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Chevy Performance Tech Q&A - December 2014

Kevin McClelland Oct 20, 2014
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The Old Switcheroo!

As you readers know, The McClellands are drag racers. Sure, we have dipped our toes in other types of motorsports, but we always come back to that black dyno. It can be very rewarding, and it can be humbling at the same time. As my good friend Ted Seipel has always said, “You have instant results, as you get a report card at the end of each run.” There's no doubt if you done good or really stunk things up.

As I finished up my column last month, Daniel was off on a business trip to Europe. I'd originally built our '80 Malibu wagon so I could double-enter that car in Stock Eliminator while also racing my roadster in Super Gas. Well, as Daniel came of age it was natural for him to take the wheel of the wagon, and he's done a great job. I rarely get to race it now, but I have way more fun sitting and watching him go rounds. With him out of town, there was a Summit ET series points meeting that weekend. I decided to try my hand at the double-entry thing and race the roadster in Super Pro and run the wagon in Pro. I figured I could beat a couple of guys in his class and not let them gain a ton of points on Daniel.

Super Pro is an Electronics class, and we use delay boxes to adjust the timing from the release of the transmission brake 'til the car actually takes off. For instance, we leave on the first flash of yellow on the Christmas Tree, since you usually have around 1.100 seconds of delay to try and cut a perfect light. We adjust this delay based on the weather and track conditions and the amount of power with which you leave the starting line. Some people say it's easy to do, but I beg to differ.

Now, Pro Eliminator is No Electronics. You leave on the last yellow and adjust your reaction time by changing front tire pressures, rear tire pressures, launch rpm, ignition timing, and staging techniques. I can probably count on both hands the number of times I've raced “bottom bulb” in the past 20 years. It is very hard to focus on the bottom bulb and hit the same mark for a consistent reaction time. Also, when you get excited, it's extra challenging to be consistent.

As I rolled in for the weekend, everyone was looking for Daniel around the wagon. I told them I was racing it for the weekend and that Daniel was off in Germany. This was received with some level of skepticism, as no one had ever seen me race the wagon. As the day rolled on, and the rounds went by, the other racers took to ribbing this old man running around trying to keep two cars cooled, fueled, charged, and back to the lanes. My luck ran out in the Semis in both the wagon and the roadster. I can tell you that making 15 runs in two cars in one day will put some wear and tear on ya.

The next day I rolled into the track for the second race and lost in the first round in the roadster and in the third round in the wagon. My racer friends kept coming up to me saying, “What is Daniel doing in Germany?!” I told them that he was working, but what they knew and I didn't (because I'm not a big Facebook guy), was that while we were drag racing, he was renting a race-prepped Renault and making laps around the famous Nürburgring racetrack in Nürburg, Germany. This storied track is 12.9 miles long, and he and a buddy made four laps, two each with his GoPro recording all the way. Most of our friends agreed that they would have rather been running around the Nürburgring than being at the Summit race!

The next weekend, Lisa and I struck off on a nine-day vacation up and down the California coast visiting friends and family. I told Daniel that he could race either my roadster or his car at the upcoming NMCA race that weekend. He had raced my car several times at NHRA divisional events, but nobody at Fontana knew this—or that he even had the license to drive it. This was the first time he had taken it out on his own without me. It was his turn for the ribbing. “Does your dad know you have his car!?” Daniel would immediately retort “No, he doesn't. And don't tell him!” Well, he double-entered the car in both the Super Quick 32 qualified bracket race and Pro Comp, which is a combination of 9.90, 8.90, and 7.90 index cars. He held his own, losing in the quarterfinal round of Pro Comp and the semis of Super Quick! Not bad for the first time out on his own.

As I've always told Daniel, “Yes it's great to win, but at least they knew we were there.” The next time they pull up to us on the starting line, they know we'll be there. And as always, we'll have our report card in our hand to see what kind of grade we earned.

Have fun this month, and go out and do something to remember!

Go Magnum

Q: I read your column regularly and hope you can help me with a problem.

I live in Canada, where parts suppliers for hot rodders are not always the best. I am trying diligently to find an upgraded bolt-in transmission to replace the T-56 six-speed in my car. I can buy stock replacements but they are a little weak for what I'm trying to put together. Do you know of a supplier that can provide an upgraded T-56 bolt-in for a '97 Camaro SS with an LT1 and the T-56?

Thank you.

Ed Worthing
Lloydminster, AB, Canada

A: We can help with your transmission dilemma. Tremec is now the producer of the famous T-56 transmissions since it bought the transmission line from Borg-Warner in 1998, and is now the OE supplier for Chrysler, Ford, and GM. Tremecs can be found in standard production vehicles and the OE's best supercars, like the ZR1 Corvette and the ACR Viper.

The top of the line is the T-56 Magnum double-overdrive six-speed transmission, which takes the very best from Tremec's current OEM technologies and pairs it with the most popular features of the TKO five-speed. The massive transmission is able to withstand 700 lb-ft of torque and a peak rpm rating of 7,800! It features 4616 chromoly gears and shafts, a one-piece countershaft, triple-cone synchros, and a very precise short throw shifter for great positive feel. No other transmission offers as much combined strength, versatility, and general ease of use as the T-56 Magnum.

In the OE circles, this transmission is known as the TR-6060. The Magnum is an aftermarket version of the same transmission. Tremec offers the transmission in two different gear ratio combinations for your specific application. The first gives you ratios of 2.66 First, 1.78 Second, 1.30 Third, 1.00 Fourth, 0.80 Fifth, and a final Overdrive of 0.63. The next gearset comes in at 2.97 First, 2.10 Second, 1.46 Third, 1.00 Fourth, 0.74 Fifth, and a very deep 0.50 final Overdrive. This would keep your Camaro loafing down the freeway.

For more information give Tremec a call at 800.401.9866 and get hooked up with a dealer nearest you in the Great White North. Hopefully, this will fit the bill for your SS Camaro build.

Source: tremec.com

Another L79 build

Q: I just read the “No Replacement for Displacement” article and want to discuss my project. Like Mr. Derek Knapp's '65 Chevelle, I also have a '65 Malibu SS under restoration. And like him, I have a period-correct 327 engine. I have attempted to duplicate the L79 engine in appearance, as well as internal components and performance. I looked at bigger displacement but opted for a stock 327. I had the camel-back heads opened up with 2.02/1.60-inch valves (I live at sea level in Seattle) and some porting and polishing done, roller rocker tips (I wanted to use stock valve covers so I did not order roller shafts), the correct intake manifold, an aftermarket 600-cfm Holley carb, the correct air cleaner, and so on.

The cam is a COMP XE268H-10 series, 224/231-degree duration, with 0.477/0.480-inch max lift at 110 degrees lobe separation. With this setup the performance was not a good driver. I had it at a shop and the carb was rejetted to get the air/fuel down to 14:1, as it was 18:1 when we started. This improved the driveability somewhat, and on the dyno it made 300 hp at the wheels (with a Muncie M20 four-speed and a 12-bolt 3.55:1 rearend) and close to 280 lb-ft torque. It was still jerky in normal driving in the lower rpm, but above 3,000 rpm it is very strong (in my opinion). It was suggested that I could improve the low-end performance by retiming the cam, by adjusting the crankshaft gear to cam gear position. The crankshaft gear has three available positions (0, A, and R) on it and it was set up on the 0 initially. I have since changed this gear to the A (advance) position and I'm happy to report the driveability is much smoother, with better low-end torque. I understand that I may have lost some top-end performance, but how much is unknown unless I get it back on the dyno.

It makes 12 inches of manifold vacuum at 800 rpm (before and after the cam adjustment) and I have power brakes. I have not observed any problem with this setup but wonder if I may at a higher altitude? Is 12 inches of vacuum normal? Is there something I can do to improve this? I seem to think that 20 inches would be preferable but have no basis for this thought. Next, the engine has 9.5:1 compression ratio and I'm running premium unleaded. To get the engine to run well, I'm at 12-14 degrees of timing advance on the distributor. Anything less than that and it runs lousily with poor performance. It does not ping so I'm assuming it's OK. This amount of timing advance is foreign to me and my experience dates back to the 1960s, when 4-6 degrees was the max allowed. I'm using a distributor with a vacuum advance system and the source for the vacuum is above the venturi. Is this the correct location to supply vacuum to the distributor or should I be using manifold vacuum?

Finally, since retiming the cam, the idle mixture is lean to the point of burning my eyes (too lean) when standing near the running car. This was the same symptom I experienced before rejetting the carb. Do I need to rejet the carb since I retimed the cam?

Can you please let me know your thoughts? I love that my engine looks stock and I get the current performance.

Al Hewitt
Via email

A: Thanks for checking in with your L79 build. It's very cool that you guys are trying to make your engine combinations more current, with the '60's look. We've been known to grind off all the numbers and identifications from an Edelbrock manifold and paint the whole engine Chevy Orange to conceal the evidence. Sleepers are us!

We're not sure we would have advanced your cam that far. Most of the lower crank gears that have the three selections you're referring to advance the crankshaft gear at least 4 degrees; some timing sets advance the camshaft up to 8 degrees. Your COMP cam is ground with 4 degrees advance from the factory. The as-ground intake centerline is 106 degrees. If you're 4 degrees ahead with your timing change you're in at 102, and if it moves the full 8, the centerline is in at 98 degrees after bottom dead center. The more you advance the camshaft the earlier the exhaust valve opens, letting out the combustion gases into the exhaust, and the intake valve closes earlier, giving you a higher dynamic compression ratio. With your 9.5:1 compression you've been able to get away with the camshaft advances this far without spark knock or detonation. If you had the factory 11:1 L79 factory compression you'd have an issue.

With a static compression ratio of 9.5:1 we'd be happy with the 12 inches of idle vacuum you have, as the COMP Cams XE268 has a fair bit of overlap with its 224/231 degrees of duration and its 110 separation angle. This should be adequate to support your power brakes as you have mentioned. As you go up in altitude you'll lose idle vacuum, but we doubt you'll notice much increase in pedal effort with the slightly lower vacuum. Twenty inches of idle vacuum is the most you will see out of a factory stock engine. And actually, 18-19 is the most usually for a no-load idle.

As we've already spoken about your 9.5:1 compression, an initial spark advance of 12-14 degrees isn't out of the question when you're running a camshaft with the overlap you have. The timing does give you much better throttle response and driveability. We wouldn't be concerned at all to run that much initial. That said, you don't want to have more than about 34 degrees total mechanical advance around 3,200 rpm. This, in conjunction with a 10-degree vacuum advance, can give you a total cruising advance of 44 degrees, which will give you the best cruising performance and mileage. As for your vacuum source, you want to run a ported vacuum source, which on your 600-cfm Holley would be the vacuum port, located on the primary metering block on the right-hand side, just above the idle feed screw.

Now to your watery eyes. You can experience the burning eyes from too much fuel or a lean misfire. Camshafts with a fair amount of overlap give you a nice lopey or choppy idle. This idle condition is really the engine misfiring at idle and you have unburned hydrocarbons coming out the tailpipe. Either an over-rich or lean misfire gives you that nasty exhaust experience. The best way to tune your idle air/fuel ratio is by using a vacuum gauge and adjusting the idle fuel screws in your 600 Holley to the highest idle vacuum. First, make sure you have the timing set correctly. Then for a baseline setting, lightly screw in your idle fuel screws until they seat, and back them both out one turn from the fully seated position. Next, fire your fully warmed-up engine and set your idle speed screw to 800 rpm. Using a manifold vacuum gauge, slowly enrichen one idle feed screw until you have achieved the highest manifold vacuum. As you are doing this, you'll probably need to reduce the idle speed back down to your target 800 rpm because as the vacuum climbs the engine speed does as well. Then go to your second feed screw and repeat the procedure. With your L79 dual-plane manifold, you may have the two idle feed screws out differing amounts. With a single-plane-type manifold, you'd want to balance the feed screws. This process should give you the best idle quality, transition to the main circuit, and, hopefully, the best eye care!

Good luck with your Chevelle. Color us jealous!

Sources: compcams.com, holley.com

Not All ZZs are Created Equal

Q: I am 72 years young and still love and have loved GM cars all my life. I just bought an '81 SS El Camino with a ZZ3 H.O. 350 in it. Could you tell me the differences between the ZZ3 and the ZZ4? Thanks!

Dave Stiver
Via email

A: The ZZ family of H.O. 350 engines started and won the crate engine wars between Chevy, Chrysler, and Ford. Yes, there were more powerful and larger crate engines, but no one built and sold more performance crate engines than GM with the H.O. 350. The engine was first released in 1989, the ZZZ engine designator. These engines had four-bolt mains, forged one-piece rear main seal crankshafts, L98 Corvette aluminum cylinder heads, and a 9.8:1 compression. The pistons were hypereutectic high-silica alloy piston that had on-center piston pins. These engines were well known for their signature piston slap (knock) when cold because of the on-center pins. The camshaft was an aggressive 235-degree duration camshaft at 0.050-inch tappet lift, single-pattern, with 0.480-inch max lift, and was ground on 114 centers. The engine was topped off with the original Z-28 aluminum high-rise intake with a square-bore Holley flange. These engines were originally rated at 345 hp and 370 lb-ft of torque.

Next came the ZZ1 and ZZ2, very similar in all ways to the original ZZZ except for the second design piston, which featured off-center pins to quiet the nasty piston slap when cold.

Right around this time is when we became intimately involved in the ZZ engine family, working with Mark McPhail, a Chevy Race Shop engineer who was tasked with stuffing the ZZ engine into a mid-'80s Camaro to upgrade the wimpy LG4 305 165hp engine. The only problem was that the engine had to pass all emissions and get California's blessing to have an emissions-legal engine swap. After several years of development we released the ZZ3 engine in late 1991. With this we had redesigned the high-rise intake manifold with a dual-pattern carb flange to accept both Holley square-flange carburetors and Rochester Q-jet carbs. The 235-degree-duration camshaft also had to go. We worked with the engineers at the GM Bay City camshaft plant and went through more than 20 designs until we landed on the 208/221-degree-duration dual-pattern at 0.050-inch tappet lift, 0.474/0.510-inch max lift, ground on 112 centers. Our goal was to lose no horsepower and gain as much torque as possible. We achieved the 345 hp at 5,200 rpm, and 395 lb-ft of torque at 3,500 rpm. This was a nice boost in torque over the original ZZZ, -1, and -2. The purists didn't really like it because it sounded like a grocery getter until you stood on the throttle. The torque really planted you in the seat.

The ZZ4 was the final upgrade to the ZZ engine family, and this is the engine you can purchase today. The ZZ4 really benefited from the LT1/LT4 Gen II small-block engine. Released in the mid-'90s, the ZZ4's pistons were upgraded again to the flat-top Mahle design, which was the original equipment LT1 piston. These were a lightweight cast piston featuring a low-drag metric ring package, and boosted the compression to 10:1. The engine also used the powdered metal connecting rods and the undercut and rolled fillet nodular iron crankshaft from the LT4 Corvette engine. This crankshaft was stronger than the forged unit in the earlier engines. The final upgrades were in the cylinder heads. First, they went with radius valve seat inserts for better flow and upgraded valvespring package with the lightweight LT4 Ovate wound 1.340-inch single valvespring. The ZZ3 would occasionally have spring failures with the high acceleration rate 208 intake lobe on the ZZ3 camshaft, and the 0.510-inch max lift on the exhaust. The LT4 eliminated all issues with the springs.

We hope this gives you all the information you needed on the ZZ crate engine family. The only upgrade you need to consider is going with the LT4 spring package on your ZZ3. The set of 16 springs is sold under PN 12551483, the lightweight retainers are PN 19169661, and the spring seats PN 10212809. This will give you peace of mind.

Source: chevrolet.com/performance

Reverse-flow water pump

Q: I enjoy reading your Q&A … so I know I'm not the only guy with problems. Anyway, I hope I haven't royally screwed up while combining parts for my '65 Impala SS convertible. I have a Mark IV BBC, which I purchased in long-block form from a machine shop, rated at 450 hp, nothing radical. I wanted the ease of a serpentine belt setup but didn't want to spend thousands on an aluminum show kit. So I found a setup in the GMPP catalog that included alternator, power steering, and a water pump. I thought, Cool! It's GM PN 9172806 and the water pump is PN 12456326, a reverse-flow pump.

First, will this setup even work with my block? Next, what thermostat do I need? And how do I route my heater hoses, since there isn't an outlet on the water pump for the heater hose or a way to return it to the radiator? The radiator I have is a Griffin down-flow HP series. So, will the serpentine setup work with that radiator or will I need to get a cross-flow? Thanks in advance. Hoping to cruise with my daughter all the way to New York this summer with the top down!

Brian Cyrus
Via email

A: The reverse-rotation pump is only in regards to the direction the pump shaft turns in relationship to the crankshaft. It is not like the reverse coolant flow systems on the Gen II small-blocks. This pump will bolt right up to your Mark IV big-block, and also the Gen Vs and Gen VIs. A standard 180-degree thermostat is the correct piece for your engine.

As you have noticed, the reverse-rotation pump doesn't have the return port in the pump from your heater. The late-model trucks brought the water back into the cool side radiator tank. Check with our good friend Mike Knell at JTR (Jags that Run), which offers an endless supply of items to make engine swaps a breeze. Check out the radiator hose tees, which give you the ability to cut the lower radiator hose in a convenient location and install this steel tee, with either a 5/8- or 3/4-inch nipple. These tees come in radiator sizes for 1 1/4-, 1 1/2-, and 1 3/4-inch hoses. Give JTR a call at 925.462.3619.

Your Griffin down-flow HP series radiator will work perfectly with your serpentine drive system and keep your big-block's temp gauge in the cool zone. We hope your daughter enjoys TDM (top down motoring). Enjoy your cruiser and good luck finishing your project.

Source: jagsthatrun.com



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