No way this is right?

[78SierraGrandeTX]

Hello everyone,

I recently purchased a 1978 GMC C2500 Sierra Grande and I have been fixing it up these past couple months. I’m not sure if the engine itself is original, but do believe the serpentine to be from a 1994-ish small block.

I am now stepping into some territory that I’m learning as I go ( as far as engine work).

The truck runs and drives but as I have been fixing up power steering, alternator and some other smaller parts I have noticed a couple of issues that don’t seem to be correct.

First off regarding the carburetor, there is a gap between the carb and the manifold. Is this just the wrong carb for the manifold? Or was it installed poorly? Both the carb and manifold are edelbrock.


Secondly, where is this supposed to connect too? It comes from the rear of the driver side valve cover.


Thanks in advance.

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[78SierraGrandeTX]

Better picture of the gap I am referring too.

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[Vbb199]

Based off those valve covers (center bolt) I'd say it's from a 88 or so and up truck.
I can't remember the exact year. But you're right in your hunch about the serpentine setup.

I'm gonna say that's a throttle body injected motor, and there's some sort of adapter put on it for a carb.

The hose that's just chilling and not hooked up to anything is for the PCV valve. Since there's now a carb on there, it would go on one of the inlets sticking out of the carb.
The PCV reciruclates air from the crank case and uses it as additional fuel of some type, gases basically.


Is there a hose coming from the other valve cover going to the carb? There should be.




Looking at it better, I'm gonna say someone used to have a Throttle body spacer on there, and then just removed the throttle body and put a carb on top.

 

[SDJunkMan]

That looks like an adapter plate under the carb, the hose probably went to the stock air cleaner. A 78 did not come with serpentine belts.

 

[75gmck25]

It may be an Edelbrock Perfomer 2101 manifold, which is tapped for both squarebore and Quadrajet. The holes you see under the gasket are the 2nd set of holes for the Quadrajet. It may not be an issue if the gasket is sealing right, but its something you should verify.

The hose off the passenger side valve cover usually connects to a small filter that is clipped into the air cleaner body. It provides filtered air for the PCV (which is pulling air through the PCV valve mounted in the other valve cover. Since you have an aftermarket air cleaner they should have used a push-in filter in the valve cover, similar to this one. https://www.autozone.com/external-engine/breather-cap/edelbrock-chrome-breather-filter-4405/10700_0

Where is the PCV hose from the carburetor connected to? I can see it in the picture, but not where it goes.

I've seen many cars with butchered PCV systems because guys somehow think they are part of "that emissions crap" - not true!
A working PCV system is important for engine health because it vents and pulls moisture out of the crankcase. Older engines did not have a PCV because they had a road draft tube, but those tubes are long gone.

Bruce

 

[78SierraGrandeTX]

There’s not a hose on the other valve cover going to the carb.

I am not familiar with a throttle body, however that would make sense since the throttle set up is just kind of resting behind the carb.

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[Vbb199]

This.

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[Vbb199]

On a throttle body injected motor, the passenger side hose from the valve cover goes into the front of the throttle body, and drivers side hose would go into the air cleaner.

The side that's just cut off and not hooked can potentially blow oil all over the place.

Out of curiosity, does it have a 4 speed automatic transmission?
I think I can see a TV cable running off the carb.

 

[75gmck25]

It looks like your PCV valve is mounted in the passenger side valve cover, which works fine if there is some type of filtered air intake in the other valve cover. I don't know how it was plumbed on a centerbolt valve cover engine, but it sounds like they just swapped the PCV to the other side.

My original '75 SBC 350 had the PCV valve grommet and oil filler cap in the driver's side valve cover, and the breather grommet (which connected to the air cleaner) in the passenger side valve cover. I now have aftermarket valve covers with only one hole in each one, so my PCV valve grommet is also where I have to add oil.

The principle is that under vacuum load the PCV pulls air in through carburetor base to vent the crankcase and remove moisture. It needs somewere to allow the air in the other side, which is why you need a flitered breather or the connection to the air cleaner.

Bruce

 

[78SierraGrandeTX]

Okay great thanks, I’m currently not with the truck and knew that there was not another hose in the rear of the passenger side valve cover, the same location as the driver side.

 

[Markmx6]

I believe you should take out the PCV valve from the driver side cover. You have one on the passenger side and it pulls air into the carb/manifold. If you have 2 PCV valves then you are not letting air back into the motor, which is why they usually pull clean air from the air filter housing or a filtered breather cap.

In my opinion with 2 pcv valves you will pull a vacuum on the crankcase which could collapse your crank seals, or valve seals or even cause extra piston blow by.

 

[78SierraGrandeTX]

Markmx6,

So will the part that was recommended earlier solve that issue?

- Putting a breather filter over the valve?

 

[78SierraGrandeTX]

Yes it is an automatic transmission.

 

[Markmx6]

Markmx6,

So will the part that was recommended earlier solve that issue?

- Putting a breather filter over the valve?

That should do the trick and solve the problem.

 

[Vbb199]

Yes it is an automatic transmission.

A 4 speed or 3 speed? I'm just curious now.