The steam holes on factory 400 heads are 3/16" on the intake side and 1/4" on exhaust side. The intake side holes may not be drilled on all aluminum heads. Edelbrock only recommends drilling the holes closest to the exhaust. Check with the manufacturer first. The exhaust side of the head is going to run hotter anyways. So, the 1/4" exhaust side holes may be adequate for a lot of applications. Good video. have a good day.
I have always keep steam holes in my 421 small block strokers! Here is a good story....a mechanic in the 80's in Arizona said wrong head gasket or corrosive water no antifreeze were the engines that cracked or blew head gaskets from clogged holes! I would keep holes never had a problem since 1982 first 400 sbc!
Ran 305 heads on a 400 block for circle track for many years, never had any problems. Didn’t run rear crossover either. Filled with water, made sure no air pockets, 7000 rpm .
That horsepower level it really isn't a concern. The 305 and 350 cast heads flow 180-195cfm so roughly a 360-390hp engine. When in the 550hp plus range is when it just makes sense. Most critical 750hp plus. IMO it just good practice in these applications.
@@diyracing3049 yeah we hogged the heads to the Max and put larger intake valve, clearance between intake and exhaust was .012 thou. Couldn’t believe we didn’t have problems but did several engines.
local speed shop told me they havent drilled those in years and years. Said thats where the blocks crack and recommended filling it before we deck the block. this is definitely a street engine.
There alot of different thoughts on this. I go with what I know. I do understand what they are saying and I'm sure it will work. I just like having the holes as designed.
Correct. it's not as much about over heating. It's about making the system more efficient around the cylinders,helping with hot spots, The more power you make the more it becomes a priority. You will notice racing engines add rear coolant crossover & the aftermarket heads have bosses for center cylinder coolant cross ports for this reason.
That would be perpendicular to the head not flush😉😆 jk. Glad I came across this video, I'm putting together a 400. It's nice to see someone talking from experience. Thanks for the video.
I bought a 400 from a guy, because it constantly overheated,. He had 350 heads on it, without the holes, I figured that was why it overheated, I planned to refresh it and plop on the aluminum heads I have! Now I'm not quite sure what to do! I didn't think drilling a few holes was this difficult!
Good Video. How did you come up with your angle on the top holes? Have you run these heads yet? Any issues with the hold being so close on the first head?
I had a buddy . Cuttin every corner he could puttin his 400 tqgether . I found some fresh rebuilt heads fr a 350 . Told my buddy we need ta drill these steam holes . 4 holes each head . Gave him a 400 head gasket . This will locate the 4 holes for ya . Great he says ! Calls me a day later . Ok , i got all 7 holes drilled in each head ! 7 holes ? Only supposed ta be 4 WTF ! Lol
To a degree yes. But say you have a 1000hp turbo combo its a good idea to have them in my opinion. When you're pushing the limits it helps to keep hot spots out between the cylinders. Again imo.
You dont have to have it, It does help with cooling flow/steam between the cylinders.It helps to prevent hot spots. I like the idea so I use it. Its just like when people add cooling to center on sbc heads to avoid hot spots and adding rear intake crossflow. All things I run in racing applications. You don't have to have any of these things but they all help.
Im saying smaller is better. I would drill them smaller. like I did on this head. The first head drilled, was drilled at reccomend manufacturer size and it was larger then id like.
The holes came out fine. But yes as stated makes more sense to spend $75 when new. If you buy used you have no choice. Also the hole can be easily welded and milled for $150. So not a huge deal if you mess up. Just not something a beginner should try.
You dont have to drill them correct. Drilling them helps cylinder head temp. I like drilling them for the fact im making the cooling system more efficient.
Siamese cylinders is the reason for them no coolant going between the cylinders when the coolant does hit that hot spot it boils hense the steam holes those cylinders have to be really hot on the sides compared to 350 blocks so anything that can be done to help that and save the block to fight another day is my thoughts they are getting harder to find anymore espesially one complete and running in a car all factory un molested
