305 V6 to sm465 Transmission
 

Hello All,

I have an 84 K20 Chevy . I use it for hay and hauling wood. It's got a tired 305 v8 in it. It was an original 350 powered truck . I'm interested in using a 305 v6 to repower it. Question I have is: what bell housing to use? My truck has an sm465 with the driver side fork. Not hydraulic. I understand that the block bolt pattern is different? Is there anything else I need to address?

I see from the archive that the 465 has the same pattern then. Is that the case? So I could use my existing sm465 bell housing that is bolted to my smallblock right now?

Re: 305 V6 to sm465 Transmission
 

Put a Chevy 350 back in it. Don't create headaches if you need the truck for work or chores. You could run into: 465 does not fit GMC bell housing and/or Chevy bell housing does not fit Chevy motor and the fork may be on different side and motor mount problems and driveshaft length problems and radiator hose alignment problems and gauge/sender problems.......... Nobody would put a GMC 305 V6 in a Chevy. Makes no sense. 305 V8 has no relationship to a 305 V6, if that is why you are thinking GMC, completely different.

Re: 305 V6 to sm465 Transmission
 

I have a 305 v6 engine. I do not have a 350 v8. If I wanted to put a Chevy v8 in the truck then I would do so. This post is in "Other Rides and Projects" and is therefore in the appropriate posting area. It appears to me that you either don't have any knowledge of this particular build or don't care to share anything.

Re: 305 V6 to sm465 Transmission
 

The correct bell housing to use for a V6 swap would be a 68-74 V6 light or medium duty truck bell housing that came with the SM 465, Np435 and other Np transmissions. I can get you the part number by this Sunday:thumbsup:

Re: 305 V6 to sm465 Transmission
 

A 60-66 bell housing can also be used but will require machining to accept the SM 465 trans

Re: 305 V6 to sm465 Transmission
 

Thanks AZKen. Good speaking with you. If there's anything I can ever help you with then I'd be happy to.

Re: 305 V6 to sm465 Transmission
 

What an interesting project, Ur991. It's good to see the reliable V6 getting new life in your truck. All too often the engine swap is the other way around. Please keep us updated on your progress.

Re: 305 V6 to sm465 Transmission
 

Interesting....... guy did a swap in a 63 Chevy. Some of us are rebels.



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Re: 305 V6 to sm465 Transmission
 

Out of curiosity, what year is the v6 you have?

Re: 305 V6 to sm465 Transmission
 

I'd like to see this swap happen!

Re: 305 V6 to sm465 Transmission
 

It's a 66 model out of a grain truck TJ.

Re: 305 V6 to sm465 Transmission
 

Thank you Big Block V6 I'll be glad to get the bell housing part number.

Re: 305 V6 to sm465 Transmission
 

Greetings TJ!

The swap of a GMC 305 V-6 into an '84 Chevy sounds like an interesting and unique project. Definitely would be a true "one of a kind" truck! Given that there is a correct GMC V-6 bell housing available for the SM465 Trans to bolt up to, the only other problem I can see is the engine mounts themselves. There should be no problems with drive shaft length since GMC also used the SM465 Trans. There are differences between the Chevy engine mounts, and those of the GMC Big Block V-6. Since I had two complete trucks to work with, swapping the GMC 305 V-6 into my '63 Chevy was fairly easy. I still wish I had that truck! People were astonished when I had the hood open and they saw that monstrous GMC V-6 sitting where there should have been a Chevy 292 I-6!

Re: 305 V6 to sm465 Transmission
 

Thank you George. Good information. I figured on getting the mounts from the 4000 series the motor is coming out of.

Re: 305 V6 to sm465 Transmission
 

Much as I love my 292's, my 305 pulls a load better and I don't have to rev it as high to do so. :thumbsup:

Re: 305 V6 to sm465 Transmission
 

I like the torque rating. I pull mountain roads in this area (Cotopaxi, Colorado). Torque is important to me. I don't need high engine rpm. You can't drive fast on these roads. I pull loads on steep roads. It only makes sense to use a commercial duty engine. After studying the engine design I find it superior to any other design I've seen before. I like the Cam bath and the high volume coolant circulation.

Re: 305 V6 to sm465 Transmission
 

Fuel economy is secondary here. The most important things to consider are: will the engine hold together and will it do the job. I believe the big block v6 will be a better performer than the standard line of v8's.

Re: 305 V6 to sm465 Transmission
 

It will do much better than chevy's line of v8's. These were industrial engines built to last. Cool thing is a guy who lives about 2 hours from me has a GMC with a 305 v6 and it is currently at 650K miles. All he's done is change the oil regularly and drive them how you should.

I love the torque mine has over stock v8's near it's cubic inches....considering I was towing 10k with the truck and could pull a grade a 1500 RPM in 4th and accelerate....I'm happy. :thumbsup:

Re: 305 V6 to sm465 Transmission
 

Greetings ur991!

You should have no problem with your big Block GMC V-6 holding together so long as you don't over-rev the engine. This is just my opinion, and I might be wrong, but anything over 3500 RPM might be pushing it a little bit, but I doubt that you want to make a speedster out of your truck. These engines were designed for high torque at low engine speeds. I was warned before I put the GMC V-6 in my 63 Chevy that it would be a gas guzzler, however, there wasn't a dimes worth of difference in fuel economy between the Chevy 292 I-6 and the GMC 305 V-6, and the V-6 would definitely outdo the 292 on low end torque. It will definitely outdo your small block V-8 on torque, and be competitive on fuel economy. The GMC Big Block V-6 engines are perhaps the most durable engine line ever developed by GM, and it's a crying shame that they are no longer in production.

Re: 305 V6 to sm465 Transmission
 

That's going to be a cool project, ur991! I had a '62 Chevy 4x4 someone had put a 305 V-6 in that was a great runner. but the body was shot. It had the sm420 four speed. I should have kept it to swap into something but needed some cash at one time.

When you say steep roads where you live that's kind of an understatement! I took this pic in the Parkdale, CO area 3 years ago. If I remember correctly this view is looking in the general direction of Cotopaxi! This is the Royal Gorge area.

Looking forward to following along on your build.

DAC

Re: 305 V6 to sm465 Transmission
 

That's about 12 miles from my house GMCDAC . My driveway is 10 degree incline. Many thanks George and TJ. I'm looking forward to this retrofit. I believe in reusing what you have instead of constantly buying new. Online communities like the GMC 60-66 Club bring minds together into a collective force. I'm humbled to be a part of it now. This is the first such online activity that I have ever done.

Re: 305 V6 to sm465 Transmission
 

I'll be taking a little vacation for the next week. Then I'll get parts together(I need to get the bell housing), and then detail a plan and get started.

Re: 305 V6 to sm465 Transmission
 

Thanks to all you guys. Much obliged. I'm looking forward to this project.

Re: 305 V6 to sm465 Transmission
 

Hello folks, I'm back. I tried replying to you bigblockv6 but your mailbox is full at this time. I'd like to start searching for the 68-74 bell housing. If it's not to much inconvenience I'd like to get the part number.

Re: 305 V6 to sm465 Transmission
 

The part number is 643191:upyes:

Re: 305 V6 to sm465 Transmission
 

Thank you bigblockv6! I appreciate it.

Re: 305 V6 to sm465 Transmission
 

Never a problem, always happy to help:thumbsup: