Cooling uprated components in a C4 Convertible

High resolution versions of all photos can be found here.

Questions or clarifications can be sent to mike ahat millertwinracing daht com

 

I'm going to warn you up front. This is long (and probably dull), so you may want to Cut to the Chase if you just want to see how I did this.

 

I'm neck deep into a project that no sane person would do. I'm doing a piece by piece restoration of a C4 Corvette from the inside out. One of the main precepts of the project was to make better from stock every part I possibly could. That means more horsepower, better braking, stronger parts, and generally making the car more than competitive with the current cars available from auto manufacturers. It may be a flawed premise, but it's my premise, and I'm sticking to it.

 

There's a whole industry built up around making power in the Small Block Chevy. It's a lucrative business because they know something the average Chevy owner doesn't: When you take a vehicle and boost the performance of an aspect much beyond stock, you'll start to play the game of 'find the next weakest link'. You'll either do this with conscious effort: 'While I'm in here, I should improve this piece, so I won't have to deal with replacing it when it breaks later.' Or you end up doing it after the fact: 'Gee, I didn't expect THAT to happen!' while grabbing the pushbroom and kitty litter.

 

Unfortunately, the topic of this discourse was the end result of the latter. I'd dropped in the 383, slapped up the stock transmission, and went along my merry way knowing that sooner or later (it was sooner) that the transmission wouldn't last. IIRC (this was awhile ago) it didn't make 1000 miles before 4th went away. Half a mile later, 3rd went away, and I spent an hour or so driving home in 2nd gear.

 

The transmission is another topic for another time, suffice it to say, the expert that built the system said this as I walked out the door with my new, spiffy, hardened, kickbutt, expensive, transmission in hand:

 

'Get a temp gauge and cooler on that ASAP or we'll be doing this again.'

 

         I got the car back on the road and was, largely, overjoyed at the results. Shifts were firm, things happened Right Now (tm), and I didn't follow his advice. On a side note, the speedo stopped working. I troubleshot everything but the system I shoulda: The one I touched last. The driving gear retainer snapped and the gear walked forward on the shaft.

 

         If you have no speedo, the car doesn't know how fast it's going. If it doesn't know that, it won't lockup the torque converter. If it doesn't do that, the transmission makes a lot of heat, and the car isn't very fast. Somewhere along the line I plumbed in a TC lockup switch, but I suspect the damage had already been done. Of course, it's hard to tell that when you don't have a tranny temp gauge.

 

Broken Part         So, long story less long: The tranny failed in a worthwhile fashion, I got to exercise my AAA card, and I shamefully returned to the transmission shop to do everything again.

 

         Thumb thru Summit

         I noticed on the back of the Summit Racing catalog, that they had a full kit that'd cool both the transmission and oil in one fell swoop for a Benjamin. Eureka! Visa in hand, I ordered the kit (with some fear of ordering something, sight unseen, that was to fit in a very small space) The kit arrived and it looked like it'd do the job.

 

         Then I talked to the Engine builder. 'You REALLY need to use braided hose near the headers. The LAST thing you want is a busted hose pouring oil on your headersunless you WANT an insurance writeoff.'

 

  • Uh, okay, I thought. I'll just replace those hoses with braided ones.

 

  • Further research shows that, in a street car, you want a thermostat on the oil to let it get up to temp in cooler weather.

 

  • Uh, okay, I'll order an additional piece. Cost $60.

 

  • Oh, and the Summit kit uses all hose-clamps and barbed ends, where the T-stat is a race part and uses funky o-ring connectors.

 

  • And By the Way, The voice of research-I-shoulda-done-first says; that cooler in the summit kit is not very efficient.

 

  • My brain explodes at this point and I decide to take a breather.

 

Industrial Hydraulics and You

 

Looking at how a $100 project was skyrocketing, I spent some time on the phone with my Father. The common direction was to use braided stainless hose with AN fittings. Going locally, I was looking at spending $350 for the raw materials, leaving me with a hacksaw and metal bits in my fingertips. It was at this time my dad reminded me he'd been in industrial hydraulics for most of his working career. We started talking about a different solution.

 

Hose fittings use a standard numbering system. To make a long story short, we took good measurements, made sure all the holes would be filled, and took the pieces to a hydraulics supplier for a solution that fit the following criteria:

 

  • All hose ends had female swivels this allows for consistency in the design, and makes sure you don't end up with a setup that can't be put together (to fit part a to part b, you've got to spin the car around this hose here.)
  • Nearly all oil hose attachments were size 8, 37 degree flared fittings. There were a few pieces that required 10 size fittings, work with what you've got, it's why you take all the pieces with you to the supplier.
  • All tranny cooler lines used size 6 lines, mating to the stock hard lines using ferrels and single flared connections.
  • Hoses near the headers had to deal with header heat.
  • Braided hose is an EXCELLENT low speed file, it'll eat thru ANYTHING! Scrap rubber hose with an inner diameter as big as the braded hose's outer diameter is used to isolate the lines.
  • Don't blow off the transmission cooler, thinking the oil cooler is more important. (This bit me in the derrire eventually)

 

By going this route, we gave up the pretty red and blue of AN fittings for parts that:

        Don't need special tools to assemble

        Are rated at 1500 psi (or better, in the case of the tranny lines)

        20-30% cheaper than AN

        Will outlast the car.

 

Things to remember when building a fluid carrying system:

  • All hoses MUST be cleaned prior to use. Debris from cutting the hoses to length is NOT something you want pulled through your motor! Cleaning can be performed in a number of ways: using a pressure washer (think carwash) and compressed air to dry the hoses is probably the most readily available solution.
  • All hose fittings need to be cleaned before assembly. I used MEK (Methyl Ethel Ketone), but kerosene, brake cleaner, and others will work. 37 degree flared fittings rely on a flat, clean, surface for sealing, NOT goop or high torque on the fasteners.
  • All non-flared fittings MUST be sealed. Recommendations are a Teflon impregnated pipe dope. I used this in all but one fitting as it takes a drying period for the seal to work. The last fitting I used Teflon tape as I didn't want to wait for a drying period. Using Tape is a problem in that it requires a steady hand in wrapping the tape against the thread so that it doesn't unwrap as you tighten the piece. Further, you do NOT want Teflon tape pieces falling into the fluid and doing unexpected things like reduce flow or block passages.
  • When assembling, you MUST use two wrenches on the fitting. This isolates the pressure you're applying from anything else that may be connected to your assembly. I accidentally bent one of the intake fittings on one of the coolers. Luckily, I didn't bend it enough to make things leaklearn from my mistake.
  • Snug is probably good enough. I'd estimate the flared fittings take no more than 15 to 20 ft-lbs of torque to seal. Don't go Gorilla on them!

 

 

If this is the path you take, I hope you find a helpful hydraulics guy, if you mention AN fittings and automotive terminology, he'll look at you funny. These guys don't 'do' cars. Tell them what you need in general terms, then let them do their job.

 

Cut to the chase already!

 

Parts used in the this project include (by are not be limited to)

        2 B&M fluid coolers, 70266 this is their race part and includes no (ultimately wasted) bits and pieces. (2 x $70)

        1500 psi Teflon/braided stainless steel hydraulic hose and fittings ($280)

        5000 psi hydraulic hose (for transmission lines) ($50)

        Earls oil thermostat p/n 501ERL (size 10 female o-ring fittings, one extended 90 degree to clear. ($60)

        Autometer Transmission Temp gauge and sensor ($125)

        Snapstrap stainless steel strap ties ($20 for a lifetime supply)

        Aluminized insulation ($20)

        Pipe sealant, Paste. ($12)

        Bunches of Zipties

        Summit Kit, of which I used maybe 10% ($100)

        A trip or four to the hardware store (receipts intentionally lost)

 

Rough cost: $800 (Figure $700 if you purchase more wisely than I did)

 

Cooler mounting and orientation

 

Note that the fittings on the coolers are upright, this is to minimize the chance of air voids in the system. Upright coolers mean all of the oil won't run back into the pan, possibly over filling, and/or starving the motor on startup.

 

Installation Assistance

 

Installation

 

Finding a location of the filter was a difficult thing to do in a Corvette, everything is REALLY tightly packed, and with the car being as close to the ground as it is, care for under-car clearance is critical. I originally tried to mount the filter in the well ahead of the driver's front tire. I spec'd the length of hoses to this as it's better to have slightly too much hose than 1/16th on an inch too little.

 

I found a section on the cross member, just ahead of the motor that works fairly well. It's angled slightly to give everything the maximum clearance, easily accessible for maintenance, and away from any clearance issues that would crop up with other locations. (Sure would be an easier project if this were a late 60's muscle car.)

 

The filter mount

The remote filter mount was fabricated using 1' square aluminum box tubing. The cross member it attaches to is roughly 2' deep and 4' high. Clearance on the underside of that brace is limited due to power steering hard-lines. The filter mount itself is cast aluminum, and the mounting holes are roughly 2.5' on center, making it pretty much impossible to drill and tap holes on the cross brace to mount it directly. By 'pinching' the brace, there's also leeway to mount it to clear other objects.

 

While this is the best place I could find to mount the filter, it still makes accessing the front of the motor problematic. At the very least, I think you have to remove the filter to remove the accessory belt. Better pictures of the filter location can be seen on the images page: http://www.millertwinracing.com/coolers/Images/

 

The mount includes a drip tab to redirect oil away from the cross brace, although I think it will still drip on the anti-sway bar.

 

The bottom bracket is a U shaped piece I made by hack-sawing the box section in half. By making it that shape, it clears the power steering lines, and still retains some structural integrity.

 

I was concerned that the mount might move due to heat and vibration, so I epoxied some rubber to the underside so that it would stay put and reduce vibration to the filter assembly.

 

The thermostat location

The thermostat was located as close to the oil cooler as possible to simplify hose routing. Luckily, there's enough clearance on the bottom of the cooling stack housing to mount it right under the cooler. (The Radiator and AC condenser should be resting on rubber pads to isolate them, be sure there's no interference between the mounting bolts on the thermostat and anything else in the area!) The thermostat takes O-ring fittings that are pretty standard with one exception, the fittings on the engine side are too close together to allow two 90 degree fittings. An extended length 90 degree fitting was used to clear. It's critically important to follow the routing instructions included with the T-stat, failure to do so can either result in unfiltered oil running through the thermostat and cooler, or an oil restriction preventing oil from returning to the pan. An optional check-valve is included in the diagram which stumped us for quite awhile. It's there to prevent a full cooling system from back-draining into the crank case and is unnecessary in a C4 application. The thermostat only blocks about 85% of the oil in all situations. This permits the system to bleed out any air bubbles.

 

 

The coolers (and tranny cooler temp location)

The cooler location is pretty obvious from the included photos. They're mounted to the AC condenser using special zip-tie fasteners designed specifically for this application. Be sure to make them tight, and don't forget the rubber or closed cell foam isolators that keep them off the condenser. I found that an awl or other suitable metal probe makes locating the coolers easier. About the only part of this project I wasn't happy with is this: the coolers are mounted to a 15 year old condenser. The system is well sealed and pumps cold. I would have MUCH rather attached the coolers outside the car on a new condenser. C'est la vie, I guess.

 

Transmission temp sensors are often drilled and tapped into the tranny pan. I don't like this as it reports the coolest possible temperature in the system. The oil coming out of the transmission can be considerably hotter elsewhere in the system. I placed the sensor between the inlet and outlet of the new cooler. I plan on swapping the hoses to see if the temperature gets hotter or colder (essentially reporting the temperature going into the cooler, or after it's been cooled.) By tapping into the system where I did, I still have the benefit of the stock cooler in the radiator.

 

Hose routing

Braided hoses (as mentioned elsewhere in here, I'm sure) make excellent low speed files and will eventually wear their way through just about ANYTHING you don't properly handle. It's pretty easy to see where the hoses go on the front of the engine compartment, what's harder to show is that they arc gently out of the oil filter block off plate, past the engine mount (between the mount and the block) and follow the routing of the power steering hoses. The block off plate is clearly marked with an 'Out' and an 'In'. The Hose attached to 'Out' needs to be the one that enters the oil filter. The other goes down to the Thermostat exit. The hose from the oil filter goes down to the thermostat input. This is critical as it makes sure that all oil leaving the block will pass through the filter.

 

The hoses on the cooler side of the Thermostat aren't really as critical. Just make sure they don't leak.

 

The Test Drive

 

'In weight lifting, I don't think sudden, uncontrolled urination should automatically disqualify you.' Jack Handey

 

What I haven't yet mentioned was the single biggest mistake I made in this project. I had a deadline. I got in a hurry. The RocketSled had a date with a Dyno that it just had to make. After filling the Vette with fluids, I took the car out for its first test drive. At night. By myself. Without a flashlight. Too far.

 

I got about a mile away from home and decided I'd gone far enough under the circumstances and turned around. In the darkness between the Streetlights, I noticed fourth gear had gone away.Then Third. In the light of the approaching intersection, I could see smoke billowing out of the wheel wells and some unknown fluid was sprinkling on the windshield.

 

Cursing and muttering, I put the car in neutral, turned off the motor, and tried to figure out how to turn the hazard lights on in a car I hadn't driven in almost a year. Mentally I said the following prayer: 'Dear Lord, don't let the car catch fire.but if it does, burn it to the ground.'

 

I coasted into a gas station, and made it into a lit area so I could appraise the damage. I was in shock for about 5 minutes. Giddy for another, and after that, resigned that I just had more to fix.

Lifting the hood, it looked like I'd armoralled the engine compartment. Everything was nice and shiny, and except for the smoke wisping off the headers, and the growing crimson stain seeping out from under the car, it could have been ready for a show.

 When someone over at the Irish Pub across the parking lot started playing Amazing Grace on the bagpipes, I tried not to think it was an omen.

 

One of the tranny cooler hoses obviously wasn't adequately clamped on. It a very short period of time, it managed to pump 7 quarts of Redline Synthetic all over the highway (the stain stayed there for two weeks). If I hadn't been 'fortunate' enough to not have a speedometer, I would have burnt up the transmission. As it is, the Torque Converter wasn't locked up. When the fluid pumped out of it, it decoupled from the pump, which meant the clutch packs didn't have any pressure applied to them, which saved me from visiting the Tranny Guy a third time.

 

Anyway, two hours later, a flatbed brought the car the remaining half mile back to the garage, where the car sat for a few days.

 

Good enough sometimes isn't

 

I'm Card carrying member #1 of the Bonehead Mechanics Association of America. I'm not afraid to admit I've made mistakes in the past, some of them SPECTACULAR. One of the purposes of this page is to help you NOT make the mistakes I've made. The illustration above shows the original hoseclamp and flared line method of attaching the transmission cooler to the existing lines. The theory is: you flare the line, push the hose over the flare, and double hoseclamp the line. In theory, this is a perfectly acceptable way to connect these pieces together. In MY case, it amounted to a catastrophic failure of the transmssion cooling system to hold onto its lifeblood.

 

If you DO the following, you will FAIL:

1.   Make the flare inadequately large

2.   Lubricate the hose with something that won't easily be removed. I used a silicone lubricant to aid pushing the hose over the flaire. Use soapy water as it loses its lubricating qualities after the water evaporates

3.   Use two different sized hoseclamps. What I thought was increasing the clamping load only succeeded in showing me the larger clamps were too big.

4.   Not get the hose far enough over the flare.

 

To cure the problem, I went with 5000psi hydraulic hose (the trasnsmission maxes out at about 325 psi), and flared fittings like the REST of the cooling system project:

 

 

 

Factoids from the edge of reason

 

        Remote oil filter mounts are nearly 100% Ford dimension. While you MAY be able to find a Chevy remote mount, life it a lot easier if you just buck up and buy the biggest Ford filter you can find (In this case, I'm using a WIX 51515) and use a Ford part.

        While hose clamps over flared fittings may be adequate, cleaning 7 qts. of Redline transmission fluid out of everything isn't worth the time saved in going cheap. The original barbed/hoseclamped lines cost, maybe, $15 a piece. The super duper hydraulic lines cost $25 a piece. The 7 quarts of lost tranny fluid cost $60.

        Remove the shroud. It's, like, 6 extra bolts and lets you reach EVERYTHING until such time as you fab up a new shroud, or replace the stock one.

        With a kick out 7 qt. pan, the system takes 8 quarts of Mobil 1 to fill.

        The Transmission probably took 14.5 to 15 quarts of tranny fluid. Use cheap cheap cheap Type-F until you have everything tuned to your satisfaction. ONLY THEN do you replace with Redline!

        I made dyno day.