Is this a small block or big block engine?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Ewhitaker0020

Full Access Member
Joined
Apr 21, 2019
Posts
272
Reaction score
90
Location
Kentucky
First Name
Eric
Truck Year
1984
Truck Model
K10
Engine Size
305 5.0
I was wondering if somebody could help me tell if this engine is a Chevy 350 like it's supposed to be or a big block engine. The only reason why I'm wondering is because the exhaust manifold bolts are very different than my 84 Chevy K10 with a 305. This engine is out of a 80 Chevy c30 truck and I'm going to get a fuel pump for it. I just wanted to make sure I had the right engine before I ordered one.

In the picture you can see how the exhaust manifold has bolts going in at an angle and my 305 small block doesn't have anything like that. So it's making me question whether or not this is a small block. Plus the years are so similar I can imagine the blocks would be that much different for a small block.

You must be registered for see images attach


You must be registered for see images attach
 

legopnuematic

Licensed Junk Dealer
Supporting Member
Joined
Oct 27, 2016
Posts
1,709
Reaction score
3,659
Location
MO
First Name
Spencer
Truck Year
1971, 1̶9̶7̶4, 1976, 1979,1̶9̶8̶5, 2002
Truck Model
Dart Swinger, Sierra 10, C10 Cheyenne, C10 Big Ten, Silverado 10, Ram 2500
Engine Size
225/6, 350 c.i., 350 c.i., 5.9l Cummins
Small block, those "bolts" are actually plugs for where the A.I.R tubes would have gone.

Big Blocks have much wider valve covers and has no Siamese ports, so the manifolds have 4 equally spaced ports.
You must be registered for see images attach
 

Green79Scottsdale

Full Access Member
Joined
Aug 8, 2010
Posts
2,834
Reaction score
7,483
Location
G.R. - MI
First Name
Bob
Truck Year
1979
Truck Model
K20
Engine Size
400
Small block. Giveaway is the center exhaust ports are next to each other. Big blocks have separated exhaust locations. Those bolts you are referring to are most likely ports for the smog system. From the factory there are some metal tubes that go through those areas and lead to, well, I honestly don't remember. Whoever had the truck before you has done away with the system, and put those bolts into the manifolds to plug the leak. At least that's my story.
 

Ewhitaker0020

Full Access Member
Joined
Apr 21, 2019
Posts
272
Reaction score
90
Location
Kentucky
First Name
Eric
Truck Year
1984
Truck Model
K10
Engine Size
305 5.0
Small block, those "bolts" are actually plugs for where the A.I.R tubes would have gone.

Big Blocks have much wider valve covers and has no Siamese ports, so the manifolds have 4 equally spaced ports.
You must be registered for see images attach

Awesome, thanks for the info. Now I'll always know how to identify a small vs big block. Why is a 2 line fuel pump for this engine so hard to find? Everything I see has 3 lines.
 

Ewhitaker0020

Full Access Member
Joined
Apr 21, 2019
Posts
272
Reaction score
90
Location
Kentucky
First Name
Eric
Truck Year
1984
Truck Model
K10
Engine Size
305 5.0
Small block. Giveaway is the center exhaust ports are next to each other. Big blocks have separated exhaust locations. Those bolts you are referring to are most likely ports for the smog system. From the factory there are some metal tubes that go through those areas and lead to, well, I honestly don't remember. Whoever had the truck before you has done away with the system, and put those bolts into the manifolds to plug the leak. At least that's my story.


Thanks. My truck still had exhaust tubes and I had my muffler guy snip them off with a torch and he brazed the holes closed.
 

legopnuematic

Licensed Junk Dealer
Supporting Member
Joined
Oct 27, 2016
Posts
1,709
Reaction score
3,659
Location
MO
First Name
Spencer
Truck Year
1971, 1̶9̶7̶4, 1976, 1979,1̶9̶8̶5, 2002
Truck Model
Dart Swinger, Sierra 10, C10 Cheyenne, C10 Big Ten, Silverado 10, Ram 2500
Engine Size
225/6, 350 c.i., 350 c.i., 5.9l Cummins
M6624 is the Carter pn for a 2 line small block pump.

I am not certain when, but I know that from the early to the late 70's there was a switch from returnless to a return style pump on 2wd's. My 76 c10 is a 2 line but my 79 C10 is a 3 line. My friends 75 K5 is a 3 line system.
 

Ewhitaker0020

Full Access Member
Joined
Apr 21, 2019
Posts
272
Reaction score
90
Location
Kentucky
First Name
Eric
Truck Year
1984
Truck Model
K10
Engine Size
305 5.0
M6624 is the Carter pn for a 2 line small block pump.

I am not certain when, but I know that from the early to the late 70's there was a switch from returnless to a return style pump on 2wd's. My 76 c10 is a 2 line but my 79 C10 is a 3 line. My friends 75 K5 is a 3 line system.

I will double check that the fuel pump is only 2 line, but just from feeling I'm pretty sure it was.
 

80BrownK10

Full Access Member
Joined
Oct 22, 2019
Posts
1,878
Reaction score
1,240
Location
Greenwood, SC
First Name
Nate
Truck Year
1980
Truck Model
K10
Engine Size
350
I was wondering if somebody could help me tell if this engine is a Chevy 350 like it's supposed to be or a big block engine. The only reason why I'm wondering is because the exhaust manifold bolts are very different than my 84 Chevy K10 with a 305. This engine is out of a 80 Chevy c30 truck and I'm going to get a fuel pump for it. I just wanted to make sure I had the right engine before I ordered one.

In the picture you can see how the exhaust manifold has bolts going in at an angle and my 305 small block doesn't have anything like that. So it's making me question whether or not this is a small block. Plus the years are so similar I can imagine the blocks would be that much different for a small block.

You must be registered for see images attach


You must be registered for see images attach
Small block. Looks like small block exhaust to me?:33:
 

80BrownK10

Full Access Member
Joined
Oct 22, 2019
Posts
1,878
Reaction score
1,240
Location
Greenwood, SC
First Name
Nate
Truck Year
1980
Truck Model
K10
Engine Size
350
Awesome, thanks for the info. Now I'll always know how to identify a small vs big block. Why is a 2 line fuel pump for this engine so hard to find? Everything I see has 3 lines.
Look at rock Auto. Last I looked not that long ago there was several of each one.
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,135
Reaction score
4,984
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Definitely a small block as others have said. 1980 should be a 3-line fuel pump.. My 1980 K25 with a 350 has a 3-line pump. Feed and return from/to the tank and the outlet going up to the carburetor.
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,135
Reaction score
4,984
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Rockauto does have both a 2 line and 3 line available. If it is a 2 line pump, it should have a smaller return line outlet right next to the flare fitting outlet port on the pump. The larger push on fuel inlet on the pump should be more towards the middle of the bottom of the pump.
 

Catbox

Full Access Member
Joined
Jul 12, 2018
Posts
3,968
Reaction score
14,481
Location
Just Outside of Portland Oregon
First Name
Peter
Truck Year
1979
Truck Model
C20 Silverado Camper Special
Engine Size
461
Another easy peasy way to tell is the number of valve cover bolts.
Small block has 4 total, 2 on bottom and 2 on top.
Big block has 7 total, 4 on the bottom and 3 on the top.
 

Ewhitaker0020

Full Access Member
Joined
Apr 21, 2019
Posts
272
Reaction score
90
Location
Kentucky
First Name
Eric
Truck Year
1984
Truck Model
K10
Engine Size
305 5.0
Definitely a small block as others have said. 1980 should be a 3-line fuel pump.. My 1980 K25 with a 350 has a 3-line pump. Feed and return from/to the tank and the outlet going up to the carburetor.
I'm definitely going to check again then, before I order a pump. Can a failing fuel pump cause bad hesitation, backfiring, and missing?

My father in law had a really hard time getting the truck home the other day. We just changed out the carb for an Edelbrock 600 CFM that I rebuilt and I'm really reluctant to say it might be the carb. I was pretty thorough with it and didn't have any trouble. Besides the fuel baffle being gone, but we didn't have a single problem with that for a week after the swap. We already replaced the distributor guts and rotor cap and button. Along with the spark plugs and wires. So unless the actual distributor coil is going bad I'm reluctant to say it's a problem with spark. It's not a problem with air, so I'm thinking it's a problem with fuel.

Sent from my SM-G950U using Tapatalk
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,135
Reaction score
4,984
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
I'm definitely going to check again then, before I order a pump. Can a failing fuel pump cause bad hesitation, backfiring, and missing?

My father in law had a really hard time getting the truck home the other day. We just changed out the carb for an Edelbrock 600 CFM that I rebuilt and I'm really reluctant to say it might be the carb. I was pretty thorough with it and didn't have any trouble. Besides the fuel baffle being gone, but we didn't have a single problem with that for a week after the swap. We already replaced the distributor guts and rotor cap and button. Along with the spark plugs and wires. So unless the actual distributor coil is going bad I'm reluctant to say it's a problem with spark. It's not a problem with air, so I'm thinking it's a problem with fuel.

Sent from my SM-G950U using Tapatalk

It can... probably not though. What seems to be more common is the edelbrock getting TOO MUCH fuel pressure and flooding out the engine. I would start with a fuel pressure test and see what that looks like. The same guage can tell you what your vacuum looks like. Check both.

Hesitation, backfire, and missing could be lots of things.

I would start by testing a few things first.
  1. Fuel pressure should be between 3-6psi for the edelbrock. Any more than that will cause the fuel to push past the float and flood the engine.
  2. Vacuum should be between 16-24 in. hg.(depending on where you are located and temperature)
  3. Vacuum needle should be steady while idleing.
  4. Check timing. Base timing should be between 8-12deg BTDC
  5. Verify you installed the spark plug wires in the correct firing order.
  6. Spray carb cleaner around the intake manifold and base of the carburetor. If the engine revs up when you spray a certain spot, you have an intake leak.
If any of that doesn't look good, come back and let us know exactly what you see and we can go from there.

If all of that looks good, do a compression test and see if you lost something mechanically in the engine. I had similar engine running issues and it turned out I had broken a valve spring and had 0 compression in one cylinder. It could be a wiped cam lobe, broken/bent valvetrain component, or a bunch of other stuff.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Definitely a small block as others have said. 1980 should be a 3-line fuel pump.. My 1980 K25 with a 350 has a 3-line pump. Feed and return from/to the tank and the outlet going up to the carburetor.
My 1980 which is also a k25 with a 350 also has a 3 line fuel pump.
 

Latest posts

Forum statistics

Threads
41,856
Posts
903,618
Members
33,369
Latest member
mitchell1128
Top