Boring a gen V 454 bowtie 4 bolt maint to .120"?
 

Sorry, I meant .125 in the topic


Can anyone confirm this?

I'm tossing around my future engine upgrades, and right now I am debating between sticking to a na setup and boring n maybe a little stroking.

If I can get .125 with just a bore, then I should be able to stroke to a 510 or so I believe?

My other option in which I am way more familiar with is turbocharging the 454 with the next overbore size needed. Turbos are fun, and hp can be gained or lowered with the turn if a knob with any standalone.

Obviously I would have to go closed loop on my cooling, whic I have already thought about doing with the stock setup. Fabbing the manifolds would be pretty easy, along with building a new intake.

A part of me wants to go with a bored n stroked na build, since I am not going for speed records, the turbos seem overkill, but it might be a cheaper build since I can fab up most of the parts and turbos are pretty cheap if you know what you are looking for.


Anyhow, if anyone can school me on my particular version of the 454, and what would be a good path on it, I would be greatly appreciate it.

You would deffinately want to have the cylinder walls sonic tested first which is a couple hundred bucks. I know some of the older Mark IV's you can bore .125" over. Mines at .100" over now with 4.25" stroke for 505 in's.

+ 1 for cylinder wall sonic test before invest waste monney

Turbos in a car, and turbos in a marine application, are quite different. Theres a reason if you look around this site, 90% of the forced induction marine engines are running roots or screw blowers. They just work. Not that a turbo cant, but unless you know how to set them up in a marine application, you're gonna be replacing things more than you're boating. More to than adjusting a knob to change your boost. If you want some extra power, and have a 454, here is what I would do.

I would keep the bore as small as possible. Overboring gains a little power, but even if you saw a 25HP gain from it, that doesn't mean squat in a boat. Having the extra meat in the cylinders and room for future rebuilds imo far outweigh the performance benefits of the boring.

Id consider a stroker crank with .250 rods, and build a 489, or 496CI. Get yourself a good pair of cylinder heads. Forget the GM oval port iron stuff that gets so much praise on the internet. These aren't gonna be stoplight to stoplight engines. Look into some Dart 310 Pro 1's, AFR 290, etc. Go with a mild hydraulic roller cam, spec'd for the application. Bolt on a 8-71 roots blower, B&M 420 blower, and enjoy a reliable 800HP engine that will last.

I have a pair of 468CI engines, that made 804HP 6 lbs of boost. Pump gas, no intercooler, B&M Mega Blower. Nothing exotic.

Dont forget after 20k on the 800 hp engine u are going to need a different drive!!!

the gen 5 blocks are thin,.060 over is as far as i would go without sonic checking,thats just my experiance.

If its a saltwater boat I would never go over .060

Airbats,
If your block is, in fact, a Gen V Bowtie (9.800”/10.2”) block, you’re in great shape for the proposed modifications.
Gen V Bowtie blocks were a siamesed cylinder case with elliptical bores. They were delivered with a raw bore size of 4.250” and a minimum wall thickness of .500”. A bore size of 4.500” (in your case .250” over) was conservative, and the block was designed to provide a .325” wall thickness on the major and minor thrust faces @ 4.600” bore dimension. The recommended max stroke was 4.600”.
Regarding HP rating for the blocks, the nodular cap block was conservatively rated to 800 HP and the 8620 cap block was rated to 1200 HP. Again, this information is predicated upon you having a Gen V Bow Tie block. If you need the casting numbers validated, let me know.

Bob

i have the same bowtie block only 10.2 deck .gm parts hp parts catalog states can go .250 over mine are .125 over now @511 ci

i missed the bowtie part of the post,i was refuring to a std production block,sorry for any confusion.