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Author Topic:   305's on a 400
RACEINMUD
Dirt Forum Racer

Total posts: 76
posted February 26, 2003 09:13 AM
Anyone run 305 heads on a stock 400? Do I need the steamholes for racing? Thanks for the help! RIM

ctfarm
Dirt Roller

Total posts: 21
posted February 26, 2003 10:55 AM
You don't need the steam holes,but you will have to plug the coolant holes around sparkplugs.If you don't you'll get water in the cylinders.

RACEINMUD
Dirt Forum Racer

Total posts: 76
posted February 26, 2003 12:35 PM
Do you mean the steam holes on the block? Will a 400 headgasket show me which holes if I compare to head?

jnewman44
Dirt Full Roller

Total posts: 72
posted February 26, 2003 07:47 PM
If you dont open the chambers up to match the 400 bore size the valves will be severly shrouded, this hurts flow. 305s have small valves for a 400 too.

ctfarm
Dirt Roller

Total posts: 21
posted February 26, 2003 08:46 PM
On the sparkplug side of the head there are two holes ,one each side of the plug,their about 3/16's to a 1/4" diameter.They need to be plugged.If your not sure which ones,ask your local machine shop.After plugging,fill the cavity with JB weld and file smooth to head surface.Hope this helps.

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