Hi guys. Just wondering what size holes most are using in their oil spray bars? I will be using straight 40 weight oil. I also assume they really drip more than spray (which is all they really need to do). The spray bars from Indy come with pretty large holes and seem like they would flood the top of the engine with oil. I would rather keep more oil where it belongs if possible. Anyone done any experimenting with this?

I can pin guage my w8 covers for you tomorrow am, the rails are gun drilled, I'm thinking they are .010 to .015 without measuring them.

The spray bars from Indy usually come with a restrictor in the fitting that goes into the valve cover. It's normally a drilled out grub screw. It is more of a drip, as you state and we've run them on the 528, 572 and 655 with no issues.
HTH's

That would be helpful. Thanks.

Do you have any pictures of the "restrictor" that Indy uses? I have a set of their covers and there is no restrictor or provision for one present. Maybe my covers were converted to spray bar by someone else...

It might be a little difficult to photograph, the - 4AN T piece, that's fitted to the valve cover, is tapped to accept a drilled out grub screw. I'll try to photograph one tomorrow, there is a spare set on one of the shelves

Brian, the holes in mine are .020 for each valve, fed by a 1/8npt that screws into the vc rail. Not sure it will help you. Just what mine have.

Thanks. I think I will just do #77 drill and be done. Should be pretty close and I can always do the restrictor thing if I need to restrict more.

I think the smaller the hole the more likely it is to actually "spray". After all, it is a combination of the pressure and the orifice size that creates the spray. Too large of a hole and too little pressure (flow) will yield the drip some are experiencing. I'd be inclined to go with very small holes and no restrictors - let the holes be the restriction. Just my thoughts !!!

I agree with Stanton - the smaller hole at the spray gives the best effect, and the overall delivery rate should be controlled by a restrictor in the feed line to the cover: highest pressure in the small lines.
However: long history in motorcycle engines says that even an .020" hole will eventually clog with debris, shredded gasket, dust, etc. The hole must be larger if you never service/inspect it, like .030". A filter in the big line may cure this and allow smaller holes, but it's got to be pretty fine to help.
I have a feeling that the hole edge should remain sharp to disrupt the flow (rather than radiused or counter-bored).

Thanks Poly and Stanton. All good points and well noted items to observe.