SBC to BBC conversion in 2wd Blazer - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BabyBlue · 05-28-2007, 08:17 PM

I've been thinking about taking the old ratty 305 outta my blazer and dropping in a BBC. I found an original 454 that came out of a corvette and has right around 60k original to buy, but I just had to stop myself from an impulsive decision and thought I'd ask around. What exactly do I need to do this conversion? besides the motor, and the mounts....what else? I have a Turbo-350, 12 bolt rear end with 3.73 gears and posi, is there anything as far as dropping the motor in that I need? If I end up going through with this I'll probably be using this thread for more questions and for posting updates. But for now I'd just like to know what I need, how long it might take, and what, if any special tools do I need. Thanks in advance.

Bowed · 05-29-2007, 12:56 AM

Different fan shroud and maybe a larger radiator depending on what you have now . The 454 accessory brackets are different . I have used the same sb motor mounts. No special tools except for the engine crane and a few hours to swap depending on your speed .

.

rcbildr · 05-29-2007, 05:30 AM

Recently, I finished doing the opposite...going from a 454 to a 350. I had to buy different exhaust manifolds, pulleys, and radiator shroud. I also had to modify the exhaust a little bit. The stock exhaust was 2.5" all the way up to the manifolds and the SBC manifolds had something like a 2" outlet. I had another Burb with the right exhaust pieces I needed to I made them work. I also used the stock HEI distributor with new wires. Hope this helps.

BabyBlue · 05-31-2007, 10:55 PM

As far as motor mounts go, do I have to buy BB motor mounts for the same year trucks? Thats the only way it looks like I can do it.

**kwmech** · 05-31-2007, 11:43 PM

Unless the 305 mounts are toast, you can use them. Same as BB

*Ozona* · 06-01-2007, 09:19 AM

I've found that the swap is pretty involved..more so than you might think if you're trying to use stock parts for big blocks, etc. About to wrap my swap up this weekend I hope..if it stops flippin raining.

BabyBlue · 06-01-2007, 05:33 PM

Quote:

Originally Posted by Ozona

I've found that the swap is pretty involved..more so than you might think if you're trying to use stock parts for big blocks, etc. About to wrap my swap up this weekend I hope..if it stops flippin raining.

Well any help would be appreciated, I just picked it up tonight and I'll have it on an engine stand on saturday....definately be posting pictures then. Any suggestions besides gaskets, new fluids and the reg. dress up? 168 tooth BB externally balanced flexplate correct?

**kwmech** · 06-02-2007, 12:07 AM

That is correct on the flexplate

Bowed · 06-02-2007, 12:22 AM

When you buy your flexplate make sure the holes match your converter.

BabyBlue · 06-02-2007, 04:30 PM

Thanks guys, I guess not comes the not so fun part....What do I need? Flexplate, motor mounts (Will the suburban mounts on the motor work?), fuel lines, hoses, fuel pump. Will I need a different starter or anything like that? This is my first sbc to bbc motor swap, so I'm definately needing some help. I'm also assuming that it would be easier to take my front end off to do the motor swap?

block # reads 3999289

screwballl · 06-04-2007, 05:42 PM

Anytime you go from SB to BB you should also replace the radiator which means the radiator supports as it has a different coolant requirement. Going from BB to SB, this is less of a problem because the water pump will only pull as much as it is designed for so the extra capability of the BB radiator can handle it without a problem.
The mounts should be the same but as it is out of a corvette, you may need to see if a low profile mount was used on this block. If so then you will need to replace the mounts with standard mounts.
Since you got the basic block, you will need 454 headers or exhaust manifold and the usual intake/outake crap.
Looks like the PCV and breathers are there so the rest would be the flexplate and other stuff mentioned here.

BabyBlue · 06-04-2007, 07:26 PM

Well, I already bought the flexplate, its a TCI, the radiator is next on the list...I'll probably get that when I exchange my SBC headers that didn't work. Now, how do I tell just by looking if the motor mounts are low profile or not? How tall should they be? And a last question of, will just taking my hood, inner fenders, and fan shroud be enough to do the motor swap or if I should really take the whole front clip off?

rcbildr · 06-05-2007, 01:30 AM

I've removed the hood, fann, shroud, and radiator when I did my engine swap. Just be sure to mark/outline where the hinges bolt on to the hood.

05-28-2007, 08:17 PM	#1
BabyBlue The Peacemaker Join Date: Feb 2005 Location: Kannapolis, NC Posts: 783	SBC to BBC conversion in 2wd Blazer I've been thinking about taking the old ratty 305 outta my blazer and dropping in a BBC. I found an original 454 that came out of a corvette and has right around 60k original to buy, but I just had to stop myself from an impulsive decision and thought I'd ask around. What exactly do I need to do this conversion? besides the motor, and the mounts....what else? I have a Turbo-350, 12 bolt rear end with 3.73 gears and posi, is there anything as far as dropping the motor in that I need? If I end up going through with this I'll probably be using this thread for more questions and for posting updates. But for now I'd just like to know what I need, how long it might take, and what, if any special tools do I need. Thanks in advance. __________________ 1978 Chevy 2wd Stepside aka "Audrey" Cordova brown with mandarin guts 79k original miles & being restored 1979 Chevy 2wd Short Wide aka "Emma-Jayne" Cordova brown with mandarin guts 2019 Chevy Tahoe LT Previous rides: -2002 Firehawk T/A, 2006 Trailblazer SS AWD, 2014 GMC Sierra RCSB, 1971 2wd Blazer, 1996 SNB, 1997 2dr 2wd Yukon, 2001 Silverado RCSB, 2011 Silverado Z71 4x4, 1982 2wd Blazer, 1997 2dr Tahoe, 1970 Chevelle SS, 1972 2wd Blazer, 1986 Silverado Stepside, 1995 S-10, 1985 Silverado SWB.

05-29-2007, 12:56 AM	#2
Bowed Registered User Join Date: Oct 2002 Location: where it's hot Posts: 1,059	Re: SBC to BBC conversion in 2wd Blazer Different fan shroud and maybe a larger radiator depending on what you have now . The 454 accessory brackets are different . I have used the same sb motor mounts. No special tools except for the engine crane and a few hours to swap depending on your speed . .

05-29-2007, 05:30 AM	#3
rcbildr Registered User Join Date: Sep 2000 Location: Gold Bar, WA Posts: 1,216	Re: SBC to BBC conversion in 2wd Blazer Recently, I finished doing the opposite...going from a 454 to a 350. I had to buy different exhaust manifolds, pulleys, and radiator shroud. I also had to modify the exhaust a little bit. The stock exhaust was 2.5" all the way up to the manifolds and the SBC manifolds had something like a 2" outlet. I had another Burb with the right exhaust pieces I needed to I made them work. I also used the stock HEI distributor with new wires. Hope this helps. __________________ My Projects: 1960 GMC 1/2ton with 305 V6 (daily driver) 1963 Chevy 1/2ton 2wd...converting to 4x4 1967 Suburban 1/2ton 2wd My Girlfriends Projects 1985 Chevy Suburban 3/4ton 4x4 with 6.2L diesel, 4" lift, converted to TH-400, Warn Premium manual hubs, & Wildcat 315/75/R16 tires. (daily driver) 1978 Camaro Type LT with a Marine 350 & vortec heads, Rochester Carb, & roller cam 1978 Camaro Z28

05-31-2007, 10:55 PM	#4
BabyBlue The Peacemaker Join Date: Feb 2005 Location: Kannapolis, NC Posts: 783	Re: SBC to BBC conversion in 2wd Blazer As far as motor mounts go, do I have to buy BB motor mounts for the same year trucks? Thats the only way it looks like I can do it. __________________ 1978 Chevy 2wd Stepside aka "Audrey" Cordova brown with mandarin guts 79k original miles & being restored 1979 Chevy 2wd Short Wide aka "Emma-Jayne" Cordova brown with mandarin guts 2019 Chevy Tahoe LT Previous rides: -2002 Firehawk T/A, 2006 Trailblazer SS AWD, 2014 GMC Sierra RCSB, 1971 2wd Blazer, 1996 SNB, 1997 2dr 2wd Yukon, 2001 Silverado RCSB, 2011 Silverado Z71 4x4, 1982 2wd Blazer, 1997 2dr Tahoe, 1970 Chevelle SS, 1972 2wd Blazer, 1986 Silverado Stepside, 1995 S-10, 1985 Silverado SWB.

05-31-2007, 11:43 PM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,628	Re: SBC to BBC conversion in 2wd Blazer Unless the 305 mounts are toast, you can use them. Same as BB

06-01-2007, 09:19 AM	#6
Ozona Account Suspended Join Date: Jan 2006 Location: Fort Worth Posts: 155	Re: SBC to BBC conversion in 2wd Blazer I've found that the swap is pretty involved..more so than you might think if you're trying to use stock parts for big blocks, etc. About to wrap my swap up this weekend I hope..if it stops flippin raining.

06-02-2007, 12:07 AM	#8
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,628	Re: SBC to BBC conversion in 2wd Blazer That is correct on the flexplate

06-02-2007, 12:22 AM	#9
Bowed Registered User Join Date: Oct 2002 Location: where it's hot Posts: 1,059	Re: SBC to BBC conversion in 2wd Blazer When you buy your flexplate make sure the holes match your converter.

06-02-2007, 04:30 PM	#10
BabyBlue The Peacemaker Join Date: Feb 2005 Location: Kannapolis, NC Posts: 783	Re: SBC to BBC conversion in 2wd Blazer Thanks guys, I guess not comes the not so fun part....What do I need? Flexplate, motor mounts (Will the suburban mounts on the motor work?), fuel lines, hoses, fuel pump. Will I need a different starter or anything like that? This is my first sbc to bbc motor swap, so I'm definately needing some help. I'm also assuming that it would be easier to take my front end off to do the motor swap? block # reads 3999289 __________________ 1978 Chevy 2wd Stepside aka "Audrey" Cordova brown with mandarin guts 79k original miles & being restored 1979 Chevy 2wd Short Wide aka "Emma-Jayne" Cordova brown with mandarin guts 2019 Chevy Tahoe LT Previous rides: -2002 Firehawk T/A, 2006 Trailblazer SS AWD, 2014 GMC Sierra RCSB, 1971 2wd Blazer, 1996 SNB, 1997 2dr 2wd Yukon, 2001 Silverado RCSB, 2011 Silverado Z71 4x4, 1982 2wd Blazer, 1997 2dr Tahoe, 1970 Chevelle SS, 1972 2wd Blazer, 1986 Silverado Stepside, 1995 S-10, 1985 Silverado SWB. Last edited by BabyBlue; 06-02-2007 at 08:16 PM. Reason: pics

06-04-2007, 05:42 PM	#11
screwballl Tonawanda 454 Join Date: Mar 2004 Location: Liquid Sunshine State Posts: 2,754	Re: SBC to BBC conversion in 2wd Blazer Anytime you go from SB to BB you should also replace the radiator which means the radiator supports as it has a different coolant requirement. Going from BB to SB, this is less of a problem because the water pump will only pull as much as it is designed for so the extra capability of the BB radiator can handle it without a problem. The mounts should be the same but as it is out of a corvette, you may need to see if a low profile mount was used on this block. If so then you will need to replace the mounts with standard mounts. Since you got the basic block, you will need 454 headers or exhaust manifold and the usual intake/outake crap. Looks like the PCV and breathers are there so the rest would be the flexplate and other stuff mentioned here. __________________ 91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. -------------------

06-04-2007, 07:26 PM	#12
BabyBlue The Peacemaker Join Date: Feb 2005 Location: Kannapolis, NC Posts: 783	Re: SBC to BBC conversion in 2wd Blazer Well, I already bought the flexplate, its a TCI, the radiator is next on the list...I'll probably get that when I exchange my SBC headers that didn't work. Now, how do I tell just by looking if the motor mounts are low profile or not? How tall should they be? And a last question of, will just taking my hood, inner fenders, and fan shroud be enough to do the motor swap or if I should really take the whole front clip off? __________________ 1978 Chevy 2wd Stepside aka "Audrey" Cordova brown with mandarin guts 79k original miles & being restored 1979 Chevy 2wd Short Wide aka "Emma-Jayne" Cordova brown with mandarin guts 2019 Chevy Tahoe LT Previous rides: -2002 Firehawk T/A, 2006 Trailblazer SS AWD, 2014 GMC Sierra RCSB, 1971 2wd Blazer, 1996 SNB, 1997 2dr 2wd Yukon, 2001 Silverado RCSB, 2011 Silverado Z71 4x4, 1982 2wd Blazer, 1997 2dr Tahoe, 1970 Chevelle SS, 1972 2wd Blazer, 1986 Silverado Stepside, 1995 S-10, 1985 Silverado SWB.

06-05-2007, 01:30 AM	#13
rcbildr Registered User Join Date: Sep 2000 Location: Gold Bar, WA Posts: 1,216	Re: SBC to BBC conversion in 2wd Blazer I've removed the hood, fann, shroud, and radiator when I did my engine swap. Just be sure to mark/outline where the hinges bolt on to the hood. __________________ My Projects: 1960 GMC 1/2ton with 305 V6 (daily driver) 1963 Chevy 1/2ton 2wd...converting to 4x4 1967 Suburban 1/2ton 2wd My Girlfriends Projects 1985 Chevy Suburban 3/4ton 4x4 with 6.2L diesel, 4" lift, converted to TH-400, Warn Premium manual hubs, & Wildcat 315/75/R16 tires. (daily driver) 1978 Camaro Type LT with a Marine 350 & vortec heads, Rochester Carb, & roller cam 1978 Camaro Z28



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