well, I got some bad news today. the machine shop called and said that a .030 bore won't clean up the cylinders on my 400, my question is, can the 400 go to .060 without any problems. I have always heard the the motor will overheat if you go that deep on the bore. I need to let the shop know soon.


if not, anybody want to by a 400 crank,flexplate,harmonic balancer ????

 

why not +.040, i'm sure there's pistons out there for it. i never liked taking anything +.060. if it's just one hole or a few i'd consider a sleeve.

 

thanks, ede. the shop says .040 won't touch it. they said that .060 might get it and its all cylinders, the block sat \outside for a few years and the hole got rusty.

 

Well look at it this way... what choice do you have? Either you do nothing, and the block is junk; or you get it bored .060", and then either it works or it doesn't. All you're out is the cost of boring. Not a great risk, but at this point, if you're stuck with that motor, your options are soewhat limited.

 

thanks, RBL. fortunatly I'm not stuck with the motor, I have a new 305 in the car right now, I just wanted some more power and I got a good deal on the motor ( I thought ). I hate to spend the money to build the 400 and then have it crack or something due to the bore (.060). if I thought the motor would be ok at .060 over I would go ahead and spend the money to get more power.

 

I meant "stuck with it" like "can't take it back to the junkyard and exchange it"... which of course would be the best course of action if possible.

 

I bought it from a friend of a friend so I cannot take it back, the guy was very honest about the motor and said it might not be usable but he wasn't sure. I guess its my bad luck (again).

If I go ahead and have the work done and build this motor what do yall think the odds are it will last, the motor will be 99% street driven with the occasional pass at the track.

 

What models /years did the 400 come in.... Is it stroked and bored more than a 350.......Which is usually prefered?

 

400's have more bore and stroke. The stroke part can be done to a 350, but a bore that large is possible by siamesing the cylinders together which is why they require 'steam holes'


Not all 400 blocks can go +.060" I'd have it sonic checked before wasting the money and ending up with paper thin cylinder walls. Check where the camshaft hole is located. Is it off center with the flat area? These are signs of core shift and makes the cylinders thin on one side. A cheaper and less accurate way is to get a set of the 'old style' vernier calipers and reach down into the water jacket hole from the head deck surface. Then measure the adjusting bolt so you can set it back (You need to loosen it to take it out of the deck) Then use an inside mic and measure the calipers. You can only measure two spots on the cylinder, if they are way different, this is another sign of core shift. Other areas to look are at the lifter bores. Are they in center?

Hopefully you got alot of meat to work with...

 

400's have more bore and stroke. The stroke part can be done to a 350, but a bore that large is possible by siamesing the cylinders together which is why they require 'steam holes' As for preferable, increased stroke promotes bottom end torque. It also limits RPM potential and wears rings faster.


Not all 400 blocks can go +.060" I'd have it sonic checked before wasting the money and ending up with paper thin cylinder walls. Check where the camshaft hole is located. Is it off center with the flat area? These are signs of core shift and makes the cylinders thin on one side. A cheaper and less accurate way is to get a set of the 'old style' vernier calipers and reach down into the water jacket hole from the head deck surface. Then measure the adjusting bolt so you can set it back (You need to loosen it to take it out of the deck) Then use an inside mic and measure the calipers. You can only measure two spots on the cylinder, if they are way different, this is another sign of core shift. Other areas to look are at the lifter bores. Are they in center?

Hopefully you got alot of meat to work with...

 

If it turns out you cannot bore the block, I will take the harmonic balancer and flywheel for spare parts for my engine. My email is ward_21@hotmail.com

 

everybody, thanks for your input in this matter. I found out today that the block is trashed and .060 won't even touch it, the good news is that the crank is ok and only need minor work to be usable. so I can sell it along with the flexplate and balancer.

ANYBODY INTERESTED ?? $150.00 +shipping

E-mail me at lilnorm1@***.net

 

I would really consider having it sleeved....and then use it. Diesel engines use sleeves a lot and they seem to run fine. The 400 should NOT be used with more than a .040 overbore because the cylinder walls are too thin.

Get a quote on how much to sleeve and go from there. When you say that the block is trashed...you mean cracked? Or just rusty in the bores?

Good luck...

 

sorry to hear about your engine trouble. i wouldn't even mess with the 400 small block. i'm thinking a 400 won't tolerate anything more than 20 over. i'm pretty sure you'd run into water jackets at anything more than 20 or 30 over. so i'd probable just scrap the block - hang onto the crank and rods though - you can use them to make a stroker out of a 350 or a 305 bored out to 350. but i wouldn't waste money have the block machined, because you may be able to get away with broing it out, but then you'll probably have to sleeve it. and if you do the block, you're gonna have to rebuild it - 400 stuff isn't cheap - and then you might put it in and have hot engine problems for days and have to scrap the project after the huge investment you've made in the block - you'll have all kinds of radical stuff and no block to use it in. so i wouldn't even take the chance. lord knows these cars have enough cooling problems as it is, why take the risk and get burned. so i'd yank out the 305 and have it punched out to 350, then put your 400 rods and crank in and you'll have a bad *** 383 stroker. good luck.

 

your mileage may vary..

but i had about 19hours on a new motor when water started coming a cyl.

 

Thunder87...Your heart is in the right place, but your facts are really FUBAR.

1. I have a .030 400 that works great...you can go to a max of .040 on a 400...

2. You don't just bore a 305 block to a 350 and go...you go buy a 350.

3. To make a 383 from a 400 crank means you have to take the crank to a machine shop and have the mains ground down from 3.65 to 3.48 (if memory serves me). It is far simpler to just buy a new cast crank for $200-$225.

Good luck.

 

that has been proved otherwise

nope cant bore a 305 to 350 cubic inches.

many people have had no cooling problems with 400s

 

1986 redbird, if end up looking for another 400sbc. I have one sitting in my garage fresh out of the machine shop still in the grease-bag that has been line-bored/honed, bored .030/finish honed/ magnafluxed, tanked/ the works that I would sell. email me at bradkeith@hotmail.com if interested