AMC 4 bolt mains back in production

[Elliott]

Here's the link, they aren't listed in the catalog yet, but you can contact them to order: http://www.pro-gram.com/
The three middle ones are 4 bolt ($200/set), the two end caps are 2 bolt ($66/f, $189/r).

[Stuka]

what is required to doo to the block? I havent see the belly of a AMC V8 block yet...

[bigblack'74]

on the 401 it looks like you just have to drill the block out for the extra bolts much like a chevy..but maybe there is more..

[sandmanb]

would this mod realy be worth the money on our rigs? could someone please exlpain the advantages on this.

[Cliff]

This would only be necessary for the most radical engines. The AMC V-8 bottom end is pretty stout, and I know many racers, and none of them has gone with 4-bolt mains. But, very few AMC racers go below the 9 second range in drag racing. Perhaps this product could take the old motor to the next level.

[Cecil14]

Don't 401s have 4 bolt mains from the factory?

Anthony

[Stuka]

very few amc v8's had 4 bolt mains for racing applications way back when.

But in my experiance, the 4 bolt mains are infamouse for stress cracks, as there is less metal there. I personally havent seen a V8 that has had the main cap bolts snap. Its generally the crank that snaps before they do...

[Josh D]

A few 360 blocks were factory 4 bolt mains to homologenate for Trans Am racing. They are rare if not non existant.

[mdill]

Saw one of the thick wall 360 race blocks go on ebay a while back, think
it was pretty run out and went for too many $'s. The Chevy 400 small
block factory 4 bolt blocks were notetoious for cracking the webs, hence
the 2 bolt 400 blocks were/are more desirable.

Mike D.

[Elliott]

401 blocks had probably the highest percentage of nickle in the block then any block manufactured, ask a machinist who dulls his hones on them.
401's also ran a forged crank... all of them.
I'm not sure what years, but from what I've read many blocks were predrilled for the extra two bolts so if your block was gonna be crackin' there it would have already.
As far as I know, these 4 bolt mains haven't been available since Miloden quite makin' 'em.
Granted... there not for everyone obviously, but if you plan to build a 401 to whomp on yer neighbor's chevy 400, well... that's why they're back in production.
Blocks that weren't drilled are easily modified. If I was building a 360 it probably wouldn't be worth it. 401's you can pull a pretty easy 500 hp and if your building for over 350 hp it's a nice measure IMO.

[Ranger]

Hi. NO AMC block came from the factory with 4-bolt mains. The "special" 360 block was just a 360-401 service replacement block (from a 401 casting) that the factory only machined out to 4.08 instead of 4.165. There is mention in the (often misunderstood) performance book that the 360 had "provision" for 4-bolt mains. It was just that it was the 401 casting (see below) and they made the bore to only 4.08.

This 360 block (which was also what AMC used if a 360 blew up under warranty), and ALL the 390 and 401 blocks are the only ones that you can add 4-bolt mains to due to the fact that they have much thicker webbing in the bottom of the block. (Turn a 360 and a 401 upside down and pull the pan off of each if you ever have a chance)

There has been much discussion over this on the AMC lists over a period of time.

[Ranger]

No blocks were drilled from the factory that I know of. "Provision" just meant that there was enough metal there to drill.

[Elliott]

Thanks for the post Ranger.

[Ranger]

Sorry for coming across as a smart***, I do that sometimes.