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  #1  
Old 10-11-2015, 12:37 PM
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GeoffInCarlsbad GeoffInCarlsbad is offline
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Default Road Draft v. PCV

My '61 390FE has a Road Draft Tube, and I assume this is in place instead of a more traditional PCV for this 390FE.

It seems the only serviceable part is replacing the oil filler cap, where the filter in its intake is very, very dirty. The Shop Manual talks about both, but...it's not clear to me.

I am seeing smoke from the Road Draft Tube at when idling hot. I cannot judge if its excessive or not, because I don't know what it the norm.

If I replace the oil filler cap with a clean one, does that help? Also, should I consider a conversion to PCV? If so, how difficult and expensive is that? Is there really any reason to do a conversion?
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  #2  
Old 10-11-2015, 01:36 PM
Joe Johnston Joe Johnston is offline
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Default

Conversion will eliminate the smoke, fumes, smell and drips to the outside. A PCV system will not keep these emissions from happening, just return them to combustion chamber. Definitely a "must do" in my book (I did it to my 57 Y-Block).
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Old 10-11-2015, 09:19 PM
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X2 with Joe.

The new clean cap "should" allow more air into the crankcase and actually increase the amount of smoke out of the road draft tube.

On my original 352 (road draft) I tried plumbing the road draft tube to the air cleaner in hopes of returning the smoke and fumes to the combustion chamber. It worked but at idle there was not enough vacuum to pull all the fumes out of the crankcase into the air cleaner so still had a little out of the oil filler cap. Also tried a different oil filler cap with a vent tube and plumbed that to the same point on the air cleaner which helped but since the caps are push on style and not sealed it still puffed a little smoke at idle out of the cap.



My original 352 finally called it quits so I replaced it with a 390.



That replacement 390 did not have the oil filler neck in the intake so I changed to chrome valve covers with holes (and some 312 valve cover stickers ). Bought one of the carb spacers that has PCV input. One hole in the valve covers I use as the oil fill and PCV filter cap the other I installed a PCV grommet and valve. Ran the PCV output to the carb spacer input.

Works nicely.



Eric

(sorry about the small pics - dropshots wont let me access my full size pics at the moment, Hopefully the description works. Never use dropshots for pics - they are the worst pile of you know what)

Think the 61-63 Tbird PCV carb spacer (or maybe later) had this style spacer which also has provision for coolant to keep the mixture at a constant temp but I didn't use that style.


I used this style but don't know what it came from. 428? 429? There are also 2 types of this style - draws from different holes so need to make sure your PCV draws from the primary not the secondary ports.

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Old 10-11-2015, 11:46 PM
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Default

If your rings are so badly worn that they produce copious amounts of stink, NO PCV system will work completely. You will need an engine overhaul.

There are two basic types of PCV, passive and active. Back in '61 nobody took crankcase ventilation seriously.

The first systems brought the 'draft tube' to the air cleaner for recycling. Of course, this was installed on new engines.

Y-Blocks depend on this crankcase 'smoke' to oil the timing chain set UNLESS you incorporated serious oil modifications in your overhaul.

Active PCV uses a special PCV Valve to stop carb backfire from injecting fuel mixture into your crankcase if your car backfires. This valve is a CHECK VALVE in one direction and it limits flow in the other direction. All this is accomplished by use of a 'prindle' and spring inside the valve. DO NOT pipe a hose from your intake to your crankcase without a PCV Valve.

There are many PCV systems on the internet. I suggest you learn what's best for your engine because there is a lot to this. - Dave
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Old 10-12-2015, 12:22 AM
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Default Thanks, men.

Hi Eric, Dave, Joe:

Thanks for the info. I think when I reseat and seal my intake manifold, I am going to install some form of PCV. The information provided is great, and I'll do some additional research.
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Old 10-12-2015, 10:41 PM
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Slightly better pics




Know you said you were going to check but if you go the carb spacer route check to see if you need a flat style (similar to the silver one) or an angled/tapered style like the brown one. The 58-60 Squarebird engine sits at an angle so you need the angled or tapered brown style.

This pic was during my engine swap and I was trying the flat (silver) style. Realized it wouldn't work after buying new longer carb studs etc. That's when I switched to the chrome valve covers and tapered carb spacer.


Good luck with your PCV project - your blue convertible looks sharp.

Eric
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