Why???
Senior Member since 1492
Joined: Aug 2000
Posts: 87,880
Likes: 156
From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Don't know why they're plugged. There were 2 on my BB too.
I used these with a 0.024 hole (I think that's the size) drilled in them to vent.
I used these with a 0.024 hole (I think that's the size) drilled in them to vent.
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Originally Posted by evalu8r
That's what feeds oil to the lifters and cam. Consider it an main artery from the heart of the beast.
Chris
Chris
Eddie
Pro
Joined: Mar 2002
Posts: 511
Likes: 0
From: St. Louis MO
Those are the main oil galleys. The main reason to have them drilled and tapped for pipe plugs is insurance. Normally you would stick a pressed(more like hammered in) plug simillar to a freeze plug. Now say you have these pressed in plugs and you stick in a high volume, HIGH pressure oil pump and your good old boy machinist forgot his loctite that day and was a little tippsy from the night before and he wasn't totally level with the world and one of those hammered in plugs was a little cooked and not tight in the hole. Few days on the road and bam, there goes your oil pressure and well your engine.
Put in the pipe plugs, it doesn't cost that much and its good insurance. Aslo when you get your block back and your cleaning everything with a tooth brush, pipe cleaners and hot soap and water you'll be able to take those plugs in and out to clean up those main galleys.
Be careful when you put them back in that you don't block the first cam bearings oil hole. that would eat up that cam bearing quick if you block its oil passage.
Put in the pipe plugs, it doesn't cost that much and its good insurance. Aslo when you get your block back and your cleaning everything with a tooth brush, pipe cleaners and hot soap and water you'll be able to take those plugs in and out to clean up those main galleys.
Be careful when you put them back in that you don't block the first cam bearings oil hole. that would eat up that cam bearing quick if you block its oil passage.
Burning Brakes
Joined: Oct 2002
Posts: 1,040
Likes: 109
Originally Posted by Edzred72
What is the purpose of having these holes above the cam bearing tapped and plugged on a 400 SB? When I get my block machined...should I have the shop do this???
Eddie
Eddie
to keep the plugs from coming loose is the reason they are tapped
you can do this if you can usa a tap
and the small holes provide oil to the back of the cam gear
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Thanks for the replies guys. Maybe I didn't word my question properly. You all graciously answered why they are tapped for screw in plugs. (instead of press fit plugs) I'd like to know why are these holes plugged? Does plugging them re-direct oil flow? What happens if I DON'T plug them?
Thanks for all the replies
Eddie
Thanks for all the replies
Eddie
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Advanced
Joined: Aug 2005
Posts: 59
Likes: 5
If they are not plugged you will have no oil pressure. The block was drilled or cast with the oil passages running through the block so that the lifters would oil (under pressure), but you just can't leave that big of a hole in the oil passages and expect to have any oil pressure.
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Originally Posted by COPO TOM
If they are not plugged you will have no oil pressure. The block was drilled or cast with the oil passages running through the block so that the lifters would oil (under pressure), but you just can't leave that big of a hole in the oil passages and expect to have any oil pressure.
Race Director
Joined: Apr 2000
Posts: 17,650
Likes: 190
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
They are in the back too, that is where you put oil restrictors if so desired, I have them in my 406 to restrict flow to the upper valve train and keep more oil around my solid roller. Seems to be working my lifters look brand new after 10,000 miles 
Safety Car
Joined: Jun 2002
Posts: 4,135
Likes: 1
Originally Posted by Edzred72
Thank you Tom
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
Likes: 384
From: South of giving a damn
St. Jude Donor '11, '17
The holes have to be there for casting, where else is the sand going to go? It's the same if the holes are drilled in the rough casting, you can't drill without leaving a hole. Having the hole going through both ends gives the factory a visual check that the galley holes are drilled in the correct spot. Then they get plug so the system will pressure up.