C1 61 RPO 242 (smog)

[Richard Geiger]

My car came from California with positive crankcase ventilation. When I acquired it (2nd owner)it had a breating oil filler cap and it had what looked like a piece of green garden hose hanging down into the transmission tunnel off the brass block behind the catalitic converter. My question is, did the 270 hp RPO 242 fitted corvette come from the factory with a breathing cap?
(it is a late '61- probably mid June). Also, would a correct RPO 242 have a plug in the brass block where the hose presently hangs into transmission well.
Nolan Adam says it is a rare option and it seems there isn't too much written detail about it. I'm thinking the original owner may have tried to bypass the converter by puttting on the hose and a breathing cap. Should I use a closed cap and get a plug for the 242 brass block or a breathing cap and leave the hose on, or is there another combination to keep it correct and original??
Thank you in advance

[Dennis C.]

Richard, If you have a '61 fitted w/a catalitic...

...converter from the factory, that would be one rare bird to say the least. The best way to approach this would be for you to acquire a 1961 AIM from the store here and study up a bit on that option. I would only add that the oil breather question is a valid issue as the AIM (IMHO) does not address that. I think it should have a breather type cap, and the rear view mirror instruction tag would lead you to believe that. A study of how those PCV systems work would certainly lead you to believe that. Suggest you check back after a little homework is completed. Best, Dennis

[Richard Geiger]

steel bit w/ AC on it...

Dennis,I'm no mechanic- I thought this thing was a cat.converter. In the back of block next to distributer is a domed cad plated thing. Attached to that is a round piece of steel with AC on it that sounds like it has a ball in it , and from that there is the brass block with the hose to back of front carb and a hose hanging into transmission well.

[Richard Geiger]

Re: steel bit w/ AC on it...

actually the brass comes before the steel thing with the ball in it. Also I looked at my AIM. Dare I say that it is not correct? The adapter ( cone shaped thing that bolts into block) has the brass tee # 444148 screwed into it then the valve assembly ( the thing I called a cat.conv.) with the hose (still with AC markings)that runs to the back of the front carb. As far as I know, this has never been messed with. It has the original gasket on the attaching bolt and under the adapter, the original valve assembly with AC ( part numbers too I think but I'll have to look again) and the original clamps and hose to the carb. Is it possible it was too difficult to fit the brass tee between the carbs ( one end of the tee would be virtually unusable in there anyway) so they started putting them onto the adapter in late cars or after the assembly manual was printed?

[Dave Suesz]

[Loren L.]

61 #5992 was a CA car that I had circa 1993

that had a system; just went back and looked for a picture - can't find one. Maybe the current owner of this original motor (base), PG car (with 891 distributor, no less) will check in - last I heard it was in NY.

[Dennis A.]

Re: steel bit w/ AC on it...

The California smog system (RPO-242)a adaptor was mounted on the intake manifold where the draft tube was removed. The pcv valve was screwed into an adaptor at the back of the carburetor. A large hose connected the valve to the fitting on the carb. Several changes were made during 1961, The "domed thing" could be the adaptor #5645826???

[Mike E.]

Re: 61 #5992 was a CA car that I had circa 1993

Richard--
Interesting questions you're asking--we're working on trying to answer some of this in anticipation of the next 61-62 judging manual. Several items:
1) The adapter you have on the top of the back of the block is extremely difficult to find. Don't let it out of your sight. It is different than the 62 and later adapter, which is much more common.
2) I'm guessing that your "catalytic convertor" (which is really the PCV valve) is a dark-colored valve with the AC part number on it, as you mentioned. It would be very helpful to have that part number--does it match the number in the AIM? If it does, that valve is also a very difficult piece to find. The cad-plated wrong-number replacement ones are on ebay all the time.
3) What is the configuration of the cap on the oil fill tube in front? Oil/oil? AC/Oil? Is it cad plated, chromed, or black painted? As the top bends down to the sides, is it pretty much a rounded 90degree bend, or is there a angular taper before it reaches the vertical sides?
I've just been doing some research on this and noting the differences between 61 and later--your question is quite timely.
Thanks,
Mike Ernst

[Richard Geiger]

PCV numbers

The PCV valve has the # 5645907 stamped in it. It also has a cirled AC with dash on each side and arrows on each side with 'to manifold' stamped in it too. I have taken digital photos. I hope to get someone to show me how to post them soon. On the back of the front carb is a brass block to accept the black AC hose.The AIM as I recall(it's down at my shed)only shows a sigle carb with the PVC valve screwed into the L shaped brass fitting on the carb end of the black hose.The brass T block with the PVC valve on my car would not fit between the two carbs.I'm suggesting that any dual carb car with RPO242 the factory must have mounted the PVC valve on the brass T in the back of the engine with the adapter out of the block. I'll try to get the photos up in the next 8-10 hrs.
I can't help with the oil filler cap because amongst the stupid things I've done in my life is losing- (probably thought it would not clean up any longer and thru it out) my original cap. I do clearly remember it was a breathing cap. It had holes around the bottom of it and one could see the metal strands inside the oil cap body. I cleaned it periodically with cleaning solvent but I can not recall the markings. I am certain it was black with a cleaning instruction lable on it. Photos soon

[Richard Geiger]

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[Richard Geiger]

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[Richard Geiger]

Re: PCV numbers *NM*

[Mike E.]

Re: PCV numbers

Don't worry about having thrown away the original cap--it wsn't original if it was black--originals were cad until early 62 when they went to flash chrome.

[Richard Geiger]

Re: PCV numbers

The fitting pointing down had a hose on it. The numbers match for the valve shown in AIM for rpo 579-582. There is no number on the valve in RPO 468-469 drawing. Most likely used the same PVC valve. So back to the original question, RPO 242 had to have a breathing cap to work correctly didn't it? Air would flow down the oil filler tube to crank case and the crank case air is sucked thru the PVC valve thru the black hose to carb and then combusted. If that is correct what do you make of the fitting pointing down that had a hose on it. It seems to me that would greatly reduce the suction on the crankcase. Maybe it was just to add some clean air to the crankcase air so that it combusts better.

[John H.]

Re: PCV numbers

Richard -

The photos don't show up here (just the "red x" box), but I did the right-click > properties > cut-and-paste trick, and they showed up, but there awfully tiny - couldn't make out any detail. I usually shoot at 640x480 and it makes an image just right for posting (doesn't require scrolling).