Justhereforinfo

iTrader: (2)

I'm currently freshening up an aluminum 5.7 ls1 short block that will be going into my 2003 silverado. I will be using the stock 4l60 trans. The goal for this engine is to make 400/400 at the tires, or very damn near that. It will be used as a spare vehicle to haul surfboards and fishing gear, and to tear some *** around town. No track use, no racing.

The original plan was to use the ls1 short block, and all ls6 stuff on top. That was before I started lurking aroun ls1tech and found out that alot of people are making around the same power level with just a cam in an ls1.

243 heads are not very common to come by in So Fla, because everyone knows they are good heads. I've only found 2 sets so far, priced around $300-$400 and they didnt even have valves.

Im considering picking up a set of 241 heads, if I can still hit my goal. I'll still be using an LS6 instake, and a custom cam.

Without porting or cnc work, how much power will i be sacrificing by using a 241 head, versus the 243?

Are my goals achievable with the stock 4l60e?

Thanks

PREDATOR-Z

Yes it is achievable but it wont be with stock heads.

Justhereforinfo

iTrader: (2)

Are you saying that I cannot achieve 400whp with stock 241/243 heads through an auto?

The_Bishop

iTrader: (10)

Yeah, pretty much. Especially in a cam profile that's truck friendly.

Justhereforinfo

iTrader: (2)

Very well then, I will just have to increase my budget or lower my expectations. Well thats done, 350whp will work for me. lol

Seriously though, what would the real world power difference be (in my setup) between the two heads?

MikeWS6

Depends on the dyno. My car w/ Tsp prc 2.5 5.3 heads / Tsp 228R put down 414/387. On a different dyno it could make 430 or more. That was through an m6.

PREDATOR-Z

Depends who does the heads. Should be at least 30rwhp to 50 rwhp stock vs ported.

Always2Slow

iTrader: (8)

A properly ported 241 head with a quality valve job will get you there no problem and do it for the least amount of money with the current local availability you have.

PREDATOR-Z

Any properly ported head will do, even other LS1 castings.

Justhereforinfo

iTrader: (2)

I have no plans on porting either head. I wouldn't trust anyone locally to hand port them, and see most cnc jobs are about a grand. That's not in the budget.

So stock for stock I'm looking at around a 30 hp bump with the 243?

Since I don't own either head at the moment, it would make sense to wait for a 243/799 casting.

Is $280 a good price for a valve job, resurfacing, and to have my springs installed/setup?

1BAD98LS1

iTrader: (33)

It's more like a 20whp difference between the 2 sets of heads (stock that is). That's a good price for machine work and setup though. Seen 241's go for less than 100 bucks....add the 280 and you have a nice set of 241's for less than 400 bucks. Just a thought

Justhereforinfo

iTrader: (2)

This is true, but 20whp is worth $200 bucks! If I could find a set of 241's for $100 it would be hard to pass up, though.

243's are the plan, but we'll see what I can find.

Thanks

96capricemgr

iTrader: (1)

I would suggest you start over on your research.

No way in hell would I bother with a 5.7l block in the truck, sell it to someone else and pick up a complete 6.0l for what you can sell the 5.7l shortblock for. The 317s on the 6.0l are equal flow to 243s. The truck intake is so close to as good as the LS6 intake that it would be fairly stupid to **** away the effort and cost of an LS6 intake on a truck. It is the true LS1 intake that is not great the truck intake is good like within a couple hp of the LS6.

I would put a transgo kit with at least a "Vette" servo in the tranny, the 2nd gear servo is smaller than they used in the 90s LT1 cars which were a lot lighter with less power.

Hell I would also say with your willingness to accept less power if you have a 5.3l now put CNC'd heads on it with the truck intake and sell the 5.7l. I would think 350rwhp achievable on a budget that way. Yeah you will spend money on heads but the sale of the 5.7l and not wasting money on a LS6 intake would have you cash ahead of the current plan.

1BAD98LS1

iTrader: (33)

Classifieds....

1BAD98LS1

iTrader: (33)

Btw the 241's would be better than the stock 243's AFTER you got um back from the machine shop...close toss up, depends on what you want to do really. Some people are hell bent on 243's so they go that route regardless LOL

JakeFusion

iTrader: (7)

Stock for stock, 20rwhp difference.

Do you already have the 5.7L block? If not, get a 6L block with 317 heads as previously mentioned and mill the heads and run a truck-friendly cam profile. With a 6L intake, some headers, and a cam, with milled heads, you could see 400rwhp with that setup.

redtan

iTrader: (5)

If this truck is mainly used for carrying stuff and having fun around town (no street or drag racing), then why do you care so much about how much your engine makes at peak?

Unless you're racing through several gears, power at 6000rpm is going to be almost meaningless. What's going to be more beneficial for you is power and torque under the curve which is where you'll be spending 99% of your time.

I would try not to focus on peak numbers (400/400) and set your goal on the most power and torque throughout the power band. If that only nets you 370hp then so be it, it will be a more fun truck than one that makes 400hp but has shitty power under the curve.

Justhereforinfo

iTrader: (2)

I have not placed any focus on the cam or the intake, in this thread. Those are the two major role players in powerband. So I dont know what prompted you to comment on "6000rpm power" or me "caring about peak power". I even commented that I would take less peak power... Right now im talking about the power difference between the two heads. I've found the answers I was looking for.

Since another member mentioned the stock truck intake is actually an upgrade from the LS1 intake, I will definately be considering using that instead of the LS6 intake, since it will help keep my powerband more truck freindly.

While I appreciate the fact that there are better setups, I'm building an aluminum block ls1/6. You can build whatever you like Sir. A stock LS6 motor will be a very nice upgrade to my tired old 4.8. No denying a 6.0 would be better, but I dont have one, unless you're willing to donate...?

96capricemgr

iTrader: (1)

Far as I know the truck intake wont affect powerband. The "truck parts are for torque" thing get BLINDLY applied to things often. There are two reasons you don't see truck intakes on LS1 cars, one it is TALL and hard to fit in many vehicles, two it is ugly once you remove the cover.

IMO the 5.7l are almost the last of the LS variants I would ever consider, they command a premium price and can't hardly handle an overbore. Heck the newer 4.8l comes with the 243/799 heads. I have debated looking for one as the truck intakes on those are a little better than the one on my 2005 5.3l as well as those obviously being the heads everyone wants.

spy2520

iTrader: (3)

What did I miss? 400rwhp impossible with a cam and 243s? Call me crazy, but I feel I've seen several cam only ls1 cars in the the 400rwhp range without those heads. Only things I see holding it up are it's an auto, which means you'll need a stall, which means it'll kill any dyno numbers you want to see. Also, I dunno if the ls6 intake will hold you up or not. And you're probably gonna need a big *** cam. My advice is don't even worry about dyno numbers. It is a truck after all.