400 Steam Holes
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
400 Steam Holes
OK...OK...I cracked under pressure. 
After some extensive reading coupled with Forum member suggestions I decided to steam hole my 406 build. Way too many builders agree for me take a chance.
I pulled 6 of the 12 plugs from the block tonight and will finish the rest tomorow. My heads go in for drilling on Thursday.
With a shop vac hose right next to the plug, I center punched, then drilled a hole smaller than the plug. Tapped the hole for 6-32, threaded a stainless screw in....then yanked! Tedious...but easy. Gonna flush the block too when finished.
Eddie
After some extensive reading coupled with Forum member suggestions I decided to steam hole my 406 build. Way too many builders agree for me take a chance. I pulled 6 of the 12 plugs from the block tonight and will finish the rest tomorow. My heads go in for drilling on Thursday.
With a shop vac hose right next to the plug, I center punched, then drilled a hole smaller than the plug. Tapped the hole for 6-32, threaded a stainless screw in....then yanked! Tedious...but easy. Gonna flush the block too when finished.
Eddie
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
Well, there you go!!
When it's all back together, you'll be able to sleep at night...
Edit: Here's a link of a sample...
Drill Steam Holes
When it's all back together, you'll be able to sleep at night...
Edit: Here's a link of a sample...
Drill Steam Holes
Last edited by Z-man; Aug 15, 2006 at 11:53 PM.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
6 of 12 plugs? Shop Vac? Center Punch? Tapping? Stainless screws? Coolant flush?
What in the world are you speaking of?
If you've chosen to drill steam holes, they're drilled in to your heads. Your machine shop will have the specs.
Your head gaskets (for SB-400) and block already have the holes.
Or am I missing something?
What in the world are you speaking of?
If you've chosen to drill steam holes, they're drilled in to your heads. Your machine shop will have the specs.
Your head gaskets (for SB-400) and block already have the holes.
Or am I missing something?
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Originally Posted by 73, Dark Blue 454
6 of 12 plugs? Shop Vac? Center Punch? Tapping? Stainless screws? Coolant flush?
What in the world are you speaking of?
If you've chosen to drill steam holes, they're drilled in to your heads. Your machine shop will have the specs.
Your head gaskets (for SB-400) and block already have the holes.
Or am I missing something?
What in the world are you speaking of?
If you've chosen to drill steam holes, they're drilled in to your heads. Your machine shop will have the specs.
Your head gaskets (for SB-400) and block already have the holes.
Or am I missing something?
Burning Brakes
Joined: Aug 2004
Posts: 971
Likes: 7
From: roanoke va
I'am glad you decided to drill the steam holes. The reason the holes are there in the first place is because the 400 cly. walls are together between the cly. walls and it needs to be drilled so coolant will flow.
And it also helps to remove any air pockets. The 400 is the only small block with this setup. All other small block have air space between cly's.
and that is why they do not require any steam holes.
And it also helps to remove any air pockets. The 400 is the only small block with this setup. All other small block have air space between cly's.
and that is why they do not require any steam holes.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Good choice! They were put there for a reason on the stock 400's. If they weren't neccesary GM wouldn't have done it on the original 400's and they were low horsepower usually 2 bbl. motors. A high performance engine requires better cooling and generate more heat than stock. Nothing to gain and much to lose by plugging them. 
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Ahhh,..I didn't know there was a first chapter.
Yes,..drill them! The engineers at Chevy thought they were necessary and that's all I need to know.
And don't swayed by the folks with this line,.."I don't have steam holes and my engine chugs along at 180* all day long". Yes, the temp sender could report 180* but the localized boiling and resulting steam is undetected. Meanwhile, Bubba can't figure out why his 400's don't last,..cooked oil, valves, rings, cracked heads, block, etc.
Yes,..drill them! The engineers at Chevy thought they were necessary and that's all I need to know.
And don't swayed by the folks with this line,.."I don't have steam holes and my engine chugs along at 180* all day long". Yes, the temp sender could report 180* but the localized boiling and resulting steam is undetected. Meanwhile, Bubba can't figure out why his 400's don't last,..cooked oil, valves, rings, cracked heads, block, etc.
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