The general train of thought is they are weaker due to the thin walls. Overheat and prone to cracking and having head bolts pull out.
Also that 2 bolt mains are better but still can't handle a lot of HP.

Then I read all the sucess stories people on here have with them. So are you guys with 406's just lucky or do you just not post the problems you encounter with a 406?

I'm torn between another 383 or a 406 and want to hear the good and BAD stories you've experianced.
Thanks

 

I have no bad stories, only good ones.

But I've only built a handful of 400s, 10 or so different ones I suppose, personally, and I've only owned about 3 or 4 of them; some were "406"s, some "400"s. I call them all 400s because that's what they are, regardless of whether they've had peridic scheduled maintenance or not.

I have no experience with thin walls, cracking, head bolts pulling out, or overheating. I think those are all rumors spread by circle-track guys to make everybody else lose interest in them so they could buy them all cheaper.

 

not sure about the other questions.. the reason people say 2 bolt mains are better then a factory 4 bolt block is that factory 4 bolt mains are prone to cracking due to the fact the holes are next to eachother where as on a 2 bolt block you can go with splayed 4 bolt mains which are stronger then factory because they are offset at an angle

 

Nope...no problems at all with mine. Others I know have pushed 10's and 9's with factory 4 bolt blocks without problems either. The webbing in the factory 4 bolt blocks is suppose to be weaker than the 2 bolt blocks but haven't seen problems with that. I know of a 377 with a factory 4 bolt 400 block that spins up to 7000 rpm that's been running the past few years without a problem either.
Just do the prep work and everything will be fine. The over-heating happened because of not having the steam holes drilled out in the heads or gaskets. There are some 400's that don't have the steam holes, so watch out for those. I've come across 2 myself. Using deck plugs help stiffen the deck surface, but still have not seen any problems with blocks not using deck plugs. I haven't seen a problem with head bolts pulling out either. The siamesed walls of the 400 block is thinner than the 350 blocks. But since the walls are siamesed, they are interlaced together causing a more rigid block. The only time the siamesed walls become a problem is when the blocks are over-bored to .060". With a .030" or .040" over-bore you'll be fine.
I tend to use marine gaskets like the one's from Cometic Gaskets. Marine engines tend to spin more rpm's so the gaskets are more heavy duty than standard gaskets. Using the longer 5.7" rods over the factory 5.4" helps with reduced load against the cylinder walls. There are pistons made to be used with 6" rods but they do cost more.
Alot of the problems you hear about with 400's are old wives tales and are do to improper preparation.

 

yeah.. factory 4 bolt blocks are by no means weak, they are stronger then a factory 2 bolt block in stock form, but when you start getting more to the radical side with your build up i.e. forced induction, high compression ratios, high revs, etc. a splayed 2 bolt block is stronger.

 

Does anyone else think that if you plan on keeping the stock caps a 4 bolt 400 is stronger?
It was always said they didnt have enough meat to bite in to.

 

wow ok i forgot what the topic was.. i was thinking of a 350.. to tell ya the truth im not so sure about the 4 bolt 400's i have heard that they are notoriously weak before but personally i have no experience with em nor am i positive that its true.. sorry im no help.. lol

 

its not the caps, its where the outter bolts screw into the block.. very thin in that area.

Use ARP studs and a 2bolt will take anything a drag car can throw at it. Endurance racing is another deal.

 

All the 400 probelms Ive seen were rod failures. Granted Ive seen many 350-305 rod failures but I havent seen a 400 without some sort of rod knock. If I had a 400 Id be using it so....