305 V6 to sm465 Transmission

[ur991]

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

[ur991]

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

[George Bongert]

Originally Posted by TJ's GMC

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



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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!

[ur991]

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

[TJ's GMC]

Originally Posted by George Bongert

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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!

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.

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[ur991]

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.

[ur991]

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.

[TJ's GMC]

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.

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[George Bongert]

Originally Posted by ur991

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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.

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.

[GMCDAC]

Originally Posted by ur991

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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.

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