounting holes unlike its other V6 counterparts which use 6 bolts.

Only a custom made flywheel or a flywheel from a 379 V6 will work. The 379's flywheel also has an eight bolt pattern, is externally balanced, and will fit within the light duty bellhousing. Fortunately I have a 379 sitting around that I bought a few months ago. This is an extremely rare engine only found in 1973,1974 in 6000 series trucks.

I need to get the 379's flywheel drilled and tapped to receive the smaller pressure plate found in the light duty trucks.

Next I need to have the light duty bellhousing bored out a bit to accept the larger input shaft retainer of the SM465 I will be using.

Edited by staff

Here is the truck


Here is the 478 Magnum, notice the air compressor on the right.


I will have many more photos tomorrow of all the parts.

[Rezzato]

I thought i might post this swap as it is pretty unique. I have a 1962 GMC 1000 that had a 305 V6 in it. It got me interested in these V6 engines and I discovered there were many more offered in various displacements. I wanted a larger V6, so i found a 478 Magnum on craigslist that I am getting ready to put in. The block will bolt right in but changes need to be made with the flywheel and bellhousing.

The 478 comes with a heavy duty truck bell housing that houses a massive flywheel, clutch, and pressure plate. This bellhousing is too large to fit into my 1962 GMC 1000 and I will need to replace it with the light duty bellhousing found on the original 305.

Unfortunately the 478's flywheel will not fit in the light duty bellhousing and needs to be replaced. The problem is that the 478 is externally balanced using its flywheel as a ballancer. This flywheel also has an eight mounting holes unlike its other V6 counterparts which use 6 bolts.

Only a custom made flywheel or a flywheel from a 379 V6 will work. The 379's flywheel also has an eight bolt pattern, is externally balanced, and will fit within the light duty bellhousing. Fortunately I have a 379 sitting around that I bought a few months ago. This is an extremely rare engine only found in 1973,1974 in 6000 series trucks.

I need to get the 379's flywheel drilled and tapped to receive the smaller pressure plate found in the light duty trucks.

Next I need to have the light duty bellhousing bored out a bit to accept the larger input shaft retainer of the SM465 I will be using.

Then I need to find a two piece drive shaft and a different transmission cover pan because the truck originally came with a 3 speed SM318. I am looking for these parts so if someone wants to get ride of them PM me. Thanks

Here is the truck


Here is the 478 Magnum, notice the air compressor on the right.


I will have many more photos tomorrow of all the parts.

[tincan1966]

I like it! No substitution for cubic inches- AND it's different! Cool project!

[tincan1966]

I like it! No substitution for cubic inches- AND it's different! Cool project!

[scottofksu]

WOW! I've never heard of such a big 6! Awesome project indeed!

[scottofksu]

WOW! I've never heard of such a big 6! Awesome project indeed!

[awbrown]

always wondered what the performance of our trucks would have been if they had offered it with a 478..cant wait to see the results .. hey take it to the strip like it is now and get some times , then again after the swap !!! there are some good posts in here somewhere on modifying the manifold to accept a bigger carb ,you may need it ! Good luck ...

[awbrown]

always wondered what the performance of our trucks would have been if they had offered it with a 478..cant wait to see the results .. hey take it to the strip like it is now and get some times , then again after the swap !!! there are some good posts in here somewhere on modifying the manifold to accept a bigger carb ,you may need it ! Good luck ...

[padresag]

In 1962 the 478 V6 was introduced for use in the 6500 series trucks.
the 478 installation is becoming popular in l/duty trucks. I got a 478 for my neighbour here about 6 months ago. he is putting it in his hyster in place of a 305. rescued it from the scrapman
ron

[padresag]

In 1962 the 478 V6 was introduced for use in the 6500 series trucks.
the 478 installation is becoming popular in l/duty trucks. I got a 478 for my neighbour here about 6 months ago. he is putting it in his hyster in place of a 305. rescued it from the scrapman
ron

[duallyjams]

Are you going to convert the front of the engine also = timing chain & cover , water pump ect. Do you need a spin on oil filter adapter.

[duallyjams]

Are you going to convert the front of the engine also = timing chain & cover , water pump ect. Do you need a spin on oil filter adapter.

[61_FL_Apache]

Nice project!! The air comp can come in handy if you go with an air ride setup.

[61_FL_Apache]

Nice project!! The air comp can come in handy if you go with an air ride setup.

[Corts60]

Looks like you've done your research for sure. Have you been posting over on 6066gmcguy.org as well? I'm sure they'd love to see the project. Also, that 478 weighs about 200lbs more than the 305. Have you thought about what to do with the front suspension?

Sweet build man, I'm excited to see it come along.

[Corts60]

Looks like you've done your research for sure. Have you been posting over on 6066gmcguy.org as well? I'm sure they'd love to see the project. Also, that 478 weighs about 200lbs more than the 305. Have you thought about what to do with the front suspension?

Sweet build man, I'm excited to see it come along.

[markeb01]

Looking forward to the finished product. That is going to be very cool, and unique.

[markeb01]

Looking forward to the finished product. That is going to be very cool, and unique.

[Rezzato]

Originally Posted by duallyjams

Are you going to convert the front of the engine also = timing chain & cover , water pump ect. Do you need a spin on oil filter adapter.

I am actually just going to put a different fan on the water pump pulley and move the radiator up a few inches. The fan should still clear the hood, if not I'll just put an electric cooling fan in.

[Rezzato]

Originally Posted by duallyjams

Are you going to convert the front of the engine also = timing chain & cover , water pump ect. Do you need a spin on oil filter adapter.

I am actually just going to put a different fan on the water pump pulley and move the radiator up a few inches. The fan should still clear the hood, if not I'll just put an electric cooling fan in.

[Rezzato]

Originally Posted by Corts60

Looks like you've done your research for sure. Have you been posting over on 6066gmcguy.org as well? I'm sure they'd love to see the project. Also, that 478 weighs about 200lbs more than the 305. Have you thought about what to do with the front suspension?

Sweet build man, I'm excited to see it come along.

Yeah I did think about that. I really don't know what to do with the torsion bar set up. Hopefully it won't make a drastic change. I could always relocated the battery :p

[Rezzato]

Originally Posted by Corts60

Looks like you've done your research for sure. Have you been posting over on 6066gmcguy.org as well? I'm sure they'd love to see the project. Also, that 478 weighs about 200lbs more than the 305. Have you thought about what to do with the front suspension?

Sweet build man, I'm excited to see it come along.

Yeah I did think about that. I really don't know what to do with the torsion bar set up. Hopefully it won't make a drastic change. I could always relocated the battery :p

[MusicMan70]

In regards to the extra 200lbs engine weight, here's some info from the Jolly site;

" I am going to throw in my two cents on the weight of the 478 vs 305's. As Jolly pointed out, most all parts of the 478 are heavier than the 305. All together they add up to about 200 lbs.

Note here: Most of the 305's exterior parts (with minor modifications) can be
used on the 478 thus saving most of that 200lbs.

Rick Rusconi"


"And my 2-cents worth on a 478's weight:

Maybe that also includes the air compressor, heavy duty alternator, starter,
and power steering pump. I know that engine is a heavy thing, because it made
my cheap Chinese-made engine stand groan when I put it on. I had to prop up the front of the block with a 2x4 to keep the engine stand from breaking. The dual-disc clutch, flywheel, and bellhousing would probably account for
most of the difference. My bellhousing was seriously cracked at the block
flange, and I had to throw it away. I'll be needing a pickup-truck style of
bellhousing when I get to the engine installation phase.

Andy Harman"

So it looks like some parts trading may save some weight and not affect the front suspension too much.

[MusicMan70]

In regards to the extra 200lbs engine weight, here's some info from the Jolly site;

" I am going to throw in my two cents on the weight of the 478 vs 305's. As Jolly pointed out, most all parts of the 478 are heavier than the 305. All together they add up to about 200 lbs.

Note here: Most of the 305's exterior parts (with minor modifications) can be
used on the 478 thus saving most of that 200lbs.

Rick Rusconi"


"And my 2-cents worth on a 478's weight:

Maybe that also includes the air compressor, heavy duty alternator, starter,
and power steering pump. I know that engine is a heavy thing, because it made
my cheap Chinese-made engine stand groan when I put it on. I had to prop up the front of the block with a 2x4 to keep the engine stand from breaking. The dual-disc clutch, flywheel, and bellhousing would probably account for
most of the difference. My bellhousing was seriously cracked at the block
flange, and I had to throw it away. I'll be needing a pickup-truck style of
bellhousing when I get to the engine installation phase.

Andy Harman"

So it looks like some parts trading may save some weight and not affect the front suspension too much.

[padresag]

the major difference in weight would be the water pump and mounting casting. they do not inc flywheel, compressor, alternator or p/s pump. a complete basic engine only
changing the water pump and mounting reduces weight and makes for more room, but there are other changes to do such as timing chains and gears and a few other things
ron