Does anyone have a diagram or information on what angle/ drill bit size for the steam holes to be drilled in my alum. heads for my 400.

Never done it myself.

However have read several times about folks that really messed it up.

What heads you trying to drill?

Iv got a set of edelbrock RPM heads. ill probably be doing this tomorrow, iv drilled a set a few years back but dont remember how it goes. also these were cast iron heads.

It's not bad to do....I've done it, I've got the measurements and angles written down in my notebook in the shop....I'll try to dig it out...

But if ur having any work done to the heads at all, the machine shops usually do mine for free...so obviously I haven't had to do it awhile.

im not having any head work done, but maybe i can have it done for free......i doubt it.

ski_dwn_it and Corkvette over on CorvetteForum did not get their aluminum heads drilled for steam holes.
Both of them are running 406ci SBCs and both swear up and down that drilling steam holes is redundant.
Today's cooling systems are more efficient than the cooling systems of yore.
Supposedly it increases your chance of a blown gasket if you drill the holes.

Makes sense to me but I'm a little anxious about going against what has always been a given when it comes to 400s - YOU NEED TO DRILL STEAMHOLES.

Now I'm not so sure anymore.

steve, you NEED them on any street driven 400..... the cyl walls are so close together that a steam pocket will develop if you dont have one.


most machine shops do it for free or at MOST $20 when they're doing any other work on the heads... its cheap insurance.

you're stupid NOT to do it.. its a needless risk.

Aight.
It just threw me for a loop.
They both vehemently posted that they had more problems WITH steam holes than without.
And I know they're both running low 11s NA.

FYI, I just got done speaking to a reputable machine shop today about my 400. I asked about the heads and steamholes and they explained the same thing...no need to drill them, due to the cooling system advancements, and that if you do drill them you have more of a chance of blowing a gasket.

FYI: I'm no engine builder...just trying to educate myself. I do not know weither to do this or not!

lets put it this way.

no matter how advanced the rest of the world gets, unless you have a updated "advanced" design for the 400, you're still going to have a location under the deck where steam pockets can form.

the coolent is the same. esp if you're running mostly water like most 400 guys... and the green coolent is the same... and the red coolent (not advised) wont change that either.


its DESIGNED for the holes. it has ZERO effect on you "blowing a gasket"
go look at a gasket, and you tell me what you think. they're tiny little holes. thats it. just a little place for the steam to get let out so theres no hot spot.

I do agree they are tiny holes, and personally I dont see the harm in drilling them...nor am I saying I'm going to go one way or the other...just tyring to see what the concensus is. Trying to figure out why some feel so strongly and others do not...seems to be no middle ground on this one

Mr. Dude, can you drop me an email @ poorboy08@gmail.com

Thx...your PM box is filled, and no email addy avail!

There is a good diagram on the Trickflow website:

http://trickflow.com/product/chevycy...stallation.asp

i didnt realize it was full.. its emptied out now...

or we can just talk about it here. public is usually better, that way people can search later and read it.

btw, i just thought id say this:

ive never heard anyone give any reasonable reason to not drill them.


i have heard people say that you can "get away" with not drilling them.

ive also heard and seen horror regret stories from people who wish they drilled them.

ive never even heard about a person who regrets drilling them. even with them drilled, they work on ANY SBC.. including 350s that dont have steam holes...




in otherwords, its cheap insurance with alot of pluses, and no problems.

I don't have any personal experience with drilling the steam holes, other than having heard for my entire life that it needs to be done. I figure it this way: in 1980 it needed to be done. In 1985 it needed to be done. In 1990 it needed to be done. Maybe advancements have been made since then, but if you're running a late-70's or early-80's block then odds are, it still needs the steam holes.

Oh and just as a side note.....ski_dwn_it isn't the most reputable source in the world. In fact, I wouldn't trust his advice as far as I can throw a 400.

having thrown a 400 bare block, i can estimate this distance to be about 5ft.

NOTE: Was not going on ski_dwn_it advice :-)

I'm 6 foot and 145 lbs. Upper body strength is NOT my strong point.


3 feet tops.

:shrug: