SBC 400 Steam Holes w/L-98 Heads?? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-21-2006, 08:48 PM
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SBC 400 Steam Holes w/L-98 Heads??

I just got my L-98 aluminum heads back from the shop and they didn't drill the steam holes for the 400 block as I had requested. When I asked why, they commented that it really wasn't necessary with the aluminum heads and I won't have any cooling issues. They also commented that the coolant passages on these heads were a little tricky to drill into and the labor to do it wouldn't be worth my while.

Has anyone else heard or run into this?
They usually have no problem with taking my money, so I am not sure if they are being sincere with this info or if they just didn't want to do it?

I was under the impression that the steam holes were to assist in BLOCK cooling, not head cooling- If those holes are blocked at the heads, I still imagine the 'steam' issue will still be apparent in the block.
Am I wrong?
Do I just take my trusty drill and make the holes myself or do I get a second opinion?
Thanks!
Elm.

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Old 02-21-2006, 08:52 PM
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I drilled a set for a friend of mine.......
I just used a head gasket as a template.
I also has a drill stop on the drill.....I used a very small drill as a pilot hole and then came back with the proper size......

Works great on his 406.....

Deuce...
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Old 02-22-2006, 01:14 AM
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Next time I would find a different shop! I think they forgot to drill the holes and told you that to get 'em off the hook!
You do indeed need the steam holes.. there is a tendency for coolant to get "air-logged" at the top of the block and the steam bubbles must get out. You can do like Deuce said.. using a hand-drill.. very easy to do. Most aftermarket heads are now pre-drilled for the steam holes. My Trick-Flow Twisted Wedge heads were.
You need the holes and you will never have problems!
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Old 02-22-2006, 01:32 AM
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You can drill only the lower (exhaust side) holes.

3 holes per head, easy to do with a hand drill. Use gasket as template, center punch, drill with a 1/8th bit, deburr, and go.
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Old 02-22-2006, 07:45 AM
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Why only 3 holes?

I can only drill the 3 exhaust side holes because the intake side has no access to the coolant passages from that location?
Just clarifying.
Thanks!
Elm.
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Old 02-22-2006, 07:49 AM
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i have have an article in chevy high performance just for problem.shows how and where to drill.gives great info.if you can give me part of the day maybe less i'll locate it.
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Old 02-22-2006, 08:23 AM
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Thanks!

That would be most appreciated.
Thanks!
Elm
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Old 02-22-2006, 01:57 PM
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You can drill the exhaust side only because that is the side the air )steam bubbles) will get trapped. The intake side, if bubbles develop will simply travel up to the coolant holes that are very close.

The block deck is at a 45* angle as sitting in the car, air travels upward, so if steam pockets do develop, they will try to go up. The intake side can do so, the exhaust can't because of the siamesed cylinders.

Some head manufacturers recommend drilling just the three holes I specified.

Also Stewart Components says if you have the coolant pressure and flow high enough, steam pockets cannot develop...

Lots of debate on this but I would recommend just drilling the 3 holes per side in any street application.
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Old 02-22-2006, 04:02 PM
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http://www.chevyhiperformance.com/te...30/index1.html
ok i found it.now i don't know about the 98 heads except to say that i know that they are used on 400's.this should give you what you need to know.put some tape on your drill bit for a dept gauge or get a dept gauge from the hardware store.good luck
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Old 02-23-2006, 06:13 AM
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As bubbles/air pockets rise to the highest point in the block, I'd be inclined to only drill the holes on the intake side of the head if it suits your needs. Having holes at the lower side of the head would offer no benefit
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Old 02-23-2006, 11:44 AM
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Quote:
Originally Posted by club327
As bubbles/air pockets rise to the highest point in the block, I'd be inclined to only drill the holes on the intake side of the head if it suits your needs. Having holes at the lower side of the head would offer no benefit
You are incorrect.
The lower holes (exhaust side of head) need to be drilled as I specified. The uppers do not.
The upper or intake side of head holes are on the "top" side of the siamesed cylinders, so any steam pocket created will simply rise to the deck coolant transfer passages already in place.
The lower side of the siamesed cylinders, air will get trapped, hence the steam holes....
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Old 02-23-2006, 02:07 PM
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You also want to make sure you have this hole in your block. Some of them don't have it, and it greatly improves the cooling around the center exhaust ports.
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Old 02-23-2006, 10:55 PM
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ive seen a kit from jegs or summit that comes with the drilling template bit and everything else you will need to drill those holes your self. that other guyis wrong. my dad is a profesional engine builder and i asked him he said both intake and exhaust will have to be drilled to get good cooling. he is a credible engine builder he ownes the shop tha use to do the miss Budwiser hydroplane. trust me
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Old 02-24-2006, 01:04 AM
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Quote:
Originally Posted by chevymastermind
ive seen a kit from jegs or summit that comes with the drilling template bit and everything else you will need to drill those holes your self. that other guyis wrong. my dad is a profesional engine builder and i asked him he said both intake and exhaust will have to be drilled to get good cooling. he is a credible engine builder he ownes the shop tha use to do the miss Budwiser hydroplane. trust me
I would say as a Master Auto Technician and Machinist I am qualified to make the recommendation I made.

If you don't trust me, call Edelbrock's tech line and ask for their instructions...

I've built a few hundred motors...
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Old 02-24-2006, 01:40 AM
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it couldent hurt to just drill the extra holes now could it. nothing against you but why does it matter if he drills those holes or not. if chevy did it from the factory then he should do it! why not
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