chrisf695

iTrader: (3)

So I just got done talking to my engine builder and the 400 block he has for me is going to be bored 60 over... I've herd some mixed opinions on this from my uncle's and a few buddys of mine. whats your take on this? Im not looking to make a 500hp monster or a 7k rpm motor. Hes looking for a rpm range of 4500-4800k, using standard 400 rods, vortech heads, hydraulic cam, and it will be a stroker compression will be about 9:1. He said the HP range will be 350-360...

whats your take? Should i be asking more questions? Should I be good with this or do I need to stop him from building this?

machloosy

I would advise away from a .060 over block. There just isn't the metal on the cylinder walls needed. Just my $.02 though. A street light racer or drag car is one thing, but the sustained 4K+ cruising is what will do it in. A .030 block is plenty and you won't loose enough hp to notice.

Raylar

Older 400 blocks have some pretty big differences in bore wall thicknesses at some points many times due to core shift in some castings. The cylinders should be sonic meaured before boring and if they test thin in spots stay with +.30" oversize and be safe.
As for power I would think and hope with a good intake/carb, camshaft and good exhaust the engine should really be in the 400HP plus range for what you will be building.
Very best of luck with the build, have fun.

Best Regards,
Ray @ Raylar

FIXX

iTrader: (2)

im with ray,always sonic test the block for proper clearances..you really only have to worrie about between the cylinders on a 400 block..make sure you drill the steam ports in the heads or you may have some troubles between the cylinders..we use to go .060 over on the 400's on the stock car motors,,most lived and some did not,only because we stuck 4.00'' stroke crankes in the block which weakened it..

articfriends

iTrader: (1)

I built a .060 400 years ago and even with the extra cooling "steam" holes it ran HOT and was hard to deal with, would NEVER bore one that big again, Smitty

chrisf695

iTrader: (3)

Thanks for the replys, I will bring this up to the builder and see what he says... hes building this motor for 3k...

snapmorgan

iTrader: (2)

I wouldn't do it. i built lots of 400's back in the day for stock cars. Had problems with .040 blocks running hot. It will not last with the short rods, needs at least 6" rods, and you have no more room to bore it. The stock blocks crack through the steam holes and you also have to drill holes in the heads which make them prone to cracking. I would not build a boat engine with a stock 400 block unless it was standard bore, which you will never find. I think it will be a waste of $3K and probably ruin your summer.

mike tkach

iTrader: (3)

im just wondering,with a endless supply of fairly cool water,would overheating be a problem with a properly set up cooling system,i think in a car heat would be more of a problem,and i think overheating is the cause of cracking at the steam holes..060 over in a stock car would be a hot mofo,if the block sonic checks ok,i would not be afraid to use it in the boat.

chrisf695

iTrader: (3)

Im giving him the ok to build the motor, he said the overheating wont be a problem because of the cool water that will be constant through the block. I guess we'll see... motor should be built in a week hes telling me.

rws

iTrader: (3)

I would consider using MLS head gaskets such as the FelPro 17030 . I believe you would have to drill the steam holes.
I have not ever ran one that was more than .040" over, a sonic check is a must.
I have built 5 different (3 511 casting and 2 509 casting) stock block 400 Marine engines and have had sealing issues with the center cyls.
The last engine that I built for my 20 CIG has additional #6 cooling lines tapped into the heads to cool the center cyl. this is popular with circle track engine builders.
I had no sealing issues the last time I tore it down for freshening after 5 seasons .