How critical are the steam ports for the sb 400 heads?

I've been told that you can get by without having them machined in aftermarket heads.

Is that only application specific?

btw This is for a 400 block.

you need the steam holes in the heads on a 400SBC

The guy that did all my machine work told me I didn't need the holes in my aftermarket steel heads also

I drilled them anyway. So I don't know if the aftermarkets need it or not. I wasn't going to trust all the money I had in the engine though

dosen't really hurt anything if you have them and don't need them but if you need them and don't have them is another story.

Can only tell you my experience. Did not drill steam holes for my vortec heads on my 400SBC.

No overheating problems at all. Tested in heavy stop and go traffic etc, etc.

One of the reasons these motors origionaly ran hot and got the "reputation" was the stock GM emissions tuning of the era.
lean mixtures, restrictive exhaust, hot thermostats and retarded ignition timing all played a factor.
The stock GM 400 cylinder heads were also crap, back then.

Not telling you absolutely that you don't need to drill steam holes, but, my setup doesn't seem to need it.

Thanks everyone.

I did a little more digging on the subject, and found that steam ports aren't necessary if I'm running high rpm's, as in race applications.

However, if I plan to use my rig as a daily driver it's probably a good idea to have them drilled.

I plan on getting some Dart Iron Eagle heads w 2.02/1.60, 165 cc runners and 72 cc comb. cambers.

I have seen the vortec heads run w/o steam ports drilled without any problems.

The 400 I have is currently in my truck, but plan a transplant to a 91 rs camaro.

Here' s the truck

and the engine.

But for the third gen it should be n/p. Still, if you have it apart, it is good insurance.

Add em. Takes 5 minutes, hurts nothing, may save your chestnuts someday. All advantages and no drawbacks. You'll have no way of knowing whether you needed them, until you let the car sit and idle for a while and it overheats and spews coolant everywhere, while the temp gauge (which of course isn't measuring how hot it's getting where the steam holes should have been) says it's OK.

I think, it's as simple as a gasket and a drill. So i say add them. Nothing really to gain, with a lot to lose.

Like RB said..drill them! takes very little time to do it......if you don't drill them and put the motor together only to find out that you needed them.....hummm...takes alot more time that way

Thanks everyone for the input, better safe than sorry.
I'll drill the new heads.

Do sbc400 steam holes 'match up' to holes in the cyl heads?

The holes don't "match up" to anything, until you drill them. Unless the heads have already been drilled for a 400 block, which most heads aren't unleess they've already been on a 400, they don't exist.

To drill them, lay a 400 head gasket on the deck, mark with a center punch, and drill. Size is not critical. They need to be no larger than the holes in the head gasket. I usually use about a 3/16" drill. On most aftermarket heads especially, the ones on the intake side need to be at an angle, toward the exhaust side, away from the head bolt holes.

Here's a set of heads that I drilled.

I guess I would drill the holes. Mine aren't drilled and I don't have any problems, but it is not that hard and it could save you a lot of trouble.

Why do you want heads that are so small? 165cc is puny for that big of a motor. I have the 200's and I wish I would have gone for the 215's. It makes tons of torque with the 200's, so I don't think you need to worry about that. My motor combo is in the sig.

Exactly what I was thinking, S-10 minds think alike...

I have a set of the 215s on my 352(400 block/327 crank) but I can only tell you it runs nice in the garage, havent put it in a car yet