I used to drive a 99 WS6 TA. It made 315 RWHP with only a lid and cut-out. I then made 394 RWHP with headers and a TR-224 cam. I've seen cam and head LS1's make upwards of 430 RWHP.

I sold my TA and bought a 1992 corvette with a 383. The 92 corvette made 380 RWHP NA, close to 500 on juice, and was an absolute joy to drive. I was always curious about the power though. Coming from the LS1 camp, a stroked engine with heads and cam making less than 400 RWHP is a joke. I kinda figured the 383 had some mis-matched parts, or some other problem that was preventing it from making the power it should. I sold that car, and bought the 1991 I have now.

When I had the LS1, the only thing that turned me off were the absolutely astonishing prices of mods. In 2000, a set of headers for an LS1 was ~$1500, a set of heads was easily upwards of 2k, etc... That's when my interest in the generic SBC really started to come around. Cheaper parts, and the same power potential as the LS1 once you started modding, or so I thought.

I can't count the number of head/cam/intake L98 cars I see on here making 310 RWHP, sometimes less. What's the deal?

LS1 heads, in stock trim flow ~255 with decent low lift numbers. Those heads routinely take 346 cubic inches to 400 RWHP.

Why when you put an equal flowing head on a conventional SBC, do they not make anywhere near the power? From what I have seen on here, you'll never approach 400 RWHP with a stock bottom end L98. Even after changing the heads/cam/intake.

LS1's have cathedral port heads, and they are a 15 degree head, but is that really where the power comes from? I figured 255 CFM of air would support the same amount of power regardless of how it entered the engine.

What's the deal?

 

I hear what you are saying. I wanted to do head/cam/intake when I first bought my car. My mods I had planned were TFS heads(260cfm)/219 cam/accel base with high flowing runners. Most guys say that combo is only good for 310-320 rwhp, and 370-380rwtq. And that's if it's tuned really well.

I changed my mind after seeing LSx with slight mods dyno 325rwhp. I thought to myselve, What the hell! Here I am with good heads, a notbad cam, and a better flowing TPI that should make power all the way up to 5500 due to the cam, and the heads. I dont get it either!!

Reason I originally wanted this was, because I wanted to pop my hood, and the motor look close to stock as I could and run 12.4-12.7 range. Maybe this could be done, I truly dont know. I read about the problems guys have with head/cam/intake and the ****ty power they make, and it pisses me off.

 

 

Isn't a LS1 like 4-5K stock?? I think for a little more in price you can make a hot L98 383 with the works and forced induction making a hell of a lot more hp than the stock LS1...

 

A crate LS1 is 4-5k yes. I can buy an LS1 F-body for less than $8500 though, and it will kill any stock L98 C4, and LT1 C4, and it will beat 1/2 of the LT4 C4's I run into. With less than 1k in mods it will make 400 HP, and kill any stock C4, except maybe a late model ZR1.

If you think you can build a stroker L98 with forced induction in a C4 for 5k you're out of your mind. Just the supercharger kit will run you more than 5k by the time you add the fuel system and other supporting components.

I'm not trying to be an ******* here, but you don't really know what you're talking about. Posting just because you have nothing better to do, doesn't really contribute anything to this thread. It makes more difficult and time consuming for those who have some legit tech to add, and it forces other people like you, who are coming here seeking knowledge, to read through your useless ramblings about things you know nothing about.

I'm sure you're a good guy, and meant well; but sometimes discretion is the better part of valor. Just hang back and lurk if your interested, no need to muddle up the post with, "This is what I think I might have read somewhere else on the Internet, but I don't have any real knowledge of."

Like I said man, I'm not trying to be mean, but that is how I am going to come off. If we could keep this one close to 100% tech, that'd be awesome. Then, when it turns up in searches it'll be 100 times more helpful to other newbies.

 

Neat knows his stuff. He has owned a few cars in the past, and has driven them hard. I hope there are some guys that can jump in here, and answer Neat's thread.

 

ALOT of it is that valve angle, its a superior design, LS engines are basically race motors. The intake manifold design is also.

 

In short, yes, the main difference between the LSx engines and the LTx/L98 engines is the top-end. The heads flow just as well as LT4 heads, but the intake is a far superior as well keeping a nice broad torque curve. The runner lenght, if I remember right is right between the L98's long runner and the LTx short runner.

When you start modding is where the real difference begins though, the port design on the LSx heads is really where the gains come from. A better angle for one, cathedral design, and better spacing so they have a MUCH straighter shot to the combustion chamber. That's why you can get 440+ RWHP out of a heads/cam LS1 and 460+RWHP out of a heads cam LS2.

 

Vader took the words right outta my mouth.

The EASE that an LSx can suck in that 255 cfm requires less effort to bring in and expell than on an SBC.

The siamesed ports on the SBC heads were always that engines' achilles heel. No matter what you did, the engine would have to be so peaky and tempermental to generate the kinda power the LSx sees as a matter of course.

Remember, the LSx is a result of 50+ years of V8 engineering. It is the dream motor... can you imagine the amount of power the NASCAR guys could get if they could use the LSx family of engines? It makes me shiver to think about it.

The LSx is so totally new... it shares only bore center with the SBC... no part is interchangable.

 

From a physics standpoint, the ease of the air being brought in doesn't mean anything. 255 CFM of air contains the same amount of oxygen regardless of how it is achieved. That oxygen will burn a set amount of fuel, no more. If you are burning 255 CFM of oxygen with a gen 2 SBC and an LS1, why does the LS1 create more power? The same amount of gasoline is being burned, releasing the same amount of energy. I could see a small pumping loss from a slightly less efficient head design, but 100+ HP?

Why do the siamese ports make the power band peaky?

I agree that the LS1 in vastly superior, but I guess I really want to know why. Beyond the obvious of "The heads are better." What actually makes them better? I know, "15 degree's of valve angle makes it easier for the air charge to enter the cylinder." I could see that making a big difference on an all out race engine, but at the relatively modest HP levels were are discussing (less than 500 HP) how big of a deal is it? I still fail to understand how 255 CFM through an LS1 head creates more power than 255 CFM through an SBC gen 2 head. It's the SAME amount of air, so you are burning the SAME amount of fuel. I can't imagine the engine is losing 100+ HP because it has to 'inhale' harder to get that same 255 CFM.

I know. It's not quite new, it's nearly 10 years old, but I see you point.

 

There are a couple heads/cam C5's making 500rwhp!!! and many in the 460-70 range. LSx is God's motor! Mostly the heads are where the engine is so much better, then probably the intake. I asked a head porter once if an LSx head and LT head flowed the same, would the LSx still make more power?...he said yes. The thing i really like about the C5 LS engine is that there are so many aftermarket parts available and they respond to mods so well, and a lot of the C6 and probably future Vette parts will fit. I think you can get the LS7 heads for around $1500 and they flow 360cfm!

 

When my LS1 was making 394 RWHP, it was inhaling ~410 Grams per second of air, via the reading of the mass air sensor. Roughly 1 RWHP per gram of air. If I understand you guys properly, 410 grams air per second ingested through a gen 2 SBC will not make ~390 HP.

I just don't understand how that can be possible.

 

LSx is very new compared to the SBC. ; )

When you go from a 23 degree head to a 15 degree head, who's to say the power you gain isn't 100 plus rwhp?

The difference is also port velocity too. With easier air path comes faster air velocity. Multiply that with bigger cams and more air from mods, and you see the major difference.

 

"From a physics standpoint, the ease of the air being brought in doesn't mean anything. 255 CFM of air contains the same amount of oxygen regardless of how it is achieved. That oxygen will burn a set amount of fuel, no more. If you are burning 255 CFM of oxygen with a gen 2 SBC and an LS1, why does the LS1 create more power? The same amount of gasoline is being burned, releasing the same amount of energy. I could see a small pumping loss from a slightly less efficient head design, but 100+ HP?"

I believe that it is the efficiency of the head design that makes all the difference. I am far from the guru but my understanding is that the velocity of the airflow is is not being taken into account in your quote above. It's like the difference between putting a SBC head with lagre ports flowing high cfm versus a smaller port flowing a slightly smaller of cfm but at higher velocity. I'm not an engineer so the actual science is beyond me but this is what I have read in numerous sources.

 

It does when you look at port velocity. A head for Gen I and Gen III may flow the same peak CFM at steady state, but if you integrate that flow over time between 1000-7000rpm (for instance), you'll see that the Gen III head will suck in more air. If you give the air a straighter shot to the chamber, youre going to make less turbulence in the flow, which equates to being able to maintain velocities.

 

The real difference between the power output on Gen I or Gen II engines when compared to the LS1 with similar flowing heads is the power band. The intake design on the LS1 engine is optimized to make good power over a wide power band and the its preferred power band is 3500 to 6500. If you look at the actual power band of the typical modded TPI car on this board you will notice that the peak power occures at 4500 TPI to maybe 5500 with superam intake because the intake runners are very long (entire intake path 15" to 23" depending on intake used). The long intake length promotes good torque at low RPM but it gives up HP on the top end. If you were to install a good flowing medium length intake (similar in length to the LS1 intake) like the stealth ram on a modded TPI car that had similar flowing heads and you will see similar power outputs. Do a search on an article called ten times the torque in this article they played around with 10 different intakes on a mild 383 and it made anywhere from 400 HP with the stock TPI to 505 HP with the mini ram. If you look at the specifications of the 383 you will notice it only has 10 to 1 compression, a relatively small cam when compared to what a lot of LS1 guys run, and decient heads that flow around the same as a stock LS1 head.

If the parts in the gen I engine are actually similar (in function and design) to what is on the LS1 engine the power output will be the same.

 

LS1 is the smallblock of the future, embrace it. Our L98/LT1 arent even in the same league from a design standpoint. Cubic inch for cubic inch, not much comes close. Have a good friend who designs the LS cylinder heads. His H/C (224 @.050) vette made over 480rwhp and sounded stock. Streetable 11 sec car. New motor goes 610chp, and the tune isnt even perfect yet. Driveable 10.7 car.
SBC has come a long way for sure. The port design and airspeed of the LS heads works so well you can use a 200+cc head and make good street power and get iot all upstairs. If I ever build another motor its going big CI LS.
Only thing I wish GM had done is apply another 15 years tech to the LT5, think of the possibilities.

 

Come on guys, it's so simple...maybe you need a refresher course....It's all ball bearings these days...

 

They have, Northstar is derived from lessons learned by LT5 development.

They just havent pushed it as much in terms of "power" performance for street engines, with the Cadillac LeMans prototypes being killed off rather early in development. Why they did that, I dont know.

They are concentrating their research on fuel economy areas, but with Caddy aiming for MB and BMW, they'll soon push it for power. They just feel that the LS engine will be better and cheaper for the time being, I suppose.

 

Anyone know why GM has moved away from cathedral intake ports on the LS7? There doesn't seem much information around on this yet. This makes the topic even more interesting as some believe the cathedral style ports have a lot to do with the performance/efficiency potential?? How do the C5/6R intake ports compare? Maybe the valve angle has a greater significance than port shape, that and the chamber design. The chamber design on the Vortec SB1 seemed to help a lot with power potential, at least within its port size/capacity limitation anyway.