mike c.

iTrader: (1)

what would be a good seat of heads for a 427ci? i thought AFR 225's would be enough.

black_knight

iTrader: (1)

ETP has heads that go up to 265, I think. Stock LS7 heads are also great. Both of those will run the LS7 intake, which is said to outflow the FAST 90 by a bit.

383ss

iTrader: (14)

an LS7 intake outflows a Fast 90 by a huge amount. also, only ETP ls7 heads will fit an ls7 intake, not the rest of the ETP line. just clarifying.

black_knight

iTrader: (1)

Yes, that's right. Thanks for mentioning it.

Beast96Z

iTrader: (21)

If you go 427, get the LS7 stuff. You'll deffiantlly maximize the potential.

mike c.

iTrader: (1)

here are a few things that i don't get. right now i have a 346ci w/g5x4 cam,AFR 205 heads,fast 90 w/ N/K-th-body,85mm mass,1 3/4 headers m6 car 12bolt 4.11's. i made 463hp 413.9tq mustang dyno,no short belt tricks no ele waterpump. . BLACK KNIGHT & 383SS-help me out here please. if the ls7 heads are good flowing heads(as stated by black night) and the ls7 intake out flows the fast intake by a huge amount(stated by 383ss)and the ls7 is 427ci why am i making more power and tq on a ls1 346ci through a 12 bolt when the ls7 is supposed to out flow/perform what i have? i have seen the ls7 making between 430hp and 455rwhp & around 400tq. i want to get around 600hp on motor for the money i'll have to spend on this ls7. what do i have to do to do that? sorry for the trouble guys.
thanks, mike c.

black_knight

iTrader: (1)

Mike,

The LS7 suffers from a lack of cam, a lack of exhaust (both the heads and the headers), and a lack of tune. LS7's with longtube headers, big cams, and good tunes are already pushing past 600RWHP. Look around in the dyno section and here and see the people that are making the #'s you're looking for. It can be done.

rjkZ28

hey guys im looking into a 427ci setup my self, and i was really considering doing ETP ls7 heads and ls7 intake, not sure one cam size yet. i also i want to spray like 175-200 shot on top as well. my goal is the car to go somewhere in the 10s on motor on hopefully in the 9s with a shot. i know its gonna take alot of money but i think it would be one hell of a setup.

disco192

Im sorry, but you will see little gain in HP by simply adding cubes. Adding bore will allow for more airflow, but you are typically limited by intake port mach number.

If you increase the displacement by ~5% then your peak HP will decrease by ~5% and your TQ will increase ~5%.

Adding cubes and not compensating with more port, then you wont see any added power.

Ive been saying this for a long time. Power (and RPM) potential is all in the heads.

A stroker just allows for more TQ and a flatter curve. With larger heads, you can increase power along with TQ (and curve).

Its not that complicated really.

Patrick G

iTrader: (14)

Going from a 402 to a 427 gains 25 cubic inches. Since the stroke is the same, you will get less valve shrouding with the larger 427 bore. Most good street strip motors make 1.35 times their displacement in hp and 1.25 times their displacement in torque when optimized.

That means:
543/502 rwhp/tq for the 402
576/534 rwhp/tq for the 427

The problem here lies with the fact that you'll be taking heads and cam optimized for a 402 and adding them to the larger 427. The 427 won't be optimized. Therefore, it won't achieve the 1.35/1.25 ratio. Basically, you will get less of a gain for the 427...more like 25/25 rwhp/rwtq gain.

mike c.

iTrader: (1)

i see how it works.gotta do it right the first time. i'll start looking into a e.t ls7 head and intake for a 427ci set up. you guys have provided lots of great help and info here,thanks. mike c.

slow trap

iTrader: (22)

well crap,this has got me second guessing my 427 plans also.isn't the fast 90/90 a pretty big restriction past the 525-550 rw range more so than say a set of afr 225 or any of the heads that flow 320+ and capable of fwhp in the 650 range ? 25/25 at the wheels is still a decent gain.wouldn't the 427 have quite a bit more power under the curve?i'm not asking for much,i was just wanting 550 rwhp,525 tq with something like the giant cam or the 244/248,427 ci with 12:2 cr with a dcr around 8.5 or so.

383ss

iTrader: (14)

a well built 408 will get you close to those numbers with a ported fast 90/90

black_knight

iTrader: (1)

Well said!

rjkZ28

i herd the ls7 intake out flows the fast instake, now do you think fast is gonna come out with a new intake or would it just be better at that point to have a sheet metal? im really looking into puttin the ls7 top end on a 427ci build, i want to make it 12.1 -12.5 compression ratio, whats the most hp i can make with that setup?

81LsElky

going with etp ls7 heads and an ls7 intake on top of a 427 with a 244/248 cam, you will see 600rwhp+ guaranteed with a good tuner! btw yes the ls7 intake does outflow the fast 90 intake by a lot and can be picked up for about a 1/3 of the cost. if fast industries did come out with another intake that would outflow the ls7 intake, it would run big$$$ then the gains most likely would be nominal over the current ls7 intake! just my thoughts.

Stang's Bane

iTrader: (22)

https://ls1tech.com/forums/generation-iv-internal-engine/559481-fast-intake-ls7.html

Stang's Bane

iTrader: (22)

By the way, I don't believe 600 rwhp is a given with that small of a cam. Look up Jason at Katech's response to the question. I know the heads and intake flow great, but 600rwhp is very stout on a 427. I am going to go with a sheet metal on PORTED ls7's and a 25x x 26x and see how much that gets me. Also with the way that the ls7 style heads flow with a big intake bias, more split is in order than 4 deg. With how high the intake flow is on these heads, the exhaust would have to flow damn near 300 itself to justify that little split. someone please correct me if I am wrong, this is just what I have gathered from hundreds of hours of research and asking lot's of stupid questions. Patrick G., do you have any thoughts on cam setup on a ls7 head and sheetmetal topend. I realize driveability will prob. suck ***, but it will be a weekend toy, and most of those weekends will be going down the track. Sorry for the hijack.

mike c.

iTrader: (1)

i've been talking w/sponcers about a 427ci. LME-has a nice 427ci longblock w/gm ls7 heads reworked(ported)and a ls7 ported intake. it comes w/every thing needed to put it in a f-body. do you guys think the ET head is better then a gm ported ls7 head??? what do you guys think of the quality at LME??

11 Bravo

iTrader: (3)

No. I think the best setup for a 427 is with LS7 heads and intake. Unless you want to start talking about big bucks with a Harrop intake. The ET heads are nice for sure, but they don't seem to have taken the big motors to the next level like everyone was hoping. I'm sure the intake is a big part of it. They should have designed the heads to fit a LS7 intake. Especially since it's cheaper than the FAST.