71 chevy

iTrader: (18)

hehe, you are talking about 41 cubic inches of difference in bore size.

if an engine only made 1 hp per cubic inch,(which is super low in the cammed ls world) the 6.0 would still make 41hp more than the 5.3, NA. Think about it.

Sarg

iTrader: (6)

Now take into account the fact that for the same turbo combo on the 5.3 vs the 6.0 the 5.3 could be right smack dab in the middle of the efficiency range of the turbo compressor AND turbine and make more hp. It is all about the combo. Displacement to an extent is irrelevant (to an extent) unless all other variables are known, turbo being one of them. The S475 with an 83mm turbine will be much more efficient on a smaller displacement than a larger one. Consequently a S591 with a 110mm turbine wheel will definitely work better on the 6.0 (or larger!) motor. You can not say that x displacement will always make more than Y displacement. Try making 750 AWHP with a single GT35R on a 7.2 liter motor. Throw that same turbo on a little 4 banger and it is not out of the realms of possibility.

It is never going to be an apples to apples comparison. If I am specing a turbo for a 2.5 liter 4 cylinder it is going to be much different than one for a 6.0. 5.3 to 6.0 is much closer, but I would still choose different turbos for the two motors.

jridenour31

OK? So with the EXACT same setup (heads, cam, intake, compression...) and the only difference being bore size, you really think it's going to make that big of a difference? No way in hell. Hp is not determined by cubic inches. You're not going to add hp just by adding cubes.

71 chevy

iTrader: (18)

hear me. please. it is not a good idea to pick out a turbo then buid a combo for it. A good idea is to pick out your combo then select the appropriate turbo for it. I dont know how to say it differently.

even bankrupt gm didnt put the same cam or heads on the 5.3 as they did on the 6.0. lol. why would you think its a good idea to put the same cam in two different sized engines.


i HONESTLY thought it was obvious that if you have a bigger engine you need a bigger cam. I also thought it was plain old vanilla common sense that there is no replacement for displacement. Obviously I was wrong.

the only 2 stock shortblock with stock heads engines that have ever run in the 9s NA have both been 6.0s. why do you think this is the case?

silver_82

your joking right? re-read your last sentence.

Yes you will add hp and torque if the only thing you do is open up the bore. Cylinder pressure is what moves the piston down, so lets say you have X psi in a cylinder with 3.78 bore and the same pressure on a 4.00 bore. The 4.00 bore will make more power.

Sarg

iTrader: (6)

I think you need to go re-read my above statement. Who said it was a good idea to spec a build around a turbo (unless limited by class rules)? My thought is settle on an engine (for whatever reasons) and then get a turbo to go with it. The turbo is determined by the engine, not vice versa. But by merely saying that for ANY given combo a 6.0L will make more than a 2.5L just because it displaces more is just not true. It depends on the set up. And AGAIN, I would spec DIFFERENT turbos for the two.

silver_82

Call911, Here is my recomendation, take it however you want.

It does not sound like you want to build a purpose built drag setup, but more of a fun on the street and whoop up on some fast cars and bikes kinda ride. Also sounds like you want to have good reliablity. You also mention that you will be using an M6 trans, and the track visits will be slim.

Build a 5.3 (better yet a L33, aluminum 5.3) with the 7675 or a BW s374 or s380, these turbos are easier to package, the s475/s480 are badass turbos but you do not sound like the type of person that wants to deal with a 5" downpipe. Can you reduce the downpipe to something manageable? YES but you would be giving up the benifit of that turbo which is a high flowing hotside. The turbos I mentioned are going to be alot more fun on a stick car. downshifting to 3500rpm vs 5000rpm for example to make boost instantly

Will a 6.0 make more power easier? Yes, and Ill agree with 71 chevy, itll make a substantial amount more, but the 5.3 does offer more ridgitity SP? and your looking for duribility. Either engine will make enough power to melt your tires and have you begging for traction long before you hit 800whp

No one is going to have white labcoat scientific data comparing this ****.

Either engine will make good power and both have their benifits and drawbacks, its time to tell everyone what kinda car you want to build so you can get more accuate recomendations.

Sarg

iTrader: (6)

Or a good set of twins on either the 6.0 or the 5.3. The main thing is choose the engine, get turbo(s) to match said engine as well as the purpose of the car. With a highway queen I would say go with something with a little more top end than say an autocross car! Define to yourself the goals for the car, the purpose and what you are living to deal with (monster downpipe, no ac, etc) on the build and go from there. I think there is plenty of information in the thread to make an informed decision and as Silver pointed out either will work and both have advantages and disadvantages.

jridenour31

This!!!! All I'm saying is that your (71chevy) blanket statement that a 6.0 will make more power, end of story, is flat out wrong. I don't see why it's so obvious that a bigger motor needs bigger parts. Yes, it will make more power but it will also need to be spun higher to take full advantage. With those same parts, the 5.3 is still capable of making that amount of power, just needs rpm. A 5.3 with 799 heads will make similar hp to a 6.0 with 317's.

71 chevy

iTrader: (18)

i think you are trolling. because your logic makes no gd sense.

jridenour31

Are you kidding me!? Torque!!! These motors weren't built for going fast, they were built for heavy trucks. Why would I think it's a good idea to put the same size cam in different engines? I never said I would. I simply said that with the same setup they would make the same hp. The bigger motor will be more streetable with the same setup. while making

jridenour31

Yes, I'm trolling. I'm clearly the one that doesn't understand volumetric efficiency.

Sarg

iTrader: (6)

Here is a fun little exercise. Perfect world type of deal with a S475 87mm turbine on a 1.10 ar housing. 5.3@20 beats it out, but just by a hair. 71chevy was pretty close to his guess of the two being equal in a perfect world, 6.0@15 and 5.3@20. Interesting part is the 6.0@15 psi has almost as much backpressure as a 5.3@20psi. Again this is a perfect ideal scenario, but interesting none the less. 5.3 is almost on the compressor map at the end, the 6.0 with the lower boost is definitely a good ways off.

5.3@20 psi

6.0@15

CALL911

iTrader: (17)

My goals are power and reliability based. I want a cheap (fairly reliable) 800+ RWHP car.

I would like to keep the AC. My Z traps 135 MPH in the 1/4 and still dead hooks on cold DRs on the street in 1st gear. I know by adding another 200 HP to the setup I will loose traction down low. But I am already expecting that and would gladly give that up for 800+ to the tires.

It seems the 5.3 with the 7675 may be the best route, although I wouldn't mind learning more about the S374 and S380 assuming they all will fit the power goals.

I still don't see the numbers on 100+ extra HP given the same psi LQ4 over the 5.3, but do agree the LQ4 probably will make more power.

Thanks for the inputs.

T76s10

iTrader: (6)

You should do twins like sarg suggested.

skinnies

iTrader: (33)

From testing we've seen I don't believe this to be true, I'd have to look up old dyno graphs, but I don't see 100hp gain IMO.

I'm not against the 6.0, we've used them in some builds, but for the 7675 and wanting 800+ rwhp, the 5.3 is much better suited. IMO for 800rwhp you can't beat the 5.3 7675 combo, instant spool, great tq and low end, and a fairly reliable setup. As mentioned we've done over 850rwhp, one setup was just ls6 cam, 3" exhaust(with wg routed back into dp even) and VERY safe timing. One of these days I'll strap the ltd back on the dyno with the exhaust opened up and see what it'll really make, I would be shocked if it came in under 900rwhp with the 5.3 7675 combo and the good tuneup on it.

If someone wanted 700rwhp and STUPID fast spool, 6.0 with 5.3 heads, tc78 .96 housing, e85, and it'll blow your mind how fast it'll spool. It'll only make power to around 5800rpm before it starts to drop off, but even with the old rods, this setup could be stupid reliable with a good tuneup and knowing what you are doing.

People try to put too much into a setup, keep it simple, light, and use what works.

silver_82

The way the power comes in on a turbo car is alot different than your procharged lt1, your procharged combo has a nice linear power curve cause boost is based on engine speed, the turbo setup will have less power at first but after spool the power and torque jump up giving you alot more average power.

You could put small gate springs in it and use a good boost controller to bring the boost in slower to aid with traction. I had 13-14 lbs springs in mine earlier this year and it was awesome on gate alone. The power came in like a 500hp shot of nitrous at about 4500rpm. Now its got 9 lb springs and a controller I bring it in slower so its easier on the tires

Camaro9969

iTrader: (12)

800rwhp is great and all but with a m6 its going to be damn near impossible to hook you will be lucky to run 10s and better have one strong *** drivetrain.

GIMPY02

Anyone ever heard the saying. Theres no replacement for displacement. in other words id take the 6.0 over the 5.3 just to have the extra cubes. but as far as thenprice between them ill stay with the 5.3. easier to get and cheap if i blow it up. but on the other hand we have made more power with less cubes with a off the shelf gt47-88. On a grand national. also made over 1100 rwhp on 4.6 mod motor. so as far as someone saying 41cube difference i6.0 makes a 100 more hp. who cares turn the boost up and let that little 5.3 eat

Sarg

iTrader: (6)

Personally I would step up to the s4xx turbo as you will not be able to take full advantage of the compressor wheel with the smaller 300 series housing. If you want a little more spool go for an 87mm turbine and T4 turbine, but I would still use the larger compressor housing. You can really see the differences between the 6 and the 5.3 in the two compressor map links I posted above and where a 5.3 will land on the compressor map vs the 6.0 with similar power levels and why aa 5.3 works better with the 75 or 76mm turbine. Not to say you could not do it with the 6.0 but you will be pushing the turbo more. Most turbos were designed to be efficient within a certain pressure ratio. Explore those ratios to match a turbo to whatever motor you choose.