Brandon98TA

I'm just curious why all the 422/427 LS1s are only making 510ish rwhp and now some of the 346s are putting out 470rwhp. Why aren't the big cubes closer to 540+rwhp. Just trying to make some sense out of it.

Brandon98TA

Just did some math. If a 346 can make 470 rwhp, a 427 SHOULD be able to make 580. Anyone wanna help out here? Are the 427 guys just not using aggressive cams? Thanks in advance for the info.

Brandon.

WeatherGuy

470 RWHP 346s are running solid roller cams or extremely big hyrdraulic cams. Check out the HP of the very few solid roller large cube motors. One solid roller big-cubed motor just pulled 750 FWHP on an engine dyno ~ 620 RWHP. But that motor had a custom sheet metal intake.

BIGBOS

There are a lot of different setups out there...there are a lot of big cube motors putting out some power, and then there are a lot of conserative ones.... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I'm sure if you built a solid roller 434 c.i. C5R motor you would have some fun... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Brandon98TA

Is it possible to build a 427 making 540ish rwhp, <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" /> L88 style? Semi-streetable?

<small>[ February 23, 2003, 11:15 PM: Message edited by: Brandon98TA ]</small>

Nine Ball

iTrader: (38)

Don't compare peak rwhp values. If you overlay the hp curves of a stroker on top of a 346ci setup, the difference would be mega-obvious, especially in the torque department.

Why aren't the bigger engines making more power? Because we are all still using the restrictive LS6 intake. That intake only flows 280 cfm, and my heads flow 335 cfm. The bigger the engine, the more it is choked up by that intake. That is the primary reason.

My 434ci pulled 525 rwhp. That isn't bad considering it was thru a 12-bolt rear, 4.10 gears, 3.5" heavy-duty steel driveshaft, and on 28" drag slicks. In a stock driveline 6-speed, this engine would probably put down 540-550 rwhp. All that on 93 octane too.

Tony

Nine Ball

iTrader: (38)

This will help illustrate the differences that cubes can make on dyno graphs. All three of these vehicles have ported LS6 heads, LS6 intakes.

<img src="https://ls1tech.com/dynojet/346vs382vs434.gif" alt=" - " />

In other words, cubes rule! <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />

Brandon98TA

What options are there in the field of intake manifolds? Wasn't there an Australian guy making a new one? If this was going in a C5 and firewall wasn't an issue, could you maybe use the larger intake from the 6.0L trucks? Thanks for the info so far guys.

Brandon.

DONAIMIAN

iTrader: (18)

The only thing that stops us from using the truck intake is the fact of the cowl is in the way, the firewall dosent really pose a problem. If it was an all out race car, **** I would get a plastic windshield and cut the cowl some of the window and put 4 inch+ cowl hood on it that came all the way back to the windshield. <img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />

Brandon98TA

The cowl is what I meant. Does it still get in the way on the C5s?

Plan B

You could get a GTO. No probs fitting the truck intake then.

<img src="http://www.purefect.com.au/planb/Truck%20Intake.jpg" alt=" - " />

<small>[ February 24, 2003, 04:04 AM: Message edited by: Plan B ]</small>

ls1290

iTrader: (20)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Brandon98TA:
<strong>Does it still get in the way on the C5s? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes, but not as bad as the Fbodies.

Chicago Crew UnderBoss

iTrader: (1)

What Nineball said is right on man and the one huge difference is the mega torque made through out the whole entire rpm band which dwarfs the torque made by 346s.

And as the old saying goes, torque wins races! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

MTI 427 C5 Roadster

Lost Time

How much better flowing is the truck intake? I wasn't aware there was that much of a difference between the two. I've got a hybrid car that shouldn't have any clearance issues. If it's worth the swap I might have a brand new LS6 intake for sale. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

CW 99 Z

There was a post back a little bit ago about the different intakes. The truck intake flows a little better than the ls1, but not as much as the Ls6

white2001s10

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Wide Open Throttle:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
Why aren't the bigger engines making more power? Because we are all still using the restrictive LS6 intake. That intake only flows 280 cfm, and my heads flow 335 cfm. The bigger the engine, the more it is choked up by that intake. That is the primary reason.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Definitely the intake. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I also agree. 75mm intake neck combined with 10"+ runner length is just not matched well to a big cube engine.

HP-GURU

The intake hurts some, but from the dyno's that nine ball produced, the increase in cubes did about proportionatly increase the tq curves.

For really high results, the intake manifold would need to be a bit shorter and have higher flowing runners.

At some point for the big strokers, to make more power, you will need a head that flows 400CFM or so. Of course this will hurt low speed tq production some, but you still should have way more tq than a 346 will have.

C$

If the LS6 intake is so bad, how did the SAM car trap almost 140 with a stock LS6 intake on a 418? Im not saying that it cant be improved, but that it is extremely effective for its relatively small size.

HP-GURU

C$,

I'm sure you are well aware that intake manifolds, just like headers are "designed". They have an operational range for a cubic inch displacmement.

The LS6 intake was certainly not designed for a 418 stroker that rev's to 7500.

At some point a intake designed for this level of operation will crush the LS6.

All I'm saying.

The LS6 intake is doing very good.

Dennis

strokedls1

iTrader: (1)

What most people don't realize is that the big displacement engines are backed up by th350, th400 tranies, and a 9" or 12 bolt rearend with steeper gears. Drivetrain effiency is decreased, and the ls6 intake bottle neck is just one other factor. It's all about torque, and there is just no replacement for displacement. The numbers will increase as more engineering developement comes to light. There are just more people putting the time into the 346 ci blocks to find all the power that is possible. A lot more people can afford a head cam swap over the cost of the 427ci build up.