C1 61 RPO 242 (smog)

[Dave Suesz]

[Michael H.]

Richard Geiger's Picture *NM*

[John H.]

Re: Richard Geiger's Picture

The illustration at the top of page 359 in Noland's book shows the RPO 242 installation on the 1961 2x4 engines, with the PCV valve attached to the adapter at the block vent, and a hose from there to a 90* fitting in the rear of the front (secondary) carburetor. The setup in the posted photo appears to be a previous owner-inspired modification of some sort.

[Richard Geiger]

Re:oil cap and PCV numbers, Nolan Adams said

on page 372 photo of RPO 468 or 469 engine of 1961," the chrome oil filler cap is only incorrect item." I bought this car in 1968. I am the second owner and I know it had a black breathing cap. Nolan Adams also said on page 373 that RPO 468 used a closed oil filler cap, part # 1552719, designed to prevent oil vapor carryover during high-speed operation. The problem is, with rpo 242 crankcase ventilation you really need a breathing cap to introduce air into the crank case.
I've done a little reading on this PVC valve and system.The system sucks crankcase vapors into the intake manifold to be burned in the combustion chambers.The flow of the vapors is controlled by the ventilator valve (PVC). The valve is actuated by engine vacuum working against spring tension. The high vacuum at engine idle provides minimum ventilation; low vacuum at road speeds provides maximum ventilation.
I realise it is possible that the original owner modified the venting system by installing the brass block at the adapter in order to reduce the amount of crankcase air going to combustion or to add cooler air to crankcase vapor. But, it is also possible that this brass T was factory installed. It looks very much like part # 444148 Tee in the AIM and in the Nolan Adams picture top right on page 359 that was used with PCV on RPO 579-582.
I still believe this is original and I plan to put it back like it was when I aquired the car in 1968 unless anyone has some conclusive evidence to the contrary. I think the factory must have changed to the base cap ( breathing ) when they put on RPO 242. A BLACK breathing cap. I can not explain the T with the hose running into trany tunnel.I don't know if it would totally defeat the PVC value operation or just mix and dillute or cool the air drawn through the PCV valve to combustion. I would appreciate any theories on this.

[Mike E.]

Re:oil cap and PCV numbers, Nolan Adams said

Richard--
Page 56--paragraph 1, 61-62 judging manual indicates that all 61 oil filler caps, both breather and non-breather, were cad plated, as were early 62's until they went to chrome on both later in 62.
All they had at St. Louis for the assembly line were cad plated caps in 1961. I wouldn't hang my hat on a black one being original just because that's wat was on it when you bought the car--especially when there has been a bit of other changing on the PCV system.
The burden of proof lies on your ability to demonstrate that it came on the car. Road test pics of 61's have cad plated caps as well. We haven't been studying these cars over the last 30 years irresponsibly---
Mike

[Richard Geiger]

breathing or not

Mike, I guess I'm coming around- I think I'll screw the PVC into the adapter like the AIM shows and keep the brass block in my spare parts for old times sake. What do you think regarding which type cad plated cap to use. Rpo 468 apparently used a closed cap but doesn't RPO242 Positive Crankcase Ventalation need a breathing cap to operate correctly? In other words do you think the factory may have put a breathing cap on a Rpo242 equiped 270hp? Thanks, Richard

[Mike E.]

Re: breathing or not

The few cars that I really believe to be original have had non-vented caps--doesn't make a lot of sense to me--but the one that I have that has a repro non-vented cap has no breathing problems.
Mike