Hib Halverson's Big Block From Hell Series

Hib Halverson's Big Block From Hell Series

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Part 10 ... The Big-Block from Hell, Finally! The Oil Cooler

by Hib Halverson

Before we get into the gearhead stuff, we'd like to thank readers who've recently called or written the magazine about this project. We know of five of you who are duplicating it either partially or fully. For each person we hear from, there are probably several more from whom we don't, but may have similar projects going. Obviously the Big Block from Hell is developing a loyal following. Please keep those calls and letters coming!

This month, you get the oil cooler article we've promised for some time. We offer the usual excuses...delay caused by circumstances beyond our control along with a task more challenging than we expected.

To Cool or not to cool.

BBfH has used Red Line Synthetic lubricants from the project's inception. After reading us endorse synthetic oil, you're probably saying, "Okay, if Red Line is so frigging good; why do you need to cool it?"

Red Line's President, Tim Kerrigan, told Vette Magazine during a telephone interview that an acceptable temperature range for the 10W-40 oil we run is 180-240°F and a shorter spread of 200-220° is ideal for best performance. Maximum safe oil temperature is 300°F.

It's true, in cases of aggressive street use with occasional trips to the drag strip, if one uses synthetic oil; cooling is unnecessary. Most of the time you will be in the acceptable range. As for the Big-Block from Hell, however, we figure there will be times, like track testing or extended high-rpm operation, when sustained oil temperature will stray past 240°. The right oil cooler would keep oil temperature in the ideal range rather than just within acceptable limits. If you do not use synthetic oil, the need for oil temperature control is more acute as there are serious durability problems with even the best mineral-based oils at 250°F or higher.

Each of you working on a similar project must decide whether or not to go to an oil cooler. The benefit is increased durability if you run your car very hard. The liability is that installing an oil cooler on a street-driven, '68-'82 big-block is difficult and requires metal fabrication and welding skills.

In fact, the job is such a task, we first tried a short cut: an aftermarket oil pan from Milodon (BBfH 6) that offered lower temperature via extra oil capacity. We never checked out the pan's coolness because we discovered it did not function properly. Oil pressure would drop under braking–certainly uncool and hardly acceptable for any car, much less the Big-Block from Hell!

A hard lesson learned, we went back to a production Corvette pan. If we find an aftermarket unit that works; we may try switching again...oil pan manufacturers, are you reading? As for the temperature issue; we decided on a cooler.

We had many choices: everything from budget-priced, fin-and-tube units that take clamp-on hoses and are barely acceptable as automatic tranny coolers to pretty damn good competition units that would do a Winston Cup car justice.

The ZR-1 and the last of the Caprice 9C1/1A2 police cars had, as standard equipment, separate oil coolers. Knowing any company getting parts through GM durability testing must be pretty good; we inquired with friends at Chevrolet about the manufacturer of those coolers.

Our quest ended in Ontario, California at the Fluidyne Racing Division of Thermal Dynamics where coolers for the King and cop cars were made. Thermal Dynamics does business with all the Detroit OE's and has a substantial product line of fluid cooling devices for heavy industry. An operation that size can afford pretty neat R&D programs. That, with the company's interest in motorsport, has produced some innovative high-performance and racing oil coolers.

Though Fluidyne has traditional oil-to-air coolers that are sturdy and efficient; its, "THERM-Hx" unit (p/n 30500) intrigued us as it is an oil-to-coolant device. The name comes from the word "thermal" and the letters "Hx" which are engineering nomenclature for "heat exchanger," the technically correct name for what we gearheads call an "oil cooler."

With the THERM-Hx cooler, during normal engine operation, oil temperature will be about coolant temperature. Under severe load, information supplied to us by Darin Hawks, Motorsports Manager, shows the cooler is capable of holding about a 220°F outlet oil temperature when coolant is 190°F and the oil inlet temperature is 250°F. Cooling system improvements done previously (BBfH part 7) had our engine coolant temperature stabilizing at 180°F in anything other than stop-and-go driving. We expect slightly lower maximum oil temperature than predicted by Fluidyne because our system's temperature gradient appears steeper.

With a street-driven Corvette, an added advantage of the THERM-Hx comes on cold starts. Initially, the cooler's temperature gradient will reverse; that is, the coolant, warms the oil to operating temperature faster than normal. This may reduce engine wear. Additionally, during the abnormal situation of extended, light-throttle operation in cold temperatures; a THERM-Hx will prevent excessive cooling of the oil which many engine builders believe is detrimental.

The core of this piece of equipment is similar in appearance to a typical oil/air cooler but is housed inside a heliarced, aluminum case in which coolant circulates. The core is manufactured using Dunham-Bush's NOCOLOK process. For you metallurgists out there, that is a thermochemical-joining, aluminum brazing procedure that has durability and quality advantages over more common vacuum or chloride aluminum brazing methods, ah...right. Forget the technical jargon, but understand that this gives the customer a more efficient, longer lasting product.

Interesting about Fluidyne coolers is cleanliness after manufacturing. OE coolers meet stringent contamination standards because, in the assembly plant environment, no OE flushes a cooler before installation. Plant workers simply reach into a bin, pick the first cooler in the stack and bolt it onto the job going by them on the line. As a result, coolers must be surgically clean as when the job gets to the end of the line and the engine is started the first time, there must be no "stuff" in the cooler to be pumped into the engine. Consequently, provided the protective caps are removed just prior to hose connection, a Fluidyne THERM-Hx can be just bolted on and used. No flushing is necessary.


The first thing was to mount the heat exchanger. The THERM-Hx, since it's an oil/coolant device, needs no airflow to function. That opens up places other than in front of the radiator (already a crowded area on our car) for mounting. On '68-'82s with air, most of the HVAC pieces are mounted on the firewall, right of the engine. Thus, no-air cars, like the Big-Block from Hell, have unused space there and that's where we put the cooler.

We drained the coolant then temporarily removed the heater hoses and the radiator fill tank. We permanently removed the windshield washer bottle and the windshield wiper door vacuum relay and its hoses. The washer bottle we'll relocate at a later date. The vacuum relay valve was pitched and its vacuum source plugged because we eliminated the wiper door when we installed a different hood from Ecklers (BBfH part 5). To gain access to the installation area, we removed part of the right inner fender.

Then we welded up brackets for the cooler out of steel flat stock and installed them between the right-side "A" body mount and the right inner fender and bolted the Fluidyne unit into them.

Since the car's engine block has no factory oil cooler connections; we replaced the stock oil filter mount with an adapter plate having connections for oil lines. We selected a unit (p/n T109B) manufactured by Traco Engineering. Use of an adapter plate requires a remote oil filter and we got that (p/n T101L) from Traco, also. Unfortunately, by the time this installment of the Big Block from Hell series was reedited for the Idaho Corvette web site, Traco had gone out of business. BBfH fans wanting to duplicate this installation will have to look elsewhere for the adapter and remote filter hardware. Fortunately, this type of hardware is fairly common in the racing parts market.

Because of space restrictions posed by the clutch linkage and the exhaust headers; what we really needed was an adapter plate with one vertical and one horizontal connection. As nothing like that was available, we modified the Traco adapter by having Mark DeGroff's Cylinder Head Service and Machine Shop, which did all our head work early in this series, relocate the oil outlet connection. DeGroff chucked the plate onto a mill, drilled a 23/32-in vertical hole into the existing horizontal outlet passage then tapped it with a 1/2-in. pipe thread. This job must be done on at least a good drill press and preferably a mill. Do not do this with a hand drill.

The Traco adapter plate was installed on the block's oil filter pad. The remote filter mount was installed on the lower part of the right inner fender next to the oil cooler. It accepts a Chevrolet-type, spin-on oil filter and we used a K&N (p/n HP3002) for its low restriction and good filtration ability. Additionally, K&N puts a 1" hex head on the bottom of the filter which makes removal a snap. Just use an open end wrench–cool!

Note that the installation of the Traco adapter plate eliminates the stock Chevrolet oil filter by-pass valve. The Traco remote filter mount is intended for motorsports use and, thus, has no filter by-pass. Lack of a by-pass eliminates the protection from restricted or plugged oil filters. As a result, it is imperative to change your oil filter at proper intervals.. We do it on the Big-Block from Hell every 12 months or 2500 miles.

Lining Up

Doing the hose runs was a daunting task because of the tight spaces towards the rear the engine. For oil lines, AN fittings and braided, stainless steel covered, high-pressure hoses are mandatory. They offer: 1) durability good enough to outlast the car, 2) leakproof connections through S.A.E. 37° compression-type hose end fittings and 3) attractive appearance. There are several sources for this product, but we believe the good stuff comes from the Performance Products Division of the Aeroquip Corporation.

Size AN-12 braided lines are recommended on V8s. We used 15 feet of Aeroquip "AQP Racing Hose" (p/n FCA1215). Aeroquip's "dash twelve" hose specifications are: an inside diameter of .69-inch, outside diameter of .94-in., a rated operating pressure of 1000 psi and a burst strength of 4000 psi–that'll work.

Due to the expense of Aeroquip AQP Hose, the trial and error method of determining hose length is undesirable. Mock-up the lines with garden hose–we have an old, used one from which we cut sections. That way you know how much braided line to buy and which fittings you need before you do the job .

Any bend in a line will cause restriction. Try to use wide-radius bends in the lines and straight hose ends. When you need an angled connection, use an curved hose end. Only as a last resort in the most confined areas should angled AN adapters be used because they are the most restrictive.

Aeroquip AQP hose can be cut with a hack saw or a cutoff wheel. To prevent braid flare-out, wrap the hose at the cut point with masking or duct tape. Then, cut through the tape.

To install fittings, first disassemble each unit. Coat the inside of the hose, the nipple and threads with Aeroquip Hose Assembly Lube (p/n FBM3553). Then, insert the hose into the fitting socket end until it butts up against the socket's threaded portion. Mark the hose just below the socket. The hose ends are best assembled in a vise fitted with Aeroquip vise-jaw inserts (p/n FCM3661). They are aluminum and have notches that grip an AN fitting's lower wrench hex. They positively hold and protect a fitting during assembly.

Once the socket is in the vice inserts, push the nipple into the hose and engage threads. Hold the hose in position with your other hand. Make sure the hose doesn't push out of the socket by checking the mark made earlier. Tighten the nipple using Aeroquip aluminum wrenches intended for use with AN fittings. Tighten such that the gap between the wrench hexes on the nipple and socket is a maximum of .030-in. Your thumbnail is an excellent measuring device.

Finished lines must thoroughly cleaned and flushed before installation. The Aeroquip Performance Hose and Fittings catalog contains additional instructions on assembly and information on how to design and select performance plumbing. If you're installing Aeroquip, this booklet is necessary reading. Get it from their dealers.

We cut our Aeroquip into sections that matched garden hose mock-ups we made earlier (see sidebar). The hose routing was: 1) from the Traco adapter plate outlet, a curve around the left exhaust header to the bottom of the frame rail, up towards the rear of the engine, over the back of the block, between the #6 and #8 header pipes and to the filter inlet, 2) from the filter outlet up to the cooler inlet and 3) from the cooler outlet, along the firewall above the heater connections, over the back of the block, around the end of the left cylinder head and down to the adapter plate inlet.

To prepare each hose, we first added Aeroquip Fire sleeve (FBS1600), a heat retardant shielding, to sections of lines running near exhaust headers. Next, we took the hose ends apart, prelubed them, then installed them onto the hoses. See the accompanying sidebar for detailed installation data.

We screwed 1/2NPT-to-AN-12 adapters (p/n FCM2010) into the Traco pieces. Teflon tape or liquid pipe sealant with Teflon should be used to seal threads. A variety of Aeroquip AQP Racing Hose End Fittings were necessary to make connections. Line #1 used a 90° fitting (p/n FCM4035) at the engine block outlet and a 45° fitting (FCM4025) at the filter mount inlet. Line #2 took a 45° unit at the filter mount outlet and a 150° fitting (FCM4055) at the cooler inlet. Line #3, from the cooler outlet to the engine block inlet, took two 120° fittings (FCM4045). Socket-head, pipe plugs (FCM3749) were installed into unused, horizontal outlets on the Traco adapter plate and filter mount.

We secured the hoses running across the back of the engine with Aeroquip Support Clamps (p/n FCM3488). This is an important step as the engine moves but the body (where the cooler is mounted) does not. The places were hoses flex as a result of engine movement must be selected such that they do not rub against sharp edges . Clamping the hoses to the heads confines hose flex to safe areas.

Our last fabrication step was to make two shields. The first was used to protect the section of oil line that ran along the bottom of the left frame rail behind the left front tire. The second partially replaced the section of the right inner fender removed to facilitate the installation of the cooler mounting brackets. Additionally, this shield is removable and provides increased protection and access to the oil filter.

For the coolant connections at the Fluidyne THERM-Hx we used heater hose. Goodyear, who makes the tires we use on BBfH, also has a comprehensive line of hose products. We selected "Goodyear Hi-Miler" heater hose, intended for commercial and fleet use. It's made with synthetic rubber reinforced with "Flexten," Goodyear's name for super-strong, arimid cord. Both 5/8-in. and 3/4-in. Hi-Miler hose has a burst strength of 400 psi and is extremely durable.

Two 3/4-pipe-to-5/8ths hose barb fittings were screwed into the THERM-Hx. We ran 5/8-in. hose from the heater outlet on the intake manifold to the cooler inlet and from the cooler outlet to the heater core inlet. We used 3/4-in Goodyear Hi-Miler from the heater to the radiator filler tank and back to the engine. Lastly, we installed a Goodyear, molded water pump by-pass hose (p/n 63394).

Final Touches

To monitor the oil cooler's effectiveness we installed an Auto Meter, Pro Comp mechanical oil temperature gauge (p/n 5441). These units are known for their accuracy; have large, attractively-styled 2 5/8-in. dials and are liquid-filled to eliminate vibration errors. We selected a Pro Comp gauge because it is the highest quality product Auto Meter makes and it matches the volt meter (p/n 5491) we installed previously (BBf part 9)).

The gauge was mounted in an Auto Meter gauge panel (p/n 3231) we installed under the dashboard on the passenger side. Part of the gauge assembly is a capillary tube that ends in a probe that's inserted somewhere in the oiling system. Typically, one drops the oil pan and welds a fitting into it for that probe. However, Fluidyne saves you trouble by putting a probe mount on the outlet of the THERM-Hx, an ideal place to monitor oil temperature.

Before you fire the engine the first time, fill the cooling system and overfill the crankcase by a quart. It takes a while to build oil pressure because the oil pump must first fill the empty volume in the cooler and lines. We suggest, rather than running the engine for several seconds without oil pressure; that you pull the distributor, install a pre-lube device made by B&B Performance (p/n 6510) and drive it with a 3/8ths drill until you see oil pressure. Reinstall the distributor, then fire the motor.

Run it briefly, shut down, check the oil and add as necessary. With our particular installation, we found that the cooler, filter and lines hold about 2 1/2 quarts. That gave us a grand total of 8 1/2 quarts of Red Line 10W-40 in the Big-Block from Hell.

The last step is to refire the engine and run it to operating temperature while checking all connections for leaks and making sure, once the thermostat opens, that coolant is at the proper level.

Initially, because of the large amount of curved fittings on the oil lines, we were concerned about pressure drop due to restriction in the system. Reality was, that drop is less than 10%. Our L88/ZL1 oil pump and synthetic oil makes that insignificant. However, those worried about pressure loss due to restriction can just drop oil pan and shim the oil pump pressure relief valve spring with a washer.

As for the effectiveness of the Dunham-Bush THERM-Hx unit, so far we have noticed that oil temperature in normal driving is about the same as coolant temperature where before it used to fluctuate quite a bit. We saw the promised 25° reduction during more demanding duty.

The next installment of the Big-Block from Hell will cover a major thrash of the car's fuel system. Be looking for it in a couple of months.


Aeroquip Performance Products
3000 Strayer Rd.
Maumee, Ohio 43537-0700
419 891 7600
Auto Meter Products Corporation
413 W. Elm St.
Sycamore, IL 60178
B&B Performance
29752 Avenida De Las Banderas
Rancho Santa Margarita, CA 926588
Fluidyne Racing Division
4850 E. Airport Dr.
Ontario, CA 91761
Goodyear Tire and Rubber Co.
see your local retailer
Mark DeGroff's Cylinder Head Service and Machine Shop
18736 Parthenia Unit 2
Northridge, CA 91324
Red Line Synthetic Oil Corp.
6100 Egret Court
Benicia CA 94510

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