Stronger, greater, and higher, the now-469ci big-block Chevy drops again into the 1965 Bel Air. You’d assume there’s loads of room in a fullsize Chevy, however Smith says, “It was difficult to get the engine in and clear the carbs with just a single-chain hoist. We could have used one of those engine-tilter chains with the adjustable leveler.”
The Rescue So Far
The Chevy Rat in Schmiege’s 1965 Chevy Bel Air died. Final month, we fastened the short-block. Now, we’ll repair the remaining issues.
When the big-block Chevy in Eric Schmiege’s 1965 Bel Air swallowed a nut, it cracked a cylinder wall and broken a piston. Additional evaluation by former HOT ROD editor Jeff Smith revealed an out-of-square block with extreme cylinder-wall taper and extreme principal and rod bearing clearances. Final month, Jim Grubbs Motorsports sleeved the cracked cylinder, bored the engine zero.zero70-inch over, and remachined the block to sq. it up. Smith then reassembled the block, putting in new SRP cast pistons and premium rings. He additionally changed the Bel Air’s previous hydraulic flat-tappet cam with an Isky hydraulic-roller profile that higher matches the Bel Air’s drivetrain gearing and Schmiege’s driving type. Nevertheless, piston deck peak, valvetrain, oil system, and driveability points nonetheless remained to be handled.
Jeff Smith fastened the sick 469ci short-block. This month, he offers with piston deck clearance, valvetrain, oil pan, and driveability points.
The Repair: Deck Peak
On steel-rod engines, high-perf big-block Chevy builders often shoot for near-zero piston-to-block deck heights (the piston deck is about flush with the block deck at prime lifeless middle, or TDC). With typical zero.038–zero.041-inch compressed-thickness composition head gaskets, this achieves good quench with the Rat motor’s complicated combustion chamber and nonetheless leaves an satisfactory piston-to-head, high-rpm clearance security margin.
That was definitely Smith’s unique intent, however, as he explains, “Before we sent the block out to Grubbs for repair and machining, we checked the old piston-to-deck clearance and found the block decks were not even close to square. They were out almost 0.008 inch relative to the crank centerline front-to-rear with the front portion high, which is why we had Grubbs mill the block to square it up. But now when we went and installed the new pistons, we discovered they were sticking up out of the block by about 0.013 inch on average, probably because the deck had been previously milled in a prior rebuild, but not relative to the crank centerline. Fortunately, Fel-Pro saved our bacon with its 0.053-inch compressed-thickness MLS [multilayer steel] PermaTorque gasket that also offers superior sealing potential with the proper deck surface finish. If our deck was zero, we would have used a 0.041 head gasket, and the compression would have been almost exactly the same.” Even with all of the deck and head milling, piston-to-valve clearance was nonetheless greater than ample, coming in at zero.190 inch or greater on the closest strategy for each the consumption and exhaust valves.
SRP’s pistons have been zero.013 inch above the block deck at TDC (prime) inflicting each excessively excessive static compression for pump fuel in addition to insufficient piston-to-head clearance. Fel-Professional got here to the rescue with its thick, zero.053-inch compressed-thickness MLS head gasket (middle) yielding a pleasant zero.040-inch piston-to-head-deck clearance worth. It additionally decreased the compression ratio to a pump-gas-friendly 10.03:1 with the Edelbrock heads’ 108–109cc chambers (as measured by Smith, backside). To make use of an MLS gasket, each the top and block deck surfaces have to be mirror-smooth as they have been on Schmiege’s newly machined elements. Fel-Professional presents MLS Rat-motor gaskets in zero.041-, zero.053-, zero.061-, and even zero.071-inch compressed thicknesses.
The Repair: Valvetrain
Isky’s new hydraulic-roller cam required a complementary valvespring and retainer improve.
Utilizing a valvespring micrometer (prime), Smith arrange Isky’s hydraulic-roller-cam-compatible springs with 120 kilos of strain at a 1.875-inch put in peak. “We had to add 0.060-inch worth of shims (center) to get the installed height correct on Edelbrock’s large ‘roval’-port heads,” Smith explains. “That’s in addition to the steel spring seats.” Absolutely assembled right here on Edelbrock’s Performer RPM aluminum heads (backside) Isky’s twin with damper valvesprings develops round 315 kilos over the nostril.Usually, the Edelbrock head’s D-shaped exhaust ports name for a round-port header gasket corresponding to Fel-Professional PN 1411 (prime), however Smith discovered the Bel Air’s small 1¾-inch, square-flange headers wanted a corresponding Fel-Professional PN 1410 small square-flange header gasket (backside) to correctly seal.
As for the lifters, Smith went with Isky’s “real McCoy” Johnson short-travel retrofit models with paired information bars. With correct preload, shorter lifter journey presents extra high-rpm stability in comparison with standard-travel hydraulics.
Isky short-travel lifters like much less preload than regular. “Limit preload to 0.030–0.040 inch,” Smith says. “A ½-20 fine-thread rocker stud has 20 threads/inch, so each complete thread is worth a 0.050-inch change in the preload distance. This means you want to preload the lifter at zero-lash plus three-quarter turn or less, which puts the preload in at 0.0375; half a turn would equal 0.025.
Smith bolted the heads onto the block using ARP performance head bolts.
ARP head bolt kit PN 135-3610 fits most Edelbrock Performer RPM big-block Chevy heads. On head bolts that go into the water jackets, use ARP Teflon-based sealer on the threads; it’s formulated to prevent coolant leakage while duplicating ARP’s recommended preload levels.
Next up was checking the valvetrain geometry. “I like to use that old trick, where with the lobe on the cam base circle, you want to place the roller tip-to-pushrod contact point at roughly one-third in from the pushrod side of the valve stem tip. This pushes the rocker tip across the centerline at max lift and then back again. At max lift, the center of force should ideally be exerted on the center of the valve tip.
“To get there, we needed pushrods that were shorter than recommended, probably because the heads and deck had been cut so many times. Using an adjustable pushrod, we ended up spec’ing 7.600-inch for the intake and 8.550 for the exhaust side. These can be special-ordered from Isky, but there is a two-week wait, so Isky sent us a set of 7.650 and 8.600 lengths they had in stock.
“I looked at the contact point with the pushrods still ‘off’ a little, and it looked OK—not ideal, but acceptable. I think this shows with a stud-mount rocker, you can be off 0.050 inch or so and still be OK—at least on a mild street car.”
Milodon’s engine-plug set consists of all these hard-to-find engine cup and screw-in plugs. The freeze plugs are corrosion-resistant brass. The old-school Chevy orange paint is by Dupli-Colour. Two FRAM tough-guard oil filters have been expended: one for preliminary run-in, one for after. Lucas provided the motor oil.
The Repair: Oil Pan
Among the many remaining points: With the Bel Air’s front-end lowered 2½ inches, the prevailing oil pan stored bouncing off the drag hyperlink.Milodon’s extra-low-profile oil pan, high-volume oil pump, and matching pickup and display resolved the Bel Air’s oil pan points.
Smith additionally took the time to deal with some annoying issues Schmiege had been dwelling with earlier than the main engine failure introduced issues to a head. The Bel Air had been lowered 2 inches with dropped spindles, inflicting the prevailing oil pan of unknown pedigree to bounce and rub towards the steering drag hyperlink. Smith changed the pan with a Milodon 6-quart pan; listed for a 1957 Chevy, the sump doesn’t prolong as far ahead, offering extra clearance. It required an identical Milodon pickup and display meeting. With a brand new pickup, Smith figured he’d might as nicely substitute the previous oil pump with a Milodon high-volume/high-pressure pump.
The prevailing non-ARP rear principal cap stud was too lengthy,” Smith says. “I had to cut it down and use a spare 12-point nut to clear the Milodon high-volume pump’s thicker casting” (prime). ARP sells particular person 180,000-psi 12-point nuts should you want one. Use ARP Extremely-Torque lubricant on the threads and between the nut or bolt head and washer prime (by no means the washer backside). Fel-Professional brings trendy sealing tech to the 1965–1990 Mark IV Rats with its one-piece, zero.094-inch-thick oil pan gasket produced from molded rubber with a inflexible service (middle). Measuring off the pan rail with gasket in place, subtract the oil pump display distance from the pan sump depth (backside). “I like to see ⅜ inch from the screen to the bottom of the pan,” Smith says. “Ours was closer to ½ inch—close enough because Schmiege isn’t going racing.
The Fix: Tune-Up
Car owner Schmiege prelubes the engine before fire-up on Smith’s Summit Racing test stand. Note the complete pressurized cooling system, full exhaust with Borla mufflers, and the Bel Air’s actual dual Holley 600-cfm carbs. Schmiege, along with his old hot rodding buddies Doug Eisberg and Eric Rosendahl, helped Smith out a ton with the grunt work.
That left only the Bel Air’s part-throttle ping, which could have been caused by any combination of too-high compression, a mismatched cam, an overly aggressive spark curve, or carb miscalibration. The first two items were addressed during the engine rebuild, so after bolting on Schmiege’s old Offy dual-quad intake, 600-cfm Holley carbs, and MSD distributor (Isky’s roller cam doesn’t need a special drive gear), Smith set up the engine on his Summit test stand. “We preset the timing at 12 degrees BTDC and used the electric fuel pump on the stand to prefill the carburetors. We hit the accelerator pumps about four times and then let the fuel vaporize for about 30 seconds before attempting to start the engine. It started immediately.
Car owner Eric Schmiege readies the motor for run-in on a Summit test stand, complete with pressurized cooling system and full exhaust.
“But we had an idle-quality issue that initially made it hard to maintain reasonable initial timing under 1,000 rpm. We found the advance curve in Schmiege’s MSD distributor came in way too quickly: all in by 1,100 rpm. Installing a heavier centrifugal advance spring slowed the curve down, letting us achieve a smooth idle at 850 rpm while also curing the car’s previous part-throttle ping. We stayed conservative, limiting total advance to 33 degrees with MSD’s blue stop-bushing and our initial 12 degrees timing.
The centrifugal advance curve did need some rework. With the existing soft “ballpoint pen” light-blue springs, Smith says the “advance curve was all in by 1,100 rpm! It wouldn’t idle under 1,100 rpm at anything less than 25 degrees initial, even with the vacuum advance disconnected.” Changing one of many mild springs with a heavy silver “garage-door” spring was the remedy.
“We wanted to break the new rings in properly, so we limited the time on the test stand to 10 minutes. With the engine in the car and no leaks, we put the engine on the road at light cruise until oil and water temp normalized, then immediately began loading the engine with light to heavy throttle. After 10 minutes of driving, we hit it to WOT [wide-open throttle] for a few seconds and allowed it to pull back down. This allows the rings to seat properly.”
Smith repaired a leaky Holley carb gasoline transfer-tube with new O-rings and, within the case of 1 broken gasoline bowl, somewhat J-B Weld. Smith reviews the carb calibration itself was almost spot-on: “Using my O2 sensor, we found the carbs were pretty close. The idle mixture screws needed to be leaned out about ⅟₁₆ of a turn. The car cruises at a 13.4–13.5 air/fuel ratio.”
The Rat that roared: After Smith threw a curve within the distributor, Schmiege hit the street and drove straight house to San Diego.
Schmiege was capable of drive the automotive house to San Diego from Smith’s northern Los Angeles store that very same afternoon after the engine had first been fired, a 4½-hour drive in visitors, with no driveability glitches and no cooling points. With 16 inches of idle vacuum, the facility brakes work nice. When Schmiege will get on it, the Isky hydraulic curler cam’s broad torque curve is properly matched to the large fullsize Bel Air. “It drives like a champ, better than it did before,” Schmiege says fortunately. “I’ve got my car back mechanically!”
The one glitch: “Idle oil pressure is a bit higher than I would like,” Smith says. “With oil up to temp, it idles at 55 to 60 psi with Lucas 10W-30 oil. So we will change it to 5W-20 when it’s time for the next oil change. I am trying to avoid loading the distributor gear when the engine is cold with high oil pressure, which now is as high as 80 psi.”
Don’t rush. Carry out mock-ups with the elements you’ll truly be utilizing through the ultimate construct. “Getting all these little details right demands hours of work to resolve,” Smith says. It might take 50 hours or extra to assemble an engine to the standard requirements proven right here—and that’s only for a light road scorching rod motor!
|All dimensions in linear inches besides as famous under.|
|Engine sort||Chevrolet OHV Mark IV massive V8|
|Bore x stroke||four.320 x four|
|Ignition timing||12° base, 33° complete|
|Gasoline||91-octane unleaded pump fuel|
|Crucial Volumes And Clearances|
|Most important bearings||Nos. 1–four: zero.zero022, No. 5: zero.0032|
|Rod aspect clearance||zero.017–zero.020|
|Piston ring hole||No. 1: zero.020; No. 2: zero.022|
|Piston quantity||14cc dome|
|Piston deck peak||–zero.013 (above deck)|
|Head gasket vol.||14.5 cc (compressed)|
|Piston-to-head||zero.040 (w/ head gasket)|
|Piston-to-valve (int.)||zero.190 @ four° ATDC|
|Piston-to-valve (exh.)||zero.350 @ 2° BTDC|
|Valve Lash||Zero plus ½–¾ flip|
|Valvespring (seat)||120 lbs @ 1.875|
|Valvespring (open)||345 lbs @ 1.260|
|Coil-bind clearance||zero.169 remaining to coil-bind|
|With ARP Extremely-Torque lubricant besides as famous under.|
|Major cap studs||110 lb-ft|
|Rod bolts||zero.0055–zero.0060 stretch|
|Harmonic balancer||110 lb-ft|
|Head bolts||Brief: 65 lb-ft, lengthy: 75 lb-ft*|
|Cam bolts||30 lb-ft|
|Oil pump stud||70 lb-ft|
|Flexplate bolts||75 lb-ft|
|*ARP thread sealer on threads; ARP Extremely-Torque between bolt-head and washer prime.|