SB to BB swap on my 74 3/4.....same motor mounts? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chev406 · 03-01-2005, 09:42 AM

My truck was originally a 454 but I had a small block in it for the last 4 years or so. I'm ready to intall the 454 again, but don't remember if I had to change motor mounts or not?

My neighbors are pricks even though my yard is well maintained, so I'll have to make this swap quick! A delay would be bad news, and leave me vulnerable to attacks from the county! I have to be stealth.

motor mounts, engine bracket, are the same on 74.............right!

Thanks!

superchevy · 03-01-2005, 10:38 AM

They aren't the same...at least the ones in my '77 C20 aren't.
I pulled the original 454 to swap in the 468...went down to the local parts house to get new mounts...parts guy says "Chevy used same mounts for small and big blocks after '73" so he gives me the mounts...I take them home and compare to originals...they are not the same...go to different parts house and show them originals and ones I just bought...after a little research in the parts book - yes, an actual book, not computer...we find the right mounts for the big block.
Just my 2 cents
SC

Gray Ghost · 03-01-2005, 11:22 AM

My 73 3/4 ton truck used the same mounts when the PO swapped in the 350 I just swapped out for a new one. As far as I know it will use the same ones.

bigblock73 · 03-01-2005, 01:39 PM

I have always believed them to be the same as well. I replaced the 350 in Yeller with a 454...used the same mounts and everything bolted up fine. I also even used the same engine stands...even tho people have told me the big block and small block stands are the same. I alse went as far as to buy "BBC" stands from another board member, but they do not line up without having to drill holes..so I never used them. Perhaps the difference is the frames (1/2, 3/4, and 1 ton)?

Superchevy, do you happen to have a pic of yours, or a part number. I am curious and would like to find out the real story about the "sbc and bbc mounts the same?" questions that keep popping up here (for my own good as well).

BIGCHEVYMAN · 03-01-2005, 07:29 PM

when i pulled the 350 from my truck i swapped the block mounts from the 350 to the 454 and used the original frame mounts with no problems at all.

superchevy · 03-01-2005, 09:55 PM

Yes, I will take a pic tomorrow. They are not the same...they are very similar, but not the same.
SC

*1FaastC10* · 03-01-2005, 10:58 PM

are we talking about the clamshell engine mounts that bolt to the frame?

bigblock73 · 03-02-2005, 12:16 AM

Quote:

Originally Posted by 1FaastC10

are we talking about the clamshell engine mounts that bolt to the frame?

Technically the clam shells do not bolt to the frame, they bolt to towers/stands/plates (what ever you want to call them)...and they bolt to the frame.

1971ChevyTruck · 03-01-2005, 11:06 PM

Big block motor mounts= Small Block motor mounts

chev406 · 03-01-2005, 11:49 PM

Dudes you rock

I gotta get it done fast before the neighbors have a chance to

*1FaastC10* · 03-02-2005, 12:32 AM

ok smartass, are those what we are discussing here?

bigblock73 · 03-02-2005, 07:57 AM

As far as I know, we are talking about the mounts...not the stands/towers.

MSL · 03-02-2005, 08:45 AM

On my 78 chevy 1/2 ton i swapped to a 454 from my small block and nothing changed other than repostioning how you mount the motor mount to the front cross member. also the block mounts where the same too.

bigblock73 · 03-02-2005, 09:05 AM

Quote:

Originally Posted by MSL

On my 78 chevy 1/2 ton i swapped to a 454 from my small block and nothing changed other than repostioning how you mount the motor mount to the front cross member. also the block mounts where the same too.

What do you mean? Did you mount the engine mounts in a different position on the engine stands, or did you mount the engine stands in a different position on the frame? I know the engine stands have two different sets of holes, one labeled "6" (for inline sixes), the other labeled "8" (for v8's). I am curious to know how you all have done your swaps. Mine went fine, but I don't have much clearance between my trans and floor (but I am using a 700r4 too). Swervins trans clearance is the same as mine..but it just seems too close. I have been wondering if I have things set up incorrect.

MSL · 03-02-2005, 05:20 PM

Here you go this is what i used out of my truck manual i hope this helps and ifg anyone wants a larger pic email me at ml2418@yahoo.com maybe someone can put it on there webpage or make it a sticky. I mounted my stuff as showed and it all worked out fine.

bigblock73 · 03-02-2005, 06:29 PM

MSL, thanks for the diagram! I mounted mine the same way the pics show, except my motor mounts are the 350 variety...so I wasn't able to mount them the way "view A" shows. By looking at this diagram, it appears the clam shell motor mounts are different only in how they bolt to the towers...but not really in size. I still wish I knew the truth about the towers, and if there really is a BB and SB version...and what the differences are.

MSL · 03-02-2005, 06:59 PM

Well i took my motor out of a 74 chevy 3/4 ton and the towers where the same as mine and the 74 truck was factory with the 454 so i myself would assume no difference in SB or BB.

**Captkaos** · 03-02-2005, 07:41 PM

I still stand by my original statement that there is not difference in BBC vs. SBC engine stands.

BIGCHEVYMAN · 03-02-2005, 08:12 PM

i agree with the captain.

longhorn71 · 03-02-2005, 10:43 PM

Quote:

Originally Posted by BIGCHEVYMAN

i agree with the captain.

me too.changed to a big block in my 85 and it dropped into the small block mounts.

superchevy · 03-02-2005, 11:14 PM

The mounts are not the same...they might work, but they're not the same. The pics below show the differences. The mount on the right is for a '77 C20 with a smallblock (these are the mounts given to me by the parts guy because "they're all the same")...the mount on the left is the original GM mount out of my '77 C20 454/T400 truck.
Do they look the same to ya'll?
The 454 mount is longer, taller, has a different mount thru-bolt location, and has a different mount-to-tower bolt pattern.
That's why I took the smallblock mounts back and went to a different parts store to get the right mounts...the 2395's...they were exactly like the originals...I kept the box so I would know which ones to get again in the future.
So in my opinion, 3/4 ton mounts for small blocks and big blocks are different, but the book shows that a 1/2 ton trucks do use the same "small block" mount...the 2292's shown in the pics...interesting, huh?
SC

Gray Ghost · 03-03-2005, 08:32 AM

He's talking about a 74...they are the same for that year as well as the 73 on the 3/4 ton trucks. Not sure why the 77's are different.

corn · 03-02-2005, 10:25 PM

On mine, I unbolted the 305 & bolted the 402 right in. Only issue I had was one header tube didnt want to clear the cup style mount(DR side) on the engine but it clears now...corn

03-01-2005, 09:42 AM	#1
chev406 Registered User Join Date: Feb 2005 Location: Sacramento, Ca. Posts: 30	SB to BB swap on my 74 3/4.....same motor mounts? My truck was originally a 454 but I had a small block in it for the last 4 years or so. I'm ready to intall the 454 again, but don't remember if I had to change motor mounts or not? My neighbors are pricks even though my yard is well maintained, so I'll have to make this swap quick! A delay would be bad news, and leave me vulnerable to attacks from the county! I have to be stealth. motor mounts, engine bracket, are the same on 74.............right! Thanks!

03-01-2005, 10:38 AM	#2
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	They aren't the same...at least the ones in my '77 C20 aren't. I pulled the original 454 to swap in the 468...went down to the local parts house to get new mounts...parts guy says "Chevy used same mounts for small and big blocks after '73" so he gives me the mounts...I take them home and compare to originals...they are not the same...go to different parts house and show them originals and ones I just bought...after a little research in the parts book - yes, an actual book, not computer...we find the right mounts for the big block. Just my 2 cents SC __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

03-01-2005, 11:22 AM	#3
Gray Ghost Senior Member Join Date: Sep 2004 Location: Terrell, TX Posts: 1,967	My 73 3/4 ton truck used the same mounts when the PO swapped in the 350 I just swapped out for a new one. As far as I know it will use the same ones. __________________ Kelly '05 GMC Sierra SLE Z71 Bone stock except for new bed rail caps.

03-01-2005, 01:39 PM	#4
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	I have always believed them to be the same as well. I replaced the 350 in Yeller with a 454...used the same mounts and everything bolted up fine. I also even used the same engine stands...even tho people have told me the big block and small block stands are the same. I alse went as far as to buy "BBC" stands from another board member, but they do not line up without having to drill holes..so I never used them. Perhaps the difference is the frames (1/2, 3/4, and 1 ton)? Superchevy, do you happen to have a pic of yours, or a part number. I am curious and would like to find out the real story about the "sbc and bbc mounts the same?" questions that keep popping up here (for my own good as well). __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

03-01-2005, 07:29 PM	#5
BIGCHEVYMAN Senior Member Join Date: Apr 2002 Location: Portland , Tennessee , United States Posts: 1,024	same when i pulled the 350 from my truck i swapped the block mounts from the 350 to the 454 and used the original frame mounts with no problems at all.

03-01-2005, 09:55 PM	#6
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	Yes, I will take a pic tomorrow. They are not the same...they are very similar, but not the same. SC __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

03-01-2005, 10:58 PM	#7
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	are we talking about the clamshell engine mounts that bolt to the frame?

03-01-2005, 11:06 PM	#9
1971ChevyTruck Registered User Join Date: Jan 2005 Location: Illinois Posts: 1,006	Big block motor mounts= Small Block motor mounts

03-01-2005, 11:49 PM	#10
chev406 Registered User Join Date: Feb 2005 Location: Sacramento, Ca. Posts: 30	Dudes you rock I gotta get it done fast before the neighbors have a chance to

03-02-2005, 12:32 AM	#11
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	ok smartass, are those what we are discussing here?

03-02-2005, 07:57 AM	#12
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	As far as I know, we are talking about the mounts...not the stands/towers. __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

03-02-2005, 08:45 AM	#13
MSL Registered User Join Date: Mar 2003 Location: So.Oregon Posts: 765	On my 78 chevy 1/2 ton i swapped to a 454 from my small block and nothing changed other than repostioning how you mount the motor mount to the front cross member. also the block mounts where the same too.

03-02-2005, 05:20 PM	#15
MSL Registered User Join Date: Mar 2003 Location: So.Oregon Posts: 765	Here you go this is what i used out of my truck manual i hope this helps and ifg anyone wants a larger pic email me at ml2418@yahoo.com maybe someone can put it on there webpage or make it a sticky. I mounted my stuff as showed and it all worked out fine. Attached Images

03-02-2005, 06:29 PM	#16
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	MSL, thanks for the diagram! I mounted mine the same way the pics show, except my motor mounts are the 350 variety...so I wasn't able to mount them the way "view A" shows. By looking at this diagram, it appears the clam shell motor mounts are different only in how they bolt to the towers...but not really in size. I still wish I knew the truth about the towers, and if there really is a BB and SB version...and what the differences are. __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

03-02-2005, 06:59 PM	#17
MSL Registered User Join Date: Mar 2003 Location: So.Oregon Posts: 765	Well i took my motor out of a 74 chevy 3/4 ton and the towers where the same as mine and the 74 truck was factory with the 454 so i myself would assume no difference in SB or BB.



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03-02-2005, 07:41 PM	#18
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	I still stand by my original statement that there is not difference in BBC vs. SBC engine stands. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

03-02-2005, 08:12 PM	#19
BIGCHEVYMAN Senior Member Join Date: Apr 2002 Location: Portland , Tennessee , United States Posts: 1,024	yup i agree with the captain.

03-02-2005, 11:14 PM	#21
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	The mounts are not the same...they might work, but they're not the same. The pics below show the differences. The mount on the right is for a '77 C20 with a smallblock (these are the mounts given to me by the parts guy because "they're all the same")...the mount on the left is the original GM mount out of my '77 C20 454/T400 truck. Do they look the same to ya'll? The 454 mount is longer, taller, has a different mount thru-bolt location, and has a different mount-to-tower bolt pattern. That's why I took the smallblock mounts back and went to a different parts store to get the right mounts...the 2395's...they were exactly like the originals...I kept the box so I would know which ones to get again in the future. So in my opinion, 3/4 ton mounts for small blocks and big blocks are different, but the book shows that a 1/2 ton trucks do use the same "small block" mount...the 2292's shown in the pics...interesting, huh? SC Attached Images __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

03-03-2005, 08:32 AM	#22
Gray Ghost Senior Member Join Date: Sep 2004 Location: Terrell, TX Posts: 1,967	He's talking about a 74...they are the same for that year as well as the 73 on the 3/4 ton trucks. Not sure why the 77's are different. __________________ Kelly '05 GMC Sierra SLE Z71 Bone stock except for new bed rail caps.

03-02-2005, 10:25 PM	#23
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	On mine, I unbolted the 305 & bolted the 402 right in. Only issue I had was one header tube didnt want to clear the cup style mount(DR side) on the engine but it clears now...corn

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