02sierraz71_5.3

iTrader: (2)

Interested in what you guys think or would do to create some heads going on a 6.0 in a truck, looking for max Tq.

Porting is fine for higher HP configurations but it seems to sacrifice some lower end tq numbers for upper end hp. Is it the increased velocity (smaller ports) lower in the rpm range increases tq? Also adding larger valves

On a cam to match these heads. Thinking lower lsa with some advance ground in around 228/230 duration medium lift.

Any criticism is welcome

xfactor_pitbulls

iTrader: (16)

The 6.0 is going to produce better torque from the get go as opposed to the 5.7. But you would want a good advance (+4) and strong mid range and low end flow. Both are benefitted with a good clean port. The biggest thing in producing strong lower lift numbers is to have a good "line of site" from the runner opening to the seat. No dramatic curves right before the seat is important, while it helps higher in the lift, midrange sacrifices here. A 2.05 valve with a good 4/5 angle matched valve job can yield great low lift numbers with just the valve guide garbage taken out, removing the rocker arm boss and blending the larger seat into the bowl. The interior :curved wall into the short turn is what makes the difference in a 290cfm head and 310cfm head. Really that is a fairly easy way to go 205cfm at .300 and 290cfm at .600. I think you are right about the cam specs, but maybe even go alittle more on the duration and keep lift around .580-.590.

Brandon

slowpoke96z28

iTrader: (2)

Brandon, would you recommend milling the head for a little more compression and better quench?

jrp

iTrader: (16)

AFR 205's.

02sierraz71_5.3

iTrader: (2)

the main interest with these heads would be creating mid range torque, it seems as though alot of head builders sacrifice that for top end hp and big numbers at .600 lift. I was wondering about trade offs, keeping high velocity at lower lift numbers. Not going after hogged out heads just for the sake of flowing more air.
I was under the impression that higher torque numbers come from velocity more so than just flowing alot of air. If that makes any sense. like the amount of water going through a garden hose vs a fire house with the same pumping force behind.

PREDATOR-Z

Uhhhh, AFR 205's

marleyskater420

You are right about the velocity.

That is why the S2k doesn't have much tq, because the intake flows SO well, it doesn't push the air through with a great enough velocity.

Torque=force x lever arm(at least I sorta stayed awake in physics) and the force is the velocity of the air(well...one part of it..)

This same reason, is why pushrods have more lowend torque than DOHC motors. N/A of course. The average pushrod design won't flow as well as DOHC(1 vs 2) and so it will give increased velocity to the incoming air, and thus produced greater torque.

02sierraz71_5.3

iTrader: (2)

you and jrp are right afr's would be killer only one problem dont have the budget for those would be nice though.

This is a rehtorical thread more interested in what makes those higher tq numbers so maybe I can design some silimar heads or know what to look for at a cheaper price. I seriously doubt they would ever stand up to afr's but money doesnt grow on trees.

Any recommendations on how I could devise some heads that would meet what Im looking for. One tell tail sign might be good flow numbers at lower lift vs heads with higher numbers at higher lift.

PREDATOR-Z

Cost effective?, 5.3L, 2.02 int/ 1.55 exht, torq cam (vinci 047), 1 5/8 headers and the Big uggly intake.

02sierraz71_5.3

iTrader: (2)

Problem with that is the cc is so small on 5.3 heads, what would you do in order to keep compression around 11:1

Has anyone ever tried 5.3 heads on a 6.0?

slowpoke96z28

iTrader: (2)

if the combustion chamber is too small, you can use a thicker head gasket

Adrenaline_Z

Using a thicker head gasket will sacrifice the quench height. Not a good idea
if you want to maintain the LSx combustion characteristics. It would be better
to install a negative dome piston to eat the volume and keep the quench height
the same (peformance and technically speaking, not cost wise).


Milling the head wont improve quench. The clearance between the piston
dome and head remain the same.

I disagree. The S2K has less TQ because of the smaller piston bore and
shorter stroke.

If you go by that theory, the DOHC LT5 should have made less torque at
lower RPM using similar bore and stroke of an LS1.

Torque produced is actually the amount of cylinder pressure exerting over
the surface area of the piston X stroke.

What you are referring to would be Volumetric Efficiency over the RPM range
(which can be used to figure torque).

The intake runners are tuned for higher band RPM but that doesn't necessarily
mean the air is not entering the cylinder. That has more to do with pressure
in the manifold and lower pressure in the cylinder, along with pulse tuning.

Most people associate low torque with DOHC because they are normally
compared with small displacement import motors which require high RPM to
make decent power.

ssheets

iTrader: (1)

Sounds like my LS1 sans the intake.

02sierraz71_5.3

iTrader: (2)

just thought Id share this post I found on cams sort of blends with this post

Originally Posted by Harold of UltraDyne
The simple answer is depending upon how much air & gas is in the cylinder. Stock cams with a lot of S/C boost make a lot of torque, because the blower pushes a lot of air & gas into the cylinder.
Here's how you do it without a supercharger/turbocharger......
The 1st thing that happens in a cam cycle is that the exhaust cam opens. The further away from BDC, the more top-end, the closer to BDC, the more bottom-end. Naturally, the exhaust cam will be a compromise between these 2 choices. I keep the exhaust valve shut as long as I can, this adds torque to the crank at ALL RPMs. Because it opened late, it must open fast, to make up for lost time. A critical velocity builds up in the exhaust before BDC, which helps evacuate the cylinder during the exhaust stroke. If you are below the critical velocity, the crank takes HP from other cylinders to pump out the exhaust--This is called 'Pumping Loss', and subtracts BHP from your total produced.
The 2nd thing that happens is the intake valve opens, BEFORE TOP-DEAD-CENTER. At the point of intake valve opening, there exists in the combustion chamber and cylinder a certain volume of exhaust gas, and at a certain POSITIVE back-pressure. The intake valve opening causes an exhaust pressure spike to pulse into the intake port, followed by exhaust gases. Remember, the piston is pushing exhaust gases out of the cylinder, and you've just opened up a low-pressure escape route.
It's clear, the earlier you open the intake valve, more and higher-pressure exhaust gas enters into the intake port, blocking and delaying future clean air-flow. And of course, the later you can delay opening the intake valve, AND still have a high enough intake valve lift After Top Dead Center, the sooner you start good air flow, and the higher port velocity you can achieve.
The critical part of the intake cam is that part from TDC to about 75° ATDC. During this part of the intake cycle, the piston is ACCELERATING! After 75° ATDC, the piston starts to slow down and continues to slow down until BDC, when it starts moving upward again and picking up velocity.
The port velocity is the rate of filling the cylinder. The high lift area after .200" cam lift on the opening side, and the entire closing side, is the time or duration, for filling the cylinder. If you're filling the cylinder fast, and you've got a lot of time to do it, you will make a lot of torque. We call this 'Inertia Ram', because the column of air & gas in the intake port actually has a mass and a velocity, and therefore inertia, and will continue to fill the cylinder even after BDC.
The 3rd thing to happen is the exhaust closing ATDC. This has the least effect on the cycle, and affects low-end torque the most. Because at low RPMs there are more milliseconds ATDC when the exhaust is still open, there is more time for residual gases to be pulled back into the combustion chamber and dilute the intake charge. This is why wide LSA cams seem to have very good off-idle power, the exhaust closes earlier ATDC...
The last thing to happen in the cycle is the intake valve closes ABDC. If you've done your homework correctly, the intake is still shoving clean charge into the cylinder at this point. Some designers who haven't slam the valve shut in order to trap whatever charge has entered. As long as the charge is still being rammed in by inertia, shutting the valve relatively softer helps RPMs and spring life. Remember, it's the TOTAL amount of clean charge trapped in the cylinder when the intake valve finally closes that determines how much torque an engine will produce.
It's taken a number of years to figure all this out, and to put it all into effect.
Some people still haven't.....

UDHarold

marleyskater420

I agree that the s2k makes less torque because of the piston bore,etc. I was merely using the intake because it also greatly effected the torque and airflow.

I wasnt basing the torque soley on the intake, but I was saying the size of the runners effects the airflow velocity.

I wasn't saying that the air isn't entering the cylinder, I was saying that the pressure at lower rpms does not give great velocity for the air, and thus it does not perform as well down low as opposed to up top.

You said what I tried to say, but failed.