Project Corn Star: Summit Racing To The Rescue With A BluePrint 370

If you’ve ever had a project vehicle, you know things don’t always go your way. And while sometimes magazines like ours can make installs seems simple when they are anything but, we wanted to share with you one such struggle of ours. Our major setback came when we were preparing Project Corn Star for LS Fest West and discovered that the block on our LS1 just happened to be cracked and was thus unusable—especially considering the boost we were about to show it. So what do you do? Well, if you’re us, you turn to Summit Racing to save your bacon.

This Is Your Motor On Crack

In case you haven’t been following along with Project Corn Star, our original concept for the car was to take advantage of the E85 fuel system we had just finished installing by adding a little boost to the equation via a Huron Speed turbo kit and a Precision PT7675 Gen 2 turbo. We covered all of the highlights of the components we are using here, but one component we didn’t plan on changing was the engine.

Our road map had us boosting the stock(ish) LS1 to show you just how capable the platform can be on E85 with a little boost thrown into the equation. Alas, fate had different plans for our 2002 Camaro SS. As we dove into our project, we decided it would be best to drop the entire drivetrain out of the car to install the turbo kit and check on our newly installed SPEC clutch.

The crack is visible in the head bolt thread boss that sits between cylinders just next to the engine mount.

Since we had to pull the engine crossmember in order to change it for a turbo version from BMR and drill and tap the oil pan, it seemed like a no brainer to yank the whole thing. This isn’t absolutely necessary to install the turbo kit, but since we were also adding head studs it wasn’t too much more work just to pull it, so we did. And it’s a damn good thing we did.

Once we had the engine out of the car, the process of busting down the LS1 so we could install the ARP Pro Series LS1 heads studs (PN234-4316) began. After removing the stock cylinder heads, the head studs were slowly placed by hand. If you’ve never done head studs before, you actually don’t tighten them down. You put them in place roughly hand-tight and call it good (per the ARP instructions). However, when we went to thread the studs on the front driver’s side of the engine, there was quite a bit of resistance to the stud threading.

A closer look shows the severity of the crack.

Since we didn’t want to force things, a tap was used to clean up the threads. But as we wound the tap out of the block we discovered a lot of thread sealant in the thread boss. This is a telltale sign that the block had been cracked previously and upon further inspection, our suspicions turned out to be very accurate. There were hairline fractures on two of the thread bosses that were visible from the surface of the block.

Why Us?

You may be wondering how this happens. Well, it’s actually a lot more common that you would think. Usually it happens when someone removes the heads to replace the lifters on the motor when doing a cam upgrade—ours already had a TR230 cam installed by the previous owner. When the heads are lifted, coolant spills into the thread bosses. While this isn’t a problem by itself, if the coolant isn’t cleared before the head bolts are torqued back down, the coolant has nowhere to go under the bolts. And since water doesn’t compress, it flexes the block until it cracks.

Everything else on our LS1 looked to be in great shape, but looks can be deceiving. This is exactly why project cars can get the better of you, especially if you don't know if the previous owner completed the work competently.

The reason we suspected the block was cracked when we discovered the sealant is that many will try to avoid having to replace the block by simply sealing the threads on the head bolts so coolant doesn’t leak out. This is exactly what the previous owner had done to band-aid his mistake.

What To Do

Since, at this point, we were only four weeks out from LS Fest West, we knew we had to do something quickly if we still wanted to try to make the show with the car. Many ideas were thrown around such as rebuilding a junker or building a stroker. However, since we were so close to show time, we needed a much quicker solution.

Almost out of ideas, we turned to the guys over at Summit Racing to see if they could salvage our hopes of making the big day. After taking our build into consideration, they recommend we go with a BluePrint GM 364 Iron LS short-block. Not only was it the perfect recommendation, since it would work perfectly with all of our existing components, they were willing to expedite it to us as well. And thanks in large part to Summit’s expansive distribution network, we had the engine in our possession a mere three days later.

Let that sink in for a second. We had a huge setback in our project, a cracked block is no joke, and Summit Racing had us back up and running in just three days. Needless to say, they really went the distance when it came to saving our project from obscurity.

Our New Mill

We were thrilled with the recommendation Summit Racing made because it aligned perfectly with our goals and wouldn’t have us changing much to meet our needs. In fact, it’s arguably a better starting point for our boosted project than our stock LS1. While no one wants to find out that they have to replace their short-block—us included—replacing it with the 6.0-liter iron block was definitely a step up.

Our 370 came to us from BluePrint painted orange but they are available in black as well. The forged Mahle pistons seen here have valve reliefs cut into them providing additional room for a more aggressive cam should we choose to go that route in the future.

To find out more about our new mill, we turned to the guys over at BluePrint to explain exactly why this would be the perfect motor for our project.

“The 6.0-liter short-block uses Mahle 4032 forged pistons,” said Dru Freeze of BluePrint Engines. “We made this decision to give our end users the ability to add power adders to their build—which made it the perfect option for this project. On top of that, the metric piston rings are specifically designed by Mahle making them a formidable combo for boosted applications.”

The Mahle forgings will definitely be a step in the right direction for a boosted application and will allow us to increase cylinder pressures without the fear of breaking a ring land on one of the pistons. Not only that, but the block is actually bored .030-inch, bumping this engine’s displacement to 370 cubic inches—an engine size that you are likely pretty familiar with.

“Most of the blocks we use started life as an LQ4, LQ9, or some other 6.0-liter variant,” Freeze said. “We receive them mostly as traded in cores that we then rebuild. Each block is magna fluxed to ensure there are no cracks, then sent off to be reconditioned, bored, and honed to proper specifications.”

Summit Racing BluePrint 370

The LS1 and the 370 side by side, you can tell that the 370’s cylinders are much larger than the stock LS1’s.

While the pistons are new forgings, the connecting rods and crankshafts are GM OE pieces. And though they may be factory cast, they’ve been shown to be able to handle some serious power—although we may have to upgrade them at some point. The cranks are turned to a maximum undersizing of .010-inch. If the necessary machining falls outside of this specification they are discarded.

Once all of the machine work is complete, the engine is assembled using Clevite or Federal Mogul bearings throughout. On the bottom end, the rod caps are secured using ARP 2000 bolts—making this mill even more capable of handling the boost we are about to throw at it.

Here you can see the 24x reluctor wheel and the ARP 2000 rod bolts.

However, there are a few considerations to take into account before selecting this engine for your build as Freeze explained. “The BPLS3640C series is supplied with a 24x reluctor wheel which is not compatible with the later model 58x reluctor ignition systems. The engine is also capable of utilizing LS3 heads, which would require one to purchase a new intake if they are planning on swapping their existing parts over.”

Since our LS1 used the 24x reluctor wheel, it was a straight drop in for us. Though we are gaining some weight by going with an iron block, what we are sacrificing in weight we more than gain back in ridgity and thus “boost-ability.” Since the block is less likely to distort or push water under higher boost and power levels, we can make more of both reliably – making it the perfect selection for Corn Star. We’d eventually like to see the car make 1,000+ rwhp and this new short-block will be more than enough to take us there with an improved crank and rods down the line.

Forging Ahead

With our new short-block in the shop, we were ready to get back to work on Corn Star. Since the new block we were using was newer than 2003, we first had to exchange our head studs. When it comes to LS engines, not all years were built the same. On pre-2003 LS engines, the head bolts—or in this case studs—are shorter at each corner, meaning you have four studs in a kit that are shorter than the rest. In a post-2003 LS, all of the studs/bolt are exactly the same length.

Pictured above is the set of LS1 head studs. You'll notice that there are four medium length head studs that are used at the corners on all pre-2003 LS engines. Our new mill, however, uses a post-2003 design and thus uses the newer style studs which are all the same length aside from the smaller intake-side studs.

Luckily for us, ARP is only 45 minutes from our front door, so exchanging them was a breeze. After hand tightening our new studs in place (PN 234-4317), we were ready for the head gaskets and heads to go back on.

Naturally, in a situation such as this, you’re going to want to upgrade your head gaskets. In our case, we had no choice since our stock gaskets were for an LS1 and the larger bore of our new 370 wouldn’t allow their use. But even if we could, we wouldn’t. For the gaskets we turned to Cometic for a set of MLS head gaskets.

Though the Cometic set is a bit more than a set of stock GM gaskets, they provide significantly better sealing in return. Combined with the ARP head studs, the Cometic gaskets will provided a formidable combination for keeping all of our cylinder pressure where it should be. They feature load-controlled embossments that create an exceptional seal with less clamp load.

With the ARP studs in the block, the Cometic MLS head gaskets are set in place.

We selected our set in a 4.030 bore size and .051-inch compressed thickness (PN H1295SP5051S) per BluePrint’s recommendations. Combined with a 70cc combustion chamber, this gasket provides a conservative 9.8:1 compression ratio on our 370, though we had something a little tighter in mind.

Get Your Head Right

Since our original motor was down for the count, and we knew boost was on the way, we decided that now would probably be the best time to upgrade our heads while we were already this deep. And, as luck would have it, we had a set of Edelbrock E-CNC 215 (PN 79949) on our flow bench that we just completed testing on.

While the stock LS1 heads are lightyears ahead of their Gen I/II small-block progenitors when it comes to flow, there is always still room for improvement and Edlebrock has done just that. And though the heads retain the cathedral ports of the original castings, these particular heads were designed from the ground up.

One of the most appealing aspects of the E-CNC head for us was the increased 5/8-inch deck thickness. This will help keep our cylinder pressures contained and are much less prone to “lifting” than the standard 241 GM castings.

The intake and exhaust ports have been CNC machined out to 212cc and 76cc respectively. This leads to a substantial improvement in flow characteristics by as much as 45+ cfm at lifts above .500-inch. They retain the stock 15-degree valve angle but increase the valve size to 2.02- and 1.57-inches on the intake and exhaust respectively. Ours came complete with conical or “beehive” springs good up to .600 inch lift, and since our cam comes in well under that, we decided to keep them for now.

The E-CNC 215 head is also 50-state emissions legal and are capable of supporting well north of 450 horsepower. So if you are looking for an emissions-compliant head for your LS1, LS2, or even a custom 370 such as ours, these are arguably one of your best bets for passing those strict CARB restrictions.

The combustion chamber comes in near the factory LS1 heads at 65cc. While we could have gone with a head with a larger chamber for a lower compression ratio, the smaller chamber still gives us a very tolerable 10.4:1 compression ratio—which just so happens to only be .3 points higher than the stock LS1. On E85, this shouldn’t be a problem and will actually bring our turbo online quicker than had we went with a lower compression ratio.

Wrapping Up

With the lifters in place and the timing set swapped over, the heads on the engine were torqued to spec. We were now ready to put the engine back together and begin the mock up on our turbo system before it went back in the car. The timing set that came off the LS1 was still fairly new, having been installed recently by the previous owner. And since it was an LS2 timing set, their was no real reason to replace it.

The heads are torqued to spec and the 7.400-inch pushrods are sprayed with parts cleaner to ensure nothing obstructs the oil flow.

We also reused the high volume ported LS6 oil pump that came with our LS1, again there was simply no reason to replace it since it had seen minimal millage. The TR230 was slipped back into the block and, luckily for us, the use of the Edelbrock heads didn’t necessitate the use of different length pushrods. We verified that the 7.400 pushrods would work by coloring the tips of the valves, installing the rockers, turning the motor over, and then inspecting the wipe pattern. In our case, they were dead center and thus could be reused without a problem.

The camshaft, lifters, timing set, and LS6 oil pump were all installed prior to torquing the heads in place.

After verifying the valvetrain, our next, and arguably most difficult, task was to drill and tap the engine block to work with the Camaro front accessory drive. This sounds a lot harder than it actually is. The bracket works as a template and after marking where the hole needed to go, we used a 5/16-inch drill bit to create one. We then used the appropriate tap to make the necessary threads for the stock bolt. While drilling your brand new engine block can be (and is) daunting, taking your time will ensure an easy solution. 

Here you can see the ear on the block is already cast and simply requires drilling and tapping. Though this may seem daunting, taking your time and keeping the drill level should allow you to easily complete this task.

 The valvecovers, intake manifold, front drive, water pump, power steering pump, and alternator were reinstalled. After the oil pan was drilled, tapped and welded for the turbo drain, it was the finishing touch to our emergency engine build.

After the bottom end was buttoned up, we were clear to get all of the accessories bolted back on the engine and start mocking up the turbo kit for final installation.

Though we certainly didn’t expect to have to replace Corn Star’s engine, it turned out to be a pertinent, albeit unplanned, upgrade. Combined with our PT7675, this combination should have no problems making very healthy power numbers. And what’s more is the larger displacement will make for a very street-friendly turbo combination as the turbo will spool almost instantly.

Stay tuned as we finish up our turbo install in the coming chapters of Project Corn Star.

Article Sources

About the author

Chase Christensen

Chase Christensen hails from Salt Lake City, and grew up around high-performance GM vehicles. He took possession of his very first F-body— an ’86 Trans Am— at the age of 13 and has been wrenching ever since.
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