By now, it’s no secret that GM’s direct-injected LT1, LT4 and upcoming LT5 engines are potent mills straight from the factory, delivering a remarkable balance of performance, efficiency, and durability. While these sophisticated powerplants are impressive right out of the box, that doesn’t mean that there’s no room for design improvements.
With the expectation of these engines being installed in performance cars, trucks, and full-sized SUVs, engineers had their work cut out for them when it came to packaging, especially when you consider the tight confines of both the C7 Corvette and sixth-generation Camaro.
The ongoing quest to keep a particular engine family compatible with an automaker’s various platforms occasionally translate to engineering decisions that are steeped in production pragmatism rather than the best-performing design for a particular component – a frustrating, but ultimately necessary, byproduct of parts sharing.
A few years ago, Edelbrock identified such an issue with GM’s Gen-V cylinder head design and has since been hard at work developing an alternative that provides a real solution. The problem is that the exhaust ports on a Gen-V LT snake around instead of exiting inline with the exhaust valve. This bend inhibits flow and leaves flow gains on the table, in turn providing an opportunity for the Edelbrock team.
The result of their efforts is the Victor Jr. LT1 and LT4 cylinder heads, which feature some interesting changes versus the factory design. We sat down with Rick Roberts – the director of engineering for Edelbrock and the man who spearheaded the design and development of these new cylinder heads – to get the lowdown on what they discovered about the factory units and how they addressed it with the Victor Jr. heads.
The Mass Production Compromise
“I remember I was at the SEMA Show a few years ago and they had on display one of these stock heads,” Roberts recalls. “I was looking at it, and the first thing that struck me was that the valves had been canted, that it was not an inline valve head. My eyebrows went up and I went, ‘Whoa! That’s cool.’ And then I rolled it over and I looked at that exhaust port and my jaw just about hit the floor. I looked over for somebody – anybody that I knew – so I could grab them and say, ‘did you see what they did here?’”
Suffice it to say, Roberts wasn’t exactly thrilled with the layout. “The idea to straighten out the exhaust port was there from day one,” he explains.
LT1/LT4 Victor Jr. Cylinder Head Specifications
• Exhaust port exit relocated 1.5 inches from stock facilitating better exhaust and intake port flow
• Intake and exhaust valve positions and angles both altered from stock geometry
• Intake 2.200-inch diameter 11.6-degree valve angle x 4.50 cant angle
• Exhaust 1.600-inch diameter 11.4-degree valve angle x 1.1° cant angle
• Ports and chambers fully CNC ported
• 21-4N stainless steel valves (hollow stem intake)
• Intake peak flow improved 16 percent over stock
• Exhaust peak flow improved 15 percent over stock
• Compatible with both factory LT1 and LT4 intake patterns
• 57cc combustion chamber volume • 3.5 sq. in. intake port cross-sectional area
• Angled spark plug location
• Uses all factory rocker arms
• Factory intake manifold location and height
• Factory exhaust bolt pattern
• Factory accessory mounts
• Factory valve cover
• Extremely thick deck (314″ minimum)
• Compatible with both factory and aftermarket head fasteners.
• Available with beryllium seats, high lift PAC springs, and titanium retainers
77119 – LT1, Performer RPM, Complete
77139 – LT1, Victor Jr., Complete
77149 – LT1, Victor Jr., Bare
77059 – LT1, Victor Jr., .750-inch Max Lift, Complete
77069 – LT1, Victor Jr., CHE B1 & Bx Seats, Bare
Gen-V LT4 (Pending Release)
77279 – LT4, Performer RPM, Complete
77249 – LT4, Victor Jr., Complete
77259 – LT4, Victor Jr., Bare
77329 – LT4, Victor Jr., .750-inch Max Lift, Complete
77449 – LT4, Victor Jr., CHE B1 & Bx Seats, Bare
Roberts added that he’d heard from some other folks in the industry that having the exhaust pointing that way helps with evacuating the cylinder and setting up the intake charge. “I’m just not buying it,” he says.
Whatever the rationale behind it, Roberts saw an opportunity to address what he saw as a compromised cylinder head design. “In essence, the Victor Jr. LT1 heads from Edelbrock have the exhaust exits moved an inch and a half – forward on one side and backward on the other side,” he tells us.
This makes the exhaust port straight, rather than having it wrap around the intake port. Not only does straightening the exhaust port out make the exhaust better, it also amounts to a better design for the intake port, so it’s an improvement from both sides of the equation. Still, there are some required caveats when one chooses to go off-script.
When we first started talking about developing this head two years ago, I was pretty surprised that upper management allowed me to consider doing this. In the past, this design might have been considered too radical. -Rick Roberts, Edelbrock
The upshot is that, in order to utilize this cylinder head, builders will likely need to either switch over to a custom set of headers or modify their existing exhaust. “We’ve recently come to find out that it’s actually not as tough a swap as we originally thought it might be,” he says. “On a Camaro, if you shorten the collector on the side that’s moved backward and lengthen the other side at the collector, there’s not too much else that gets in the way. So it may not be as difficult as you think.”
For those that want an out of the box solution though, Kooks has been developing a header specifically for this modification, and headers should start becoming available by spring of 2018. Roberts also provides some insight into the use-case for these heads, making a very apt point in the process.
“With a head like this – oversized intake valves, bigger ports, better flow – it’s likely you aren’t going to want to use the stock exhaust system anyway. You’re probably going to want a two-inch header because it’s going to pair better with the rest of the package.”
Roberts explains that Edelbrock contacted George Kook and asked if they wanted to work with them on the project. “George is a racer at heart, so he was all over the idea,” Roberts says. “He’s done a wonderful job with his company and they make a quality part, which is one of the reasons why we wanted to work with him.”
Roberts says that while they’re planning to start out with a header purpose-built for this head swap in C7 Corvette and another for a sixth-generation Camaro, it’s the market demand that will largely dictate how many different platforms that Kooks will offer an off-the-shelf solution for.
Bringing It All Together
“One thing I’m particularly proud of with this project is that we have had the courage to be a ‘first,’” Roberts tells us. “There have been times in our past where we have waited to see how situations would play out before jumping into the mix, but in this case, we didn’t do that. And I think it reflects the attitude of the company now. There’s only one first to market, and you become the standard. So I’m quite proud of the company for having the courage to embark on this.”
By the time you read this, Edelbrock’s Victor Jr. LT1/LT4 series heads should be available to order. And while you might have to wait a few months for an off-the-shelf header solution, Roberts points out that builders are, of course, not dead in the water if they’re willing to throw in some DIY ingenuity of their own.
“While it’s not necessarily going to give you the best performance, if you’re willing to make some modifications to the stock exhaust system in a car like the Camaro – or modify aftermarket headers, for that matter – you can get these heads working without too much hassle,” he says. “The flange and bolt patterns are all the same as stock, it just moves those elements forward on one side and backward on the other versus where they normally sit in a stock vehicle.”
Victor Jr. CNC Ported Head Flow Data
- Superflow 1020 flow bench
- 4.060-inch diameter bore
- 28-inch water pressure difference
- Plastic intake flow entry
- No exhaust pipe extension
- 2.200-inch intake valve
- 1.600-inch exhaust valve
“We will also have a version that will be sold without valves and valve springs that will have beryllium exhaust and bronze intake seats,” Roberts explains. “Some people who use titanium valves prefer those alloy seats for heat transfer, stuff like that.”
The third version will retain the ductile seats and stainless steel valves but will include beefier valve springs with titanium retainers that will allow for the use of camshafts with up to .750-inch lift.
“We’ll also offer a Pro-Port version,” says Roberts. “That one will come unported aside from the base machining, and the seats and guides won’t be installed. This way, a head porter can take the cylinder head and do their own port designs with it.”
Recipe For Power Gains
Roberts says that while doing a head swap on an otherwise stock LT1 or LT4 engine won’t yield crazy gains – and is an unlikely scenario given the nature of the modification to begin with – the performance potential on an engine that’s properly configured to utilize this design is formidable.
“What I can tell you about is the testing we’ve done on the dyno,” Roberts explains. “And that is with a stock bore LT1 run with a special version of our Edelbrock 2300 supercharger, one of our cams, and two-inch headers. The test was using the smallest pulley we make for that set-up, and boost was around 12 pounds, and that engine made 878 hp at 6,400 rpm and 827 lb-ft of torque at 4,500 rpm on VP C12 race gas. Those heads were also in a configuration for use with the lower-lift springs, so the cam was under .650-inch lift.”
Roberts says that one element of the testing that he found particularly encouraging was the predictable progression of power output – going from the Victor Jr. head to Edelbrock’s version of stock heads (Performer RPM), and then in turn, down to the factory GM heads, each step showed clearly the gains that were attainable. “We had this combination that we ran with the Victor Jr. head, then we thought, ‘What if we take the big badass head off and put on our stock version (Performer RPM) of the head?’ We did that, ran it again, and then switched over to the GM stock head and ran it again. It really illustrated the steady progression in performance gains that can be had as you move up the chain.”
By straightening that exhaust port out it becomes much better, so a camshaft appropriate for the stock exhaust port now becomes inappropriate for the straightened exhaust port. In testing we have yet to see the best that the head has to offer. -Rick Roberts, Edelbrock
But that doesn’t mean that Edelbrock is waiting for someone else to discover the ideal camshaft for this cylinder head design. “We’re working with a company that uses a program called GT-Power,” Roberts says.
“Using this simulation software, we found that the software’s results jived with what we were seeing in the real world. The beauty of that is that we can hypothetically test 50 different camshaft designs overnight, collect the data, and figure out which one is the best. It has made that kind of development dramatically easier.”
Roberts says that while getting the simulation’s parameters in tune with the baseline configuration of the engine they’re using takes some work, once it’s dialed in the savings in both cost and time are revelatory. In addition, the results are far more precise than in the old days when they’d grind a few cams, do dyno pulls, and adjust based on those results. “We’re really putting some horsepower behind this development process,” he explains. “It’s not like it was back in the day – just trying some things and seeing what works. We’re a lot more scientific about it now.”
So, don’t be surprised if Edelbrock comes out with a full package based on this new cylinder head sometime in the not-so-distant future. But in the meantime, these Victor Jr. series heads should available by the time these pixels meet your eyeballs. If you’ve been looking for a way to unlock additional performance from your Gen V motor, this new head might be just the ticket.