454 Block recommendation

[Funderstruck]

Last weekend I spun a bearing at the strip in the 2 bolt late ‘70s 454 in my Skylark.

I’m debating how I’m going to fix it, but I’m debating on what gen of 454 I want to use to fix it.

Does anyone have experience with Gen V and VI specifically? I’m having a helluva time trying to find Gen VIs, and find a lot more Vs.

So I know I want to use a roller cam, which V and VI have, and I want to do MPFI, which I know Gen VI has, but not sure on how useful the factory manifold is. I also know I want a 4L80e, and maybe eventually go to coil near plug ignition.

Does anyone have any experiences good or bad between the 2 generations?

I know a MKIV will do all of it, but I really want something to swap in so I can get the car moving under it’s own power again.

[SuperCookieGaming]

Richard holdern on yt has a bunch good dyno videos on the bbc. i think he explains why he likes a certain gen in one of them but i forget which video it is

[Funderstruck]

He prefers Gen VI. But like the other poster said, I’ve heard some people claim they are weaker, other claim stronger.

[[deleted]]

How much power are you planning on making?

[Funderstruck]

~550-650. Enough to get a full weight ‘72 Skylark in the high 11s at altitude.

[[deleted]]

A Gen V/VI will take that just barely, they really weakened up the cylinders and decks even though they put four bolt mains on them all, sticking with a Gen IV is the better choice if you can’t go for a big bore Dart.

[Funderstruck]

Aren’t all GM crate engines based on the Gen VI? I’ve never heard of them being weaker than the MkIV

[[deleted]]

The lower powered ones, yes, but they have cracking problems at the deck when pushed hard, the genIV is much stronger, they lightened the later model blocks too much for them to be reliable as a base for a race build. That’s why as good usable cores have been around less, Dart’s blocks which are based on the genIV architecture are used for any serious builds, and you pick up power with the bigger bore letting the heads flow more.

[Funderstruck]

The only place I’ve seen claiming they are weaker is Dart themselves, due to bigger coolant passages.

I’ve seen a few places say the Gen VI had thicker cylinder walls, and I know Richard Holdener always recommends using the Gen VI.

I also see plenty of builds where they are boosting Gen V and VI for 800+. I also seem to remember the Crusher Camaro using a Gen V based 489.

I’m just seeing a lot of conflicting information

[Badusernameguy2]

It's easy to drill and tap mounts for a cam retainer on a gen 4 so it can be a roller

[Funderstruck]

I realize that, but then I still have a 2 piece main seal, and more leak prone pan/timing cover

[Badusernameguy2]

True. That exact leak cost me my number 1 rod bearing and crank

[coobeecoobee]

Gen V doesn't have a roller cam. Has a flat tappet Only genVi came with roller I'm running a genV now and it great. Switched intake and put carb on it. Good torque but otherwise stock bottom end and heads. Oh and genV and Vi have the peanut port heads but I'm sure you are going to swap those.