HOT ROD to the Rescue
Eric Schmiege bought his 1965 Chevy Bel Air for $1,700 back in 2000, a time, he says, “When you could still buy old Chevys for cheap.” As originally built, it had a lowly Chevy straight-six, but over the last 18 years, he and his hot rodding buddies have incrementally upgraded it inside, outside, and under the hood— where big-block Chevy power now resides. “I wanted a big engine with an old-school vibe,” Schmiege says. “So we built a 0.060-over 454 with Edelbrock Performer RPM aluminum heads topped by an old Offy dual-quad manifold, then modded a pair of 600-cfm, vacuumsecondary Holleys to work properly on it. I also put a fairly big flat-tappet hydraulic cam in the motor.” Behind the engine is a TH400 automatic and 2,600- to 2,800-rpm stall-speed torque converter. A 3.08:1-geared 12-bolt Posi rearend gets the power to the ground. Used as an occasional weekend cruiser and driver, the car is a regular attendee at local SoCal car shows and usually managed to make an annual sojourn up to Hot August Nights in Reno, Nevada.
After the Bel Air came out of the paint shop recently, Schmiege says, “The engine suddenly had a lot of vibration; it seemed to be running strange. I had a local shop inspect the cylinders. They removed the spark plugs and stuck a camera in there. It turns out there was a ¼-20 nut in No. 5 cylinder, probably from the air cleaner retention bracket. My friends and I pulled the passenger-side head off to see how bad the damage was. The piston top was roughed up. We smoothed out the damage in the car using a Dremel tool, then cleaned out the shavings. The head went down to Total Performance in Santee, California, who fixed up the chamber. We reinstalled the head, but the engine wasn’t running right. There was lots of blowby, and the compression in Cylinder No. 5 was still way down. The engine was toast.”
No shop wanted to take responsibility or get involved. Fortunately, Schmiege knew Jeff Smith, formerly editor at various times of HOT ROD, Car Craft, and Chevy High-Performance.
In turn Smith contacted HOT ROD, and another Rescue was underway.
The ailing Bel Air was delivered to Smith’s Los Angeles–area shop, where Smith says, “The engine was literally huffing smoke out the breathers, a pretty good indication of a pinched top ring. A ‘pinched’ ring does not seal. A ton of pressure is pushed into the crankcase and exits out the breathers as massive blowby in ‘huffs’ each time the cylinder fires.” At first, Smith thought that perhaps he could just replace the bad ring and still salvage the piston, so he pulled the problematic part out of the motor. Once fully exposed, Smith saw the piston had been deformed by the damage, and its ring lands had partially collapsed.
Still not the end of the world: Get one new piston and ring package, then slap the motor back together. Unfortunately, Smith says, “We discovered the No. 5 cylinder bore had at least 0.0005-inch taper in and out. That’s excessive, so it needed to be properly honed square. That meant—to do a professional job—the engine had to be completely disassembled for a trip to the machine shop. After complete disassembly, we measured the other seven cylinders and they were also out of square. So now we needed eight new pistons and rings and an overbore.
“Then the block failed a pressure-check,” Smith continues. “You guessed it: Although not immediately obvious—to the extent the engine overheated— Magnufluxing later confirmed the cylinder was cracked and it would require a cylinder sleeve.”
Adds Schmiege, “When the engine was vibrating and making noise, there were no bubbles in the radiator and no milkylooking stuff in the engine oil.” Go figure.
With the engine out of the car and machine shop bound, Smith decided to also address two other nagging issues plaguing Schmiege since way before the “great demise.”
• Oil pan contact: The Bel Air had been lowered 2 inches with dropped spindles, causing the oil pan to bounce and rub against the steering relay rod.
The 3,450-pound Bel Air (as weighed with half a tank of gas plus driver) pinged at part-throttle. This could be caused by any combination of excessively high compression, a cam not matched to the app and/or an overly aggressive spark curve.
THE FIX: BLOCK AND ROTATING PARTS
But first things first. The block went out to Jim Grubbs Motorsports (JGM), where the cracked cylinder was sleeved, the decks milled square perpendicular to the crank, and the 0.060-over a
10–12] Externally balanced 454 flexplate and damper unbalance amounts are usually standardized, allowing easy field replacement with standard 454 parts as needed. But the Bel Air’s existing flexplate and damper weights were way too heavy; the balancer alone was off by 65 grams! Installing a new Summit 454 degree’d balancer ( 10) and flexplate ( 11) put the external balance within 10 grams of blueprint specs, an amount easily handled internally when JGM rebalanced the motor. ARP’s 190,000-psi harmonic balancer bolt ( 12) features an extratall 12-point head that accepts a deep socket so it won’t round-off when hand-rotating the motor. standard 454 motor’s 4.25-inch bore was taken out another 0.010 inch to square up the cylinders. With the now 4.320-inch-id cylinders and the existing 4-inchstroke crank, this yielded 469 ci. JE’S Sportsman Racing Pistons (SRP) division supplied 0.070over forged pistons, rings, and pins that fit the new bore diameter. The slightly domed piston develops just over 10:3:1 com-
pression with a 110cc chamber.
The 0.010-under crank and rod journals weren’t damaged, but measured bearing clearances were a little higher than optimum and slightly inconsistent. Meticulous Smith put the clearances in exactly where he wanted by select fitting and mixing and matching Speed-Pro/Federal Mogul 0.010- and 0.011-inch undersize Competition Series main and rod bearing shell halves on the same journal as needed. Smith says the larger clearance shell should go on the top side of the mains and the bottom side of the rods. “This is to ensure good oil flow into the bearings. The mains are loaded on the bottom while the rods are loaded on the top, so the extraclearance shell should be placed in the sides opposite to the load.”
The new pistons required rebalancing the externally balanced, 454-based motor. During this process, Smith’s balanceshop, Treutelaar Equipment
Sales (TES), discovered the
Bel Air’s existing flexplate and harmonic balancer had much more external weight added than normal for Mark IV 454 parts. Installing a new Summit 454 balancer and SFI-certified, 168-tooth, 14-inch-od flexplate solved this latest glitch.
THE FIX: CAM
To better complement the drivetrain gearing, modern “starburst-symbol” motor oils’ lack of zinc, and Schmiege’s driving profile, Smith replaced the existing hydraulic flat-tappet cam with an Isky hydraulic roller profile. Comparing the cam specs (see table, right), Smith provides a telling analysis: “At every data point on the lift curve, the roller will achieve lift earlier in the duration curve—which essentially makes the cam larger within the limits of the lift curve. This is the advantage of a roller cam over a flat-tappet.
“We also need to compare the difference in advertised duration versus 0.050 duration. The flattappet’s advertised intake duration is 39 degrees longer than the roller cam while at 0.050-inch tappet lift the duration difference has shrunk to 20 degrees
(238 − 218 = 20)—yet the lift is very close to the same for both cams: The roller has a little less intake lift, and a little more on the exhaust side. This will make for outstanding torque with better throttle-response while giving up only a slight amount of peak horsepower.”
“I told Eric it was a risk just to bolt the head back on without pulling the piston, but it would be OK to try it. They would know right away if it didn’t work. It didn’t.” — Jeff Smith
It’s better to install the new cam before the piston and rods to ensure it fits easily through the cam bearings. “Sometimes the bearings are a touch too tight in the housing and won’t allow the new cam to fit,” Smith explains. “Always check this first before assembly; it’s easier to fix before the rotating assembly is installed. On a Chevy, you should not need to persuade the cam into place. If you do, something’s not right. Usually, the cam bearing may be tight in the bore. Most times putting a different bearing in place will do the job.”
Final short-block assembly was fairly straightforward, with an added Smith touch when tightening the connecting rod bolts—he uses a specified stretch value, not a specific amount of tightening torque. Rod bolts are your motor’s most highly stressed fasteners. High-perf, high-alloy, steel bolts have a relatively narrow plateau distance between the theoretical torque value need to achieve max fastener strength and the yield point. Due to the inaccuracies of well-used (but never recalibrated) torque wrenches as well as coefficient of friction variables, tightening to achieve a specified stretch value (although time-consuming) is safer and more accurate. It may take more than the normal torque value to achieve the specified stretch.
THE RESULTS (SO FAR)
The block is repaired, a balance issue addressed, and the shortblock meticulously assembled with new pistons and a better cam. Next month: Correcting piston deck clearance, valvetrain geometry, a new oil pan and pump, and carb and ignition tuning.
Pay attention to the details. Cutting corners ends up costing time and money in the long run. Consider making a step-by-step procedural check-list if you’re new to all this.
02] Noted SoCal engine builder Jim Grubbs (Jim Grubbs Motorsports) has retired, handing the reins over to able longtime shop foreman Ryan Peart, who continues the shop’s tradition of excellence. Peart sleeved the damaged cylinder. But checking the other cylinders with a bore-gauge revealed all had excess taper and were out of square.
01] Indigestion: Swallowing a bad nut can ruin your engine’s whole day. Somehow a nut got sucked down into the No. 5 cylinder on Eric Schmiege’s big-block Chevy. Bouncing around, it pinched the piston ring land, cracked the cylinder, and damaged a combustion chamber—but remarkably missed the valves.
Eric Schmiege[ Dropped 2 inches, the car recently got a fresh coat of Toyota Blue Spectrum Mica paint. After it left the paint shop, the car ran poorly.
[ The vibrating, huffing, and puffing Rat motor’s problem was eventually traced to a nut ingested down into No. 5 cylinder.
[ San Diego’s Eric Schmiege has been hopping up his 1965 fullsize Chevy Bel Air incrementally for over 18 years.
04–05] SRP’s forged, low-expansion, high-silicon, 4032 aluminum alloy, pistons ( 04) are designed for old closed-chamber factory heads, but their relatively small CNC-machined 14cc dome profile also fits Edelbrock’s semi-open 110cc-chamber aluminum heads, yielding compression ratios in the 10 to 10.5:1 range with a Rat’s near-zero deck heights and headgasket thicknesses. They’re machined for floating pins retained by double Spirolocks, but Schmiege’s existing Scat rods weren’t bushed, so JGM press-fit the pistons and pins onto the rods’ small ends ( 05).
03] After Peart milled the decks to square up the block, the already 0.060-inch-over bores fortunately cleaned up by boring the cylinders another 0.010 over. Honing with a torque plate ensures the cylinders actually stay round when the heads and gaskets are installed.
[ SRP, Isky, Fel-Pro, Speed-Pro, Summit and ARP supplied the needed fix-it parts; Jim Grubbs Motorsports machined and balanced the motor.
[ Jeff Smith to the rescue. The verdict: a pinched ring, cracked cylinder, excessive bore taper, the wrong cam for the combo, and a balance issue.
[ Patient, critical. Open it up, stat, and get that motor out of there! Stay tuned next month as “Doctor” Smith brings a dead Rat back to life.
09] Fel-Pro performance supplied all the motor’s gaskets. For this month’s short-block assembly, that included this handy R.A.C.E. (Remainder to AssembleComplete Engine) kit that includes front and rear main seals, and front cover, water pump, fuel pump and water neck gaskets.Fel-Pro
06–08] Smith checked the crank and rod journals using an outside mike ( 06), then used those measurements to zero a dial-bore gauge to check the installed clearances of new Federal Mogul trimetal Super Duty alloy bearings. Final clearances were 0.0025-inch on Nos. 1–4 main bearings ( 07), 0.0032 on the No. 5 (rear) main, and 0.002–0.0026 on the rods. At just 0.0025-inch, crank endplay was too tight ( 08). To open up the thrust clearance to the 0.006–0.010-inch blueprint spec, Smith sanded the rear main thrust bearing surface on a glass pane.
13–14] An Isky hydraulic roller cam ( 13) replaced Schmiege’s old flattappet grind. Smith: “The shorter-duration Isky roller adds a little more power down low. We kept the duration short at 218/228 degrees at 0.050inch tappet lift, with a 112 lobe-separation angle (LSA) and 112-degree intake centerline (IC). Combined with the motor’s 10.3:1 compression ratio, this should run pretty strong in the area where Eric drives the car.” Using Schmiege’s existing double-roller, three-keyway timing chain, the cam degree’d in 1-degree advanced (111 degree IC)—about as close as you can get allowing for normal machining variables ( 14).14
16] One just doesn’t have 4.320inch bore tapered ring compressors laying around. ARP to the rescue: Its compressors are CNC machined from 6061-T6 billet aluminum tube, have a true radius for each different bore diameter, and are even relieved for wire O-rings on the bottom. Standard stocking sizes range from 3.552–4.750 inches (SAE) and 75mm–100mm (metric).16
15] With a roller cam’s nontapered lobes and a Chevy’s rear-mount distributor, the billet wants to “walk” forward in the block. Control this with an antiwalk thrust button, available in several different materials and lengths. Summit’s 0.940-inch-long aluminum button (PN 6002) required the least hand-sanding to yield the desired 0.005-inch endplay. An Isky lock plate prevents the cam sprocket bolts from loosening.15
*Valve lift with Schmiege’s existing and reused Harland Sharp 1.8:1-ratio roller rocker arms. The standard big-block Chevy ratio is 1.7:1.
17] Tightening high-tensile connecting-rod bolts to a specified torque value is preferred over using a torque wrench. Smith uses ARP’s billet stretch gauge, one of the most accurate available. If you have a known accurate torque wrench and the bolt reaches stretch before hitting the torque spec, you may have a “stretchy” bolt (discard it).17