Old Timer Story...Pinch The Oil Line Under The Rocker Cover in 235?

I was relating my saga to an old timer yesterday. I was telling him about getting an oil fouled plug on my 261 and needing to do a dry and wet compression check to see what that suggests is happening. So he says if the pressure doesn't go up on the wet test to pinch off the oil line under the rocker cover. He says it was common place back in the day that too much oil would be delivered and get into the combustion chamber and would oil foul the middle plugs. He says pinching that line a little solved a lot of that.

Starving the engine of it's oil by reducing the flow of oil to the rockers sounds like a recipe for disaster to me. Have any of you ever heard of this tip/trick/engine destruction mod? Just curious.

 

Don't know if it does more harm than good, but I've dis***embled a few 235s over the years that had a pinched line.

 

I think if you just slightly restricting the flow you should be OK just don't go crazy. I have seen a couple of 235's with pinched oil lines never thought about it till now on why though...

 

So, maybe he's right at least in the fact that it was a common mod. I've been searching stovebolt forums and found other cases of the same thing.

Here's my details if it matters. 1958 261 with 235 #848 head. I'm getting oil fouled plugs in number 2. I leak a bit of oil (not a lot), can't tell if it's coming from the side cover or head gasket. I know it's not the valve cover, so I'm going to replace the side cover gasket because it's cheap and "just in case". I'm doing a dry and wet compression check later today. I guess I should pull the valve cover to see if the line is already pinched or not for curiousity's sake.

 

Used car lot trick. Just like sawdust in the rear and leather belt mains.

I suppose it would wotk but if you are getting oil in your cylinder from the heads a set of valve seals may be in order.

 

Yeah, hopefully that's what the compression check will reveal.

 

I've pulled about four 235's apart, and they all had pinched oil lines. I thought it was a factory deal!

 

Later 235s had some changes to get oil to the top.
The blocks had the oil orifice to the top drilled out larger and the rockers were also redesigned with offset groves at the oil supply shafts and a pinched oil tube, to retain the higher pressure.

Some engines today may have been ***embled with blocks, heads and rockers and oiler tubes that don't match, resulting in either too little or too much oil flow at the top.
It doesn't take much, just sufficient minimal flow to keep the rockers oiled at the shaft and both ends.
Too much oil pressure loss at the top is obviously not good for the moving parts in the block, apart from oil getting past the valves.

 

My guess a valve guide or ring issue. Your comp. test should point you to which.

 

For the record, I have really good oil pressure at the gauge. Well above half at start up and stays at or above half during driving including idling at a light.

 

I figured that, just waiting to find out. The old timer's story intrigued me though so I thought I'd ask if anybody had heard of it and the hows and whys.

 

Any more info from the afternoon crowd?

 

I thought the fitting in the oil line behind the side cover, going from the rear of the block to the head, was already a flow restricting type fitting? If it wasn't the oil flow to the head would be at full pressure. No?
Dom

 

They did away with the oil tube that was inside the lifter cover in '58 and the blocks from that time on had oil p***ages cast in from both the front and the rear cam bearings and then up to the head. The '58 and up shop manuals mention the pinched tube on the rocker arms to restrict the oil flow on these engines.

 

Thanks for that! Any way you can scan what it says in the shop manual? Or maybe post it? Thanks a ton.



By the way, cylinder #2 was down a little at 110. 1,3,4,5,&6 were all 135 and 140. Adding a little oil in the spark plug hole got #2 up to 120. So probably worn rings there. 250 miles since changing the fouled plug and the new one looks a little black but not oily. That plug was colder but was all I could dig up at the time. I swapped in a proper plug tonight. Still runs really good.

 

So as it turns out, this doesn't really apply in my case. But I'm still curious to hear more from those in the know.

 

I hope this link works - this is from the '59 Truck supplement. The info in question is in the section ***led "Rocker Shaft ***embly Full Pressure Oiling"

http://chevy.oldcarmanualproject.com/shop/1959trucksup/59ctsms0803.html

 

Thanks for that waldo!

 

I rebuilt the 235 in my '57 chevy. The reason the oil line is crimped is because the oil was designed to flow up through the rocker arm shaft and out to the rocker arms, any excessive oil would drain around through the extra line. Because of the path of least resistance, when sludge begins to build up over time, the oil tends to dump out rather than go to the rockers. Crimping the line ensures the oil is directed properly to the rockers. Without this modification, rockers are often not oiled properly.

brandon

 

Thanks for that brandon.