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Need a little technical on PCV system for my 62

IH2LOSE

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I am in the process of putting the tri power on my 62.

So excisting manifold has a vacum tap on rear of manifold and i am using this for my power break booster

Excisting carb has a 3/8 manifold vacum tap and I am using this for my PCV valve in the breather cap on my passenger side valve cover.

Excisting carb and new carb has ported and manifold vacum taps and no change is need here.

New manifold has NO manifold vacum taps on it.

New rear carb has one 3/8" manifold vacum tap and i plan on using this for the power break booster.

I had planned on running a line from the bottom of the air cleaner to connect to the PCV valve. I was advised this will not work as there will not be enoght vacum at idle.

Do you guys agee or disagree.

If the aircleaner tap is not enough that means I will have to drill the manifold and tap it for a vacum port.

Thanks
Larry
 
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Larry, as we all know know i'm not expert on anything but i'd have to agree that the air cleaner housing isn't going to give you enough, if any vacuum at all, to run the PCV.

on my '65 the vacuum comes direct from the carb and on my '78 it connects to both the carb and the vacuum cannister. On both cars the air cleaner housing in only used for the breathing side of the system rather than the vacuum side.

I think you are going to have to drill and tap the manifold unless you think that using a "T" connection on the rear carb for both the brake booster and the PCV would work.
 
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Larry, you definitely need a full manifold vacuum source for your PCV valve; I'd drill and tap the manifold for a new fitting. Then you can use the existing carb 3/8" nipple for PCV and the new fitting for the power brake booster, or vice versa - either way will work fine. :)
 

IH2LOSE

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Thanks guys

I will drill it and tap it tomorow night. I just hate tapping for NPT as I know they have a taper on them and i am alway afraid I will over tighten and split the peice
 

cfalson

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Before you go and drill and tap the manifold I have a question. How are you going to insure there is enough material to accept the pipe thread, I think the walls are pretty thin.
 

IH2LOSE

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Before you go and drill and tap the manifold I have a question. How are you going to insure there is enough material to accept the pipe thread, I think the walls are pretty thin.


This is a good question.

I am trying to find a spot thats flat and thick and on the passenger side of the car near the PCV valve.

I am going to take my chances, as I will be taking this back off for polishing
 

Viet Nam Vett

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Larry,
are there any provisions on the aircleaner base for a Backfire arrester sysyem. In other words,did the original tripower have a backfire aressting design?

On my 4 BBL drop base air cleaner I made sure I added the backfire aresstor screen in the system. Since the line from the air cleaner base runs to the valve cover. The blow by gases travel into the air cleaner and back into the carb for reburning.

A backfire in the carb could ignite thses gases and travel back into the crank case and cause an explosion..hence the bacfire screen.
 
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Larry,
are there any provisions on the aircleaner base for a Backfire arrester sysyem. In other words,did the original tripower have a backfire aressting design?

On my 4 BBL drop base air cleaner I made sure I added the backfire aresstor screen in the system. Since the line from the air cleaner base runs to the valve cover. The blow by gases travel into the air cleaner and back into the carb for reburning.

A backfire in the carb could ignite thses gases and travel back into the crank case and cause an explosion..hence the bacfire screen.

The '67 Corvette tri-power air cleaners didn't use the flame arrestor screen unless the car had K-19 (A.I.R.); the only BB Corvette that used the flame arrestor screen was the single 4-barrel L-36. Don't know why.

:beer
 

Viet Nam Vett

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The '67 Corvette tri-power air cleaners didn't use the flame arrestor screen unless the car had K-19 (A.I.R.); the only BB Corvette that used the flame arrestor screen was the single 4-barrel L-36. Don't know why.

:beer

Thanks for that info Jhon.

Question:
Do you think a set up like Larry is installing should use a Crancase scavaging system ..In other words a line from let's say one valve cover to the air cleaner base as discribed?

Or...is there enough Crankcase Scavaging Action with the PVC system..??
 
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Thanks for that info Jhon.

Question:
Do you think a set up like Larry is installing should use a Crancase scavaging system ..In other words a line from let's say one valve cover to the air cleaner base as discribed?

Or...is there enough Crankcase Scavaging Action with the PVC system..??

I haven't seen a photo of his engine, but the PCV system has two elements - an intake side (air cleaner to pass. side valve cover on a BB), and an exhaust side (driver's side valve cover thru PCV valve to carb base on a BB). The intake vacuum sucks crankcase vapors through the PCV valve, but the system has to have an intake opening where fresh air enters the crankcase in order to have "flow" through the crankcase. Without an "intake", the system doesn't work.
 

Viet Nam Vett

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I haven't seen a photo of his engine, but the PCV system has two elements - an intake side (air cleaner to pass. side valve cover on a BB), and an exhaust side (driver's side valve cover thru PCV valve to carb base on a BB). The intake vacuum sucks crankcase vapors through the PCV valve, but the system has to have an intake opening where fresh air enters the crankcase in order to have "flow" through the crankcase. Without an "intake", the system doesn't work.


Yep makes sense.. I got it backwards a few post's back. But it does make sense. Wouldn't you say on a big block set up it would be a good idea to have this fresh air flow... thru the motor.

I would think the advantages of fresh air flowing thru the crankcase would be very helpful in regards to oil contamination and just general over all health of the motor.

Thoughts..??
 
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I would think the advantages of fresh air flowing thru the crankcase would be very helpful in regards to oil contamination and just general over all health of the motor.

Thoughts..??

Yup - draws off all the nasty contaminants that are in suspension in the hot oil vapors and burns them instead of letting them settle in the oil, making it acidic, and forming sludge. :)
 

critchie

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1. If this engine were in a boat, the Coast Guard would require this. You need flame arresters/backfire arresters in between carburetor (source of the spark/flame) and the crankcase (source of combustible gas). The PCV valve takes care of 1 route. You need a flame arrester in the other route. All a flame arrester is is a wire screen. Use stainless. I used those little screens that the hardware store sells for washing machine inlets. Install it on the air cleaner base - in the nipple for the fresh air source.

2. Why can't you use a tee? Tee off the power brake fitting. Save you from drilling holes in your intake manifold. Not sure.
 
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2. Why can't you use a tee? Tee off the power brake fitting. Save you from drilling holes in your intake manifold. Not sure.

Functionally, you could probably get away with it, but it wasn't done in production due to the possibility of PCV flow reversions allowing crankcase vapors to get into the booster.

:beer
 

Viet Nam Vett

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Functionally, you could probably get away with it, but it wasn't done in production due to the possibility of PCV flow reversions allowing crankcase vapors to get into the booster.

:beer

aahhhh..That's Not Good....Stepping o the brakes and going BOOM..!!!:L
 

66427-450

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Thanks guys

I will drill it and tap it tomorow night. I just hate tapping for NPT as I know they have a taper on them and i am alway afraid I will over tighten and split the peice
Another option is to weld small boss on the manifold, alum is really easy to work with, with a little work/skill it'll look factory. I've done that, as well as drilling a small hole and inserting a small section of alum tube and then sealing it with a small/neat fillet weld (cutting it flush inside). both are flush inside the manifold, and don't result in an obstruction in the flow path

Drilling and tapping a thin section? May work OK.....

For a PVC I'd definitely pick a spot out of the major flow path(s)..... in the side of the plenum, high, maybe between the carbs
 

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