Is this a small block or big block engine?

[Ewhitaker0020]

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]

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]

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]

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]

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]

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]

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]

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?

 

[80BrownK10]

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]

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]

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]

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]

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]

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]

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.