Frustrated: Why so many inconsistencies in reported horsepower?

[Fras]

First of all, a little back ground: I bought a my personal dream car, a 1968 Camaro that I wanted to enjoy as a daily driver/road trip/pro-touring car that I could enjoy as much as possible. I did a ton of research as the best car set up to fit my needs and wanted around 550 hp at the crank and still maintain a streetable car. I went into this knowing I was buying fine wine on a beer budget, but figured I would take my time and spend my money slowly on the right things instead of rushing.

Car Craft Article that I want to model my car after: http://www.carcraft.com/techarticles/ccrp_0705_chevrolet_ls2_l92_cylinder_heads/index.html (http://www.carcraft.com/techarticles/ccrp_0705_chevrolet_ls2_l92_cylinder_heads/index.html)

After hours and hours of research on line, car shows, and the article below, I decided to go with a stock LQ4, LS3 heads and intake, and some other minor adjustments. EVERYONE I talked to and EVERY article/post said that I could EASILY get 550 hp with this set up. So after sinking money and time into this project, it was finally time to buy the cam to go with everything. I was referred to someone by MANY members saying this would be the best $25 bucks I spent to spec out a cam. These are the replies I recieved in reference to my motor and the horsepower/driveability goals I want:

OK, I think I need to control your expectations here. A stock 9.6:1 6.0L with exhaust manifolds makes approximately 360hp. Adding an LS3 intake won't really bring that power up any. You're not running headers, you don't have high compression, you specify 87 octane and you want good street manners, yet you expect a cam to gain you 190-240 horsepower? I was looking to see where the supercharger or turbo was in your specs, but there was none. I'm sure you've heard that cams make big gains on these engine, but nowhere near what you're expecting, especially without headers. You're probably looking at 450 hp with a cam and all the mods you've outlined. Do you still want to move forward?

And his reply to the Car Craft article that I listed above and modeled my goals after:

Your setup is very different. The Car Craft engine was a 376 cubic inch engine with 10.0:1 compression, a single plane intake with a carb, and 1 3/4 long tube headers. The cam that made the 550 hp was not one that had stealth street manners. It was much closer to a race cam with a very hard chop.

My frustration is I just dont understand why there is soooo many inconsistencies. I do realize that when dealing with best seats, best console, and many other things...even the definition of "streetable" or "driveability" , its totally up to the whatever floats the drivers boat....but when dealing with hard numbers like HP, torque, compression, etc, why are soooo many of the experts on complete opposite ends of the spectrum?? I read the Car Craft article 20 times over and not once did I see where they used flat top pistons and a higher compression ratio.

This forum truly has been awesme as far as learning, Im just frustrated now as I dont know what I can realisitically expect after sinking my hard earned money into things. I completely understand that ANY business is based upon making money, but what is credability based upon. If I was an idiot for thinking my LQ4 could hit 550 hp with a few mods, then I obviously misinterperuted everything or everyone that mentored me, or is it possible that a well know expert could be wrong this time?

OK...Im off my soap box and well vented. Thanks.

[BulldawgMusclecars]

So you used a magazine article for reference, put parameters on your own build that didn't apply to the original article, and you 're upset that it's not delivering what you thought? You didn't think that manifolds vs long tube headers, a restrictive LS3 intake vs a single plane with a big carb, a smoother idle vs a choppy one, and 87 octane vs the premium fuel likely used on the dyno test would matter?

[Fras]

As stated in my first post, it was numerous people and numerous articles that talked about the power of the LQ4 even with EFI and LS3/L92 additions. The only difference between the article and my set up was the carb vs EFI....but that is responsible for 100hp? Its just going back to the basic even that are inconsistent....ie: is the cubic inches of an LQ4 376 ci or is it 364 ci? Where does a stock LQ4 listed in the article go from 9.6 to a 10 compression ratio? In another reply it was stated that the LQ4 in the article was a 6.2L....how can numbers be so inconsistent? Theres a ton of LQ4 with EFI conversions out there that meet my goals, just gets frustrating when you pay for info and the basic numbers dont even match.

Want an even simpler example....ask something as basic as this "will a boss 338 wheel fit on a 68 camaro with 3" drop..." Its dealing with numbers yet there are soooo many inconsistencies.

[srh3trinity]

Was one person referencing flywheel horsepower and another talking about rear wheel horsepower? 550 HP at the wheels is a lot of power, and when you are making the upper limits of what can be made by a naturally aspirated street engine, then all of the "little things" like compression ratio, cam specs and headers can add up to two different power numbers when you make changes to multiple variables. Is that 550 HP number that important. Anything north of 400 HP is really a lot of horsepower in an engine that has good street manners, and the chances are it will be a long time before you are going to need that extra 150 HP on an autox track.
I used to buy the best wakeboard year after year, I would upgrade boats all to make me a better wakeboarder, but eventually I learned that I needed to use my existing equipment and work on my technique and that is when I progressed. I view pro-touring the same way. I am going to build a car that is capable, safe and makes decent power on the front end, but it will take years before my driving skills eclipse my equipment.

[TT302Z28]

People who quote up numbers are pulling them out of their a$$ dyno half the time. Never believe someone who hasn't done it.

[Vegas69]

Life is full of lessons and building these cars is full of them. Be happy with what you have and learn from the experience. You clearly don't have the experience to build an engine yourself and obtain your goals.

[bigtime]

"OK, I think I need to control your expectations here. A stock 9.6:1 6.0L with exhaust manifolds makes approximately 360hp. Adding an LS3 intake won't really bring that power up any. You're not running headers, you don't have high compression, you specify 87 octane and you want good street manners, yet you expect a cam to gain you 190-240 horsepower? I was looking to see where the supercharger or turbo was in your specs, but there was none. I'm sure you've heard that cams make big gains on these engine, but nowhere near what you're expecting, especially without headers. You're probably looking at 450 hp with a cam and all the mods you've outlined. Do you still want to move forward?"


I don't know who this is but he is telling you the truth and 450 is not to shabby for a pump gas, exhaust manifold, pretty much stock engine.

[SparkyRnD]

Don't get so wrapped up in what the mags did, as many times there are things that might not have been covered. The motor you have is a great motor, gets decent mileage, and makes great power throughout. Yes, headers will get you 40-50 horsepower, and cam choice can do about the same, and the tune can help as well. You will want to run premium, and over the course of driving the car, it really isn't that much more money, but it does make a difference in power. Rather than holding to a specific hp number, I would recommend that you go for a good, solid build with a great tune that is reliable and makes really good torque / power, but does so with reasonable street manners. Tell people all day long you make 550, as none of them will know for sure if you make 475 or 550 (if telling people you have a certain hp number means that much to you).

Also, the LQ4 does have lower compression than the LQ9, which does play a part in non-boosted engine HP numbers. The best part is that down the road if it's not enough power, you can always add a turbo and change the tune and have more. I think the cam recommendation guy you spoke with gave you very good, solid advice......and I think all the people that told you that set up would make 550hp all day long don't really understand the LS motors, what they can / can't do, and what set ups are really needed to make that power. As Vegas69 said, be happy with what you have, as it really is a great platform for your car.

[hotrod69camaro]

Articles are there to sell you something. They can be very biased. You gotta do you own homework if you want your stuff to perform and work correctly together with all systems. Enjoy the ride. Enjoy the journey. But note, big horsepower numbers and high gas mileage do not have a romance together.

[NOPANTS-68]

I read that same article you did and almost followed that recipe too. To give you some sort of idea- my LS1 with a stock shortblock, TEA ported 241s, victor, race prepped 870 cfm carb, open headers, and a Trex cam gave me a trap speed of 117 mph. That's about 450hp and nowhere near 550 flywheel with a cam that was borderline streetable.

[Fras]

Was one person referencing flywheel horsepower and another talking about rear wheel horsepower? 550 HP at the wheels is a lot of power, and when you are making the upper limits of what can be made by a naturally aspirated street engine, then all of the "little things" like compression ratio, cam specs and headers can add up to two different power numbers when you make changes to multiple variables. Is that 550 HP number that important. Anything north of 400 HP is really a lot of horsepower in an engine that has good street manners, and the chances are it will be a long time before you are going to need that extra 150 HP on an autox track.
I used to buy the best wakeboard year after year, I would upgrade boats all to make me a better wakeboarder, but eventually I learned that I needed to use my existing equipment and work on my technique and that is when I progressed. I view pro-touring the same way. I am going to build a car that is capable, safe and makes decent power on the front end, but it will take years before my driving skills eclipse my equipment.

Hey Stephen,
The HP talked about was at the crank...thats why I was a little bummed to see that I was only going to be getting 450hp. I will be running a 4L80E and with that, should only expect 360ish hp at the wheels.

I can related to your wakeboad analogy....when I was a kid, I bought an underpowered, cheap boat that could barely pull me out of the water. I think thats what Im trying to avoid this time around. I realize that some of these high HP motors are not practical for me, but 360 at the wheels just isnt what I was hoping for. How do all the corvette motors crank their HP?? Especially when they are abiding by restrictive emission requirements?

[Fras]

Don't get so wrapped up in what the mags did, as many times there are things that might not have been covered. The motor you have is a great motor, gets decent mileage, and makes great power throughout. Yes, headers will get you 40-50 horsepower, and cam choice can do about the same, and the tune can help as well. You will want to run premium, and over the course of driving the car, it really isn't that much more money, but it does make a difference in power. Rather than holding to a specific hp number, I would recommend that you go for a good, solid build with a great tune that is reliable and makes really good torque / power, but does so with reasonable street manners. Tell people all day long you make 550, as none of them will know for sure if you make 475 or 550 (if telling people you have a certain hp number means that much to you).

Also, the LQ4 does have lower compression than the LQ9, which does play a part in non-boosted engine HP numbers. The best part is that down the road if it's not enough power, you can always add a turbo and change the tune and have more. I think the cam recommendation guy you spoke with gave you very good, solid advice......and I think all the people that told you that set up would make 550hp all day long don't really understand the LS motors, what they can / can't do, and what set ups are really needed to make that power. As Vegas69 said, be happy with what you have, as it really is a great platform for your car.

I was definitely one at the beginning that got caught up in HP numbers, but as time has gone on, I just have used it as a gauge for comparisons. I had a 2005 C6 Corvette that was 405hp with a manual....the car had some pep, but it was that impressive, so thats why I was bummed to hear that I wont be able to push much more hp with this LQ set up.

As Todd (Vegas69) "clearly" noticed I dont have much experience in builds...which is why I have been so reliant on other's information. Ive talked to guys from places like Texas Speed and Prodigy...they have been a great help, have a ton of experience, and didnt seem to be shocked at my goal hp with the described set up.

Anyways, thanks for everyones input....this is truly a learning experience with a few added grey hairs.

[exwestracer]

I think it's equally important to look at where the engine made peak torque and power. 5600 and 6800 rpm? Hate to tell you this, but that's a racing engine...

You'll enjoy the car much more trading off that top end for better low and midrange torque and power, especially with the auto trans. Classic example of magazine spin. The heads are really too big for the application, so they "made it work" with a big cam and carb, ripped off some big dyno numbers, and sent the article off to print.

Did anyone say anything about how it actually drove on the street?

[SparkyRnD]

Another thing to consider is that many magazines run their dyno pulls without any accessories, so that sways the numbers too. The LQ4 absolutely can make 550hp, but you will have to sacrifice low octane fuel (and gas mileage) and / or streetability. To make the higher numbers, you can't expect to do it with 87 octane, no boost, efi, and great street manners on a stock motor. The more power you want, the more those things will have to change.

[Fras]

So with the last 2 posts (Ray and Sparky), is it even worth using LS3 heads or better to go a different route? I just want this to be done correctly the first time. Thank you.

[Scott Parkhurst]

Honestly, if you want that kind of power, buy an engine that makes it. Mast and others offer complete 550+ horse LS engines. You could get a GM LS7 or LS9 crate to make that kind of power with a warranty, but they're expen$ive. Crate motors are made for guys who just want to get the engine thing overwith and make a given amount of power. That sure sounds like you.

If you want to play with engines, that's great. But be a technician, not a magician. Power has to come from cylinder pressure. You can make that with big cubic inches, higher compression, high rpm, some spray, or some boost...but you have to make it somewhere.

[tooblue]

Fras,,
Here is the setup I have in a 95 Caprice, 408hp to the wheels. I would just build a "nice" LQ4 / LQ9 to meet the intended use of the car. It appears you already have LQ4 motor? You can always change at a later date once the installation is completed running. I would say depending on your driving / intended use of the car , I would let that dictate the build and not the "horsepower chase". These LS style motors are very easy to upgrade if you decide to go a different path later (Ton of aftermarket options).

Lq4 stock shortblock
Tr224 -114 cam
L92 heads/ L76 intake (stock)
Pacesetter 1 3/4" headers 2.5" exhaust
3k stall 4l65 Trans.
3.73 gears - 10bolt
Tuned by Leading Edge Performance in Las Vegas.

Very streetable driven many times to Vegas, California, Dallas etc.. Raced at Firebird Raceway and ran 13.2 on the motor as it sits. It has gone 12.30s with a 125hp nitrous hit.. Car weighs 4347 with out me in it..
Roger

[killer69]

i have done this more than a few times, having almost exclusively dragraced for the last 20 years, I can't couunt the number of engines i have had built, rebuilt, upgraded, changed this or that and still they NEVER make as much power as you think they will. NEVER!!!

when I did the ls2 in my Nova i had NO preconceived expectations, after all it is a stock head .030 over stock intake motor with a cam that is 580 lift and 272 dur so nothing crazy it is supposed to be an emissions cam. when we dynoed it (with a GOOD carm and intake ) it made 510 hp GREAT 75 less than i wanted but honestly what could i expect after all I spent less than an hour porting the heads, yes both heads. now i dont feel it makes that much with the LS2 intake, when we were at RTTC last year and had it on the chassis dyno at Spectre (with over 100 people watching) it cranked out a whopping 328 horsepower!!! lmao really??? what ever.............. it was still enough to run the fastest (or second fastest depending on who you ask) lap on the road course against cars that make over 700 hp. now the car does not do as well in the brake stp or autoX because it is down on power, but i can drive it 500 moile to an event and still get 22mpg.
we just purchased a 555 BBC 13K for my drag car guy said it went 9.14 in bacically teh same car made 930hp on alcohol yada yada. put it in the car and it goes a 9.75 ????? changed to gas to baseline it 9.80??? put it on the dyno after the season 780hp WTF so now watch this, we want to make 950-1000hp to run high 8's so 6500 for new heads, new cam, ported intake 2000 for a alcohol carb dyno time . i will go out on a limb and make a prediction................880 hp. we will see in a few months

i have learned it is what it is when it's done. like they say horsepower is expensive how fast do you want to go? you will be plenty happy with 450hp, for a street car

[exwestracer]

If it were me, and you want to take advantage of those "budget" heads; put them on the BIGGEST bottom end you can afford, with medium compression.

[solarguy09]

A lot of great comments..

You sure wants something that is making power at 3000 RPM on...

400 HP plus, is plenty of useable Power, and unless you are putting in the New ZR-1 or Z06 Engine in, you will be Lumpy cammed, Loud, and on the edge of streetable , to get 450 HP or more...

But I am not a mechanic.. I haven't dyno'd my car...Because what numbers do I want ?? Maybe the 1/4 mile run to check time and MPH, but unless someone wants to dyno it for free, i don't worry about the HP numbers...

[69lsxamx]

OP I bought a lq4 and my goal is 500whp. I didn't do enough research before I bought it because it was a good deal. Since then I have done a lot of reading and research to find out how I can reach my goal of 500whp. It's not going to be easy. I should have bought a lq9, Im using ls3 heads and intake, 1"7/8 headers im, going to change out the rods and piston's for a set of ls2's to bring compression up, and probably a spinmonster spec cam. If you do some searching over on ls1tech and corvetteforum you can read about some of his cam's. He says they are good for 500whp on a ls3 and be very streetable. I have seen a thread of a corvette with a ls2 making 500whp. I think it had a pat g spec cam in it, with 1'7/8 headers fast intake and 102mm throttle body. They also spent about 24 hours of dyno time with it, dyno time isn't cheap though. You should also look into some of the pat g spec cams.
If you dont get the compression up atleast get some headers so you will be closer to your goal's

[406 Q-ship]

What I hear is that you want streetable power........then IGNORE horsepower numbers and build for lowend torque. Horsepower is just a math formula of torque over time, torque is what gets the weight moving. Check to see what RPM that torque comes in at too, to high or not enough at a lower RPM will make a poor driver. I would look at using earlier heads for there smaller high velocity ports, this will give great torque in a wider RPM range with improved throttle responce. Get the compression up to 10.0 with the head change, that with a good cam selection will get you in the mid 400's for HP and Torque.

I have a 1971 Monte Carlo that has a 406 SBC that has been built for useable torque and only dyno at 340 hp/440 Tq, with ramhorns and a weak dual plain intake. I changed the intake to a 7104 RPM Perfomer and a set of 1 3/4 headers, so it is pushing more power now (I estimate 410 to 425 HP and 475 Tq). Now this is not an aluminum headed and monster cam SBC that is a pain to live with, it has cast iron ported factory heads (1973 Z28 heads) with a Crane 274 High Intensity (old design) that has 10.25 compression. All that in a 4000 pound Monte Carlo that has a 2400 stall TH400 and 3.31 gear, that has out run a Corvettes, Porsches, WRX Sti, and plenty of hot street cars. The reality is that most don't have the power on the street that they believe, a good 450 HP LQ4 based engine will run away and hide from 90% of street cars. Dynos don't win races.

[andrewb70]

There have been plenty of great comments made and I will just add a bit of my own experience. First of all, engine articles are designed to illustrate an extreme example of what a proposed combination is capable of producing. A couple of observations from the Car Craft article are important to note. First thing to note is that the first test was only performed up to 6000RPM. For test two they add the L92 heads, a bigger cam, and a bigger carb. At 6000 RPM that combination only made an extra 32 HP. To me, the only valid point of comparison is at 6000RPM, because the first test, had it been taken up to 6800RPM, would probably have surpassed 500HP. Remember, HP is a derived number that is a function of TQ and RPM:

HP = (TQ x RPM)/5252

Also, look at the torque numbers for test two. The second combination looses torque on the low end, which is already kind of low because of the single plane intake. Honestly, neither combination is that desirable for a street car. The powerband, which is often defined as the spread between peak torque and peak HP is very narrow for both combinations. If either of these combinations was installed in a car with an automatic it would need to have at least a 3800-4200RPM stall converter, otherwise it would feel like a total dog on the street.

I stopped paying attention to dyno tests a long time ago. You don't drive a dyno, you drive a car. I have been playing with cars for over 25 years and I see the same mistakes being made over and over again. Too often, people chase some arbitrary power goal only to find that their car is a pig to drive. It idles rough, it stalls, it sputters, it bucks on the highway below 2500RPM, in other words it is NO FUN TO DRIVE, unless it is at WOT.

Well, I have a shocking news flash: You will drive the car at WOT approximately 1% of the time.

So, do you want an engine that works great 1% of the time or one that will work best the other 99% of the time? Oh yeah, and you want to do this on a "beer" budget.

My suggestion is that you adjust your expectations, otherwise you will not be happy.

Here is my engine combo and performance numbers, take them how you will:

L92 long block (6.2L)
Stock LS7 cam
Dual valve springs
LS3 intake, throttle body and injectors
Corvette balancer, water pump, and accessories
Edelbrock stepped, longtube headers (1 3/4" to 1 7/8")

On a chassis DynoJet chassis dyno it made 418HP and 390TQ. Peak TQ was at 4200 and HP was at 6,200, with a 10.5:1 AFR (running rich)

The car is around 4050 pounds with me driving. It idles as smooth as silk. It doesn't buck, jerk, sputter, puke, surge, or object when lugged down to 500RPM. It runs down the highway at 75mph and gets 21 mpg.

At the drag strip I have run a best of 12.51@113mph on a cool fall day and it consistently runs 12.60s @111 on 80 degree summer days. That's with Falken Rt615 tires, no adjustments at the track. Just drive it there, make a few passes, drive home.

On the street, I can take off easy in 1st gear (2.77 1st 3.77 rear gear), go to WOT at 2000 RPM and it will break the tires loose until I let off the throttle or shift into 2nd, at which point it gains a little traction and goes.

Of course, as they say, your mileage will vary.

Andrew

P.S. It took a while for me to type out what I wanted to say and it looks like Q-Ship and I were exactly on the same wave-length.

[406 Q-ship]

P.S. It took a while for me to type out what I wanted to say and it looks like Q-Ship and I were exactly on the same wave-length.


It is amazing how much we agree on.....:)

Just wish my Monte got 21 MPG, well 14 MPG is not back for a aero challanged carburated car without an OD through a stalled automatic.

[hotrod69camaro]

But still were chasing dyno numbers from an article you werent there to see. They can sway it so the article reads favorable for them..

[solarguy09]

So many variables, it will make your head spin..

The combo is the key..

I am running a close ratio Muncie with 3.73 rear gears..I have a modified true 350 LT-1 with the 2.02 heads and dual plane with the Vacumm secondary 780 holley..

When i rebuilt it, we put in a 280H Cam with roller rockers, and milled the heads, and decked the block for more compression..maybe 9.5 or so, i don't know..

It is really Lopey, but with the gearing, and it being a 4 speed, i am always in the useable power range on the street..

I can start off in third if I want to...But I don't... Power comes on at 3000, and then it is a snap of the rubber band to 6500Rpm... Like you cracked a whip ..

This is before the Billet distributor, MSD 6AL, K and N extreme, All new exhaust, and other add ons...That is just the engine bay..

My point is that I think that a dual plane manifold, vacuum secondaries, and the right cam for your Gearing, is the key..

But i am no mechanic..this is just seat of your pants experience..

[Rod]

Want an even simpler example....ask something as basic as this "will a boss 338 wheel fit on a 68 camaro with 3" drop..." Its dealing with numbers yet there are soooo many inconsistencies.

the answer is yes and no, heres the inconsistencies

wheel Diameter
wheel Face off set
wheel back spacing
wheel mounting pad thickness
desired tire diameter
overall rear end gear and final ratio needed
what is the current fender well to ground cleance

no simple questions, when building, just need a better question I.E.

" what backspacing does a Boss 338 17"x8 front and 17"x9.5 rear wheel need fit on a 68 camaro with 3" drop front and rear, and what tire size is needed for fitment also front and rear"

[exwestracer]

L92 long block (6.2L)
Stock LS7 cam
Dual valve springs
LS3 intake, throttle body and injectors
Corvette balancer, water pump, and accessories
Edelbrock stepped, longtube headers (1 3/4" to 1 7/8")

On a chassis DynoJet chassis dyno it made 418HP and 390TQ. Peak TQ was at 4200 and HP was at 6,200, with a 10.5:1 AFR (running rich)

.

THAT is plenty stout...

[MyFriendScott]

So you used a magazine article for reference, put parameters on your own build that didn't apply to the original article, and you 're upset that it's not delivering what you thought? You didn't think that manifolds vs long tube headers, a restrictive LS3 intake vs a single plane with a big carb, a smoother idle vs a choppy one, and 87 octane vs the premium fuel likely used on the dyno test would matter?

So....I won't be able to make 425HP on a 2.2L 4 cylinder with colorful spark plug wires and silicon vacuum hoses? :lol:

[Taylor1969]

From what I have heard, the article had a misprint and they actually used an LQ9 in the tests and not an LQ4. Couple that with the intake, headers and you have your missing power.

Chris

[Fras]

Want an even simpler example....ask something as basic as this "will a boss 338 wheel fit on a 68 camaro with 3" drop..." Its dealing with numbers yet there are soooo many inconsistencies.

the answer is yes and no, heres the inconsistencies

wheel Diameter
wheel Face off set
wheel back spacing
wheel mounting pad thickness
desired tire diameter
overall rear end gear and final ratio needed
what is the current fender well to ground cleance

no simple questions, when building, just need a better question I.E.

" what backspacing does a Boss 338 17"x8 front and 17"x9.5 rear wheel need fit on a 68 camaro with 3" drop front and rear, and what tire size is needed for fitment also front and rear"

That is an appropriate question for a wheel that can be properly fit to order ie a 2 or three piece wheel. The 338 will either fit with a stock width rear end or not fit.

[SparkyRnD]

to answer your question about the heads, that is purely up to you. I would talk it over with your cam selection guy, as you've already spent time talking about your project with him. As others mentioned, it's not as much about HP as it is about usable torque.