[Curtis Thornton]

I am getting different feed back from folks about whether of not I should drill the steam holes in the new heads I just purchased. I bought a set if heads from Jegs (world sportsman). I have spoke to a friend of mine whom has built several small block chevy 400 and he stated that he has never drilled the steam holes out on his 400's and it they have never ran hot.

Are there any pros out there on sb chevy 400 that can give me some insight before I put this thing together

[oldbogie]

Originally Posted by Curtis Thornton

I am getting different feed back from folks about whether of not I should drill the steam holes in the new heads I just purchased. I bought a set if heads from Jegs (world sportsman). I have spoke to a friend of mine whom has built several small block chevy 400 and he stated that he has never drilled the steam holes out on his 400's and it they have never ran hot.

Are there any pros out there on sb chevy 400 that can give me some insight before I put this thing together

They don't run hot where you can see it, that is the engine temp doesn't increase where the temp gauge sender is.

What happens without the 400 drill is that coolant can't escape from the top of the closed area where the siamesed cylinder bores meet the deck. This coolant turns to steam which is a poor conductor of heat. The local area at the top of the bore overheats and distorts. The likely outcome is cylinder wall and deck cracking in this area, especially around the normally hot running center cylinders on each side and or head gasket failure in this zone.

Bogie

[techinspector1]

The other likely outcome is hot spots that will contribute to detonation.

http://www.gregsengine.com/350to400.htm

[dawg]

overall the coolant shouldnt overheat BUT the section that we are talking about will.
you wont notice it until you have a problem.
since you got the heads off its cheap insurance that you wont have a major issue later on.
BTW make sure your head gaskets have the steam hole aswell.

[MI2600]

For $30 at the machine shop, drilling seems to be a no-brainer. The GM engineers must have a reason for the holes.

[j.d.brown.042964]

Unless you're gonna do ONLY dragracing w/ engine rpm's primarily over 3000 rpm, all the tech. sources I've ever heard from say to do 'em. My last builder chose not to do them, but I had them added because it's cheap insurance for a "street-driven" setup that will spend alot of time under 3000 rpm. I checked with my head supplier,and because I live close by their Main office-they said bring 'em in and we'll drill them for free, which they did! I agree with what the head designers/supplier say.
Remember of course to choose headgaskets that have the steamholes, as some do not. Fel pro 1014 and 8634 do have them, 1004 and 1034 do not. -Jim.

[n-gin]

I called a machine shop a week ago and they told me not to drill the holes and to plug the block I will Not be getting my block done there Gelner

Drill the steam holes its cheap insurance I say

[C-10]

I think 3 of the 6 holes drilled in each head are at a 45 degree angle. Not sure which ones, Intake or exhaust side. This was stated in my Sportsman II nomenclature.

I'd drill 'em for a siamese cylinder type block.

[techinspector1]

Originally Posted by C-10

I think 3 of the 6 holes drilled in each head are at a 45 degree angle. Not sure which ones, Intake or exhaust side. This was stated in my Sportsman II nomenclature.

I'd drill 'em for a siamese cylinder type block.

See the link I provided in post 3.

[C-10]

Originally Posted by techinspector1

See the link I provided in post 3.

10 degrees.. ah. on the intake side. check.

Now I'm going to have to dig up that paper from World products to see if it say 10 degrees also. (It's been awhile)