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?"
What We Did
Followed along on a mission to obtain 500 hp from a 327 small-block
Mission accomplished-and with a 53-horse bonus
Ignition duties were handled by a standard GM HEI distributor, suitably enhanced with an M
Three subtly different intake manifolds were tried during dyno testing. One was an out-of-