GMC. Truck owners

[mygmctruck1]

My 68 K1500 had a V-6 in it . I replaced it with a 350 V-8 .

I did not realize , there are a different set of motor cross member hole’s for the V-8 ? I never thought about the difference the location would make.
Because I used the back holes instead on the front holes . I am 3 1/4 “ to far back and dizzy hits firewall.
I sure I am correct in my assumption but would like to verify my opinion with some one who owns a 68 K1500 . With an 8 rather than a V-6 .

Here’s a pic if that helps.

[mygmctruck1]

Here’s another pic

[HO455]

Does the new engine have a HEI distributor? I know that K models have the engine set back farther than C models. And I have read where people have had problems when converting to HEI's and on some trucks there is no clearance to the firewall. That being said I don't know if the V6's had yet a different set of mounting holes. I would see if someone could get you a set of measurements to the back holes on a Chevy V8 truck to compare with your GMC's frame.
Do the holes for the rear cross member line up with the transmission? If so then I would use them and whatever holes the front mount lines up with.
Moving the engine forward will mean problems with the drive shafts, fan shroud, and shift linkages for starters. If you have an HEI it may be easier to go back to the factory distributor and convert it to a Pertronx.

[special-K]

Did you change out the motor mount towers from V6 to V8?

[mygmctruck1]

Originally Posted by HO455

Does the new engine have a HEI distributor? I know that K models have the engine set back farther than C models. And I have read where people have had problems when converting to HEI's and on some trucks there is no clearance to the firewall. That being said I don't know if the V6's had yet a different set of mounting holes. I would see if someone could get you a set of measurements to the back holes on a Chevy V8 truck to compare with your GMC's frame.
Do the holes for the rear cross member line up with the transmission? If so then I would use them and whatever holes the front mount lines up with.
Moving the engine forward will mean problems with the drive shafts, fan shroud, and shift linkages for starters. If you have an HEI it may be easier to go back to the factory distributor and convert it to a Pertronx.

It does have an HEI , as far as the fan shroud , won’t be one , electric fan . it will be a floor shifter so no issue there and this truck was a 4x4 with stick . So the cross member also had to be changed.
I took a close look at the front engine area and there’s a ton of room to move it forward.
Besides all of that even if it had the old style dizzy , because it sets so far back I would even be able to get one in or out. It would hit the top of the cowling area.
I really think a V-8 engine was meant to set forward about the 3 1/4 “ I show.

[mygmctruck1]

Originally Posted by special-K

Did you change out the motor mount towers from V6 to V8?

Yea , they had to be changed ,

[mygmctruck1]

I am still in hopes of a member seeing my problem and having an answer.

[HO455]

Here are a couple of photos first one is of a K model and the 2nd one is a 2wd truck. Notice the difference in the air cleaner clearances to the firewall. GM may have set the engine back for more oil pan clearance to the front axle. I don't know for sure.
Try reposting this question in the 4x4 section of the forum.

[special-K]

Can you show a picture of the same view as above? When you did the engine swap, did you move the transmission & transfer case location at all. Trying to get the whole picture here. So are the drive shafts installed? Was it a total tear gown or just an engine swap? I know of the motor mount positions being an issue on 2wds when going from I-6 to V8, but not sure the V6 mounts are in the same place as V6. I know GM put the transfer case in the same place for all engines... or thought that was the case. Pretty sure all driveshafts are same length. I know on 4wd V8s the mounts are in the rearward holes. When we did a 700r4 swap, longer trans, all we had to do was move the mounts forward to the I-6 holes and and everything else worked out. No driveshaft work was needed because transfer case didn't move. So, the V8 mounts are normally in the rearward holes.

[mygmctruck1]

Originally Posted by special-K

Can you show a picture of the same view as above? When you did the engine swap, did you move the transmission & transfer case location at all. Trying to get the whole picture here. So are the drive shafts installed? Was it a total tear gown or just an engine swap? I know of the motor mount positions being an issue on 2wds when going from I-6 to V8, but not sure the V6 mounts are in the same place as V6. I know GM put the transfer case in the same place for all engines... or thought that was the case. Pretty sure all driveshafts are same length. I know on 4wd V8s the mounts are in the rearward holes. When we did a 700r4 swap, longer trans, all we had to do was move the mounts forward to the I-6 holes and and everything else worked out. No driveshaft work was needed because transfer case didn't move. So, the V8 mounts are normally in the rearward holes.

Removed the std tranny & transfer case drive line and replaced it to , with a
700r and had a drive shaft built . Old tranny mount would not work at all.

There is no way my engine is in the right location , the dizzy is tight against the fire wall. Can't even get my fingers back there.


The thing is , I don’t really have a choice but move it forward. I have plenty of room to do it and there’s no way I can leave it like it is. The minute I hit a hard bump the dizzy will most likely hit the firewall and bust something. I’ll have to have the drive shaft reworked again but , that’s life.
It’s really all a matter of unbolting everything ( cross members ) lifting it to get the weight off the cross members and moving the whole assembly forward 4 “

The 68 1/2 ton 4x4 k1500 driveline is a very different animal , very few made and the V-6 part messes everything up.

[special-K]

From my experience with swapping to a 700r4(& adapting to the original NP205) to a small block, you can leave the driveshafts alone if you simply move the engine towers to the forward position. So you are surely safe to do that. Now that your driveshafts have been altered, maybe you can find some stock replacements for reasonable. Or, as you said, do it all over again.

[mygmctruck1]

Originally Posted by special-K

From my experience with swapping to a 700r4(& adapting to the original NP205) to a small block, you can leave the driveshafts alone if you simply move the engine towers to the forward position. So you are surely safe to do that. Now that your driveshafts have been altered, maybe you can find some stock replacements for reasonable. Or, as you said, do it all over again.

The original driveshaft wouldn't cut it either. Half the dia of a regular drive shaft .Different yoke too. Anyhow , moving the engine forward is my only answer and that's going to happen next wk.