v-8 replacing a in-line 6

[Brock]

My new purchase ('68 stepside) has an in-line 6, and a 3-on-the-tree. Don't know if either works. I popped the hood to let my Dad take a look at it, he's pushing 80 and was a mechanic back when this thing was new. Even with a touch of alzheimer's he declared what the motor was and that it would take some modifying to make a SB V-8 (307 for now 327 eventually...with a 700r4 tranny) work. Not that I'm doubting my Dad, but just curious how much will need to be done to get it going? I am a mechanical idiot but I can figure it out eventually....sometimes with help.

[mvfd70]

It'll take some modifying. The V-8 mounts are not quite the same as the I-6 mounts. Transmission cross member will need to be changed to fit the auto tranny. Fuel lines re-routed to get to the V-8 carb. I don't really think it's too major of a job. Lots of people are doing it. I'm keeping the 6 banger but have though of going to an 8

[houghda]

Fear not, this is a very common swap.
Havent done it in the 67 GMC but I easily accomplished it in my 55 Handyman Wagon.
If motor mounts dont bolt in (doubt it) then you'll have to get someone to weld in a set. Again, not that hard. Measure twice, weld once, measure again, then finish the welds.

[mvfd70]

Shouldn't have to weld in new mounts. Get some small block V-8 towers for your truck and they'll bolt right up to the frame and cross member. But like he said, it is a VERY common swap and not difficult. But it will take a little bit of parts swapping to make it fit right.

[thelonerife]

I had a 68 w a 327 and 3 on the tree. I swapped the tranny for a turbo 350. The hardest part for me was gettin the old trans crossmember out. I took the easy way and cut it out. I would have done a better job if I had the motor out. You will have to have a radiator with trans cooler or an external trans cooler and lines for it . The crossmember for the tranny, Linkage, If you do a turbo 350 you can use your driveshaft as is. 700r and you'll have to get it cut. Auto column or floor shifter, IF you could find a parts truck w/ all this you could get what you need and sell the rest.

[Brock]

I think I'm going with a Lokar floor shifter, external tranny cooler, My brother-in-law runs a transmission shop so he's my "professional" advisor (Dad just likes to Watch and tell stories...which is OK too).

[retodd7711]

Dad's a mechanic, Brother in law a tranny specialist. Sounds like you got the right help for the job. Take a little time to check the 250 out. Mine was a candidate for a v8 swap until I tuned, tightened, adjusted and that little sixer runs pretty good. Search old threads on here lots of answers to swap questions.

[retodd7711]

P.S. Don't throw that six or three on tree parts away. Lot's of good folks here still using those and in need of good parts.

P.P.S. WELCOME to the board!!

[thelonerife]

THATS RIGHT .. keep that 3 sp for someone who really wants it. Mine was on the floor for about an hour and some guy came by to get something else and he bought it. The linkage is also what they need.

[71tahoe]

If you're going to keep the 3sp for a while, the v8 will bolt to the I6 motor mounts. If you run headers, you will have to bend the clutch linkage zbar to clear the header. You also may have to fab a bracket where it connects to the block. I've had 4 different v8s from different years and they all had different tapped holes on the driver's side.

[Mechdawg]

I swapped out the I6 in my 67 for a 327 and I did use the I6 mounts it sits about 3 inches further back than the stock v8 would. I kept the 3 speed converted to floor shift and did have to fab a bracket for the Zbar. I also went with an electric fan setup as the motor sits so far away from the radiator now that a regular fan wouldnt work. Also watch out if you run an HEI with the V8 installed on the I6 mounts the the HEI will probally hit the firewall. Lots of lil details to make it all work just right but really nothing major the fuel line already runs to the same spot you need it for the V8 pump.before
[ATTACH][/ATTACH]

[Brock]

NICE...Hopefully mine will look like that someday...with the fenders of course. As far as the 3-speed tranny, I'm gonna trade it to a racing buddy of mine who is gonna throw on some paint for me. He paints race cars and does a decent job.

[Mechdawg]

Sounds like a nice trade and yeah it looks better now with fenders......lol