BBC swap

[Gimmie1965]

I'll apologize first off if the is a thread somewhere that already covers this. The v6 took a dump on me yesterday while I was loading it to haul some trash to the dump. Needless to say the bbc swap came sooner than expected. First off I want to say this is not my first swap into a 65 gmc. Bought my first 65 when I 16 in high school. It was a 65 gmc shortbed with 230 and 3 on the tree. I pulled UT out and dropped a 350 in it. Same mounts flywheel clutch bellhousing no problem. So I get the v6 pulled out of this one and drop in the bbc. Start off I pulled sbc mount out of a 69 at the u pull it here. I figure for 5 bucks I'll try them. I put them in the holes closer to the cab like what I've seen others have done here. Since the gmc v6 and chevy bellhousing are different I found a 68 bell. I get the BBC dropped in and have the motor mount close to being lined and look and the bell is close to about a 1-11/4 away. Now as I said I've done this before with a sbc and everything fell right into place. I measured the v6 bell from where it bolts to the block back to the crewmember pads on the bell and it's 61/2 in. The chevy bell is 51/2. So long story short is there a difference in the 63-67 bells to the 68-72 bells as far as where the rear motor mount are located. I'll take some pics so you can tell a little bit better what I'm talking about

[Gimmie1965]

Here are some pics of what I'm dealing with. Thanks for any input you may have

[PGSigns]

This has been covered in the engine and drive train section. First off the big block will need the stands from a 67 to 72 with a big block. When I did the big block in my 64 I made a set of stands. Capnfab will chime in I hope as he can spec all the parts and pieces that you need for a bolt in solution better than I can.
Jimmy

[PGSigns]

Here is a link with the info you need.
Jimmy
http://67-72chevytrucks.com/vboard/s...g+block+mounts

[Gimmie1965]

Yes I'm waiting for the BB towers to get here. Trying to find info on what people have done. Everything I find here people are installing a BB with a different tranny. Was hoping to put a BB in place of the gmc v6 and keep the sm420. The trouble I'm running into is with the engine pushed within a 1/8 in of the firewall the bellhousing is still over an in from being close enough to bolt down. The original gmc v6 bellhousing is deeper than the 68 bellhousing I got. I have nothing on this forum that addresses this issue

[Captainfab]

The easiest installation for a big block is using the '68-'71 truck big block engine mounts and frame brackets. In doing so, you will have to move your bellhousing crossmember forward. If you do not want to move the bellhousing crossmember, you will have to modify the firewall to clear the heads/valve covers. Also depending on what you use for exhaust manifolds or headers, you will have to fabricate a new clutch linkage or convert to a hydraulic clutch. The hydraulic clutch is the easiest. I make the hydraulic clutch conversion kits.

[Gimmie1965]

I have the 68-71 bbc towers coming from eBay $120. Be here next week sometime. I've been thinking about moving the crossmember foward. Not a easy task with the cab in place. That also means a new driveshaft?? Was planing on using the stock manifolds. If I move the c rossmember is it possible to move the clutch frame mount fwd as well. It shares a rivet with the trans c rossmember. I looked for your clutch conversion. Was not able to find it

[Captainfab]

To use a mechanical clutch linkage with a big block will require a lot of fabrication and trial and error. The exhaust manifolds are in the way and the big block ball stud mount is not in the correct location. Here is the for sale thread for my '63-'66 booster bracket with the hydraulic clutch conversion.

http://www.67-72chevytrucks.com/vboa...d.php?t=651200