anybody here have any problems with running 20w50 oil??
ive been told that the oil jackets in aluminum heads are smaller than iron heads? is it true or no? My reason for using 20w50 is my buddy has a 1993 Z71 with a 350 and its got 175,xxx miles on it and it doesnt leak an ounce of oil...plus i would like to bump up the oil pressure since i put the hot cam in, with out gettin a higher volume oil pump. Im fixin to put an engine oil cooler on my motor tomorrow and change my intake manifold gaskets and oil.

 

This can be a difficult question to answer and is almost always subjective.
But the main reason for using a heavier weight oil is because of greater than normal bearing clearences (as in a pure racing engine) or excessive ware. It's logical to assume that an engine with 175,000 will have a good deal of ware, but this may not be the case. The engine may be just fine. The only way to check without a tear down is by compairing oil pressure from when it was new (if you can remember) or with someone elses car. The problem with this is that all engines very some what and may confuse the matter even further.
So, what I would do is put the factory recommended oil in the car and see if the oil pressure is adequate at both idle and WOT. If it is a little low then go up on the weight, maybe a 10W40 and check it again, etc. 20W50 is relatively heavy and can rob you of power. I would not use it unless needed.
As far as the heads, there are no oil jackets (only water jackets), oil channels, or passages, except for the drain back holes. The only oil the heads see is that which is sprayed around under the valve cover. So there is no difference in this respect between aluminum and iron heads.

 

i see, yea when my friend was like the aluminum heads have smaller oil jackets, i just thought what the hell is this guy talking about? oil comes through the pushrods and rocker arms and thats how most of the oil gets to the heads... well my motor has 111,000 on it and the oil pressure is about 19-20 at idle and around 40-45 just driving around town. there is a guy in my car club with a all bore 382 LS1 SS and he uses 20w50 in his car he said with no problems...im going to try it. Im driving home to Chicago from JacksonvilleNAS soon. and that means ill be pushing 2000+ rpm for easily 6 hours at a time, its not a lot, its just a long time.

 

A 381 is a custom built motor and his builder could have used looser tolerances and that is why the thick oil, that is not a good indication of wether it will work or not in a stock engine. I am using a 5w40 synthetic in an engine under 100K and it quieted down the roller rockers a bit, but don't think I would go thicker unless it was rebuilt and that is what the builder wanted.

 

Your oil pressures look completely normal. But using the 20W50 is not going to hurt anything either. At most you may loose a couple of hp. So if it makes you feel better?

One suggestion. There are some really good synthetics in the 15W50 range. Might even be a 10w50 out there some where.

You probably know this but before there were 6 speeds running highway speeds at 3,500 to over 4,000 was common place.

Have a good trip.

 

Why an oil cooler? Frankly, I'd just stick with 10W-30 synthetic and forget the oil cooler.

Sounds like you pressure is fine. If it aint broke...JMHO