BBC to SBC driveshaft question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

fade94 · 06-01-2017, 09:10 AM

I have a BBC on factory big block perches with TH400 in the truck, 68 SWB. The motor is knocking and I have a good SBC to put in. I have a set of small block perches as well. My question is, will the driveshaft work with the small block? Do I have to change the perches to make it work?

b454rat · 06-01-2017, 09:56 AM

The driveshaft doesn't care what motor it has, but the tranny does. If you don't change the tranny, or the location of it, the won't have to change the driveshaft.

**Captainfab** · 06-01-2017, 11:27 PM

If you don't move the trans, that will not change anything with the driveshaft. I do not know if you install a SBC with the SBC mounts, if the trans will bolt up being in the BBC location.

**Ironangel** · 06-02-2017, 07:20 AM

Dont know if this will help or not because it's kinda backwards of what your attempting. I pulled a small block that sat on small block perches bolted in the forward two of three holes in the frame rail. I used the pre-72 BB perches bolted in the same two forward holes in the frame. Both SBC and BBC perches share the same two frame rail holes BUT use different lower hole locations on the crossmember. BBC uses the rear of the two crossmember holes, SBC uses the front hole. They are 3-bolt perches. I used regular SBC 3-bolt motor mounts on my BB (396) with 1971 BB perches, (have to use a washer) and my tranny never changed location. I was able to use the same tranny crossmember in the same location with the same untouched driveline. Hope this makes sense? You should be good to go as long as you use factory SBC stands (perches) with these motor mounts.

This pic has the same BBC stands and same 3-bolt SBC mounts I used...You will use the factory SBC stands, not the BBC stands shown in this pic. Let me know if you need stands and I'll ship you a pair, $30 delivered. Any auto parts will have the mounts...

**kwmech** · 06-02-2017, 11:42 AM

Really Guys? Just bolt the small block on the big block stands using the big block cushions...done. If you change the stands it will move the engine forward about 1.5'' thus changing everything else.

**Ironangel** · 06-07-2017, 03:02 AM

Quote:

Originally Posted by kwmech

Really Guys? Just bolt the small block on the big block stands using the big block cushions...done. If you change the stands it will move the engine forward about 1.5'' thus changing everything else.

"Big Block Cushions?" Got any pics? Do you mean "motor mounts?" The 69-71 stands and mounts were very different than the 72 stands and mounts. The Mark IV BBC motor mount to rear block face is 15.91" (center bolt) and the SBC is 16.15" respectively...So actually, the stands dont move the motors laterally hardly at all, maybe a 1/4". Thats why the less expensive 69-71 BBC stands with the large hole work so well with standard one piece SBC motor mounts. So yeah, drop that small block in there on the BBC stands using the regular one piece SBC motor mounts, like the ones I posted. Didn't I? Nevermind, all good

**kwmech** · 06-07-2017, 07:00 PM

What the ???. sounds like you've got it figured out. The small block stands and the big block stands both locate themselves in the front hole of the frame rail. That being said, the difference in placement of the engines, with the correct stand, is about 1.5''..... big block being set back farther. Both the small block and the big block have the engine mount boss' on the side of the block in the same place at a 16'' (or maybe 15.9 as you stated) center from the bellhousing mount.

The 1972 was a year all by itself with everything being the same with the mounts not changing a thing and this continued through to the square bodies

06-01-2017, 09:10 AM	#1
fade94 Registered User Join Date: Mar 2005 Location: Melissa, TX Posts: 799	BBC to SBC driveshaft question I have a BBC on factory big block perches with TH400 in the truck, 68 SWB. The motor is knocking and I have a good SBC to put in. I have a set of small block perches as well. My question is, will the driveshaft work with the small block? Do I have to change the perches to make it work? __________________ 68 short bed driver (71 clip on it now, swapping to 68 when weather cooperates) 67 short step project (will get SWB from the 68) 67 Camaro, #'s matching (my wife's) 03 Dodge Ram 2500 4x4 diesel 5 speed 4.10 rear

06-01-2017, 09:56 AM	#2
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	Re: BBC to SBC driveshaft question The driveshaft doesn't care what motor it has, but the tranny does. If you don't change the tranny, or the location of it, the won't have to change the driveshaft. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

06-01-2017, 11:27 PM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: BBC to SBC driveshaft question If you don't move the trans, that will not change anything with the driveshaft. I do not know if you install a SBC with the SBC mounts, if the trans will bolt up being in the BBC location. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

06-02-2017, 07:20 AM	#4
Ironangel Senior Member Join Date: Feb 2010 Location: Falls City, Nebraska "100 Miles From Nowhere" Posts: 2,219	Re: BBC to SBC driveshaft question Dont know if this will help or not because it's kinda backwards of what your attempting. I pulled a small block that sat on small block perches bolted in the forward two of three holes in the frame rail. I used the pre-72 BB perches bolted in the same two forward holes in the frame. Both SBC and BBC perches share the same two frame rail holes BUT use different lower hole locations on the crossmember. BBC uses the rear of the two crossmember holes, SBC uses the front hole. They are 3-bolt perches. I used regular SBC 3-bolt motor mounts on my BB (396) with 1971 BB perches, (have to use a washer) and my tranny never changed location. I was able to use the same tranny crossmember in the same location with the same untouched driveline. Hope this makes sense? You should be good to go as long as you use factory SBC stands (perches) with these motor mounts. This pic has the same BBC stands and same 3-bolt SBC mounts I used...You will use the factory SBC stands, not the BBC stands shown in this pic. Let me know if you need stands and I'll ship you a pair, $30 delivered. Any auto parts will have the mounts... __________________ Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" "Be American, Buy American" Last edited by Ironangel; 06-02-2017 at 07:26 AM.

06-02-2017, 11:42 AM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: BBC to SBC driveshaft question Really Guys? Just bolt the small block on the big block stands using the big block cushions...done. If you change the stands it will move the engine forward about 1.5'' thus changing everything else.

06-07-2017, 07:00 PM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: BBC to SBC driveshaft question What the ???. sounds like you've got it figured out. The small block stands and the big block stands both locate themselves in the front hole of the frame rail. That being said, the difference in placement of the engines, with the correct stand, is about 1.5''..... big block being set back farther. Both the small block and the big block have the engine mount boss' on the side of the block in the same place at a 16'' (or maybe 15.9 as you stated) center from the bellhousing mount. The 1972 was a year all by itself with everything being the same with the mounts not changing a thing and this continued through to the square bodies



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