Let’s talk PCV systems.

[ChuckN]

My original engine in the K20 Sub was an LT9 engine code M. The Goodwrench replacement is a 10067353 crate. The only changes I have made to the replacement are headers, Edelbrock 2101 intake, and an Eddy 1405 carb. The original LT9 called for ACDelco CV774C valve and I have a stash of those and they work fine in what I have at this point. I have a full flow breather on the passenger side valve cover. Anyone think these shouldn't work fine with what I have?

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It sounds as if anything is better than nothing. If you’re concerned about function of the system, you could hook a vacuum gauge up to the passenger side (inlet) and see if there is actually a vacuum occurring (you’d have to make some kind of adapter, wouldn’t be too hard) at various throttle positions.

Look at me sounding like I know what I’m talking about, lol. Basically, go back and read the article posted by Ricko in #11 of this thread.

 

[Rustisbest]

Wix 42993 might work for you if your baffle doesnt work. Thats what I have on my Tahoes valve covers because the baffle wouldnt clear the Comp XD rockers.
Not the prettiest looking thing but its got a screen and a sort of scotchbright like material on the other side to keep the oil from getting sucked into the engine. I dont remember what PCV grommet I used on it though?

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[Camar068]

read up on those earlier. I'd like to eliminate intake vacuum as the "end of flow". Use it as a source to trigger, but not in the flow.

Yeh I know, I'm thinking too far out of the box lol.

My question is, if the vacuum (edited) FLOW to the crankcase is always ON, can it hurt performance?

mewagner.com

Best pcv on the market and plenty of technical info.

 

[ChuckN]

read up on those earlier. I'd like to eliminate intake vacuum as the "end of flow". Use it as a source to trigger, but not in the flow.

Yeh I know, I'm thinking too far out of the box lol.

My question is, if the vacuum (edited) FLOW to the crankcase is always ON, can it hurt performance?

Hey bud, it’s a good question and last night I got to thinking about this, and remembered my buddy Mark talking about vacuum pumps in his race cars (import stuff, not SBC). But they’re going at it from the standpoint of gaining HP, not just scavenging unwanted junk from the engine (like I am).

So here’s an article I found. https://automotivetechinfo.com/2017/05/technical-minute-vacuum-pumps-power/

It’s worth a read if only to understand the upper limits of vacuum in a crankcase and understand the effects on oiling.

In our case with the gaskets of a SBC (they’re not inherently good) we’d probably suck in the the valve cover, china wall and oil pan gaskets before vacuum got too high. I for one think it would be a neat experiment for any PCV system to get one valve cover for the driver side with a regular breather and drill in a fitting for a vacuum gauge and run it inside the cab to see what’s going on. A guy could hide a ball valve on the vacuum side and tune it to where it’s a good average.

Yeah. I can nerd out sometimes.

 

[Camar068]

Hey bud, it’s a good question and last night I got to thinking about this, and remembered my buddy Mark talking about vacuum pumps in his race cars (import stuff, not SBC). But they’re going at it from the standpoint of gaining HP, not just scavenging unwanted junk from the engine (like I am).

So here’s an article I found. https://automotivetechinfo.com/2017/05/technical-minute-vacuum-pumps-power/

It’s worth a read if only to understand the upper limits of vacuum in a crankcase and understand the effects on oiling.

In our case with the gaskets of a SBC (they’re not inherently good) we’d probably suck in the the valve cover, china wall and oil pan gaskets before vacuum got too high. I for one think it would be a neat experiment for any PCV system to get one valve cover for the driver side with a regular breather and drill in a fitting for a vacuum gauge and run it inside the cab to see what’s going on. A guy could hide a ball valve on the vacuum side and tune it to where it’s a good average.

Yeah. I can nerd out sometimes.

very nice article, thanks. the other one I read didn't get any where near as technical as that one.

 

[texasmike]

I am a little late to this discussion but I do have one question: with the hose to the fresh air canister disconnected at the PVC valve, does it indicate a problem if I can't pull any air by sucking on the end of the hose?

 

[ChuckN]

I am a little late to this discussion but I do have one question: with the hose to the fresh air canister disconnected at the PVC valve, does it indicate a problem if I can't pull any air by sucking on the end of the hose?

Hmm, not sure I’m familiar with a fresh air canister- got a picture?

 

[texasmike]

Hmm, not sure I’m familiar with a fresh air canister- got a picture?

If you are standing in front and looking into the engine bay, the device, a little larger than a one pound coffee can, is located on the lower right and is attached next to the headlight. It is called a canister on the emissions diagram and has four hoses attached to the top. One of the hoses attaches to the PCV valve. I would think that

 

[texasmike]

If you are standing in front and looking into the engine bay, the device, a little larger than a one pound coffee can, is located on the lower right and is attached next to the headlight. It is called a canister on the emissions diagram and has four hoses attached to the top. One of the hoses attaches to the PCV valve. I would think that

.......the valve would draw filtered air from the canister??

 

[Ricko1966]

.......the valve would draw filtered air from the canister??

That's the charcoal cannister and with purge valve closed I wouldn't think you would be able to draw air through it. The purge valve gets its signal from the smallest hose. That canister is the vent for the gas tank,and the carburetor float bowl.

 

[texasmike]

I understand that on a factory setup, the top 3/16" hose on the Vapor Carbon Canister connects to the Thermal Vacuum Switch. The TVS has four ports and two of them appear to hold vacuum when the temperature rises enough to close the switch. My question is where does the canister get vacuum from and how much would it be?

 

[Ricko1966]

I understand that on a factory setup, the top 3/16" hose on the Vapor Carbon Canister connects to the Thermal Vacuum Switch. The TVS has four ports and two of them appear to hold vacuum when the temperature rises enough to close the switch. My question is where does the canister get vacuum from and how much would it be?

Do you not have the under hood sticker for your truck? Is your truck stock under the hood?

 

[texasmike]

Hey Rick, thanks for your reply and I apologize for the delayed response. The truck is stock but the air pump is removed and the Decel valve is gone. The original emission label is there and it shows two hoses going from the TVS to the carb and one going to the EGR and the other one going to the canister. Since there are no hoses going to the carb (all capped off) that is why there is no vacuum, duh. My problem is that I'm not sure where the hoses attach to the TVS. The switch, with four ports, faces the firewall and if one is sitting in the truck, can you tell me where the hoses connect to the TVS? Thanks.

 

[Ricko1966]

Hey Rick, thanks for your reply and I apologize for the delayed response. The truck is stock but the air pump is removed and the Decel valve is gone. The original emission label is there and it shows two hoses going from the TVS to the carb and one going to the EGR and the other one going to the canister. Since there are no hoses going to the carb (all capped off) that is why there is no vacuum, duh. My problem is that I'm not sure where the hoses attach to the TVS. The switch, with four ports, faces the firewall and if one is sitting in the truck, can you tell me where the hoses connect to the TVS? Thanks.

Might be a day or 2 before I can look at my truck. But I'll get it done.

 

[Ricko1966]

Hey Rick, thanks for your reply and I apologize for the delayed response. The truck is stock but the air pump is removed and the Decel valve is gone. The original emission label is there and it shows two hoses going from the TVS to the carb and one going to the EGR and the other one going to the canister. Since there are no hoses going to the carb (all capped off) that is why there is no vacuum, duh. My problem is that I'm not sure where the hoses attach to the TVS. The switch, with four ports, faces the firewall and if one is sitting in the truck, can you tell me where the hoses connect to the TVS? Thanks.

I looked at my truck. Mines an 86 either our trucks are different or I'm not looking at what you need me to look at. Take a pic of the TVS in question and maybe a pic of your emissions label.