GsxrMike
1/2 ton status
I remember reading somewhere that a 2 bolt main 400 small block is actually stronger than a 4 bolt? Is this true and if so why?
CK5
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2 bolt or 4 bolt 400?
- Thread starter GsxrMike
- Start date
fried_guy
Registered Member
the main web on the 400 isn't as strong... when you intersect it with 2 more bolts it weakens it even further. use a 2bolt and use arp studs and it'll be fine to 500HP/TQ. just make sure it's balanced well and the crank turns freely.
GsxrMike
1/2 ton status
Thx for the info!
To add to what fried_guy said, a 2 bolt block that has been converted to a 4 bolt with splayed caps will be the strongest setup. But that is only nessasary if you're turning some serious rpm or planning on more than 500hp.
And to explain what splayed caps for those who said Huh???
That is a cap that uses the 2 bolts from the original 2 bolt block and adds 2 more at an angle which gets to the stronger part of the web on the block and the fact it's at an angle makes the bolt work patly in sheer on top of pull on the threads.
Much stronger than a 4 bolt main.
GsxrMike
1/2 ton status
Do you use the original caps for converting to a 4 bolt splayed set up or do you use the original caps?
no, aftermarket caps. check in summit racing for pics and prices http://store.summitracing.com/largeimage.asp?part=ESP-C4103S&Prod=Eagle+4%2DBolt+Billet+Main+Caps&img=esp-c4103s_w.jpg
GsxrMike
1/2 ton status
Wow good info guys. Another quick question I haven't researched yet...Is a one piece rear main seal better than a two? If so what year blocks do I need to look for and what is the difference in the cranks? I have read that you can convert from two to one but I didn't pay a whole lot of attention because it wasn't what I was trying to read up on.
jones
1/2 ton status
AFIK,there were no 1pc.rear main 400 blocks as they stopped using the 400's in the early 80's.The 1pc design didn't come about til around 86-ish.
As far as converting from 2pc.to 1pc.,I've not heard/read of doing that.But just because I've not heard of it doesn't mean it can't be done.
As far as converting from 2pc.to 1pc.,I've not heard/read of doing that.But just because I've not heard of it doesn't mean it can't be done.
GsxrMike
1/2 ton status
Sorry I forgot I that I was talking about a 400. I will do some research and see if I can find a kit or does it matter?
It doesn't really matter. As long as the seal is installed corectly. The one piece rear seals are pretty idiot proof to install. But I haven't had much trouble with the two piece ones.
FWIW: There is a kit that allows the use of a two piece seal crank in a one piece block (or is it the other way
). That's only for 350 based motors though, as the 400's have differn't sized mains. I don't think there would be one for a 400, since they were never one piece seal from the factory. Even if you did find one, the cost wouldn't really justify it.
pauly383
Daddy383
They dropped the 4 bolt block shortly after introducing it , Didn't make it 3 years before they were all 2 bolt blocks . Only two casting numbers I can find for it #3951511 70-73 , and # 3951509 70-71 .
Can't be too many left , you may start with a 2 bolt block based on availability
Can't be too many left , you may start with a 2 bolt block based on availability
