When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'd really like the advise from those who have built a iron ls1,
so I got my 5.3 block back from the machine shop bored out to 5.7,
new ls1 pistons pressed to the 5.3 rods, the stock 5.3 crank was polished
i did Not get rotating assembly balanced, some people say it has to be balanced some say it doesn't, It's going to have a mild cam ported 243 heads the goal is 400whp.
I would like the input of anyone who built a iron ls1 and Did Not get it balanced to see if it worked without problems??
im on a tight budget that's why I didn't get It balanced, if it will work like this without self destructing that would be awesome. Thanks in advance
I know that the difference between a dished 4" bore LQ4 piston and a flat top 4" bore LQ9 piston is about 15g. You're going from a dished 3.780" bore piston to a flat top 3.898" bore piston, I'm sure that the weight is much greater. You need to balance the crank IMO.
And furthermore the crank might need Mallory slugs to rebalance which tends to escalate the cost exponentially
A 3-400 dollar balance charge is not unlikely here unless your machinist is creative with a hand grinder
Even if you are putting an engine together with stock parts that you know will "work" it should always be a priority to get a rotating assembly balanced before installation. Proper balancing procedures, as well as numerous other seemingly small details during assembly, are what can make the difference between a engine that'll take a beating for 50,000 miles and an engine that'll put up with the same abuse for double or triple that time. Never skimp on your short block, a few hundred saved now is a few thousand lost later on.
Why would you not balance the rotating assembly? Most shops charge like $200. that's nothing.
CORRECT !!!!! A typical make bob weights up after matching all the rods for big end and total weight, plus matching all the pistons, with pins and clips/rings etc. and then spinning a crank plus drilling counterweight holes is in the 175 to 225 range
As the OP stated he is going from lighter weight dished 3.78" pistons to flat top 4" bore pistons.
this adds a bunch to the bob weight gram total. So either the crank counter weights need to be drilled and heavy metal slugs (mallory) BTW $45 each get installed or said balancer fella needs to be an artist with a hand grinder by removing a bunch of weight off the rod throw sides. VERY time consuming either way and much more costly.
The OP's best option would be to find a decent 6.0 crank that can take a polish and have a touch up balance....IMO cheaper than trying to UP balance a 5.3 crank
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
HELP who has built a Iron LS1? 
