why not just use a gasket without the steam holes? I can't see how welding up a steam hole is a good idea especially in cast iron and trying to not distort the area of the bore.
400 with 350 parts?
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Racing and street use are two different things. The steam holes may not be needed for prolonged high RPM use or short runs (drag racing) but are needed for idling in traffic. I had a 400 that someone put some heads on that had not been drilled for steam holes. It wanted to run hot in traffic or in the drive through, without trying to run A/C. When it got warm like that, it ran poorly. GM put the steam holes there for a reason.
As Jared said GM put those holes are there for a reason. Can you run w/o them - I have but that's a drag racing scenario where the car is running for seconds. As 1221 said there is no need to weld-plug the steam hole in the block, it's getting done with the cylinder head regardless of which head gasket. If your going to drill the hole yourself buy the best drill (drills) you can especially with iron heads. there is a lot of meat to go through and you don't want a broken drill.
OK ,talked to my friend today and he said the 400 block he has is pinned, bored, and decked.(NOT WELDED) I was WRRRR next time Ill get my facts together before I move my fingers. 🙁 Sorry!
Drilling th holes, especially in an aluminum head is a non issue - easy as pie. Use a new 400 head gasket as a guide.
Unless I missed it, which is more than possible, did he mention which 350 components he was planning on using?
Unless I missed it, which is more than possible, did he mention which 350 components he was planning on using?
I believe a 383 stroker is made from some combination of those two engines 🙂
Yes a 383 was originally built with a 400 3.75" stroke crank with the main journals machined down to fit in a 350 block. Then you had your choice of what rod length and piston combo you wanted to use. Before that the 377 was another combination, where you put a 350 crank in a 400 block. The 377 was a little more desirable early on as a race engine because you could put a forged 350 crank in the engine. No one wanted to build a HP engine with a cast crank so the 383 was not really seen as a race engine. Later on when aftermarket cranks were available the 383 took over.
We never welded them we drilled and tapped them then Deck The Block.
As I recall some of the 400 blocks cracked at the steam hole this helped solve that problem.
Also the 400 2 bolt Main block is a little stronger in the main webs.
Use ARP studs on both the heads and the main caps.
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When GM designed the 400 cid sbc, to get the displacement they wanted and still have enough sleeve wall thickness, they ended up siamesing the cylinder sleeves. Instead of there being space between each cylinder sleeve, they actually touch each other and the water jacket surfaces at the point where they touch may even have been milled down to make the amount of sleeve to sleeve contact as consistent as possible. The big drawback is that with the sleeves in contact with each other, no coolant can circulate between the individual sleeves as it does with the smaller displacement mills. The coolant that does come into contact with the sleeves ends up superheating because it can't circulate as it should and it this excessive amount of absorbed heat results in it being converted to steam. This in turn creates pockets of air in the coolant which then need somewhere to go in order to cool down enough to return to being a liquid. The steam holes, drilled in both the block and the heads, offer an escape passage that the steam and bubbles can rise up and through to allow them to enter the heads and return back to normal circulation, cooling down and returning back to fluid as they do. It was this steam business that gave the 400s something of a bad reputation for overheating. You cannot mix and match heads. The 400 blocks that have those steam holes drilled in their decks have to have matching heads with hose holes or you will run into all kinds of problems. GM didn't help any as they offered at least five versions of the 400 head under the same part number and some had the holes and others didn't. Right now I am personally chasing a set of those heads with the steam holes and having no luck finding a pair.. As for the the aftermarket, asking a mfgr to drill the holes might be possible but if memory serves they are not perpendicular to the gasket surface, they go in at an angle in order to intersect the coolant passages in the heads. Wrong or no angle and you don't get the passage access needed.= trouble. Hope this helps.
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