02sslayer

iTrader: (4)

ive been looking into this motor for my ss. i heard having that bore and stroke makes for a motor that is not so strong. and there were a couple other issues with that block. so my question is, does anyone here run this motor? does anyone know anything else that would help me? thankyou

Wild85

iTrader: (1)

Are you going boost or NA? If boost, look at my signature.

02sslayer

iTrader: (4)

ill be going NA with about 11.5:1 comp.

Pwebbz28

iTrader: (31)

IF you talking about a 4.1 stroke in a 6.0 iron block it is not ideal. The cylinder walls in an iron 6.0 are the shortest of the ls family. Save a little more money and go with a LS2/LS3 block or stick with a 4.00 stroke. I would.

02sslayer

iTrader: (4)

man that is dissapointing....it says in the description that 12lbs boost is the the max and no more than a 200 shot. with the price being the same as a 408 it does seem to good to be true

FlamingTA

iTrader: (8)

I'm getting my 421 from ERL on my LS2 block. They, Wiseco, have the piston design nailed down pretty good when it comes to long strokes in these engines now.

02sslayer

iTrader: (4)

i wonder how weak the 421 block actually is? is it gonna fall apart after 10000 miles or somethin?

FlamingTA

iTrader: (8)

Why would it be weak? Even at 4.03" the sleeves are thicker then the ls1 sleeves plus it has alum between the cylinders. Now I would say that if you want to make big power with a big shot or big boost then you should pick the 4.0 stoke engine. The block is not the problem, it's the CH of the pistons. At a 4.1 or 4.125 stoke, you don't have alot of meat at the top of the piston. This is not a problem for a NA or small shot engine.

LS6427

iTrader: (2)

Save for a better set-up..........you'll wish you had if you don't.

$3,800 for a 421ci short block..........save a little more and get a resleeved LS1 block. You can find LS1 blocks pretty easily and cheap. And the LS1 block is perhaps the strongest of all the LSx blocks ever made. You can send a block to someone like RED and for roughly $2,500 you'll get it back ready to assemble.....sleeves, machine work, stress relief, installation and decking, boring, honing, align honing.

Or use a resleeved LS2 block.

Yea, its easy for us to spend your money.....but man you'll have a block that'll take a serious beating and have plenty of room left for a rebuild, or two. You can do a 441ci, have plenty of sleeve length for a 4.125 stroke and a 4.125 bore. N/A...you can bore it more if you want to or need to later. Brian Nutter at Wiseco has just the piston for long strokes......

.

02sslayer

iTrader: (4)

i dont know why it would be weak...ive just been hearing about issues i would have with the crown being to thin or something like that. thanks for all your advice, i wont be running NOS or boost, so ik guessing i should be safe

02sslayer

iTrader: (4)

ive decided to not go with the 421ci motor....there are alot more options

Sales2@Texas-speed

iTrader: (5)

It's not really a wall thickness issue, it's an issue with piston design and having amongst the shortest sleeves of all the LSx family. If it's an iron block LQ engine going in my vehicle, I'd stick with a 408ci every time.

02sslayer

iTrader: (4)

i agree 100% does the 441CI and 454 CI have the same issue as the 421?

LS6427

iTrader: (2)

Those engines are RE-sleeved with longer, thicker iron sleeves. You can stroke them and bore them much more....no issues.

.

Sales2@Texas-speed

iTrader: (5)

If built on an LS7 block it is still an issue, but on the preferred LSx tall-deck block, all of those problems are resolved

Correct, they are preferably built with either a sleeved block or an aftermarket block like the LSx or RHS block.

Firehawk441

iTrader: (41)

I have to agree with all the others. It's not a desireable combination to use for ALL the reasons mentioned and a number more that I won't get into.

There were however 2 people that were very succesful with a 421. Tom the Roofer and Tim Tosto. Once upon a time they were the 2 fastest N/A cars.

1nastyss

iTrader: (12)

Man , i was debating about the same setup, but im sticking with the 408 and putting all my money toward the topend parts

02sslayer

iTrader: (4)

im thinking about the same thing, but i really wana build an LSX 454, it would be worth it to wait a lil longer to get a motor as badass as that

1nastyss

iTrader: (12)

True that

FlamingTA

iTrader: (8)

I can't fault you for going to the 408, it is a more reliable, tried and true setup. I went for the 421 from ERL for a little something different and to get more average hp. The 421(4.03x4.125) won't make must more HP then the 408 really. It will probably make more average HP and torque. I was after that more average HP and higher flatter torque curve for my heavy as hell GTO. Good luck with the 408, I'm sure it will haul.