w1151228

iTrader: (1)

Is there any advantage to buying a LS7 Short block vs an LS3 that's stroked to be a ls7? In terms of money spent it seems like it would be cheaper to just buy the ls7 since your not spending all the money on machining etc. Does the ls3 limit head selection to just ls3 heads?

I want to end up with an LS7 I'm just trying to figure the most money friendly way to do it. Someone please give me some insight on the subject.

ToxicWS6

this also interests me so stayin to see, if i was to guess if u find a stock ls7 short block cheap some where i think it would be cheaper but u would have to wait for a good deal, so idk lol

Orange Juice

iTrader: (3)

The Ls3 is a smaller bore so it requires more stroke to obtain 427 ci. There has been some concern about having that much stroke in the ls3 sleeves.

garygnu

check Texas Speed for pricing .and check SDPC for engine prices .

DietCoke

iTrader: (18)

ls7 is going to live a lot longer, and make more power at the same CI due to less valve shrouding, rotating assembly stability due to shorter stroke, less piston rock and speed, as well as superior windage control

ToxicWS6

all good points imo, makes sense, if say some one ( i know this sounds a little far fetched since where talking about an ls7 but) was to pick a factory stock ls7 long/short block up from a junkyard or something similiar, are there some out there that are stock blocks pulled from wrecked cars that people dont want 10-12k for? lol

Mean87SS

iTrader: (21)

no...

dckmn52

theres a few other advantages too. block design allows better bay to bay breathing, lighter overall rotating assembly, like OJ said you need alot of stroke to punch it out as far as the LS7 as far as displacement goes so add R/S ratio to the mix.

are there LS7s around? sure. ive got one in my garage. 1200 bucks!

Cra-Z Larry

Gm designed the LS7 block for a 4" stroke so it has longer cylinder bores than the LS3. To get an LS3 to 427ci. you'll need a 4.1" stroke which pulls the piston farther out of the cyl. at BDC, hence piston rock and piston skirt wear. SDPC sells the LS7 block for $2725, that may be the better route unless you consider an LSX block at $2295.95 for the standard deck or $2495.95 for the tall deck. Good Luck with the build!!

BlackCowl

iTrader: (15)

Why would anyone buy a ls7 block when lsx is cheaper?

427zm

iTrader: (9)

I have a friend that just swapped a LS7 into his C5, and I'm having a LS2 based ERL 434 built now that'll run LS7 heads. Bore= power period. The LS7 (4.125 bore) or larger bore does many things for you that Diet Coke spoke to earlier. Note, Diet Coke is speaking from experience, he has a 430 cube stroked LS3 in his car. Personally, as opposed to the "buy an LS7 approach", I'd look to either ERL or R.E.D. to build a (4.125 or bigger bore) resleeved shortblock out of a LS2/3 block and throw some LS7 heads on it (MAKE SURE TO THROW NEW SS EXHAUST VLAVES IN THE LS7 HEADS!!). This will give you a solid platform for over 600 wheel (if you want it) and will run well for a long time.

The buying an LS7 approach will cost you more overall, and the pistons still aren't forged. Building a resleeved big bore will allow you to have an entirely forged bottom end.

427zm

iTrader: (9)

Weight.

doug gall

how much?

alexus6798

iTrader: (24)

Glad I saw this thread because I was considering having an LS3 based 427 built, but I plan on boosting and was told that if boosting go with a 418" LS3 instead to have a thicker crown on the piston..

ToxicWS6

nice! i guess just keep an eye out for good deals, i found local place that sold me an lq4, TB to oil pan for $350 so i guess u never know what you may find lol, its still sitting in my garage cause im not 100% sure what i wanna do with it but for that price i knew i had to snag it lol

427zm

iTrader: (9)

ERL Shortblock will run $5500 if you have a core LS2/3 block to send them; $6800 if you don't.

R.E.D. Doesn't assemble motors, they only resleeve blocks, so installation, and rotating assembly are the variables. When I figured this up, it was roughly $6200, but the hassle with running a block down, getting the parts for the motor, transporting them to my builder, so on and so forth, this approach didn't seem to be a wise choice for me.

Odds and ends like sensors, gaskets, covers, and such, will run you near 1k.

Heads are the other major cost. Going with GM LS7's will run you $12-1500 to buy used, and then another 2k or so to get WCCH to port and replace the exhaust valves. Then again, the heads will all vary depending on what you want to run: rectangle v cathedral; aftermarket v OE cast. It all about what you want.