[cmb8065]

I'm rebuilding a 400 ci sb. The heads were cracked and I have a good rebuilt set of 350 heads. They don't have the small steam holes like the 400s. Is there any way I can modify them to fit the 400 block? I have a friend who owns a machine shop and can do about any kind of machine work. Any info will be greatly appreciated. Thank you.

[cdminter59]

All you need is a set of 400 head gaskets. Here is a Wiki article on drilling the steam holes in the 350 heads. http://www.crankshaftcoalition.com/w...ck_Chevy_heads

[vinniekq2]

with the price of after market heads so reasonable,now is the time to step the engine up?

[lhmurphy]

Originally Posted by cmb8065

I'm rebuilding a 400 ci sb. The heads were cracked and I have a good rebuilt set of 350 heads. They don't have the small steam holes like the 400s. Is there any way I can modify them to fit the 400 block? I have a friend who owns a machine shop and can do about any kind of machine work. Any info will be greatly appreciated. Thank you.

I'm currently running a 406 sbc, my cylinder heads were too thick to drill out the steam holes and I didn't find not having them to hurt anything...I talked to some local guys who have a lot of experience with 400s and they have never had any overheating issues or any issues not using the steam holes...If you can have them drilled for cheap, personally I would do it just bc GM did.

[327NUT]

You didn't say which 350 heads you have but if they are the generic smoggers I wouldn't waste my time with them....even if you port them. Personaly I would invest in a set of aftermarket heads or Vortec's, don't have to be real expensive, just more modern combustion chamber and ports.
A good set of heads will make or break a perfornance build. Whichever you choose BY ALL MEANS, drill the steam holes, they are there for a reason or Chevrolet wouldn't have spent the time and money.

[spinn]

Cant the cooling hose be run over to the drivers rear, coolant fitting, on the intake? I heard that setup does not need steam holes.

[cadillacdave1]

If you have stock 350 cylinder heads they will fit and run but will end up holding back the HP and torque of a 400. Use an after market head maybe a 195 or 205 AFR or similar size head.