Blocking center oil returns on small block
03-18-2018 | 06:20 AM
#1
Thread Starter
Registered
Joined: Sep 2009
Posts: 419
Likes: 14
From: Lake Winnipesaukee, NH
Blocking center oil returns on small block
Chevydiy has this tip "If a roller cam is used, it’s practical and desirable to plug the oil return holes at the center of the lifter valley. These holes usually serve to splash oil onto the camshaft for lobe lubrication, but with a roller follower this is unnecessary.
If a flat-tappet camshaft is used, it’s possible to plug or put stand-off tubes in these holes, but only if relatively short mileages are intended. If you intend to use a flat-tappet cam on the street, don’t plug them—it will lead to increased cam wear."
Since I have some miles long runs I worry that if I keep my rpms up for a long time I may empty my pan. My engine is full roller with short travel lifters. I realize that If I was running solids I could keep even more oil in the bottom end, but I think I'd be doing my engine a favor to let the oil go down the rear and front as it returns to the pan thereby missing the cam and the crank on it's way down. The thinking is it reduces the churning that happens and the oil that stays up off the pan.
If I had the engine out I'd probably do a large pan, but it's not happening this spring unless I get a surprise or a problem.
My rings are marine gapped, so that's done. And I don't see anything else to keep me off the upper rpms except safety and speed limits. I have factory Mercruiser ignition so I expect it to limit somewhere around 5100 to 5200 rpm.
I only get a couple of chances a month to wring it out. The lake I'm on has a speed limit. So I have to pick my times.
If a flat-tappet camshaft is used, it’s possible to plug or put stand-off tubes in these holes, but only if relatively short mileages are intended. If you intend to use a flat-tappet cam on the street, don’t plug them—it will lead to increased cam wear."
Since I have some miles long runs I worry that if I keep my rpms up for a long time I may empty my pan. My engine is full roller with short travel lifters. I realize that If I was running solids I could keep even more oil in the bottom end, but I think I'd be doing my engine a favor to let the oil go down the rear and front as it returns to the pan thereby missing the cam and the crank on it's way down. The thinking is it reduces the churning that happens and the oil that stays up off the pan.
If I had the engine out I'd probably do a large pan, but it's not happening this spring unless I get a surprise or a problem.
My rings are marine gapped, so that's done. And I don't see anything else to keep me off the upper rpms except safety and speed limits. I have factory Mercruiser ignition so I expect it to limit somewhere around 5100 to 5200 rpm.
I only get a couple of chances a month to wring it out. The lake I'm on has a speed limit. So I have to pick my times.
03-18-2018 | 11:52 AM
#3
Registered
Joined: Feb 2009
Posts: 8,356
Likes: 1,515
From: NW Michigan
Honestly I wouldn't worry about tapping and plugging them. Sure their not needed but it also reduces ventilation and drain back. I've seen some that where plugged years ago and both front and rear drain backs were ground, tapered and polished to speed up draining. Are there holes or stand pipes. What year is the block. I highly doubt you'd have an issue though in regards to your oil pump sucking air if you do plug them but with your application a little extra oil draining onto your crank isn't going to make a difference. I'd prefer the stand pipes over plugging.
