327 Small Block Chevy Engine Build - The 500HP Question

For This 327, The Answer Is Yes-And Then Some

John Nelson Nov 1, 2008 0 Comment(s)
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Often the hunt for horsepower starts with a question. You know the type: "Hey, I made 480 hp-how much more would I have to do to make 500?" That's exactly the query posed by Jeff Latimer of Valencia, California's JGM Performance Engineering, who had a good combo in hand: a small-block throwing down 420 lb-ft of torque to go with all those ponies. What makes the question compelling, though, is that those numbers came from a "mere" 327. So when we learned that JGM had teamed up with its neighbors at Air Flow Research to deliver an impressive reply to the 500hp question, we didn't have to be asked twice to check out the results.

Latimer is a staunch 327 fan. "It's part of my memory from the good ol' days of Pro Stock," he told us. "Everybody was running them." So later on down the road, he built one: a 10:1, hydraulic flat tappet motor with duration at 0.050 in the 240s, and wearing AFR 180 Eliminator heads. No question, he was impressed with the result. They're great numbers for a 327-but you know where this is heading.

The foundation was another 327 block. When outfitted with ARP studs, the factory two-bolt mains were more than sufficient for the planned power level. The mains were also precisely line-honed and the bearing clearances set with the factory steel crank being utilized. The holes were bored 0.040 over; with the standard 3.250-inch stroke in place, displacement came out at 333 ci. The reciprocating assembly was fairly pedestrian: Eagle 6-inch I-beam rods topped with KB hypereutectic slugs. "They're enough for 500 hp," Latimer explained. The short-block is more than adequate, but nothing exotic, as our builder puts it.

The wealth of experience at JGM, along with some computer modeling based on cylinder head flow data and estimated cranking compression, led to more particulars. The chosen cam was an aggressive Comp solid-roller, boosted with Comp 1.6:1 Hi-Tech stainless steel rocker arms. Also of note is the piston deck height-the +0.005 figure, when combined with the cylinder heads' 60cc chamber volume, creates a fairly tight quench figure of 0.035 inch, which promotes efficient combustion.

Latimer was impressed by the performance of the 180 Eliminator heads on his first 327, and he naturally turned to Tony Mamo and the AFR crew for help in answering the 500hp question. The heads of choice were a set of the company's 195 Competition Ported Eliminators. Mamo put it in a nutshell: "Jeff and I felt these heads were ideally suited to this project, 'cause we intended to turn it pretty hard."

"Ideally suited," indeed: The horsepower goal was blown away by a good 10 percent, as in 50-plus more horsepower than the goal. Peak power came at a not totally astronomical 7,100 rpm. And as impressive as 553 hp is from a 327, check out the torque numbers. Right off the bat, 433 lb-ft at 5,600 isn't a bad peak. But this thing's at 380 lb-ft by 3,900 rpm, and stays over 400 from 4,600 all the way to 7,200 rpm. It's a screamer-but one with an impressive and flat, useable torque band. "That's why we used the 195 Comp ported heads," reiterated Mamo. "Since this engine will spend more time on the street than at the track, we were concerned about the bottom end and throttle response as well as the top end power."

Latimer is thrilled with the results, especially, we suspect, with that flat torque curve, since this mill could find a home in the '63 Chevy II he's been working on. On the other hand, more questions have already arisen, and Latimer admits that he might have used some different components if he'd known he was going to exceed the 500hp goal by so much. He's already working on it, and of course the question has already been posed: "I wonder how much more it'll make next time?"

Quick Notes
What We Did

Followed along on a mission to obtain 500 hp from a 327 small-block

Bottom Line
Mission accomplished-and with a 53-horse bonus


It's All In Your Heads
It's always nice when you can rely on your neighbors for a helping hand-especially when you're shooting for a big hairy horsepower number and your neighbor just happens to be cylinder head maestro Air Flow Research. Add in the success that Latimer had with his first 327, and it was a given that AFR would get the call for this project. AFR's Tony Mamo suggested a set of the company's 195cc Competition Ported Eliminator heads. That's right, even though emphasis here was on high-rpm horsepower, the parties involved weren't willing to entirely kiss off the lower end and wanted a better balance. And that's where the Competition porting job comes into play. Most of us hear "competition porting" and think WOT, max-rpm power. But a motor is never just at its peak. It's always moving through the rpm range, even when it's at full throttle. In that case, ultimate high-end performance is not necessarily the main reason for choosing Comp porting. "It's always best to run a smaller head that reaches your CFM target or goals, especially in any application that spends a fair amount of time on the street," explained Mamo. "When you have the same airflow through a more conservatively sized port, the torque and the low/midrange power is a lot stronger, and the snap and crispness in part-throttle operation is vastly improved, a factor you will never see measured or quantified on a dyno, but that's very welcome once you experience it." Well, couldn't they just have put a bigger head on it? Negative, said Mamo. With the 210 street heads, you'd save $500 but end up with a lazier engine and without the linear power curve. "I always recommend Comp porting to anyone who's serious about what they're doing," Mamo elaborated. "It does it all better: It has higher airspeed for better cylinder fill, it improves low/midrange torque and power output, it has better throttle response, and it improves fuel economy-it's just more efficient."

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Although Latimer was confident that his 327 creation would reach the 500 mark, he was a bit surprised to pass it by so much, and admits that he would have made some different component choices if he'd known. To that end, he's got a set of lightweight Wiseco pistons and rings on order, along with 6.250-inch rods to increase the pistons' dwell time at TDC and further enhance that rod/bore and stroke combo. Our only question is, "When can we come check it out?"

327CI Build Sheet
Specifications not listed are the same as stock. Except as noted, all dimensions are in inches or fractions thereof. All prices sourced through JGM Performance Engineering and AFR.


Engines Drivetrain
Check out what it takes to get 500hp out of a 327 Small Block Chevy Engine with this build from JGM Performance Engineering.
John Nelson Nov 1, 2008


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