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July 2012 Chevy High Performance Q&A

Chain Reactions, Part II

Kevin McClelland May 29, 2012
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Last month I gave you a blow-by-blow of the broken carnage in my Powerglide racing transmission in my roadster. When it was all said and done the pile of dead parts was extensive with the planetaries, direct drum, front pump, and input shaft lying in a pile. With the help of our pal Jimmy Galente at RaceTrans, we had spec’d out all the components needed to get me back on the track with a bulletproof trans. I’m not one for working on our cars. I much prefer racing them! So I’ll spend the extra dollars to keep me from bending the wrenches.

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With this being said, we went top shelf on all the components, which put my checkbook in serious overdraft territory. First, I knew that I wanted to go with billet 9320 1.80 straight-cut planetaries. Next, we went with a Reid SuperPump, which has upgrades throughout the pump as compared to the stock Powerglide. One major upgrade is a much larger pump assembly and passages, which increases the pump’s volume. Next, was a TCI Vasco 300 input shaft, and finally Alto Red Eagle clutches and Kolene steels. With the direct drum needing to be replaced, we upgraded from a seven-clutch pack to eight on the direct. On the reverse Alto has designed a “low-friction” clutch pack. What they have done is put neoprene buttons on the ears of the steels, which force the steels apart and give the friction plates extra clearance. When a Powerglide transmission is in high gear, the direct clutch locks the planetaries and spins the reverse frictions at the input shaft speed. Therefore, when you’re flying down the track in high gear at 7,000 rpm, the frictions are spinning at that rpm between the steels that are stationary. Any drag there slows down the car and wears the clutches.

To round out my new killer transmission I also upgraded to a Reid roller bearing case with built-in flexplate shield and transmission shield. In addition to the roller bearing case I also installed a billet roller bearing governor support. These two upgrades are to also reduce friction and give you added performance. In my roadster there is very little room for the external flexplate and transmission shields. The interior barely fits and with this case everything fits like a glove. Also, the trans case can be recertified every five years. I even swapped out the trans flexplate, so I shouldn’t have to pull out the trans for three years as that’s when the cert will be out on the flexplate.

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With all these new parts I dropped around $2,500. The reason I did this is that now I have a transmission that will live with a 1,500hp engine and should never give me one bit of trouble behind my relatively mild big-blocks. As an added bonus for spending all of this hard-earned money, I did pick up around 8 hundredths of a second, and two full mph in the quarter-mile! I was blown away with the performance gain. I was hoping to get the performance that the manufacturer promised, but sometimes it can rarely happen.

Big-block float

I have a Gen VI big-block Chevy with a hydraulic roller. It has a camshaft with 234/240 degrees of duration at 0.050-inch tappet lift, and 0.595-inch max lift. I’m running Crower 1.75 stainless rockers, Manton 3/8-inch pushrods, and performance Morel lifters. I also have Isky valvesprings (PN 8205), COMP Cams steel retainers on Brodix heads, and an Edelbrock RPM Air-Gap intake. My issue is I think I lose valve control at revs much over 5,000 rpm. The car feels as if it has a governor on it that kick on at about 5,200-5,300 rpm in high gear. It is smooth, just flat. It plains out about at the 1,000-foot mark and no matter what, goes 107 mph and it should be around 115 mph. I just pulled some springs off and I have 130-pound seat and 350 pounds over the nose. My question is what kind and how much spring do I need? I feel confident I don’t have fuel issues and I may scrap it all and install a solid flat tappet or a solid roller. I’m sick of it. Thanks for any help!

Montgomery, AL

Valve control has always been a problem with hydraulic roller big-blocks. The valvetrain weight of the big-block doesn’t lend itself to the increased weight of the hydraulic roller tappet, and the valve weight of 2.19-inch stainless valves. You can usually pick up 200-300 rpm of limiting speed by installing titanium retainers over standard steel retainers. COMP has released a nice line of Tooled Steel retainers that give you the weight savings of Ti, but with the durability of tooled steel.

As for your valvesprings, I checked out the spring book on Isky’s website. The 8205-Plus spring specs out at 128 pounds on the seat at an installed height of 1.950 inches, and you should be seeing around 430 pounds at your over the nose lift of 0.595 inch. Either you don’t have PN 8205 springs, or you have killed them by sitting at a fuss point waiting for the finish line to come. One interesting thing that I have found over the years is that engines will accelerate through unstable points of the valvetrain, but if the engine can’t rev past them quickly enough they will stop revving at those fuss points. This is what your problem sounds like. Changing the spring design by its damping style, diameter of spring, number of coils, all changes the natural frequency of which a spring resonates. You must have a valvespring with a natural frequency that goes into instability just above 5,000 rpm with the mass of the valvetrain, and acceleration rate of your camshaft. In the past I’ve increased the seat pressure by shimming the springs over 30 pounds without any change in the fuss point. I would recommend going with a set of COMP Cams valvesprings (PN 930-16), which is a dual valvespring with a flat wire damper. The springs spec out at 1.550 inches in diameter and have an installed height of 1.900 inches and a seat pressure of 153 pounds. At your 0.595-inch max lift you can expect an open pressure just above 400 pounds. Running the seat pressure much over the 15-pound mark you can run into issues with the lifters bleeding down from the excessive pressure. Along with the 930-16 springs we would run the matching Tooled Steel retainers (PN 1732-16). These retainers weigh only 2-4 grams heavier than comparable titanium retainers. These tool steel retainers utilize COMP 10 degree Steel Super locks and you will need PN 613-16 for 11/32-inch valves, and PN 612-16 for 3/8-inch valve stems.

Finally, switching to mechanical flat will take care of your problem. If you decide to go this route we would still recommend putting your valvetrain on a serious diet. You will benefit in the long run from any mass you can drop off of your valve action. Good luck.


Flat Brilliant!

After all the great advice I’ve gotten from you over the years; I have one for you. I just read about your trailer flat tire dilemma. You need to check out I have the Trailer-Aid Plus and it works amazingly well. With my 28-foot trailer fully loaded with the Biscayne, the golf cart, Snap-on toolbox full of tools, cabinets full of extra parts, and all the necessities for a weekend of racing, it tipped the scales at an even 12,000 pounds. Yet, it only took about three minutes on the side of the road to change a flat tire. Just loosen the wheel, roll the good trailer tire onto the Trailer-Aid, swap to the spare, roll off the Trailer-Aid, torque the wheel, and hit the road. I’ve had it for three years and used it many times between my friends’ and my own trailers, and it is still in excellent condition. It is a must-have for anyone who owns or tows a trailer. I thought both you and the readers could use this knowledge.

John Kimack
Concord, CA

John, thanks for the great tip. Guys and gals, John and I go back well over 36 years! I met John through his older brother, Bill, and they lived across the street from a gas station that I worked at while I was a senior in high school. I warped both of them into being gearheads from the day we met. Bill currently owns BK Automotive in Tujunga, California, and John works for the city of Concord. John has a killer ’66 Biscayne with a 454 that he bracket races constantly. I think that a little of Bill wore off on his little brother, John, as one of Bill’s first hot rods was also a Biscayne with a 454. This thing thumped for a boat of a car in the late ’70s. Boy, I sure miss those simpler times.

Thanks again for the tip. I went and checked out the Trailer-Aid website, and if you shop around you can pick one of the simple ramps for a little over $30. It sure is a lifesaver when you’re stuck on the side of the road with a dead trailer tire.


Roller Tappets on the Cheap

Is there a way to retrofit Gen III lifters and holders into a Gen I small-block? I thought I had read this somewhere and can’t seem to find out more about this swap.

I want to keep my 283 short-block, slap on some Vortec heads, and maybe a roller cam. This car would be used as a cruiser to keep me and the kids going to car shows. Thanks for any help!

Somerset, WI

Years ago we did something very similar to what you’re asking. We used the tie-bars from a Gen II LT1 and drilled and tapped the block between the lifters bores to hold down the tie-bars. This was on a 400 small-block case and was for dyno testing only. The block is very thin in this region and isn’t something that I would recommend for a durable street build. We really didn’t care if the thing broke or not as it was a dyno mule.

If you really want to go with a hydraulic roller conversion for your 283 we would recommend going with a set of retrofit hydraulic roller lifters from a reputable company like COMP Cams. You will be dollars ahead going this way rather than risk killing your ’83 block and being stuck miles from home when it decides to fail. You and your kids wouldn’t be happy on the side of the road. Sorry, we couldn’t help.


Tow Beast

I have a ’94 C3500 Crew Cab, two-wheel drive, and want to build a new engine just for towing. I have a three-car trailer, and want to pull it with no problem, but the thing is, I have an LQ9 that I was going to make into a carb 402. I also have a 454 that I was going to turn into a 496. Which engine would be better?

Lee Krucial
Detroit, MI

Well, as we’ve been pushing the LS-based engines, I’m going to have to fall back to “There is no replacement for displacement” adage. To pull around a Crew Cab dualie with a three-car trailer in tow, I would prefer the stroked 454 for this job. Yes, you may get a slight bit of efficiency with the Gen III engine design, but I’ve seen that when you put a ton of load on the LS-based large displacement engines they will eat the fuel also. A good old big-block will kick out tons of torque effortlessly for the long haul.

Make sure that when you spec out your 496 build that you stay on the conservative side and go for maximum torque production. There is no reason to build a warmed-over big-block that is going for horsepower. Go with a good set of oval port (either Gen VI irons or AFR aluminum heads) with a short hydraulic-roller. The GM H.O. 454/502 hydraulic roller would be a great choice as it specs out at 211/230 at 0.050-inch tappet lift, 0.510-/0.540-inch max lift, and is ground on 112 centers. This camshaft is sold under PN 24502611 and in your oval port 496 will make close to 600 lb-ft of torque in the low 3,000-rpm range. It will also make great power to 5,000 rpm. That thing would burn your duals for as long as you wished to keep your foot in it. Make sure that you strap those three cars down well!


Get Looped

I have argued this to the death. Now, a lot of guys loop the vent out the top of a fuel cell.

JAZ says do this. Other say not to. A loop can cause a liquid trap (not allowing air to move). Liquid traps are used on an A/C vent to keep bugs and air out. So what’s the deal? Loop or no loop?

Al Smith, SSR Engines & Carburetion
Newton, NC

Al, interesting question. Of all the cars that I’ve built over the years I’ve always looped. I’ve done this to prevent fuel from coming out of the cell during aggressive stops when the tank is completely full. As for preventing the air from getting into the cell because of a liquid lock, as the pump takes fuel away from the tank the liquid lock is drawn back into the cell. This fuel in the vent doesn’t cause much resistance to the atmospheric pressure trying to push the fuel back into that tank when the pump is sending fuel to the engine.

Now that you bring up venting fuel tanks, make sure that you run some type of filter on the vent line into your fuel cell. If you think about it, most of our race cars use anywhere between a quarter to a full gallon of fuel per run; this is after driving around the pits to the lanes, making the run, and driving back to the pits. If you look at the amount of space a gallon of fuel takes up you must bring that much air into the fuel cell. The air that is under your car can be very dirty from the exhaust blowing up dirt off the ground, and the pressurized air under the car as it travels down the track. It’s amazing how dirty my filter gets on the end of the fuel cell vent. It is caked with dirt, which would be getting into my fuel cell, plugging my fuel filter, and even worst, some getting past the filter and into my expensive MagnaFuel pump. A simple universal air filter breather will clamp right on to the end of AN-6 bulkhead fitting. These filters can be washed and reused for the life of your race car. CHP



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