How do I tell the difference 350 & 305 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72addict · 11-27-2004, 09:55 PM

I have a 1/2 ton 1987 longbox with a v8 and a turbo 400. The motor sticker on the core support says 305, but it has a turbo 400 behind it so I am wondering if someone swapped it out. Did GM put 400 turbos in half ton 305 trucks in 1987 ? It is a tbi motor.

1972 · 11-27-2004, 10:17 PM

The two automatic transmission choices in '87 were a TH400 or a 700R4. The TH400 was available behind both a 305 and 350.

MylilBowTie · 11-27-2004, 10:18 PM

I have seen plenty of 80s vans that have 305s and TH400s for transmissions. Could be the core support was changed out. If you wanted to know I would get the numbers off the engine block and the transmission. I have a book about th400s and it has some of the transmission numbers decoded. Engine numbers can be ran at Mortec.com

c-1072 · 11-27-2004, 11:45 PM

I have an all original swb 4x4 1/2 ton heavy suspension 305 / 400 truck 59k this thing kills me on gas , but it pushes snow like you wouldent believe . Just check the build tag in the glove box .

72addict · 11-28-2004, 01:59 AM

can't really see the block #'s without pulling the engine or cab. It is real tight back there and caked with crud.

MylilBowTie · 11-28-2004, 09:27 AM

There is a spot on the block right behind the alternator. Its where the block and cylinder head meet there will be a small pad that has it stamped into the block. It should have some numbers and letters this will also tell a little about the block and is the easiest to get to. Im not saying that the factory sheet is wrong but you never know what the previous owner might have done or had done to it.

cw41 · 11-28-2004, 05:26 PM

Look at the harmonic balancer, the 305 i

s wider/smaller diameter, while the 350 is larger diameter and narrower..

cliffsta · 11-28-2004, 07:27 PM

You know it's a 305 when all your friends and random people hate on you and tell you take that boat moter out.

I know because my truck has a 305, and i couldn't be happier.

phantom dually · 11-28-2004, 07:29 PM

a 305 is alot slower than a 350!!

MylilBowTie · 11-28-2004, 07:44 PM

The balancers will interchange, so that isn't a real reliable way to tell. Ive seen a lot of stuff done to vehicles that I would have never done. There are plenty of ways to correctly identify the block if the time is taken to do so.

Slonaker · 11-28-2004, 09:44 PM

My '86 305 has the numbers "305" cast into the block. You might look for that. Supposedly some of them are stamped like that.

Slonaker

leastbay · 11-28-2004, 11:02 PM

spray it with some carburetor cleaner and stick a drop light in there you should be able to see it

11-27-2004, 09:55 PM	#1
72addict Registered User Join Date: Mar 2000 Location: Mason MI, 48854 (strikezone of the mitten) Posts: 894	How do I tell the difference 350 & 305 I have a 1/2 ton 1987 longbox with a v8 and a turbo 400. The motor sticker on the core support says 305, but it has a turbo 400 behind it so I am wondering if someone swapped it out. Did GM put 400 turbos in half ton 305 trucks in 1987 ? It is a tbi motor. __________________ 1957 Cameo

11-27-2004, 10:18 PM	#3
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	I have seen plenty of 80s vans that have 305s and TH400s for transmissions. Could be the core support was changed out. If you wanted to know I would get the numbers off the engine block and the transmission. I have a book about th400s and it has some of the transmission numbers decoded. Engine numbers can be ran at Mortec.com __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

11-27-2004, 11:45 PM	#4
c-1072 Registered User Join Date: Sep 2004 Location: rochester NY Posts: 777	Th400/305 I have an all original swb 4x4 1/2 ton heavy suspension 305 / 400 truck 59k this thing kills me on gas , but it pushes snow like you wouldent believe . Just check the build tag in the glove box .

11-28-2004, 01:59 AM	#5
72addict Registered User Join Date: Mar 2000 Location: Mason MI, 48854 (strikezone of the mitten) Posts: 894	can't really see the block #'s without pulling the engine or cab. It is real tight back there and caked with crud. __________________ 1957 Cameo

11-28-2004, 09:27 AM	#6
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	There is a spot on the block right behind the alternator. Its where the block and cylinder head meet there will be a small pad that has it stamped into the block. It should have some numbers and letters this will also tell a little about the block and is the easiest to get to. Im not saying that the factory sheet is wrong but you never know what the previous owner might have done or had done to it. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

11-27-2004, 10:17 PM	#2
1972 Majician Join Date: Nov 2004 Location: In the Middle Posts: 329	The two automatic transmission choices in '87 were a TH400 or a 700R4. The TH400 was available behind both a 305 and 350.

11-28-2004, 05:26 PM	#7
cw41 Registered User Join Date: Nov 2004 Posts: 3	Harmonic balancer size Look at the harmonic balancer, the 305 i s wider/smaller diameter, while the 350 is larger diameter and narrower..

11-28-2004, 07:27 PM	#8
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	You know it's a 305 when all your friends and random people hate on you and tell you take that boat moter out. I know because my truck has a 305, and i couldn't be happier. __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

11-28-2004, 07:29 PM	#9
phantom dually Project92 SWB stepside Join Date: Feb 2003 Location: Louisville KY Posts: 4,792	a 305 is alot slower than a 350!! __________________ 92 C1500 stepside 496 Stroker Competiton Engineering Ladder bars/QA1 coilovers. Dana 60 rear with 4.10 gear and posi. Bonspeed Palisade 20x12 in rear w/335/30/20 and 20x8.5 front w/245/40/20. 5/8 drop with Belltech springs/DJM spindles/drop shocks. WWS Progress thread http://67-72chevytrucks.com/vboard/s...d.php?t=140448

11-28-2004, 07:44 PM	#10
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	The balancers will interchange, so that isn't a real reliable way to tell. Ive seen a lot of stuff done to vehicles that I would have never done. There are plenty of ways to correctly identify the block if the time is taken to do so. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

11-28-2004, 09:44 PM	#11
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	My '86 305 has the numbers "305" cast into the block. You might look for that. Supposedly some of them are stamped like that. Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

11-28-2004, 11:02 PM	#12
leastbay Registered User Join Date: Jun 2004 Location: Lake Charles, LA Posts: 206	spray it with some carburetor cleaner and stick a drop light in there you should be able to see it

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