While you got a lot of pictures - no one has said where.  Yes, down the push rod hole.

Well Paul, if you had read the (my) entire post, you would have read where I stated down the push-rod hole(s).

In fact, when properly assembled, their discharge direction has no other routing besides the push-rod hole(s). Here is another picture as you seem to enjoy them so much -

Oil Supply Return Tube  - B5A 6588-A - Supt Brkt - 6575)

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.030" seems to stick in mind.

From my reading, it seems to me the accepted wisdom is the main & cam bearing clearances in large part determine the optimum oil viscosity. I noticed it is common for many people to run high viscosity oils like 20w50 in old motors. This makes some sense in high mileage engines, or maybe racing, but after installing an oil pressure gauge I'm not sure this is necessarily sound thinking in rebuilt, re-clearanced engines or street engines. Oil flow is what we're concerned with here, especially with the Y-blocks and rocker/rocker shafts.

Assuming fresh bearing clearances on the tight side it seems to me with modern synthetics even a 5w30 would be an excellent flowing oil particularly during cold startups where most wear occurs.

So long as there is sufficient hot oil pressure with 5w30, what am I missing? Leave aside for the moment the Zinc or Zddp issue. Synthetics have good film strength and excellent cold temperature pumpability and don't break down under high temperatures. My '64 operator's manual specifies 10w30 "in practically all cases".

Ted, I've read archived posts where you recommend motor oil with a "40" in the designation, is this based on elevated zinc levels in higher viscosity oils?

Here's where I'm goin' with this. With a fresh oil pump my stock Y showed 60 PSI HOT at 2000 RPM and Valvoline 10w40, the spec is 35-55, seems to me a lighter viscosity would actually be preferable in terms of flow; again this question would be without regard to zinc levels.

It is difficult to find an oil that meets all the criteria - and doesn't cost $16 a quart! I remember when we just grabbed a can of Pennzoil in the yellow can and didn't even think about it.

I got the .030" oil grove depth figure from Mummert. He says he uses that depth for his own cams.  Rocker oiling is an issue with YBlocks and I assumed he knows them as well as anyone.  Except for cutting the grove to .030", my engine has stock oil supply and return.  My understanding is the tubes are there to oil the timing chain and the distributor/cam gear. 

I think using heavy oil in a YBlock is a bad idea.  If your engine is so worn you need syrup for oil, you probably should fix the problem.  I have no opinion on synthetic oil.  Modern engines have much tighter clearances. YBlocks are not watches. I use Valvoline 10/30W Racing oil in my engines. It's made for flat tappet engines.  Everyone has a different opinion on this. 

I'm sure increasing the depth would help but I built my engine with an Isky cam before having this info. I'm running 10-30 and have no problem with enough oil to the rockers. My other Y has a stock 57 cam and oils fine, I don't know what the depth is on the OEM cam..

A note on top oiling.  According to John at Mummert Machine, all available Y-Block cam blanks have insufficient depth oilling grooves & his shop re grooves all of them. However, I don't recall him suppling a correct groove depth figure?  Also, Ted @ Eaton Ballancing, cuts a groove in the block of all his rebuilds to guarantee proper top end oil feed..


Paul

Keep in mind that I’m in that part of Texas where the number of days exceeds 100°F for over a month at a time and in a row.  There's usually a slight break into the nineties and then back into the hundreds again.  And the winters are extremely mild with days being less than 32°F rare.  For the more mild climates, I will recommend 5W-30 or 10W-30 weight oil but engine bearing clearances are still the final determining factor for the oil viscosity.  I still have a '55 Ford that has been on TropArctic 10W-40 since new and with over a quarter million miles on it now, still runs like a top with good oil pressure.  That car was purchased in the later part of 1954 making it an early production model.  I looked at the crankshaft when it had 113K miles and it still had the original crankshaft grinding chatter marks on it from the factory and the bearings looked flawless.  I can't argue with what works.

Lorena, Texas (South of Waco)

THE WHICH OIL QUESTION ?????????
Go to Walmart and get the Walmart Brand Super Tech SAE 15W-40 oil for diesel engines.
Plenty of ZINC at a decent price. Comes in quarts and 2 gallon containers.
Works for me,
Tim
Mud Key, FL 33706

That might be an excellent choice depending on bearing clearances. I'd like to keep oil pressure on mine in "the zone" so to speak. I ran 10w40 and it read 5 pounds over spec hot. Spec is 35-55 psi at 2000 RPM, right? Using a large face mechanical gauge. I suppose accuracy might be +/- 5 I dunno.

Since the owners manual says 10w30 is adequate in "practically all cases" and figure oil pressure will be at least somewhat compared with 10w40. The point is to have good flow, after all and a thinner oil should flow better? See where I'm goin' with that?

re using diesel engine  oil  is not a good idea,modern diesel engines are all roller cams,and most will state  not for gas engines especially  flat tappet cams.when i worked for the cat dealer we had a letter warning about usering rotela t on gas engines with  flat tappet cams. as far as keeping oil bleed tubes insures rockers father from the oil in holes  suffer from low oil flows sluge will form.. withe biger grove in cam and return blocked  all rockers ,and push rides get great oiling,in fact running with covers of the engine rurning  rotating push rides spireles the oil down all pushrods. with 289 valveseals and heads with decent valve to guide clearance  ther wont be any smoke or higher  oil consumption.. just try running a 289/302 with covers of  you will have oil all over the place
 of coarse ther will be lots of different comments . most ys that have camisues  are from poor oil flow to the top end .or the new issue of diesel eng oil designed for modern emission sensitive roller cam engines

I agree, no diesel oil in a Y Block.  Wrong formula, and will have long term problems.  Short term might be ok, but read the warnings, and use conventional oil, or synthetic designed for gasoline engines.  Joe-JDC

JDC