Going from a straight 6 to a V8 in a 4x4

[FlameOut]

I recently purchased a 72 K10 SWB 3 speed manual (column shift) and wanted to replace the straight 6 with a sb 350. I've been reading where some say you need to replace the crossmember and some say you don't. But these are all 2wd I was reading about, so I'm not sure if being a 4wd will cause even more problems.

Will I be able to use an aluminum bellhousing in place of the cast iron one? At first I thought this was going to be a fairly easy swap, but now I'm thinking it will be more like a nightmare. I'm kind of getting to the point where I think I should just take my losses and scrap the truck. It needs just about everything but the bed repaired. My main project will be this engine swap, and if it's doable, I'll go one step at a time restoring this thing

Bill

[71Sixer]

I'm sure someone can chime in on this. I can tell you for sure on the 2wd trucks the crossmember for the 6 cylinder does need swapped, and you will need small block motor mounts. As for the 4wd, I'm not sure...I have a k10 now, but it had a small block in it when I got it. Do you have any pictures of the crossmember in the truck?

[argonaut]

What size straight six does have? Unless it is a 292 I would think that a small block would drop right in.
An aluminum bellhousing won't work is your current cast iron one mounts to a crossmember. Why do you need to swap the bellhousing? They are the same for sixes and for eights.

[67swb72klb]

if you are keeping the 3 speed it should bolt in may need to change the engine x member ?
not something you see every day though snap a couple pics of it if you have a chance

[FlameOut]

I'm not 100% sure of current motor, but i think it's a 250. As for the bellhousing, I thought maybe it needed changed. The starter bolts into the housing rather than the block. I certainly have no problem using anything that works though :-)

Which crossmember needs changed, the engine or trans? Not the best pic, but here's one showing both. I'll get some better ones later today

[DWilbur]

Your cross member look the same as my K20 with a V8. I think you will get a way with different motor mounts to fit the V8. the cross member should work.

[FlameOut]

Originally Posted by DWilbur

Your cross member look the same as my K20 with a V8. I think you will get a way with different motor mounts to fit the V8. the cross member should work.

That's good to know. Hopefully I'll get a chance to check it out within the next few days. I was looking at motor mounts at Summit, and they show the same ones for the 6 and 8cyl motors

[DWilbur]

To bad you live so fare a way I have a new set of motor mounts for your application.

[OLDCHEV4X4]

I did this swap before and the v8 dropped right in. The problem for me was i was using headers and the Z bar (clutch linkage) would hit the header pipe when you pushed the clutch in. We had to cut it and weld it on in a different spot.
I think we had a couple other snags too, but we worked through them.
Dont scrap it! Pennsylvania's old truck population is dwindling.

[fp1967]

The V8 will bolt right in. The 6 cylinder motor mounts are the same, although there is a pretty good chance that they are oil soaked and not in good shape anymore. The crossmembers do not have to be changed, that is a 2wd thing. If it had a 292 6 cylinder, then the engine crossmember would have to be changed, but I can see in the pic that it is not a 292 crossmember. An aluminum bellhousing will work if you get the correct starter. Check the hole diameter in the aluminum bellhousing where it fits over the tranny. Car bellhousings typically have a smaller hole than one from a truck. In the post that said the bellhousing bolts to the crossmember, again that is a 2wd thing. If using exhaust manifolds, you need to use ram horns that point straight down, not 2wd ones that angle back.

[burnin oil]

Just reuse the cast bellhousing. The starter may differ though. The swap is pretty simple so don't make it any harder than it needs. The biggest issue May be the axle gearing. In the K20s I know that the only trucks that got 4.10s gears where the factory 4spd 350 trucks. Everything else was 4.56. That was 3/4 ton so the 1/2 tons may be different.

On a 2wd I did not change the crossmember at all. Yanked the motor and dropped the SBC back in the same hole. The frame perches are different but many people do use the I6 mounts. I even used a set of headers off of a 73+ truck. That was a 67 so maybe something changed later.

[FlameOut]

Thanks for all of the useful info. I feel a lot better now. I was just out there now cleaning up the frame, tranny, transfer case and bell. I don't think any of them have every been removed in the trucks 42 year, 62,000 mile life. The frame and underside/floor of the truck are showing it's wear from spending it's life in the salt belt though. I think all of the grease on the tranny/transfer case helped preserve it. I tried uploading a few pics, but I'm guess there is trouble with the site right now?

An unrelated question. I just drained the fluids from trans and transfer case and want to remove the transfer case from the transmission (because together they are a *itch to move). If I just remove those 8 bolts connecting the trans tail to the transfer case, will it just slide right out or is there more to it?

[fp1967]

I agree with burnin oil, if the cast iron bellhousing is in good shape, I would use it.

It's easy to seperate the transmission from the transfer case. I would unbolt between the adapter and the transfer case and leave the adapter on the tranny.

[FlameOut]

Originally Posted by fp1967

I agree with burnin oil, if the cast iron bellhousing is in good shape, I would use it.

It's easy to seperate the transmission from the transfer case. I would unbolt between the adapter and the transfer case and leave the adapter on the tranny.

Bellhousing is in good shape. I just need to clean it up a little better

[67-4x4]

Im doing the same swap right now for my dads 67 but putting a bigblock in if you have any questions pm me and I will give you my number youre pretty close if you need anything

[americanmusc1e]

For reference, this is a 4x4 292 crossmember. My K20 had one and I had to swap it out to do a v8 swap. I used a modified crossmember and mounts from a 84 K10.





The modified 73-87 4x4 crossmember. Mine was from a k10 with a 6.2 diesel. it needed some welding due to the fact that it was cracked from the weight/vibrations of the diesel. I had a bear of a time getting the motor to go in the frame. I'm guessing that's because it got a little tweaked during the welding process. I couldn't say for sure. EDIT: the first picture is shortening the stands to fit the shorter 67-72 frame. The second pic shows where the crossmember was cracked due to stress.