On December 21, 1970, my wife and I bought a tired, 82,000-mile, 1962 fuel-injected Corvette. It ran OK, but it wasn't totally original. It sold new in Redding, California. We bought it in Fresno. The fuel injection was missing, the Borg-Warner four-speed transmission and shifter were 1957 issue and the heads were Power Pack 283s.
The trunk lock was inoperative, but when we got it open we found the original 461-X heads (date-coded three weeks ahead of the block) laying in the spare tire well. One had a small crack. The original, wheezing, 327 short-block had a small cast-iron intake manifold. The carb was an AFB mated to an adapter plate. We paid $600. In all, the car was like a pretty girl with a dirty face. It was a car that had been driven, but not serviced.
You can almost "see" the high nickel in this 159-pound, 1962 Corvette 327 block. The cylin
Inside of a week, we cleaned all the corroded electrical wiring, replaced the chattering clutch assembly, tightened the pinion nut and adjusted the steering box free-play. In top shape back then this car was worth $2,000.
We then replaced the tired engine with an almost new, 1967 350hp 327 Corvette long-block that had set us back a whopping $150. The rest of the '62 remained mint and original, including the interior (less carpets), front and rear bumpers, emblems and body chrome. We put the original 327 short-block on a stand and the 461-X heads in GM head boxes.
In mid-1976, we returned to California and I entered the car magazine business at Popular Hot Rodding and Super Chevy. Both happily consumed most of my waking hours for the next 19-3/4 years. From mid-1976 all the way to today, the '62 was mostly garaged. We did buy a 1962 fuel injection unit that had previously been on Marv Ripes' 1968 Stock Eliminator world champion '57 Corvette, but its nozzle lines kept plugging up from sitting.
Valley Head Service machinist Alex Pulido put our replacement crankshaft through its paces
Fast forward to 1984, when the Vette was featured in Super Chevy as "Patti's Daily Driver." We hopped up the '67 327, added Schiefer 5.13 gears, a huge cam, S&S slapper bars off my old '66 L79 Nova and Firestone Drag 500 slicks and ran high 11s at 112 mph. It was too radical to drive around town so it was parked. Again. Its chassis, unbelievably, has never been washed-not to this very day. Except for a corroded battery tray, everything throughout is rust-free and original.
When lead additive was taken out of pump gas in 1972, I began thinking how I was going to one day rebuild the car's original 327 fuel-injected engine. I drag raced in Stock and Modified Eliminator, winning 107 of 121 final rounds, but in the mid-1970s, we were also members of the NCRS (National Corvette Restorers Society). So, we were mentally caught in a perplexing dilemma. Do we rebuild to "factory-stock" with an outdated, low lift, Duntov solid lifter cam and 11.25:1 compression ratio, and keep all of our purist friends and octane booster folks happy? Or, do we lower the compression for today's pump gas and increase the camshaft profile in order to hopefully increase performance?
For your review, here's a close-up of a bob weight. A bubble balancer is used to correctly
After many years of contemplation, and mental finger-tapping, we finally decided on the latter. Here's why: Hoping to keep the 327's power output near its advertised rating of 360 at 6,200 rpm, we bought a set of 0.030-inch oversize, 10.0:1 compression Speed-Pro hypereutectic pistons (#H660CP) over the Internet. For a camshaft, we special-ordered a grind that Zora Arkus-Duntov casually talked about over dinner in 1986. We thought it would be a nice tribute to him if we used a cam with "his" specs (0.480-inch lift, 280 duration and a 106 or 108 lobe separation angle). He did not specify hydraulic or mechanical lifters. But Zora was a mechanical lifter sort of guy. No wimpy hydraulics for him.
Enter Joe Sherman Racing EnginesNow the plot thickens. Long time friend Joe Sherman stepped right into the mix when we asked for his advice. He thought that if Zora were standing here today he'd much rather approve the new Comp Cams "Thumper" roller camshaft with Comp Cams "Beehive" valve springs (0.510 intake/0.490 exhaust, 280 duration, 107 lobe separation angle). Gee, we thought, Zora's words to us were 20 years ago. We thought Sherman was right. After all, he is one of today's best engine power-makers. So, the $65 "Zora" cam we special-ordered is now headed for our hot '70 383, four-speed Malibu.
At the beginning, our crankshaft was 12 grams out of balance (22 grams equals one ounce).
Larry Ofria at Valley Head Service gladly agreed to spec out the original 327 bare block and also repair and rebuild the 461-X heads. Every blueprinting engine spec was performed. Minimal crankshaft web align-boring was needed. The block's decks were described as "lumpy," so 0.030-inch was milled off-including much of the stamped numbers. But we wrote them down and will re-stamp them deeper into the block some day.
Ironically, the milling still left 0.020-inch above piston top dead center. The eight cylinders were bored 0.027-inch and then finish-honed the remaining 0.003-inch. This left a Speed-Pro-recommended 0.015-inch piston-to-wall clearance. We like Speed-Pro hypereutectic pistons (they first engineered them in the early 1980s) because they are said to be as strong as a forged piston and have the expansion rate of a cast piston (very little). So, the piston rings will seal better and there will be no piston slap noise.
Every rod and main bearing journal was mic'd for size then micro-polished. The oil passage
I personally shot-peened a replacement set of connecting rods I bought and balanced decades ago (the original rods and crankshaft were beyond repair) as well as the 461-X heads in the VHS high-pressure blasting tank. This process removed all foreign matter and also, according to VHS, made the rods stronger. My replacement crankshaft was bent 0.003-inch so VHS' Alex Pulido straightened it in the VHS crank jig (VHS is a full service engine facility). Chevy crankshafts usually check out OK in the balance department. Ours measured 12 grams out-of-balance. Remembering that 22 grams equals one ounce, the crank was just over one-half ounce out-of-balance. Both Alex Pulido and Joe Sherman said this was OK for a stock engine, but not acceptable for a high-performance engine. Alex reduced the out-of-balance number down to a mere 1/2-gram. That equates to 1/44th of an ounce. Looking good.
The heads needed a total rebuild, including deck milling (0.010-inch), hardened exhaust valve seats, new stainless steel 1.94 and 1.50-inch valves, bronze wall valve guides and the aforementioned combustion chamber crack repair.
When Alex Pulido checked the crankshaft balance, the dials told him the 12 grams of extra
Larry Ofria called his crack repair process "drill, tap and pin." The crack was first drilled completely out. It took four 3/16-inch, side-by-side holes to eliminate it. Each hole was then pipe-tapped with a tapered metal tap. They were also dipped in a type of space-age glue and installed one at a time. Each tap was screwed firmly into place then was sawed off flush with the deck. The tops of the taps were then finish-ground flush. Ofria said "drill, tap and pin" is a very effective and ever-lasting head crack remedy.
Joe Sherman Racing Engines won the 2002 Engine Masters Challenge hosted by our sister publication, Popular Hot Rodding. Sherman graciously agreed to help me with short-block assembly and camshaft degreeing. He also said he'd dyno-test it, too. Sherman is a consummate master of the little things that make a performance difference. He had not seen an early 327 in ages. There's not much difference per se, but he was impressed with the bigger port, 1962-63 fuel-injection 461-X heads. Their intake ports have higher floors and roofs and the overall flow volume is greater than a regular 461 head. They were conceived for more high-rpm horsepower in competition SCCA road racing, fuel-injected Corvettes. Although they were legal over the years on NHRA Stock Eliminator Chevys using 461 heads, they have all but dried up today. A set (condition unknown) recently sold on eBay for over $1,200.
Sherman flowed one 461-X head and remarked that its flow volume was similar to a late-model Vortec iron head. That's good, as Vortec heads give an average 350 about 40 extra horsepower, says Sherman. We knew all along that we had no equipment or funds to clean up the ports' short side radiuses and various port bumps and lumps. Sherman said he'd help us with some very minor under-the-valve backside grinder massaging. He thought it would be worth an additional 20 more cfm and 20 additional free horsepower. We know our Chevy engines, but pale by comparison to Sherman's genius. He's been at it for 40-something years.
Here is one of the heads fully machined with hardened exhaust valve seats ready for the ne
Rochester F.I. Or Carburetor Induction?Very few readers own or know anything about early Corvette Rochester mechanical, constant-flow fuel injection. So, for the sake of a more meaningful story, Sherman recommended I use an induction setup most all of you know about and can easily relate to, an Edelbrock Performer RPM intake manifold and an Edelbrock 750-cfm carburetor.
The Rochester fuel injection system flows about 650 cfm and has port nozzles. The Edelbrock system has nearly the same runner flow so we don't think one should out-power the other by much. Fear not fuelie lovers, as we may do something with this unit further down the road to see how it has held up over time.
Next up: Engine assembly, cam degreeing, plus a dyno test on Joe Sherman Racing Engine's Super Flow dyno. We're hoping for a nice running Vette on pump gas with 370-380 hp. Sherman thinks we'll see 400 from our '62 10.0:1 331 small-block cid. Stay tuned.
|461-X HEAD CFM FLOW COMPARISON|
|INTAKE PORTS||EXHAUST PORTS|
|Stock||Valve Lift||Shermanized||Stock||Valve Lift||Shermanized|
To repair the small crack, it is first drilled out, one hole overlapping the next. Valley
Once each hole was filled with a threaded metal tap, it was sawed off then milled down fla
This photo shows three things: The repaired head crack, new bronze wall valve guides and n
This close-up photo shows the topside of the valve guide area with a new bronze wall guide
Cutting into the exhaust valve seat area is a machine shop professional job. We installed
This photo reveals the Comp Cams single "beehive" valve springs and original press-in rock
Every 1962 and 1963 fuel injection engine had 461-X heads. Each head has an "X" embossed o
We spent about one hour bead-blasting the connecting rods at Valley Head Service. Accordin
Space does not allow us to show you photos of every bare block, crank, rod and head machin
We took this photo to show you how different the top end of balanced rods can often look.
We masked off the ports, then spray-painted both heads with Chevy orange spray can enamel.
Here is one of the eight Speed-Pro hypereutectic pistons we purchased, part number H660CP,
Compared to a factory 1962 Corvette 340hp 327 aluminum intake manifold, Joe Sherman says t
The Edelbrock AFB #1407 is a great street-and-strip carburetor because it has primary mete
Joe Sherman liked these 461-X heads so much that he wanted to flow-test them stock-then cl
Joe Sherman Racing Engines
2700 California St.
Valley Head Service