The internet is full of heresay and keyboard professors. Good information is hard to come by.
The sbc400 has a bad reputation for overheating due to the siamese bores and somewhat poor water flow as a result. The general "fix" is to drill steam holes in your heads so the water between cylinders can flow into the water jackets in the heads. Though I see more than a few saying it is unnecessary if you just keep the rpms up a bit. Maybe yes, maybe no, do it, don't do it. Keyboard warriors on both sides.
I'm perfectly willing to drill holes and confident in my ability to do a good job at it. My only issue is the heads I'm going to be using (062 vortec, junkyard fresh) are notorious for cracking. I'm hesitant to give more places for cracks to start. The car will be getting 3.50:1 rear gearing and no overdrive, so keeping engine speed up shouldn't be an issue.
what say ye? To drill, or not to drill, that is the question.
The block is already drilled. They all are. Figure out where the hole is in the head gasket, mark the spot on the head, and drill.
Not rocket science. Make sure you have enough radiator and go nuts. They put those 400s in all sorts of one ton van motorhomes, and they worked fine. But they also had a massive rad.
In reply to Streetwiseguy :
I should have clarified. Yes, the heads are what I would be drilling. I'm just hesitant to drill holes in heads that are known to crack. But these survived 197k in a 3/4 ton 4x4. Should be fine.
I think the only worrying id do is making sure to put a depth stopper on the drill bit so when i break through into the coolant passage i dont jam right into the other side of it so hard that the bit wedges and the torque of the drill snaps it off below flush or starts a new crack there! And put some tape down so when the stopper hits it doesn't gouge your fire ring area all up. Does it sound like i've screwed up enough hand drilling? But yeah i'd go for it.
In reply to barefootskater :
Don't forget to radius the holes. The part where the head touches the block put a radius in that hole. I use a stone to grind it in. That reduces the tendency to crack. Although to be fair I only used aluminum heads.
barefootskater said:
In reply to Streetwiseguy :
I should have clarified. Yes, the heads are what I would be drilling. I'm just hesitant to drill holes in heads that are known to crack. But these survived 197k in a 3/4 ton 4x4. Should be fine.
I know you are drilling the heads. I'm saying, go ahead and drill. They are far more likely to crack from the hot spot than they are from the hole you drill. Just don't leave too many sharp edges.
In reply to Streetwiseguy :
Ah. I misunderstood, not enough sleep and my head has been fuzzy all day. To your other point though, I'm glad I picked the bigger radiator. If it could cool an auto 440 it should be good for a manual 400. I hope.
Gonna drill, and chamfer. Thanks, all.
Vortec heads don't crack the decks. They crack near the exhaust valve.
Drill away.
Huh. Everything bad I ever heard about the 400 was not about overheating, but about how weak the bottom end is because the main journals are perilously close to the main bolts. You can make a 400 live on the street but if you insist on stock block power (like 500-600hp, dyno horsepower not imaginary HP) you're better off with a 400 crank in a 2.45 main block, which is why everyone and their sister has a 383ci Chevy.
The good news is I can't see any cracks despite the internet saying they all do, though I have not had these magnafluxed (yet?).
And I won't be trying to make 500 hp, not on challenge budget anyway. More like 350, if the three examples of stock 350/062/.480x230*@.050 combos can be believed. And I've got 56 inches more to play with. should be enough to have fun with and run reliably.
The internet convinced a kid I know that he just had to have a T5 behind his red block Volvo turbo, so now he has a whiney 5 speed and a driveline vibration, instead of a M46 that I saw win the Canadian nation rally championship behind a big ass turbocharged B23 that would get you to about 100mph on gravel in less than 15 seconds.
And that was with the overdrive available in second, third and fourth.
I've seen one set of cracked vortec heads, and they leaked into the oil up by the rocker pedestal.
Vortec heads crack more often than others, but it's not apocalyptic. Buy another set for $300, or buy an aftermarket set that are cast heavier for $600 and never worry about it again. Vortec heads cracking is one of those internet frenzy buzzwords. They might crack 20% more often than non-vortecs, but to listen to the internet, you would think they all crack before being installed at the factory.
I have owned dozens of vortec heads. Two of them were cracked; one between the exhaust valve seat and the edge of the chamber, and the others were cracked because it was a boat motor that didn't have the water drained for the winter and it froze. That one busted beside an exhaust port on the side.
There is equal internet frenzy about 400s. They're fine. They're wonderful. I've had a few 400s built up to 427s and 434s that got abused with 600 hp come through the custom shop. If they can be bored and stroked to the max and survive BMEPs nearing 200 psi/a at 6500 rpms, they'll be just fine at 350 hp.
No 400 experience so hang on; a bigger pump and 4-core isn't the answer?
I had a 400 in my 1972 Camaro. Used some generic 350 heads and drilled the steam holes. No problems for me.
914Driver said:
No 400 experience so hang on; a bigger pump and 4-core isn't the answer?
Siamesed bores. Bubble buildup creates problems, so bleed holes are drilled just below where the bores come together.
