Does anybody know if... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Chevelle454 · 03-08-2004, 12:24 AM

A 1972 350 block has the same outside dimensions as a 1984 305 block? Also, will the 350 bolt up to my '84 700r4 tranny? I am looking to put my freshly rebuilt engine from my '72 into my '84 Caprice. I need to know if the block is the same and if it will just drop right in and have the motor mounts hook up right. So basically, are the '72 350 and '84 305 identical except for bore and stroke? Thanks...

-Scott

Blue_71 · 03-08-2004, 12:34 AM

yup they are, the only real different small block is the 400 and it'll still bolt right in place

Chevelle454 · 03-08-2004, 12:38 AM

When did they change the design of the block?

71swb4x4 · 03-08-2004, 12:40 AM

I second what Blue_71 said.

Blue_71 · 03-08-2004, 12:43 AM

i think 88 but im *almost* sure they will still bolt in, maybe have to change motor mounts though

walker · 03-08-2004, 12:43 AM

Well they did and they did'nt change the block design. Mostly they changed the intake system and the head design. Still fairly interchangeable though. I think they had one design from the '60s through about '84, one from '85 to the mid '90s, and one or two since then.

Chevelle454 · 03-08-2004, 12:59 AM

Well, the reason I am asking is because when I ordered my rebuild kit it said "Chevy 350 69-80" so I am wondering is that just internal differences?

Longhorn Man · 03-08-2004, 01:10 AM

not so much internal, but small differences here and there, like one piece rear main verses 2 piece, the aformentioned intake differences, ect.

71402BB · 03-08-2004, 02:22 AM

ya your good to go bolt em together, and have some fun! as far as I know the bell housing design is the same on all sbc.

jimfulco · 03-08-2004, 03:16 AM

Motor mount bosses are in the same place. Dipstick may be on the other side.

Tx Firefighter · 03-08-2004, 09:15 AM

It's a straight in swap except for the left side dipstick is going to foul your left side exhaust manifold. You'll have to modify your dipstick tube or run a flexible one like a Lokar.

A second issue is the heads. Your 305 has what is called "seventh bolt hole heads". If you'll look closely at your 305 heads, the very front bolt on the left side and very rear on the right side exhaust manifold bolt hole is offset. The earlier 350 has the normal arrangement with just 6 bolts per manifold.

Look closely at the left hand head in the picture below. See where the exhaust manifold bolts on? The very top is two holes right next to each other. Your 350 heads won't have that second bolt hole there, so your 305 exhaust manifolds won't be able to bolt on. It's a wierd anamoly of the 80s era engines.

I've done it before and just used good Fel-Pro gasket and left the one bolt out of each side manifold. It doesn't leak if you have good true manifolds and keep the other 5 bolts tight.

Bowtie67 · 03-08-2004, 09:29 AM

The difference in the 69 - 80 years was the dipstick being on the drivers side, they changed to the passenger side after 80 other than that most small blocks from 56 to almost current are fundamentally the same size and will bolt up to just about all chevy transmissions. The only reall issue would be the old 235 inline 6, it will not bolt up to any later model trans because of the way the bellhousing bolted up to the block. JMO

sneakysnake · 03-08-2004, 01:06 PM

What year was it that they changed the crank end and flywheels?

03-08-2004, 12:24 AM	#1
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	Does anybody know if... A 1972 350 block has the same outside dimensions as a 1984 305 block? Also, will the 350 bolt up to my '84 700r4 tranny? I am looking to put my freshly rebuilt engine from my '72 into my '84 Caprice. I need to know if the block is the same and if it will just drop right in and have the motor mounts hook up right. So basically, are the '72 350 and '84 305 identical except for bore and stroke? Thanks... -Scott __________________ 1972 C10 1972 C20

03-08-2004, 12:38 AM	#3
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	When did they change the design of the block? __________________ 1972 C10 1972 C20

03-08-2004, 12:40 AM	#4
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	I second what Blue_71 said. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

03-08-2004, 12:43 AM	#6
walker Registered User Join Date: Jul 2003 Location: north of Phx AZ about 30 miles Posts: 698	Well they did and they did'nt change the block design. Mostly they changed the intake system and the head design. Still fairly interchangeable though. I think they had one design from the '60s through about '84, one from '85 to the mid '90s, and one or two since then. __________________ Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold

03-08-2004, 12:59 AM	#7
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	Well, the reason I am asking is because when I ordered my rebuild kit it said "Chevy 350 69-80" so I am wondering is that just internal differences? __________________ 1972 C10 1972 C20

03-08-2004, 01:10 AM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	not so much internal, but small differences here and there, like one piece rear main verses 2 piece, the aformentioned intake differences, ect.

03-08-2004, 02:22 AM	#9
71402BB now thats a true COON DOG Join Date: Nov 2000 Location: Franconia, NH Posts: 1,977	ya your good to go bolt em together, and have some fun! as far as I know the bell housing design is the same on all sbc. __________________ current project 67 402BB stout th350 3.08's with a locker. Plan on tubs 18.5's out back! (thanks Burnsman!) 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's ( was crushed by a tree, bed sold, motor pulled) was my first truck!... oh well... 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE work in progress, soon to have 250-I6 with a 3-speed on the tree 4.11's and posi ( currently sitting in back yard tarped awaiting time, $$$, and lots of love!) 67 1 TON- work truck 396 sm 420 4-speed, flat bed 4.57 gears "big red" (my first landscape truck, very rusty and crusty! but still gets the job done when needed!)

03-08-2004, 03:16 AM	#10
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Motor mount bosses are in the same place. Dipstick may be on the other side.

03-08-2004, 09:15 AM	#11
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	It's a straight in swap except for the left side dipstick is going to foul your left side exhaust manifold. You'll have to modify your dipstick tube or run a flexible one like a Lokar. A second issue is the heads. Your 305 has what is called "seventh bolt hole heads". If you'll look closely at your 305 heads, the very front bolt on the left side and very rear on the right side exhaust manifold bolt hole is offset. The earlier 350 has the normal arrangement with just 6 bolts per manifold. Look closely at the left hand head in the picture below. See where the exhaust manifold bolts on? The very top is two holes right next to each other. Your 350 heads won't have that second bolt hole there, so your 305 exhaust manifolds won't be able to bolt on. It's a wierd anamoly of the 80s era engines. I've done it before and just used good Fel-Pro gasket and left the one bolt out of each side manifold. It doesn't leak if you have good true manifolds and keep the other 5 bolts tight. __________________ I'm on the Instagram- @Gearhead_Kevin

03-08-2004, 09:29 AM	#12
Bowtie67 Registered User Join Date: Jan 2004 Location: NH Posts: 2,266	The difference in the 69 - 80 years was the dipstick being on the drivers side, they changed to the passenger side after 80 other than that most small blocks from 56 to almost current are fundamentally the same size and will bolt up to just about all chevy transmissions. The only reall issue would be the old 235 inline 6, it will not bolt up to any later model trans because of the way the bellhousing bolted up to the block. JMO

03-08-2004, 01:06 PM	#13
sneakysnake It's a catastrophic success. Join Date: Jan 2003 Location: Oklahoma Posts: 2,077	What year was it that they changed the crank end and flywheels?

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