Raising the Stakes on the LS1

COMP Cams® and cylinder head specialist Greg Good team up to create unprecedented LS1 power

General Motors’ LS family of engines may just be the last great series of cam-in-block small blocks ever produced. In an era where overhead cam designs are dominant, the LS series of engines are both a throwback and a technological marvel. They keep the small package size and beautiful proportions of a cam-in-block V8 and combine it with the best of modern engineering technology, which allows for great power and torque numbers right out of the box.

This is one of the main reasons why LS engines are so popular among hot rodders, bracket racers, and just about anyone else looking for a modern, dependable engine that makes good power. Of course, for most of us, “good” isn’t good enough when describing power levels. Fortunately, going from “good” to “great” in terms of horsepower with LS motors isn’t that difficult. It can be done with just a few bolt-on parts, and “peel your eyelids back” isn’t that far behind if you make your upgrades intelligently and work with the right parts manufacturers.

And that’s exactly what cylinder head specialist Greg Good, of Greg Good Cylinder Heads in Houston, Texas, is doing with LS motors in all types of cars. One of his recent projects was the cylinder heads and valve train in a Camaro Z28 drag car for owner Joe Huneycutt. Huneycutt's desire was to race in the LSX shootouts, and he also specified he wanted to race an all-motor car (no power adders such as nitrous).

“What’s interesting about this engine,” Good says, “is we are using the original style cathedral-port heads which are the same style heads found in LS2 engines on the street. We don’t have any C5R or LS7 heads, and that made for a little bit more of a challenge. The heads we did use are from ET Performance, which, I believe, has one of the better Cathedral port head castings out there. We went with them because they leave a lot of material around the ports, which gives me room to do whatever I want to the intake ports to get the flow numbers I’m looking for.

COMP Cams LS custom grind camshaft

“We just gave them the Comp Eliminator treatment,” he continues. “With some port work I was able to get the flow up to 391 cfm on the intake ports and the exhaust around 270 cfm. Out of the box they were 350 on the intake and 245 on the exhaust. And then I got with Dean Harvey at COMP Cams®, who I trust completely, to help match up the right camshaft for it. He got me a really good cam for it. It uses Pro Stock lobes which make good power and are also very gentle on the parts. It has given us a real stable valve train. In fact, Joe says he hasn’t had any valve train problems at all—knock on wood. And that is a big deal because he’s turning that motor to 10,000 rpm. The valve train in that thing is just bulletproof.”

Good says that the 10,000 rpm goal was necessary to get the gearing that Huneycutt wanted, and that extreme rpm level dictated almost everything when it came to the valve train. The valve sizes were limited to 2.100 inches on the intake and 1.625 inches in diameter for the exhaust because of the smaller bore size with the small block design. To help the LS motor get even more air into the cylinders and act more like a big block, Good cut the valve seats at 55 degrees (compared to the standard 45 degree seat). This allowed him to cut the throats in the end of the intake ports larger than he would have been able to with a 45-degree seat. A 55-degree seat isn’t a good idea on street-only engines because it creates poor flow numbers at low valve lift, but it really shines when the valve is lifted beyond 0.600 of an inch. In Good’s LS heads the intake valve lift is 0.966 of an inch, so the flow numbers when the valve is lifted 0.400 of an inch and below really aren’t a consideration.

Also, to maintain valve control at such extreme rpm levels, both the intake and exhaust valves are titanium. But in order to maintain a decent life cycle with the exhaust valves under the high heat load they see, Good did make a concession and expand the valve stems from the 5/16 diameter used on the intakes (which are cooled by the incoming intake charge) to 11/32 of an inch in diameter. The spring pressure is an incredible 500 pounds on the seat. Good says that he normally sees that drop to around 450 pounds after 30 runs, and they are replaced after every 45 to 50 passes.

Dean Harvey of COMP Cams® says Good’s project was a unique one, but picking the right cam was mostly a matter of looking at different engine packages for which COMP® had already produced cams that were close and making the right adjustments.

Dean Harvey of COMP Cams®

“We have a huge database of knowledge that we’ve built over the years working with different engine builders and racers, along with our own research and development,” Harvey explains. “So we have a lot of resources where we can look to see what works and what doesn’t. For Good’s project, he told me what the customer wanted to do, which was to build a fast, LS1-powered, naturally aspirated drag car. This thing was going to see limited, if any, street use at all. The plan was just for it to go fast. He gave me information, such as the flow of the cylinder heads, how much compression it had, the weight of the car, etcetera. And then I was able to make lobe selections based on my experience with similar applications. I found some Pro Stock grinds that we had done, and they seemed to fit well with what he wanted.

“So I came up with some lobes to try. I told Greg right up front that while I thought I could get it close and this wasn’t necessarily a given, we may need to do some tweaking and grind a second cam after we saw how the first one performed. But it turned out that the first cam was exactly what we were looking for. It made good power and still was easy on the valve train at 10,000 rpm. And on top of that, the lobes came right out of our catalog. Of course, that’s a function of all the different lobe designs we have in our inventory.”

The engine package has certainly worked. Good says that last year Huneycutt won the Clash of the Titans race at River City Raceway in Texas and has run an 8.90 quarter mile at 153 miles per hour. There isn’t exactly an official record, but Good says he also believes it is currently the fastest naturally aspirated car in the country with an LS1 engine and T56 six-speed transmission.

So if you have an LS-series engine, is there anything to be learned from this? Of course, says Good. The first lesson is not to be afraid of running cathedral port cylinder heads. They can be made to flow well, but there are, however, weaknesses to the GM head. On the stock head, Good says the intake port is too close to the cylinder wall which causes valve shrouding (which limits airflow through the intake port). If you are looking for really high horsepower numbers, you may want to consider an aftermarket head that moves the intake closer to the exhaust valve and the center of the cylinder.

A little port work can also do wonders for an LS engine. Good cautions that many inexperienced head porters will place too much emphasis on just intake port flow and will allow the exhaust to lag, thinking that exhaust pressure will help the flow there.

“But exhaust is very important, too,” he says. “I’ve taken a lot of heads in the past and just worked on exhaust flow and the cars have been faster. The exhaust is very important because we want a clean cylinder when the intake valve opens. That’s because the intake valve opens on the tail end of the exhaust stroke. If we have a lot of exhaust still trapped in the cylinder when the intake valve opens, then it will just blow up into the intake port. You can see evidence of that by carboning of the intake port. The better your exhaust ports are, the more you can get away with on your intake ports. So if your exhaust ports are good enough that you aren’t trying to fight exhaust reversion into the intake ports, in my opinion, you can run a slightly bigger intake port cross sectional area that flows better.”

“Plus, when an engine goes into exhaust reversion at high rpm, that’s one of the causes of an engine that just nose dives right after making peak power. And we all know by now that we want an engine that just gently falls off after peak power because you can turn that engine higher going down the track. When you shift it doesn’t lug down as far, and it’s those engines that are usually faster.”

The problem for many people comes with the fact that once they’ve invested in a set of cylinder heads, they simply cannot swap it out for a new set if they notice the exhaust ports are causing some exhaust reversion. In that case, it can often be easier to make a few critical cam adjustments to solve the problem. A smart cam designer can work with the overlap, and specifically when the intake valve closes, to reduce or even eliminate reversion. “If you do have excessive reversion,” Good adds, “you can try retarding the camshaft timing a bit. I’ve seen people get into trouble trying to advance the cam too much on an engine with a lot of horsepower with big intake valves. You have to pay attention to the timing of when the intake valve opens. If it opens too early, that’s when reversion can be a problem.”

“So you see,” he continues, “it’s all tied together. If you can keep the exhaust from backing up into the intake port, then you are miles ahead. You can get away with an intake runner volume that you never thought you could use before and the car can still be drivable, even on the street.”

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