cylinder head oil drain back holes

I just changed heads from an edelbrock 6067 to a TFS street head.  I happened to notice that the oil drain back holes are smaller diameter on the TFS head.
So why is this?  Can you drill them larger?  Are there water passages close to this area?  What size is actually undersized to cause a problem with oil drain back?  Solid roller deal race only ofcourse I just don't want there to be an issue here with oil not getting back to the pan.

Thanks for comments

Before you go drilling the oil drainback holes larger on the TFS head, why don't you lay your head gasket on the head, properly registered with dowel pins. Notice the mis-alignment between the head gasket oil return holes verses, the holes in the head gaskets. Next carefully lay your head gasket on the block deck surface. Again note any mis-alignment issues. What you will find with all brands of heads is that their oil drain back holes need to be chamfered or beveled in one direction only,,, generally in an outward direction.

IMO it's better to work on the alignment of the oil drainback holes at the juncture of both the head and the blocks deck surfaces, than increasing the oil drainback's diameter.

Hope this helps,
Charlie

Thanks Charlie

Yes I have all of the oiling mods done to the block and have ran the combination with eddy heads for some time (532 with eddy head). I had previously ran a 521 with these TFS heads and was spinning bearings. I did all the oiling mods and ran longer (bushed lifter bores) before spinning but still had the issue. This engine had one of the newest forged cranks in it that was RPM I think and found that with their crank the crank journal had the lightening hole for the throw drilled too large allowing crank flex. I learned this off of this site. Can't remember where the post was but someone found this out on the dyno some time ago. So on the eddy headed engine I switched to an eagle crank bushed lifter bores and all oiling mods with oil accumulator and have had no issue since. I took the TFS heads and had them worked some time ago and figured I would switch back to the better head this winter along with a Ron's terminator kit. After bolting the heads on and the intake and the injection set-up I noticed the oil drain back hole difference in diameter. It just worried me that I could have been bringing one oiling issue back into the equation here.

Just so you remember me I used to run at Windy Hollow with two cars 78 Mustang II and 72 Maverick.....and when I moved you hand delivered my small block stuff to me at Bowlingreen that I had got done by Automotive machine and performance.

Thanks Adrian

good to hear from you Adrain.

Charlie

away wrote:  This engine had one of the newest forged cranks in it that was RPM I think and found that with their crank the crank journal had the lightening hole for the throw drilled too large allowing crank flex.  I learned this off of this site.  Can't remember where the post was but someone found this out on the dyno some time ago.  

Thanks Adrian  

Blake had this very problem years ago with an Eagle crankshaft.

As Charlie said, the hole ALIGNMENT is usually not a direct shot at the junctions. The cylinder head oil drain-back holes do not go to the valley but, directly to the crankcase and under the front cover.

Adrain,

Do you still have Andys Maverick? I met you at Windy Hollow.

I bought this Maverick out of cookeville tn around 2004-5? I believe the guy 's name was Andy lol. It was yellow at the time and all steel but back halved pretty good with a half ass cage with mustang II style front. Since then I stripped it all out built a 7.50 cert chassis off of the only good work in the car the back half. And did all the fiberglass and tin work as well. Now it is a complete different car! Now its getting the TFS head and Alky injection.

Yep Andy Lawson, he is actually from Manchester Tn.

rmcomprandy wrote:

away wrote:  This engine had one of the newest forged cranks in it that was RPM I think and found that with their crank the crank journal had the lightening hole for the throw drilled too large allowing crank flex.  I learned this off of this site.  Can't remember where the post was but someone found this out on the dyno some time ago.  

Thanks Adrian  

Blake had this very problem years ago with an Eagle crankshaft.

As Charlie said, the hole ALIGNMENT is usually not a direct shot at the junctions. The cylinder head oil drain-back holes do not go to the valley but, directly to the crankcase and under the front cover.

Yelp this was it I think but it was a cast eagle correct? I've went forged eagle.

Yes it was a cast Eagle 4.5 stroke............ Still have it. Its going in a 545 someday for the street.