HOT ROD Rescue: The Rat Rod, Fixed At Last (Yes, It Does Burnouts!)

August, 2017’s North American full solar eclipse came early for J.B. Bracken, as his finally perfected 1935 Ford rat rod truck totally blocks out the Sun.

(Photo: James Gustin/figMEDIA)

Smoke you want, smoke you got! I think we blocked out the Sun!” — 

J.B. Bracken

The Rescue So Far

The rat rod is based on a 1935 Ford truck cab set on a custom frame. Motive force is now via an 8-71-huffed, 401ci, small-block Chevy.

When Norm Brandes at Westech Automotive received J.B Bracken’s 1935 Ford Rat Rod truck (HRM, July 2017), it couldn’t do a burnout and had poor driveability—despite an 8-71-blown 383 small-block Chevy engine. The 4,000-pound truck’s huge Dana 70 dualie rearend didn’t have enough low-end inertia to spin the tires. Initial fixes included a cam change, overdriving the blower, and proper tuning—only to suffer a broken piston and Brand-X head stud failure. Gluttons for punishment, we came back in the Aug. 2017 issue with a 4.125-inch bore Dart block, turning the 383 into a 401. Brandes stuffed it with stout 2618 aluminum-alloy JE blower pistons, bolted its aluminum heads on with real ARP head studs, and did some additional tuning to seemingly bulletproof the combo. But after Bracken drove the truck for 1,500 flawless miles with no issues, he blew a head gasket while performing a massive burnout in preparation for a HOT ROD photoshoot scheduled for the following day.

The latest issue: A head gasket blew at the rear of the No. 8 cylinder across to the water jacket (circle). The primary cause would turn out to be a lazy thermostat.

The Diagnosis

The blowout occurred at the rear of the No. 8 cylinder across to the water jacket. After eliminating several other possibilities—including “soft” cylinder heads and possible gasket “crush” issues—the main “perp” turned out to be a lazy thermostat.

Was there an issue with Bracken’s “off-shore” aluminum heads? In consultation with retired Fel-Pro Performance gasket engineer Greg West, the aluminum heads were sent out to Letsch Manufacturing for Rockwell hardness (shown here), as well as surface flatness and profile checks. All were in spec.
Gasket crush height using BB-shot (pointer) was per blueprint for Fel-Pro’s MLS head gasket, using both ARP’s specified installation torque as well as with an alternative retorque method.
The alternative method involves first tightening the cylinder heads to spec per the normal pattern. The engine is then permitted to sit overnight. The next morning, each head stud nut is individually loosened and immediately retorqued. The white paint shows the added nut rotation after the second retorque, indicating there was some relaxation of tension.

In spring 2017, Bracken had brought the truck out of winter hibernation and changed the thermostat and coolant. Sudden thermal shock load and temperature spike during the burnout from the not yet thoroughly warmed-up motor and it was “goodbye, head gasket.”

The third time around, we weren’t taking any chances, delivering the engine to Dan Timm’s Advanced Engine Concepts (AEC) to evaluate coolant circulation, plus some engine-dyno torture. To the extent possible, the engine was set up on the dyno just as it would be in the rat rod.

Advance Engine Concepts’ Dan Timm evaluated the engine’s cooling system, fuel curve, and ignition timing and efficiency on his dyno.

The Fix: Thermostat

The bad thermostat was a cheapie, generic, pellet-style, 180-degree F part. On the dyno, a thermal heat gun confirmed it didn’t open until 200 to 210 degrees—way too slow for a suddenly stressed cool engine. (It didn’t help Dart’s race block lacks an internal coolant bypass passage.) The solution: a balanced-flow, Robertshaw-type, high-flow thermostat that’s less restrictive compared to pellet-type designs. Stewart Components’ iteration goes one step further, adding three ³⁄₁₆-inch holes in the unit’s body for a quick, functional, bypass that equalizes temperatures on both sides of the thermo, minimizing thermal shock, as well as steam pocket formation during initial coolant fill. On the dyno, Stewart’s 180-degree thermostat opened consistently at 182 degrees. Coolant temperatures and pressures were more uniform throughout the motor as a whole—critical, as the head’s rear corner where the gasket blew is the farthest area in the coolant-circulation chain.

A Stewart-modded Robertshaw-type 180-degree thermostat replaced the cheapie unit. Brandes and Timm found the Stewart thermo opened consistently at 182 degrees—a real lifesaver for Bracken’s highly stressed blown motor.

The Fix: Tune-up

Premium MSD ignition parts resolved the ignition issues. Clockwise, from upper left: 6AL-2 programmable controller, Blaster HVC II coil, Pro-Billet small-diameter distributor with adjustable slip-collar, small-diameter cap, two-piece adjustable rotor, 3-Bar MAP sensor for enabling boost retard, and (not shown) a universal set of 8.5mm Super Conductor, spiral-core, spark-plug wires.

The engine experienced ignition break-up on the dyno. To maintain an outwardly old-school appearance, Bracken had been running a standalone (no separate ignition box) MSD medium-cap (“points-style”) distributor with a generic round coil. It wasn’t up to the job under high boost, plus the large distributor couldn’t be rotated more than 10 to 15 degrees when adjusting the timing without hitting the blower’s rear cover. Pulling the distributor entirely required removing the supercharger rear cover to obtain sufficient clearance.

At ⅜-inch narrower and almost 1-inch shorter than a standard Chevy points-style distributor, MSD’s Pro-Billet Small Diameter design (PN 8570) solves clearance issues caused by firewall interference, tunnel-rams, or (as on the rat rod) a big blower. An adjustable slip collar (arrow) permits compensating for a machined block, heads, or intake.

Brandes replaced the standalone unit with a posse of new MSD parts, including a small-diameter Pro-Billet distributor, a programmable MSD 6AL-2 digital ignition, a high-output HVC II Blaster coil, and 8.5mm Super Conductor spark-plug wires. He also tightened up the plug gap from 0.040 inch to 0.020 to make it easier to ionize the rich, high-boost air/fuel mixture.

The Programmable 6AL-2 ignition (PN 6530) incorporates a two-step rev limiter, and puts out 535 primary volts and 135 mJ of spark energy. It’s mounted in the driver compartment to preserve the rod’s old-school engine-bay ambience. Use a PC to program custom advance curves. Boost-retard, timing delays, or other switched functions can easily be incorporated.
When used with the programmable 6AL-2, lock-out the distributor’s centrifugal advance. Verify real-time phasing under boost-retard by drilling a hole in the distributor cap in line with the No. 1 terminal and checking with a timing light.
Use the adjustable two-piece rotor (PN 84211) to optimize rotor phasing; also be sure to check rotor tang-height with MSD’s supplied gauge.

With the ignition sorted, under boost the engine was relatively insensitive to timing changes, producing nearly the same power with 25 to 28 degrees of lead as it did with 34. The timing was “locked” on the dyno between those numbers, with the higher number tested with 110-octane Rockett leaded racing gas; the lower number was with 91-octane pump gas. Later, in the truck, Brandes found the engine was happy at 37 degrees total advance (unboosted), retarding 8-degrees whenever blower-boost hit 16 psi.

The 6AL-2 was programmed for 37 degrees total advance (at the crank), retarding 8 degrees at 16 psi of boost (rpm-independent, but around 3,300 rpm at full throttle). This delivers more part-throttle cruise response, but provides a safety margin for high-boost banzai runs. The 6AL-2 sees boost via the same MAP sensor Auto Meter supplies with its boost/vacuum gauge.

Charge-air temp is a problem on 8-71 blowers running on gas; with an otherwise decent tune-up, it becomes a major detonation-sensitivity wild card. To help Bracken keep a lid on the motor, Brandes installed Auto Meter vacuum/pressure and charge-air temperature gauges. The pressure gauge gets its readings from a manifold air pressure (MAP) sensor boxed with the gauge. It’s identical to MSD’s MAP needed to enable boost retard on the 6AL-2, but you’d have to buy the MSD part separately. In this case, Auto Meter’s MAP just does double duty.

No more “oops!” Bright, high contrast, Auto Meter 2 ⅟₁₆-inch Phantom gauges help Bracken monitor critical under-blower charge-air temperatures (PN 5758, left) and (through a packaged 3-Bar MAP sensor) vacuum or boost levels (PN 5777, right).
The air-temp gauge sensors install in the lower blower manifold and can be optionally wired through a relay to the programmable 6AL-2 so it can retard timing if air temps get too high. At present, that function isn’t enabled—but it’s nice to know it’s available if ever needed.

Brandes’ existing tune-up proved pretty close, with the twin Quick Fuel carbs needing only slightly richer secondary jets on the dyno. Later, back in the truck, Brandes ended up leaning the primary jets three numbers, which slightly lowered the under-blower charge-air temperature and improved part-throttle cruise response. “When we leaned out the engine at part-throttle cruise, 60-mph charge-air temps at cruise dropped from 230 to 240 degrees to 215 to 200 degrees.”

The Dyno Results

The engine was set up on the dyno with Bracken’s restrictive headers. The exhaust pipes and mufflers closely emulated the on-truck setup’s restrictive right-angle turns.

The rat rod’s 401ci small-block was set up on the dyno to emulate as closely as possible its in-truck configuration. The rat rod’s old-time headers with their restrictive right-angle turns into the exhaust pipes and mufflers cost power, but may have helped low-end torque.
AEC’s pet set of stepped short oval-track headers, still hooked to the restrictive exhaust, yielded about a 5-percent power and torque-number improvement—around 525 hp and 540 lb-ft, according to Timm.

On 91-octane unleaded pump gas with around 21.5-psi peak boost, the dyno recorded 475 hp at 5,500 rpm, with (critical for tire-spinnin’ Bracken) 499.5 lb-ft of torque at 3,200. Average numbers over the full curve were 477 lb-ft and 384.5 hp. AEC also tested with Rockett 100-octane unleaded and 110-octane leaded race gas. 100-octane made the most peak power (498 hp); 110 made the most peak torque (519 lb-ft). Overall, 110 octane produced the fattest curve, with an average 23.3 hp and 29 lb-ft gain over 91 octane.

At 21.5-psi of peak boost on 91-octane pump gas, the 8-71-blown, 401 made 499.5 lb-ft of torque and 475.2 hp. The numbers improved slightly with Rockett 100-octane unleaded: 511.3 lb-ft and 498 hp. On Rockett 110-octane leaded race gas, the engine made 519.2 lb-ft of torque and 491.6 hp. However, running on 110-octane offers the most area under the curve. Dyno-locked timing varied from 25 to 28 degrees on these tests.
Rockett Brand Racing Fuel supplied the 100-octane unleaded and 110-octane leaded racing fuel. The 91-octane unleaded fuel was from a local gas station. On the street, Bracken runs a 50/50 mix of 91-octane and leaded racing gas.

Bracken is totally satisfied with the results. He wanted the engine to make massive, low-end torque and that’s just what it does.

The PCV valve grommet smoked slightly. Bracken had already installed a baffle inside the vintage Mickey Thompson covers. Brandes reworked the baffle and grommet hole to accept a larger, taller NAPA baffle that raised the existing right-angle valve higher (arrow). Also note MSD’s blue Blaster HVC II (PN 8253), the most powerful coil designed for sustained use with a 6AL-2 ignition. The fully-potted unit features a U-Core design and 85:1 windings ratio for high output, quick rise time, and longer spark duration. Originally mounted in the driver compartment, its 44,000-volt output generated so much EMI it interfered with programming the 6AL-2—hence this final firewall mounting position.
Inside the rocker-cover PCV valve baffle plate, Brandes stuffed PowerHouse household copper-mesh dish-scrubber to serve as a filter.
Claying Comp Cams Pro Magnum rockers shows there’s nearly ⁷⁄₁₆-inch clearance to the bottom of the baffle—more than sufficient.

Lessons Learned

As hot rodders, we would’ve liked better top-end numbers. At the macro level, cam size matters. There’s probably 50+ hp in there if Bracken went to real tuned-length headers and a hotter (but still blower-centric) cam in the high-230s/low-240s with about a 114-degree LSA. Timm says a water/alcohol injection system’s cooling effects would permit more ignition advance under boost. “I’ve seen 50 hp from alcohol injection on an engine like this one.”

At the micro level, thermostats matter. “I’ve never seen a thermostat as accurate as the Stewart-modified Robertshaw high-flow,” Brandes contends. “Spending a little more on this premium unit can save your engine!

“A blown engine really does like more timing if you want to maximize low-end torque, but be sure to add a boost retard to avoid top-end detonation. If you can afford it, race gas is good insurance. Besides, it smells good, too!”

J.B. Bracken lives life in the fast lane: burnouts by night in his rat rod; LSR racing by day in his 140 mph, 2015 Production Class, Indian Scout motorcycle.
When not burning rubber, Bracken’s rat rod serves as a return tow truck for his LSR bikes, including a Harley V-Rod that runs 191 mph with a turbo on nitrous oxide

(Photo: James Gustin)

Mission accomplished!


Need Junk Fixed? If your car has a gremlin that just won’t quit, you could be chosen for Hot Rod to the Rescue. Email us at >pitstop@HotRod.com and put “Rescue” in the subject line. Include a description of your problem, a photo, your location, and a daytime phone number.


Contacts

Advanced Engine Concepts (AEC); Green Lake, WI; 920.294.0474

Amazon.com Inc.; Seattle, WA; 866.216.1072; >Amazon.com

Auto Meter Products; Sycamore, IL; 866.248.6357 (tech support), 866.248.6356 (customer service), or 815.895.8141 (international); >Autometer.com

Letsch Manufacturing; Racine WI; 262.554.6900

MSD Performance (A Holley Brand); El Paso, TX; 888.258.3835 (toll-free), 915.857.5200 (general); or 915.855.7123 (tech); >MSDperformance.com

NAPA/Antioch Auto Parts; Antioch, IL; 847.395.3660; >NAPAonline.com/en/IL/Antioch/store/26721

National Automotive Parts Association (NAPA); Atlanta, GA; 800.LET.NAPA; >NAPAonline.com

Personal Care Products Inc.; Troy, MI; 248.971.7600; >PersonalCareProducts.org

Quick Fuel Technology; Bowling Green, KY; 270.793.0900; >QuickFuelTechnology.com

Rockett Brand Racing Fuel; Mt. Prospect, IL; 800.345.0076 (tech) or 847.795.8400 (sales); >Rockettbrand.com

Stewart Components; Escanaba, MI; 906.789.2816; >StewartComponents.com

Summit Racing Equipment; Akron, OH; 800.230.3030 (orders) or 330.630.0240 (tech); >SummitRacing.com

Westech Automotive; Silver Lake, WI; 262.889.4346; >WestechAuto.com

 

Source : http://www.hotrod.com/articles/hot-rod-rescue-rat-rod-fixed-last-yes-burnouts/

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