Well, if you change out a SBC to matching heads you have nearly identical power numbers.

 

If you go with a SBC 406 with AFR 210 Competitions, you'll see 575HP at least with a Comp XE 248/254 (and probably closer to 580-590).

Compared to an AFR 225 on a 408 (to keep the brands similar) running a 248/254 (popular Comp grind for LS1), it's not uncommon to see 530rwhp, which is about 600HP at the crank.

The numbers aren't really that far off. But, if you build them up with say Callies Forged Crank, Compstar Rods, and Mahle pistons, the price of the longblock is still a little bit cheaper for the SBC.

One reason I'm building up a SBC for my car is once you get past building up the longblock using top quality parts, it costs more to run the LSx EFI system vs a carb. And, though you can run an LSx with a carb, the parts selection is far better and much easier for the SBC to convert and older EFI system (like in my 92 Firebird) to carburetion for the DIYer.

Current parts for my 383:

87+ Roller Block 4-Bolt Mains with ARP Studs Bored .030" Over
Eagle 4340 Forged 3.75" Crank
Eagle 4340 Forged 6" H-Beam Rods
Mahle Coated and 4032 Forged Pistons with 5cc Valve Reliefs
Clevite H-Series Bearings
AFR 195 Competition Port Heads with AFR 8019 Springs
Comp Cams XE 242/248 .576"/.600" 110+4 LSA Camshaft (lift with 1.6RR)
Jesel SS 1.6:1 Shaft-Mount Aluminum Roller Rockers
Morel Hydraulic Roller Lifters
Manley Swedged End Pushrods
Edelbrock Victor Jr. (ported)
Holley 4150 HP Street 750CFM Carb
Hooker Super Comp 1-3/4" Ceramic Coated Headers
VIG 3200 Converter
Moser 12-Bolt with Eaton HD Posi and 3.73 Gear

With this setup I'll be around 11:1 CR (which gets my DCR in the low 8s, which is fine for a carb motor - don't want to run the ragged edge in the event I run rich when the weather changes and build up carbon). I hope for 550HP and an RPM range which will carry to 6800. Looking for low 11s or high 10s in a full weight car.

We'll see

 

I'm still going to disagree with bolth of you, but there is no need to keep this up any longer. You are going to have to go pretty radical to keep up with a DD LSx motor.

 

If thats what you think, you act like a similar build with a GEN I and a GEN III are going to yield 100 extra HP for the LSx but its not.

 

Zone, I have a quick question for you, how many high performance engines have you built? I usually build 5-6 per month for various street/strip, drag racing, and mostly circle track cars. I have a list of some of the best at the tracks around here, and many are season champions in there different classes running my engines. I'm trying to politely tell you that you have read too many magizine articles on your HP estimates in my opinion. If you can, tell me how much HP your new motor is going to make for you now before your build is complete.

I will say that you can get close to the peak HP number's of the LSx motors with a Gen I, but not the area under the curve. I have several freinds with dyno's and I'm going to have to say that the evidence is not on your side.

 

Whatever, all i am saying is the difference is not HUGE and when aftermarket comes to play, it really isnt much to differ at all, $$$ can make the same power of the same cubes when the doller is there. The LSx platform just makes a bit more but not a huge amount. I have built several engines, not 5 or 6 a month by any means and never will. My motor is probably looking at a bit over 550 but the over sized heads will hurt low end TQ, who gives a ****, it is a street car and the tires will not hold that well so the bit i will lose wont matter, the heads are for a 40 in the future, i am not using smaller heads for my build when i have theese. I dont need evidence, i know what i see on the street and track, whatever has the most $$$ will go the fastes, LSX based or not.

 

Well then, the best of luck to you on your 550+ HP engine!! Here is some reading material to look at. http://www.chevyhiperformance.com/te...sts/index.html

 

So the LSx platform made 1 more HP, sweet. I will not probably get the 550 i am looking for till i swap for a Vic Jr., i only have a RPM air gap right now.

 

Did you also notice that neither engine has any accessories bolted up to them or a full exhaust system. My cousin's engine dyno'd 532/491 at the rear wheels with ALL of the accesories hooked up to it and a full exhaust w/cats (as a brand new engine with zero miles on it). That puts him in the neighborhood of 620+ @ the flywheel with a 15% drivetrain loss. As I mentioned earlier this is his daily driver that has excellent street manner's. What I'm saying is that it's HARDER for your Gen I SBC's in a near race form to be able to keep up with a Gen III daily driver engine. As far as prices go, they are a near tie in the pocket book department.

 

Hmmm...near in price? The aftermarket dept has some nasty crate motors that beat the price out of any LSx platform in a crate. Building it yourself is even cheaper. Your cousin is at 590 HP if the dive train loss id 10%, you never know what the loss is, it will range from 8-20% depending on auto, stick, loose stall..ect. If he is a stick car then he is probably around 10ish. I dont know about you but i dont care too much for street manners when it comes to daily driving. A rough *** idle isnt bad. Not to mention if you put a solid roller in a SBC, which i know ALLOT of people that do, they dont even complain about daily driving. My bullshit 1000$ 383 i had in my car last killed allot of LSx's. Even the almighty heads and cam LS1. So price is on my side on a budget for sure. My buddys car made 487 RWHP with a 408. He is pissed because he sees smaller motors doing it, he is even thinking of selling the damn thing, it is a 01 Z. Some do turn out better than others but i have seen a 12 to1 355 make 525 at the fllywheel on pump gas, it was daily driven with a 3500 stall and did not idle too badly, the inly time i see a bad daily driver with complications is one loading up on fuel at idle. There are many bennifits of the LSx, yes but the SBC is not snuffed out and will not be for a long time to come. The LSx platfor is better than TPI and LTx, that is for sure but carbed built SBC is still a LSx worst enemy to come across on the street.

 

Whatever helps you sleep at night, deputy Dan.

FYI a vette's drivetrain loss is about 12-15% with a T-56 tranny.

 

Yep, every car is different, some vettes WITH a T56 might be as little as 10%, they are ALL different.

Ight special guy.

 

Actually, drivetrain loss is not a percentage. That's total BS.

Go dyno a car, let's say a C5 LS1 Vette (since I did this when I had mine). Stock is was about 300rwhp with a 350 rating. That's a 50HP loss (but it's also 15%).

To have fun with this, let's say we install a nice dual-disc clutch, beefed up T56, and new rearend with steeper gears. It now dynos 280rwhp, so we are losing 70HP (or 20%). But it can take a **** load more power.

Are you telling me that if we use these upgraded components, they would eat more horsepower behind a more powerful engine? For example a 1000HP engine would only do 800rwhp? It would now take 200HP to drive those same components? No way in hell. It'd still only lose 70HP (assuming the RPM Range is the same - if the RPM range is extended, additional friction/heat will eat power).

My 99 Vette with its 383 did 510rwhp. On the engine dyno it did 72HP more or ~582HP. That's only 13% drivetrain loss... but it was 280 before I put the 383 in and was at 20%. So the drivetrain loss percentage decreased behind a more powerful engine with all parts being the same. If it had held at 20% like the original dyno showed, it would have only dynoed at ~465rwhp, but of course it didn't take another 45HP to turn the components.

It just so happens that 15% is a close enough approximation as long as you're under 600HP. But, I just thought I'd share how silly it is to compare percentages.

 

It is just a guess unless you do as you did, i have friends that want to assume a large amount of loss after they dyno a car so they think they have more fwhp. It is just a give, an assumption, it ranges, as i stated it can be as little as 8%. Thanks you for sharing, i havenever had anyone do a engine and chassis dyno on the same motor. Great info man.

 

well said jake fusion

 

I stand corrected Jake. For my cousin's car I was going off of the info provided to me from the owner/dyno operator who works mostly on LTx & LSx cars. When I was out there we were working on almost all C5 vettes the month that I was there.