Big-Block Camaro Brake-Bleed Blues
Rose Serrano; via email: My husband and I are at our wits end with our big-block-powered 1968 Camaro. It still has the factory-installed front disc and rear drum brakes, and we can’t seem to bleed the brakes properly. I have replaced the distribution block, proportioning valve, lines, power booster, master cylinder, and wheel cylinders—the rear brakes still don’t bleed. Can you give me any pointers on why the rear drums will not bleed? I’ve kept the car in the garage for more than a year because of this problem.
Steve Magnante: Big-block Camaros are some of the coolest Bow Tie machines on the planet. I love ’em. I get visions of “Grumpy” Bill Jenkins’ refrigerator-white 1967 exploding off the line in vintage NHRA SS/C drag action. The skinny front tires and narrow 15×4-1/2-inch Cragar S/S mags droop the A-arms against the suspension stops, a foot off the strip, defying gravity. The blueprinted L78 396 smushes the beefy 10.00×15 wrinkle-wall slicks into the line an instant after the clutch is dumped at seven-grand. Aaah, good stuff, thanks for the flashback.
I wish you’d been more descriptive in your statement that the rear brakes “do not bleed.” If there is no brake fluid making its way to them and they’re dry, something is blocking the lines upstream of the wheel cylinders. Look for a pinch or a kink in every bit of the system. Inspect the tubes attacked to each axletube, inspect the brass junction block for dead-end passages (bit failure during manufacture), inspect the rubber body hose, and continue the quest along the body line all the way to the junction block and proportioning valve. Even though external appearances might be OK, don’t rule out a stubborn bit of debris inside the line. And please don’t tell me you used any Teflon tape here. The way double-flared, brake-hose connections work does not require tape—ever. But if mistakenly used, a chunk could enter a line and create a blockage. The best way to validate the system is to remove every section and blow compressed air through each component, one by one. At the junction block, you also want to confirm each connection port is matched to the correct outgoing tube. A mix up here can certainly disturb fluid and pressure routing.
Don’t forget the Camaro was introduced in 1967, just in time to receive the federally mandated, dual-circuit master cylinder. Up to 1966, most American cars (except for certain Cadillacs, Z06-equipped Corvettes, and the Studebaker Avanti) had a single-pot master cylinder. When all is fresh and new, the single-reservoir brake system worked well. But if a single leak appeared, each pump of the brake pedal sprayed vital fluid out of the circuit. Within a few pumps, the brakes were dead.
The 1967-up dual-circuit hydraulic system doubled your chances of survival. By dividing the brakes into front and rear circuits, the loss of one wheel cylinder only affected half of the system and gave the driver emergency braking ability to stop the car. The dual outlets on your Camaro’s master cylinder must be correctly matched to the brake lines. The forward-most outlet feeds the front brakes, the rear port, and the back axle. Most of the time when working with factory lines, everything is pre-bent in a way that clearly guides their correct reinstallation.
You mentioned you’ve got new brake hoses and tubing. Did you hand-bend generic sticks of parts-store tubing? If so, you might have mixed things up. And speaking of parts-store tubing, whenever I use it, I always blow compressed air through it, and before I bend anything, I peek through each stick. If you don’t see light at the other end of the stick, debris is trapped inside. I have seen dead bugs, cardboard, and other bits of shipping/warehouse storage debris jammed inside new steel tubing. Make sure this isn’t your problem.
Assuming you have fluid passing into the tubes attached to your rear axle, I’m guessing your complaint that they “do not bleed” is your way of saying fluid is dribbling from the bleeders, but you still can’t get a nice, solid pedal. Here, it all comes down to completely evacuating every last bit of air from the circuit. And that can be a tedious job, unless you’ve got a power brake bleeder or hand-operated pressure/suction pump. I’ve struggled with close-but-not-ideal brake-pedal feel over and over. Persistence is the answer.
One more thing to consider: Is your driveway or workspace on a steep hill? Air bubbles naturally tend to flow up, so it’s important to bleed brakes on a level surface. If your car is sitting on steep, tail-down terrain, you’ll face an uphill battle in bleeding the brakes (if that makes sense). Bubbles and/or the column of air you’re attempting to purge toward the opened bleeder at the rear axle will fight your efforts. Try it again on level ground.
Barring the usual stuff described already, the problem is likely based in a flawed component. I’ve seen “rebuilt” wheel cylinders with rust-clogged ports and brass distribution block/proportioning valve items with blind-drilled holes that failed to connect inside the part. It’s rare, but poorly manufactured parts do happen. I’ve also seen master cylinders with incorrectly installed lip seals—right out of the box! I’d suggest double-checking the proper connections at your master cylinder and junction block, then a close inspection of all components followed by a clear-out using compressed air. And remember, unless you’re using synthetic brake fluid, spilled fluid can eat paint. Work carefully.
Slant Six Bonneville
Robert Dally; via email: I run a 1966 Barracuda with a 170ci Slant Six at Bonneville [see Eric English’s online article on this car from November 10, 2015, at HOTROD.com]. The engine is naturally aspirated and makes about 250 hp while running at 6,500–7,000 rpm. Unfortunately, at the 2016 Speed Week, I threw a rod early on, so I’m currently building a new—but still naturally aspirated—engine for Speed Week 2017. My question involves the main bearings. We followed all the recommendations in the Mopar Performance Engine book except for running fully grooved upper and lower main bearings. I’ve asked around and get a mixed bag of responses. Some say it’s the right thing to do, others say it’s an outdated idea and will result in another disaster. With the next engine, should I go to fully grooved mains or steer clear of it?
Steve Magnante: Wow, a Slant Six question! With just less than 12,500,000 built between 1960 and 1991 (about 50,000 with die-cast aluminum blocks in 1961–1962), the math says there should be far more Slant Six questions—but no. The fact is, few people recognize the Slant Six as a performance engine. For that we can blame the cylinder head and the 225ci tall-deck version.
First, some history: In early 1957, Chrysler launched the Valiant compact-car development program, which delivered the first Mopar A-body in 1960. The A-body would go on to form the basis of the Dart, Duster, Gen-I Barracuda, and even the 1968 Hemi A-body cars. Knowing the ancient 230-inch, flathead six of the day would not match the Valiant’s modern needs, a simultaneous engine-replacement program was started in 1958. This gave us the Slant Six, also of 1960.
Because the Slant Six was initially envisioned to power the small Valiant, Chrysler engine designers settled on 170 ci. Remember, Ford’s Falcon was launched with a miniscule 144-inch six-popper and the air-cooled Chevy Corvair launched at 139 cubes in 1960, which bumped to 145 in 1961. Comparatively, the new 170-inch Slant Six for the new A-body Valiant (and Dodge Lancer for 1961) doesn’t seem so small. However, “mission creep” entered the picture, and during the engine’s development program in 1958, product planners also eyeballed the Slant Six for use in light pickups, vans, and larger Chrysler passenger cars. To get more torque for these heavier applications, a second version with an extra inch of stroke joined the 170 development program, and the tall-deck, 225ci Slant Six was born. The problem was this: When the stroke jumped from 3.125 to 4.125 inches (the bore remained at 3.40 inches for both engines), a matching cylinder head with proportionally larger ports and valves should have been devised. It didn’t happen, partly because of the sharing of the small 3.40-inch bore between both blocks to save money on pistons, boring machinery, and so on. Anything much larger than the 1.62/1.36-inch stock valve heads suffered from shrouding. So the exact cylinder head was used on the 170 and 225 engines (as well as the 1970–1974 198-incher, a destroked 225 with the same 3.40-inch bore). As a result, the 225 Slant Six emerged with excellent low- and mid-range torque output, but with its 170-sized cylinder head, breathing efficiency was compromised. Coupled to the 225’s extreme over-square configuration, high-rpm efficiency suffered a bunch. I’ve built several performance-oriented 225s, and they were all uncomfortable above 5,200 rpm. I never saw anything close to six grand—even with four-barrel carburetion. This is why in-the-know Slant Six builders and racers like Doug Dutra (and you) go with the 170, which is ideally matched to the head—and whose over-square bore and stroke ratio loved to rev. What the 170 lacks in torque, it makes up for with high-rpm horsepower potential.
As you’ve proved, 6,500 and even 7,000 rpm isn’t a fantasy with the sweetly over-square 170. Back in 1960, NASCAR invited Detroit’s new wave of so-called “compact” cars (Falcon, Corvair, Valiant, and Studebaker) to a mini-feature race before the big Daytona 500 event. With only 170 strictly-enforced cubes, Hyper-Pak–equipped Valiants blitzed the course at an average speed of 122.282 mph. That’s cranking for such a small six-banger in a car with the aerodynamics of a brick.
We suspect, however, you knew this, and that’s why you’re running a 170 instead of a 225 in your Bonneville fish. As for the bottom end, Chrysler chose to use only four main bearings in the Slant Six, at a time when seven was the going thing at Ford and GM. To make up for the reduced support and add overlap for stiffening, the Slant Six crank was given the same 2.75-inch main bearing journal size as the Max Wedge and 426 Hemi. Better still, forged cranks were used through the 1976 model year. In the 225 version, the bottom end is extremely rugged. In the 170-incher, it is nearly indestructible.
Better still, the stock oil system is excellent. About the only enhancement comes from the usual streamlining of the block’s oil-passage entries with a hand grinder during preparation. There’s also safety to be gained in “porting” the passages inside the oil-pump body to eliminate sharp edges that disturb oil flow. Here is where we get into the difference between what the engine experiences at Bonneville and any other type of non-marine, non-aviation, high-performance use. Nowhere but Bonneville (and similar closed-course speed trials like the Maxton Mile) does the engine run at wide-open throttle for so many minutes. The demands on the oiling system here are unique in the world of motorsports.
Your reference to the Mopar Performance Engine book’s suggestion of using fully grooved main bearing inserts is valid. Why did you deviate? Remember this, stock semi-grooved main bearings (grooves in block, not caps) are “timed” to open the pressurized oil-flow circuit to the rod bearings during only half of each revolution. By switching to fully grooved inserts (grooves in block and caps) the oil flow to the rods is continuous. You say you had a rod failure with your previous semi-grooved setup? The root cause is likely right here. Of course, the fully grooved mains represent a greater “leak” in the system, so expect low-rpm oil-pressure gauge readings to be spooky—like 5 psi at a traffic light with heat soaked oil. This is why street and strip engine builds shun the fully grooved approach. But your Bonneville-bound Fish needs them.
Be careful of the urge to simply “throw more oil at it” with a high-volume oil pump. Mopar Performance used to sell HV pumps (PN 4286740), but, along with everything else related to the Slant Six, it’s discontinued these days. In fact, the stock oil pump delivers enough oil, so long as internal rotor/body clearances are not worn enough to reduce pumping efficiency. Yes, you can insert a 0.040-inch flat washer behind the pressure-relief spring (or hunt down a discontinued MP extra-stiff spring, PN 2406677) to gain 5 to 8 psi. But beware any new high-volume oil pump. Back around the year 2000, Slant Six racers using high-volume oil pumps began to have failures of the small 1-1/8-inch-diameter oil-pump drive gear. Driven by spiral teeth cut into the camshaft, the teeth of the pump drive gear wore away very quickly. I experienced this failure myself one morning on the crowded Los Angeles 405 freeway commuting into my job at Hot Rod in my aluminum-block Hyper-Pak 1962 Valiant. One moment I glanced down at the oil-pressure gauge and all was well. A few minutes later, the needle was on zero.
To make a long story short, a run of improperly heat-treated drive gears somehow entered the supply chain and caused numerous failures. I was lucky. Sure I had to call a tow, but I caught it in time before it seized. Did you inspect your 170’s oil-pump drive gear after the failure? Had it stripped?
Another oil-pump concern is the fact early blocks like your 170 had a six-bolt oil-pump mounting face and require a matching six-bolt oil-pump case. Later, the pump body and block mating face were changed to five-bolt configuration. While a newer five-bolt pump will bolt to an earlier six-bolt block, a small gap will result, which allows the pump to suck air into the pump and oil circuit. Not a good thing. Since you’re playing in the rare air of Bonneville, I’ll guess you haven’t made this “rookie” mistake—have you? It’d cause bearing failure and the subsequent disaster you described.
In conclusion, get back to fully grooved main bearing inserts and avoid new, unproven oil-pump drive gears. And while your naturally aspirated Slant Six efforts are noble, check the internet for videos showing turbocharged Slant Six street cars that run easy 11s. These guys throw snails on used 225s and say they never even pull the oil pan!
Mopar 340 Rear Sump Swap
Kevin Goldberg; Crivitz, WI: I’ve been working on my 1949 Dodge pickup for 15-plus years. Recently, I took it off the road to put in a Mustang II front suspension. Many years ago, I took the truck down to the frame and swapped in a 1973 340/727 and 8-3/4 out of a rotted Challenger. After removing the front clip, engine, and Torqueflite transmission, I boxed the frame and welded in the new Mustang-based crossmember, but when reinstalling the engine, I determined the center-sump oil pan hits the new crossmember. Instead of cutting and boxing the new member, I realized a rear sump would clear. After research, it looks like I can use a rear-sump pan and pickup out of a 318-equipped truck. I can’t find anyone who has done this. Can you confirm this swap will work, or do I get to cutting? Thanks for any assistance.
Steve Magnante: Oil-pan sump placement among traditional (old-school) Detroit V8 engines is a funny thing. Generally speaking, Chevrolet pans put the sump at the rear, Fords put it at the front, and Mopars put it in the middle. The universe is in harmony until people like us start mixing and matching non-stock goodies. Many hot rodders say the Chevy small-block got to be the most popular because its rear-sump oil-pan design was the easiest to adapt to non-Chevy engine bays.
Regardless, thanks to the fact Chrysler’s LA series 273, 318, 340, and 360 small-block engine family is designed with the oil pump mounted atop the No. 5 main bearing cap (much like the Chevy small-block), your 340’s center-sump configuration is influenced by Chrysler’s K-frame and torsion-bar front suspension design—not some quirk inherent to the LA engine. Just like any Chevy small-block, the sump location can be juggled as long as a matching oil pump pickup tube is used.
I encountered a similar problem a while ago when swapping an aftermarket rack-and-pinion steering/tubular K-frame kit into a 360-powered 1970 Duster I once had. Like you, the stock, center-sump oil-pan configuration no longer fit the chassis, so I looked into the world of Dodge pickup trucks and SUVs, and sure enough, I found solutions. Due to frame architecture, 1972–1993 Dodge pickup trucks and Ramcharger/Trail Duster SUVs have rear-sump oil pans and matching pickup tubes. My measurements found the stock sump height was 8-1/2 inches, shallow enough for passenger-car use. If you don’t have immediate access to one, for mind’s eye conjuring, know that general appearance is similar to a Chevy 350 oil pan. The truck sump is backed all the way to the rear of the crank case, and as you’re aware, any 1972–1993 318 pickup truck pan is what you’re looking for, but stay away from 360-sourced oil pans. The problem with 360-sourced oil pans on your 340 (or any 273 or 318) is the fact that when Chrysler bumped the 318’s stroke from 3.31 to 3.58 inches to get to 360 cubes (plus a bore increase from 3.91 to 4.00) in 1971, it also switched from forged cranks to less-durable cast-iron cranks. Seeking to regain lost strength, Chrysler increased the main journal diameters from 2.50 to 2.81 inches to increase overlap and torsional rigidity. Thus, the 360 crank, block, and main caps are not directly interchangeable with its 273-, 318-, or 340-cube brothers. Moreover, the main-cap fastener holes drilled and tapped into the block were spaced 0.31 inch farther apart. This led to a redesign of the oil pan’s crescent-shaped cutouts (found at each end). These larger crescents are specific to 360 pans (stock or aftermarket) and are at the core of why your 340 won’t work with any 360-style oil pan (or main caps). I share this detail not only with you, Kevin, but also with any other Mopar small-block oil-pan jugglers reading this.
Since your hot rodded ’49 is a one-off, be ready for possible surprises. My measurements found that a stock pickup truck pan has a total height of 8-1/2 inches, so it’s not so deep that ground clearance is likely to be a problem. Having said that, I attempted to test-fit a typical passenger-car windage tray, but it made contact and was therefore a no go. The threaded studs attached to the main cap bolts to trap the floating windage tray made contact with the shallow, forward end of the truck pan. Since I already had a Milodon center-sump pan on the 360 and didn’t want to step backward to a stock 1972–1993 pickup-truck unit (which would have fit). I grabbed a Milodon 8-quart pan and matching pickup tube that was very, very tall. At 10-3/4 inches deep, it was designed for a high-riding truck, not a low-down drag racer. Lucky for me, the Duster’s tall, 15-inch front tires and near stock ride height delivered plenty of road clearance. But beware, truck pans tend to stand taller than passenger-car units.
If your new Mustang II front-suspension installation is typical (with the rack installed as close to the spindle centerline as possible), a stock 1972–1993 Dodge 318 pickup-truck pan and pickup tube ought to put you in the ballpark, and if that fits, chances are strong an aftermarket, rear-sump 318 truck pan (and matching extended pickup tube) of the same vintage will also work. Good luck!
The post Car Craft Ask Anything: You Ask, We Answer appeared first on Hot Rod Network.