Chevy Small Block Dyno Tests - Old School Meets New

406ci Traditional Mouse Vs. Late-Model 402ci LS2

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We initially tossed the idea of comparing a stock LS1 with a conventional small-block 350, but after questioning the angle we later realized, what's the fun in that? And dare we say, it's already been done by others who'll be the first to admit that they did a fair job of updating you with the crucial differences--but certainly did little to stimulate the gearhead factor. To kick it up a notch, and satiate our hunger for power, we set the stage to bump up the cubic inches of a later-model LS2 into a big-inch 402 and pin it against a "warmed over" 406ci small-block.

Our requirements for this challenge: All components had to be readily available, over-the-counter production pieces; nothing over 11:1 compression; we had to use a hydraulic-roller camshaft; and we had to keep the components as close as possible, meaning we had to use the same manufacturer for our cylinder heads, camshafts, and manifolds, and most importantly, both bullets had to share the same carburetor.

Doesn't seem like that big a deal, right? Wrong. You need to take a closer look at the flow capacity of an LS cylinder head. Given the nature of its 15-degee valve angle over the conventional 23-degree cylinder head, we're talking race technology that's trickled down to the consumer level. By altering the angle of the valve, you create a much more direct path, which allows a greater volume of air to traverse into the combustion chamber at a faster rate. The result is radical flow numbers that help to create big horsepower. As you can imagine, the obvious advantage already went to the LS before we even began building the engines.

The real question becomes, was either engine significantly cheaper or did one walk away as the clear winner? Follow along, and you be the judge. Don't forget to write in to us at chevyhi@ and let us know what you think of the results.

Step By Step

Inside is a complete Lunati LS1 Pro Series stroker kit assembly featuring a 4340 forged crankshaft with a 4-inch stroke, 4340E billet rods, forged pistons, and main bearings. Yeah, this baby isn't going to break anytime soon, and the added rigidity will allow for aggressive testing in upcoming issues. One thing we need to note is that the crankshaft featured a 24-tooth reluctor wheel, which was swapped for a 58-tooth wheel to work with the Edelbrock controller.

Like the LS1/LS6 and LQ9 blocks, the LS2 features a six-bolt main. The inner bolts were torqued to 58 ft-lb, 55 ft-lb for the outer, and 25 ft-lb for the cross-bolts.

One of the biggest advantages of the LS engine is having the ability to swap camshafts with minimal effort. All you have to do is remove the front timing cover, loosen the rocker arms, and slide two rods to support the lifters. Keeping that in mind, we started small with the 230/232 duration at 0.050 (PN XER281HR) and later stepped up to a larger 238/240 duration stick (PN XER287HR).

Turn Key 402ci
For this build I enlisted the help of Turn Key Engine Supply in Oceanside, California, and engine builder Chris Pollock, whom we have to give major props to. Considering our dyno session was scheduled for the following day, these guys had the entire bullet built from scratch to finish in a matter of hours. Then again, when your business is in the habit of cranking out 40-plus turnkey engines a month, it's just another day in the office.

Now I'm not going to give you a history lesson, but I do want to point out that the LS1 first debuted back in '97, and while it may seem hard to swallow, the newfangled LS variants are already going on their 10th year! Point being, it's not that new, folks. If you aren't familiar with the 6.0L LS2, don't sweat it. It's still in the same platform as the Gen III LS1/LS2 and the 5.3L and LQ9 6.0L truck engines. Matter of fact, all the parts available for this engine family are interchangeable, and it closely resembles the LQ9 truck motor, with the exception of its aluminum construction over the cast iron. Other differences include the relocation of the cam sensor from the rear of the engine to the front and the loss of dual knock sensors in the valley pan, which are now located on the side of the block.

Getting on to the mule, the initial plan was to build on a cast-iron LQ9; however, after pricing out bare blocks, we learned that the aluminum LS2 was only $300 more. Given the similar construction, it only seemed fitting to try something new. Besides, a motor that weighs significantly less only adds to the cool yet functional factor when dropped in between the fenderwells of any street machine. I'll let the following pages reveal the sordid details, including the price breakdown, the components used, and the dyno results.

If you're curious as to my interpretation of this month's test, I will say that the overall results left a permanent impression. Considering the LS2 churned out well over 560 hp and 520 lb-ft with excellent idle quality at 13 inches of vacuum, it's a true driver. And yes, that's on 91-octane. As an added bonus, we swapped the camshaft and went up another 8 degrees of duration, improving on our numbers with over 580 hp and 530 lb-ft, all the while maintaining 10 inches of vacuum at idle. As for the older Mouse, it was impressive, to say the least, but it's far more aggressive and lends itself as more of a weekend brawler when compared with this LS2. That said, dollar for dollar, at least in this comparison, the 402 LS2 proved that it can not only produce serious power, but with a relatively mild build it's perfectly suitable for the street. I'd like to see what this combination could produce with a stout solid-roller, but that's a story for another month.

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Unlike the 406ci, we produced 583 hp and 530 lb-ft on 91-octane and through the mufflers.

Peak power was had with a 72/79 jet combo through a 750-cfm Mighty Demon.

We used 13⁄4 Hooker long-tubes with mufflers for every pull.

The front timing cover, oil pan, and valve covers are all factory issue.

Turn Key offers this trick-looking balancer for $280.

Bare aluminum LS2 blocks can be had for only $995.

Dart 225cc Pro 1 LS1s are true bolt-on pieces and retail for only $1,620.

CHP: Walking through your facility was almost a mirrorlike experience to walking through a GM warehouse. What are the bulk of the builds you do on a regular monthly basis?
Kolby Enger: Our primary sellers are the 450- to 500hp versions of the LS1s, and more recently we're starting to see more 500-plus-horsepower LS2s with forced induction going out the door.
CHP: Are you noticing any kind of trend in sales with the LS-series engines?
KE: A lot of guys out there are building musclecars and outfitting them with modern-day components, including the suspension and drivetrain. Lately, we've been selling an incredible number of LS engines with retro kits that'll allow for a perfect fit underneath the stock hood while utilizing the existing motor mounts.
CHP: Is there a particular combination that outsells the rest?
KE: Our engine-swap kits for '67-69 Camaros and '55-57 Chevys seem to be really hot right now.
CHP: What is it about the LS engines that you prefer over the older conventional small-blocks?
KE: There are a few things, such as the aluminum construction and the bottom-end torque, and while the carburetor versions work well, we're partial to the electronic fuel-Injection setup. The EFI system we offer is fully programmable and capable of tuning any combination a customer can dream of. If a customer wants an out-the-door twin turbo system that can produce over 1,000 hp with a tune, we can do that too.

Step By Step

The basis for our Gen I challenger was a well-seasoned 400 small-block core, which Coast High Performance clearanced for a 4340 forged-steel crank working 6-inch rods through a 3.750-inch stroke--a combination Coast High calls its 406ci Pro Mod short-block.

You've noted that our 400 uses two-bolt mains. Our engine builder, Jun Nakawatase, pointed out that four-bolt-main 400s are actually weaker than their two-bolt brethren, since the extra bolt runs through the thinnest part of the cap and the block casting. We used ARP main studs for maximum strength.

The reciprocating assembly contained in the 406ci Pro Mod short-block consists of Probe SRS forged pistons with full-floating pins and Lightweight 4340 forged steel connecting rods. Using 6-inch rods maximized our power potential by optimizing our rod-to-stroke ratio.

Coast High Performance 406ci Stroker
In short, I felt like the man who takes a knife to a gun fight. But as it turned out, what I needed for this fight was a big 'stick--a really big 'stick. In fact, "Get the biggest dual-pattern cam you can find," was the first marching orders given to me by Coast High Performance's Shawn Mendenhall. Since this Torrance, California-based outfit specializes in building high-horsepower stroker small-blocks, I listened.

Given that the basic architecture of our starting point was created more than 50 years ago, it would be easy to label this contest "space-age versus stone-age." And there's no denying that GM has created an amazing new line of engines. On the other hand, it turns out that spacemen and cavemen have a lot in common when it comes to what's under the hood. Both engines are overhead-valve, pushrod powerplants, which means they're both air pumps. Get the mixture in, burn it, get it out. It ain't rocket science, for a Gen I engine or a whiz-bang Gen IV.Therein lay our dilemma. The Gen III/IV engines certainly have improved lower ends, but where they really shine is in breathing ability. How would we match up? The rules of this showdown required that all parts be we reached for the top shelf, going with Dart's fully CNC-ported Pro 1 227 heads. These 23-degree aluminum heads are serious breathers, moving 309 cfm at 0.700 inch lift. Dart calls them "professional-quality competition cylinder heads." Using a 400 block as our basis gave us needed displacement and room for the mondo heads to breathe. So there you have our formula: Big bore, big stroke with 6-inch rods, big cam, big heads, and lots of compression and timing make lots of power.

We did just that, and by the numbers we matched the 402ci LS2, and did it on 91-octane to boot. What's striking, however, is how far we had to go to do it. Race heads, a port-matched intake manifold, and one big hairy cam--and that's just for starters. We might go so far as to call this thing a street motor, but someone might ask, "What street?" and we'd be stuck for an answer. It would certainly be one that's driven without power brakes, since that serious 'stick doesn't provide much in the way of vacuum (6.5-7 inches). And as for idle quality...well, let's not discuss idle quality.

All in all, the component parts of the 402 are rather tame by comparison. Yet the total costs were close to equal. Essentially, we had to build a hydraulic-roller race motor to match the new kid on the block, and that we did. At this point in time, old versus new, it really comes down to what you want with your 583 hp. In human terms, one is a svelte gent, a real James Bond, simply charming until he whips out the newest of Q's gadgets and obliterates your ass. The other is a crude brute, swinging wildly from the trees like a Neanderthal until he jumps down and starts beating you over the head with a leg bone from a brontosaurus. And there's the question of the hour, friends. Spaceman or caveman? Personally, I like 'em both.

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583 hp, 533 lb-ft, and 91-octane-friendly--but not the tamest of beasts.

400 blocks are getting hard to find, but aftermarket versions are getting cheaper.

Edelbrock PN 2900 is a CNC port-matched Victor Jr. intake. Nice touch.

Dart Pro 1 227 CNC heads provide excellent flow numbers; Dart cast-aluminum valve covers top them off in style.

Comp Cams 2-piece Billet Aluminum Timing Cover allows for precise cam endplay settings.

Milodon Pro Competition Stepped Sump oil pan uses a crank scraper to free up a few extra ponies.

Hedman 13/4-inch long-tube headers with 18-inch extensions take out the junk.

CHP: We gave you a tough task, building a traditional small-block to match up with a Gen IV motor.
Shawn Mendenhall: GM did well in designing the LS-series engines. The 15-degree heads are such a huge advantage. It would have been nice if we could have used 18-degree cylinder heads.
CHP: It there anything to be said for going old school?
SM: The only advantage for the 23-degree setup is the bore. With a larger bore size, it's easier for the heads to breathe, and you can start with a factory block, which you can still get at a swap meet. It costs more to do a 4.125-inch bore in the newer motors, because you need cylinder sleeves and custom pistons.
CHP: What does the future hold for the traditional small-block configuration?
SM: Until there's no more gas, people will have fun with them. As long as there's a desire for 23-degree parts and people still have stuff stashed in their garages, they're never gonna go away. Aftermarket blocks are more within the average guy's reach.
CHP: You mentioned 18-degree heads. What are your thoughts on the subject?
SM: The 18-degree stuff is old-school racing technology. Make it user-friendly, which is already starting to happen, and it's gonna really change the market. You can make good power with 18-degree heads--they're gonna be able to make a ton of horsepower on the street.


Turn Key Powertrain
Oceanside, CA 92056
Comp Cams
Memphis, TN 38118
Dart Machinery
Troy, MI 48084
Ashland, MS 38603
Coast High Performance
Torrance, CA 90505
High Velocity Heads
Simi Valley, CA 93065
Hot Rod Performance