Found a set of small block Chevy 400 heads today. My question is, will these bolt on to a stock 305, and if so what advantage would they have? All I know is they have larger valves. If they will fit, is there anything I need to change or modify to get them on?

 

About the WORST heads made,and far worse to put on a 305.They have bigger valves,but also large 76cc chambers,which will KILL your compression.They flow bad,there is no good reason to use them for anything but a stock 400 or a doorstop.

 

Bolt on fine; needt o drill some holes in the block to match steam holes in 400 heads
Whether they would be any good is a different story.
If chambers are too big then you will drop compression =less power

Casting # on 400 heads?

 

The best mod you can do with those heads is pull one exhaust valve out, stick a rope thru the port and use it as a boat anchor...
Or just scrap them, prices are up !!!

 

I haven't bought them, apparently its not a good idea. Thanks guys. I'm about to pull the heads off my 305 to have then rebuilt. I've also found a set of another 305 heads already re-built, and ready to bolt on for $175. Pretty sure I have a blown head gasket. I'm looking for a decent set of headers also. Hint hint!

 

Actually, that's the other way around. If you put any non 400 head on a 400 block, you need to drill the steam holes in the heads. You don't need to drill holes in a 305/350 block to use 400 heads on it. Those blocks already have proper coolant flow around the cylinders.

The 400's 882 heads are garbage. Door stops and boat anchors. They have zero performance potential.

 

You dont have to drill the holes in the block when using 400 heads.
You only have to drill the HEADS if you use them on a 400 block because of the siamesed cyl walls..
305s dont have siamesed cyl walls..

 

Too many beers clouds thinking