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Old 02-12-2009, 11:07 AM   #1
Large_911
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Default Early Olds -- PCV Valve Conversion?

I have a 57 Olds 371 and I am thinking about getting rid of the road draft tube, and going w/ a PCV valve. I was thinking of a couple options and I wanted to bounce it off of everyone:

1) Machine a plate that bolts to the block where the existing road draft tube was and install the PCV valve there. I assuming I would still want to use the baffle that is on the opposite side of the road draft tube under the intake.

2) Machine a plate and completely block off the hole for the existing road draft tube and just pull from the valve cover.

Also, I have a buddy w/ a 324 and wants to switch to a PCV valve too; does anyone know if the bolt spacing and hole size in the back of the block is the same for the 324 & 371? If so, I can just make two plates at once.

Any comments & suggestions would be greatly appreciated! Thanks in advance.

Chris
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Old 02-12-2009, 11:14 AM   #2
Mr48chev
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Default Re: Early Olds -- PCV Valve Conversion?

There used to be retrofit kits that just replaced the draft tube. I think you have the right idea with making the plate or just modify the draft tube to be able to fit a pcv valve in it. I've seen that done a lot in the past.
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Old 02-12-2009, 11:23 AM   #3
Truckedup
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Default Re: Early Olds -- PCV Valve Conversion?

I've retfitted PCV systems on several vintage engines, I think it's worth the trouble.On a V-8 I take the easy route,drill the valve covers for a breather and PCV like a later Chevy V-8.If you have nice valvecovers you may not want to do it this way
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Old 02-12-2009, 01:57 PM   #4
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Default Re: Early Olds -- PCV Valve Conversion?

I was looking at my 324 the other day and noticed it seemed to be 'breathing' a bit heavy from the RDT. I was wondering about doing the same thing, as I have done the conversion on my flathead. I wondered about two ways to do it, there are more but I don't want to drill the valve covers.

1st was to measure the RDT hole and hopefully find a freeze plug that size, then drill and tap the freeze plug for a PCV valve run the hose to a vacuum port on the adaptor for the holley.

2nd was a sort of similar thing as what I did with my flathead. that would be cut the RDT about 6" long from the block that is, find a freeze plug that is roughly the right size and then weld/silastic to the open end of the RDT to completely seal it, then get a piece of flat bar and weld to the side of what is left of the RDT then drill and tap that for the PCV valve and run hose to the carb.

I have done this second one with the flatheads, as on the 8BA motors they have a tube that rises from the sump into the valley, you just cap the open end, weld on a piece of flat bar 1/4" thick will do and then drill and tap for PCV, the beauty with the flathead though is then you drill and tap into the underside of your intake so it all remains hidden in the valley.

The other reason that I wouldn't go the way of the valve cover PCV is that looking at the manual on how the gases flow through the motor, it would be best to be drawing them from the RDT area, as the flow is all directed to that exit, if you just took the PCV from one valve cover I'm not sure if you would be collecting all the gases? and getting the effect of cleaning the engine which is what your chasing.

hope this helps, if you dont quite get what I'm saying let me know as I can take photos of what I'm talking about to clarify.
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Old 02-12-2009, 02:10 PM   #5
droplord49
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Default Re: Early Olds -- PCV Valve Conversion?

On my 324, I went autozone, found a PCV grommet that fit in the road draft tube hole and PCV vavle both hanging on the rack next to the oil filters. Went home, stuck the grommet and valve in the rdt hole, ran the hose to my carb and took her for a spin. Took about 5 minutes and works great(no more smelling like engine breath).
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Old 02-12-2009, 02:21 PM   #6
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Default Re: Early Olds -- PCV Valve Conversion?

Droplord's set up probably looks something like this. used the oldest Olds pvc I could find.
Yes, keep the baffle that's inside the valley pan.
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Last edited by Bobert; 02-12-2009 at 03:34 PM. Reason: detail
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Old 02-12-2009, 02:26 PM   #7
3x2rocket
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Default Re: Early Olds -- PCV Valve Conversion?

Mine worked out exactly like droplord and Bobert's, I had a pcv and grommet laying around and the first one I tried worked perfectly, looks identical to Bobert's pics, 5 minutes.
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Old 02-12-2009, 03:47 PM   #8
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Default Re: Early Olds -- PCV Valve Conversion?

A simple pcv system. Using the draft tube base where it bolts to the block, weld a 1/2" nipple to it in place of the tube that goes down. Or if you want to maintain the look, plug the tube and add the nipple on the other side. Run a line to the inside of the airfilter in the base of the aircleaner. The inlet is the same as it always was, a filtered valve cover or filler tube breather. Doesn't appreciably upset the mixture and keeps the carb shafts lubricated.
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Old 02-12-2009, 03:48 PM   #9
Large_911
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Default Re: Early Olds -- PCV Valve Conversion?

Thanks for the input everyone -- lots of good info! It looks like it may be an easier task then I thought.
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Old 04-26-2010, 05:38 AM   #10
Large_911
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Default Re: Early Olds -- PCV Valve Conversion?

I am going to try to tackle this project this weekend. Would anyone happen to know offhand the ID of the RDT? I like the idea of putting a freeze plug in there, then drilling out for a grommet, or just going with a big grommet to fit in there. Thanks.
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Old 04-26-2010, 07:09 AM   #11
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Default Re: Early Olds -- PCV Valve Conversion?

Quote:
Originally Posted by Large_911 View Post
I am going to try to tackle this project this weekend. Would anyone happen to know offhand the ID of the RDT? I like the idea of putting a freeze plug in there, then drilling out for a grommet, or just going with a big grommet to fit in there. Thanks.

For my caddy, I took the road draft tube that I cut off after the elbow, took it up to autozone or whatever, and got a pack of assorted PCV grommets...Had to buy the whole pack to get the exact one I wanted, (about 5 dollars) but it was a perfect fit. Put a light smear of black RTV on,and plugged er in.

NAPA also carries a ton of different sizes of grommets, that you can view online.

If memory serves the grommet it was 1.25" OD...not sure this applies to your engine, but was a super easy task...
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Old 06-15-2011, 09:14 AM   #12
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Default Re: Early Olds -- PCV Valve Conversion?

Anyone know the rdt diameter on a 303 olds in a 53? Looking to do a pcv conversion tomorrow. And I can just run tue line from the pcv valve intothe airfilter or carb?
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Old 06-15-2011, 10:11 AM   #13
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Default Re: Early Olds -- PCV Valve Conversion?

Quote:
Originally Posted by Large_911 View Post
I have a 57 Olds 371 and I am thinking about getting rid of the road draft tube, and going w/ a PCV valve. I was thinking of a couple options and I wanted to bounce it off of everyone:

1) Machine a plate that bolts to the block where the existing road draft tube was and install the PCV valve there. I assuming I would still want to use the baffle that is on the opposite side of the road draft tube under the intake.

2) Machine a plate and completely block off the hole for the existing road draft tube and just pull from the valve cover.

Also, I have a buddy w/ a 324 and wants to switch to a PCV valve too; does anyone know if the bolt spacing and hole size in the back of the block is the same for the 324 & 371? If so, I can just make two plates at once.

Any comments & suggestions would be greatly appreciated! Thanks in advance.

Chris
I'll be modifying the road draft tube on my 394 along the lines of what you are considering. Yes you want to use the baffle.

Another easy approach is to block it off and poke a hole in your valley pan. You'll still need a baffle and I think that the road draft tube is a good way to go with it.
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Old 09-19-2012, 11:16 AM   #14
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Default Re: Early Olds -- PCV Valve Conversion?

Gonna try it today on my 303 Olds, but man, the bolts on that road draft tube look like a real pisser to get at. Since I don't have a vacuum port in the carb, I think I'll run it into the air cleaner and see how that works.
Tom
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Old 09-23-2012, 08:45 AM   #15
Large_911
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Default Re: Early Olds -- PCV Valve Conversion?

Quote:
Originally Posted by Terrible Tom View Post
Gonna try it today on my 303 Olds, but man, the bolts on that road draft tube look like a real pisser to get at. Since I don't have a vacuum port in the carb, I think I'll run it into the air cleaner and see how that works.
Tom
Hi Tom - Any luck?
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Old 09-23-2012, 12:14 PM   #16
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Default Re: Early Olds -- PCV Valve Conversion?

No, haven't got to it yet. I have to do all my work outside and the weather wasn't cooperating last week. Maybe this week.
Tom
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Old 09-23-2012, 12:25 PM   #17
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Default Re: Early Olds -- PCV Valve Conversion?

Quote:
Originally Posted by Terrible Tom View Post
Gonna try it today on my 303 Olds, but man, the bolts on that road draft tube look like a real pisser to get at. Since I don't have a vacuum port in the carb, I think I'll run it into the air cleaner and see how that works.
Tom
Running it into the air cleaner does not pull enough vacuum to operate the PCV correctly. It must get manifold vacuum. The hose that goes to the air cleaner on newer cars is for the intake of clean air into the crankcase.
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Old 09-23-2012, 12:35 PM   #18
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Default Re: Early Olds -- PCV Valve Conversion?

I was wondering about that. How about tapping into the manifold then?
Tom
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Old 09-24-2012, 05:48 PM   #19
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Default Re: Early Olds -- PCV Valve Conversion?

Can anyone show me where a good spot to tap in would be?
Tom
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Old 09-24-2012, 06:09 PM   #20
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Default Re: Early Olds -- PCV Valve Conversion?

Behind the carb would probably work. See if it goes into both sides of the plenum. You want to pull vacuum from both sides of the carb.
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