400 Block
 

Hey guys, I have a sbc 400 block with deck plugs, oil galley plugs, but what i find interesting is the steam holes have appeared to be welded up and then the block was decked. Have any of you ever done or seen this? Why would you go thru the trouble of doing this? My guess is for strength, but I cant imagine it would make a significant amount of differance. Also, why are the oil galley holes plugged up? Maybe keep the lifters supplied with oil? Is either of these things a good or bad practice? And why? Just trying to learn something new. Any insight is appreciated! Thanks....

Re: 400 Block
 

for the oil gally holes, probably was a racing motor at some point in time and they were plugged so the oil would drain down the back of the block and the front, though the time chain, elimantin drain back on the cam and rotating assembly for less windage which equal more horse power. As for the steam holes being plugged, I have no idea. eberything i've read and heard says if you dont have those opened, they'll over heat like crazy. Chris.

Re: 400 Block
 

yea i was under the impression steam holes = GOOD! but they did some crazy stuff way back when so ya never know

Re: 400 Block
 

On a drag engine, where your not running an extended time, we would tap and plug the steam holes then mill the deck.
400 blocks are notorious for cracking from the steam hole to the bolt hole(no big deal) or to the cylinder(bigger deal)

Re: 400 Block
 

Seen lots of 400 heads with cracks stemming from the steam hole.

If I was going to build a 400 block based motor, I would not run factory heads. They just don't have enough meat in the deck. I would get some aftermarket casting, such as Enginequest or the other brands out there that are heavy cast and have about a half inch of deck thickness. Drill the steamholes, bevel the edges of the holes slightly, then call it good.

As for the block, if you are planning on street use, it would be a good idea to drill out those steam holes.

Re: 400 Block
 

The oil valley drain holes were tapped and plugged to keep the oil drainback at the rear of the block. On a street/strip engine, I wouldn't plug these holes.
As far as the steam holes being plugged, like BigJim said, it is done a lot on drag motors, but I wouldn't plug them on a street/strip deal. Factory 400 blocks are known to crack from the steam holes to the head bolt holes, which, once again, isn't a big deal. In my opinion, if you're using a factory 400 block, then you should run both head and main studs instead of bolts. This will, among other things, keep the small deck cracks from the steam holes from becoming a bigger issue. And, by all means, drill the steam holes in the heads if they don't already have them.
Just my opinions...

Re: 400 Block
 

Thanks guy's. I am going to remove the oil galley plugs because i do drive this engine on the street from time to time. I dont want to starve my roller lifters for oil. As far as the steam holes i will leave them as is, because i have driven this engine several times on the street and have not had any cooling issues at all. The engine is studded in the mains and the heads. i have just removed my current motown 220 heads and replacing them with the AFR 227's.

Re: 400 Block
 

I had a 406 that had the steam holes plugged. I had it running for about 5 years and drove it every day and sprayed about 15 bottles at a 150 shot! I never had a problem with it , and that's driving in the Fla. heat.I ran this motor hard and never had a problem with it. :chevy:My .02