candlelit

iTrader: (21)

My brother has brought to my attention of a summer project... rebuilding my 346 ci block. Since everyone is going to ask my goals/intentions... it's going to be a DD... mostly city driving but some highway driving. I'll be working on a budget, which is why my new plan is to go ALL N/A instead of forged & FI. I hope to get at least 525-575 rwhp out of my setup.

Anyone want to throw some numbers out there for a crank size & pistons & rod lengths? I think GM recommends nothing more than a 4.25" stroke for an LSx. Would I be able to use a 4.125" crank ... or maybe just going with a LS7 4" crank? Right now my internals (besides small-mid size cam) are stock, outside I've got ported LS6 heads & intake, & hooker long tube headers. I figured with a larger bore, my CR is going to be high... which will probably prevent me from throwing turbo on anytime... and I'm fine with that.

How much power am I capable of making with my block? Maybe talking larger bore, and a big cam.
Any thoughts on using a LS7 crank & rods? Would I have to shorten the LS7 crank to fit since the LS7 is used for dry-sump applications?

smok'nZ

iTrader: (160)

slow trap

iTrader: (22)

well for starters you can only hone your shortblock,unless you take it and have it resleeved which these days you can get an ls7 or another block already resleeved for a decent price. i would stay with a 4" stroke with 6.125" rods and you have 382-383 cubes. to get 525-575 rw out of that type of combo would take a very max setup and you still may be on the low side but 475-500 rw is fairly easy with the right parts.

candlelit

iTrader: (21)

so basically 383 cubes would be the max I could get out of it? I'm leaning toward the 4" crank & the 6.125" rods. what pistons should I go with if I used that setup? will I need to get different heads?

slow trap

iTrader: (22)

it depends on the cc of your heads and cam selection to figure out what pistons you want to order. i'd say around 11:0 -11:5 scr should be around where you want to be compression wise. if your heads flow pretty well with an m6 just guessing you should be around 465-475 rw or so with a decent sized cam like say a 238/242 or so.search for 383 combos and see what others are putting down.

candlelit

iTrader: (21)

thanks man! that's GREAT info! I'll look into it

Beaflag VonRathburg

iTrader: (176)

Actually I've seen quite a few 392 cubic inch motors on here. 2 x 3.1415 x 3.905 x 3.905 x 4.1 = 392.8194587075

candlelit

iTrader: (21)

I've never been explained how they get those c.i. numbers?? such an easy & newbie question, but I'd like to know. pretty dumb on my part considering I'm talking about rebuilding the block.

Beaflag VonRathburg

iTrader: (176)

2 x pi (3.1415) x bore x bore x stroke

It's really easy

Stang's Bane

iTrader: (22)

http://www.csgnetwork.com/cubicinchdispcalc.html

NemeSS

iTrader: (127)

if u want bore, go with a .060 over 6.0 block
with stock crank u will be at 375ci
and with 4 in. crank u will be at 414ci.
the heads u have now will make a mean tq monster
i would go and have always gone with a 6.0 iron block
only 60lb. dif. over alloy block. speed pro makes replacement
hypereutectic pistons that come in around 500$ with rings.
from 4.00-4.06 bore sizes.
just sthrowing some ideas out there that have worked for me.
i would stick with the stock crank and bore a 6.0 and put the heads u got now. still would put u over 500hp with the right cam.

Beaflag VonRathburg

iTrader: (176)

Going .06 over on an iron block is asking for trouble. Can it be done? Yes, it can but sonic testing it is a must. Also at this point you are at the maximum bore capacity of the block. It can no longer be honed and is basically trash if you ever need / want to rebuild it. .030 is a much better option. There's many more off the shelf pistons available in that sizing along with greater reliability and block strength. It's not worth it to go .060 over for right around 5 cubic inches.

NemeSS

iTrader: (127)

that is true to some extent,
but im not turning 8k rpm and such,
using arp bolts for the mains and heads, i have put over 65k miles
with minor oil consumption.
i would not go .060 over for a forced induction or heavy n2o motor
i beleive he is looking for a n/a driver.
of course sonic testing would be recommended before machining and deciding
final bore size, the good thing is that these ls motors do suffer as much from
core shift like other production v8 blocks.
i made over 475 rwhp with this combo using ls6 243 heads.
on 375ci motor, .060 overbore. mild cam, all supporting mods, ls6 intake.
also have 150 dry halo shot on the motor.