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December 2011 Chevy High Performance Q&A

Kevin McClelland Oct 24, 2011
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We love letters, especially technical questions. Submit your tech questions to Kevin McClelland at Regular shout-outs and good tidings are also always welcome.

Let’s Be Proactive

By the time you read this, we will be close to the final court date for Auto Club Dragway at Fontana, California. This has been an ongoing sound control issue for several years. Just this last week there was news that we would have a limited schedule for the rest of the year until this final court date. I don’t want to talk today about Fontana’s specific issues, but rather in general how we got here.

chp 02 O  December 2011 Chevy High Performance Q A Editor 2/2

Southern California is arguably the birthplace of drag racing and the National Hot Rod Association. Back in the day, most of the drag races were held on abandoned World War II airstrips that were converted to dragstrips. These airfields were built far from population, and sound wasn’t an issue. With the growth of neighboring communities, in addition to the purpose-built dragstrips popping up around the country, it was only a matter of time before conflict began.

Well, here in Southern California, we have lost at least three dragstrips and countless circle tracks over the years to sound issues and the tracks’ neighbors. When I say, “let’s be proactive,” I mean let’s be good neighbors to the community. When I worked at Flowmaster, everyone said I was just trying to sell mufflers. Back in 1988 when I brought out my Camaro for the first time, it had mufflers on it. That was long before any muffler rules were even being considered. It made my car easier to tune and diagnose problems early, and you could hear your competition in the other lane. I had the advantage of hearing the games they were playing with their throttle.

I think it’s high time that all of us racers help by trying to be good neighbors. Also, track owners and race promoters requiring muffled race cars won’t hurt your car count. If everyone requires mufflers at our local bracket events, there would be nowhere else to race. Yes, there will be holdouts, but in time, they’ll want to be racing and outfit their cars.

Have I lost my mind? Well no. I have two perfectly good muffled race cars that are sitting idle because some of us have not taken care of our sport. I want to be doing this until I can’t get in my car any longer! Also, I want this sport passed down to my grandchildren. It’s been alive and well for three generations in my family, and I don’t want to see it end anytime soon. It’s time for a change!

Long and short of it?

Q. When building a 383 small-block, when should one use 5.7-inch rods or 6.0-inch rods? Thanks.

Morris Boggess
Pasco, WA

A. Boy, this is a question for the ages. Years ago, Smokey Yunick said that you couldn’t put too long a rod in a small-block Chevy. This was back when all they had for cylinder heads were stock iron heads ported by the latest grinder jockey! We’ve come quite a long way since then. We now have cylinder heads that flow serious air. Today the main reason you would want to run longer rods in your 383 would be to reduce side loading on the piston skirts. The stock 400 small-blocks were equipped with a very short rod of 5.565 inches, which allowed GM to use the same compression height in both the 3.48-inch stroke and 3.75-inch-stroke engines. This was done for durability, keeping heat out of the wristpins.

With the stock 400 small-block rod, you had a stroke to rod ratio of 1.484. By using a 5.7-inch rod on a 3.75-inch stroke you yield a ratio of 1.52. If you bump the rod length up to 6.0 inches, the ratio increases to 1.60:1. None of these ratios are optimum for accelerating engines. A good number for accelerating engines is in the 1.8:1 range. With long stroke engines and stock deck heights, it’s impossible to achieve this type of ratio without the wristpin getting too high in the piston. It’s not uncommon to push the wristpin up into the oil ring and you have to run spacers to support the lower segment of the oil ring. On the street, this type of design can cause oil consumption issues. Keeping the pin out of the oil ring on a street-driven engine is preferred.

If you’re building a street performance engine, we’d recommend going with the more common 5.7-inch-long rod in your build. If it’s a race-only package, you can afford to push the envelope and go with a 6.0-inch-long rod. Hope this has answered your question and given you some background as to why. Good luck.


Q. I’m hoping you guys can help me out. I bought an ’80 Corvette basket case. After rebuilding my engine in 2009 I have been using oil. I suspected valveguides, as I only had the valves ground at that time due to budget restraints. Since then I bought a ’78 Camaro, and with that purchase I got an extra set of heads that I sent out and had completely redone. My old casting numbers were for 74-80 350. The ones I had done are for an 80-85 305 HO. The temperature-sending hole on the new heads is a 3/8-inch pipe thread and my old heads had a 1/2-inch pipe thread. I went to the auto parts store, and when they looked it up and pulled the part, it was 3/8-inch pipe thread. I thought, “cool!” Well, what happened next is I was “overheating” on the gauge. After monkeying around with thermostats, changing from a 180 to a 160, my gauge is reading around 200 [205-plus sitting]. I checked the intake with a digital temperature gauge and I really am only running around 180 on the manifold below thermostat, and on the upper hose, 160-ish. Is there a sender that is calibrated to my gauge, or is the sender just faulty? Any information would be greatly appreciated.

Dan Evans
Lisbon, NY

A. You’ve got a couple of options. First, you could move the factory 1/2-inch sending unit up to the intake manifold water crossover. If you don’t have a port available in the manifold, pick up a thermostat housing with a 1/2-inch hole that was used for thermo vacuum switch for emissions control devices. This is the easiest way to handle your original temperature sender.

The 3/8-inch later-model sending units have a different resistance to temperature range compared with the earlier-model 1/2-inch sender. This is why you are registering a higher than normal reading on your temperature gauge. Now, we have two other options you can try if you wish to keep the sender in the cylinder head. We’ve taken the early-model 1/2-inch pipe threaded sender and turned it down in a lathe and re-tapped the sender to 3/8-inch pipe thread. Over the years we’ve done this trick three times and have never broken through the sender.

Finally, we’ve used what is called a bell reducer, in which the male thread is 3/8-inch pipe, and the female is 1/2-inch pipe. These bell reducers are used for plumbing and natural gas in your home. They won’t have a hex on the outside to tighten them up and you usually need to use a pipe wrench to tighten the fitting into your cylinder head. You must take your sending unit to the home improvement store to make sure it will clear the inside of the bell reducer and not bottom out before tightening. Also, after installing the reducer in the cylinder head, you must bleed the air out of the fitting so there is water touching the sender to have an accurate gauge reading.

The best way is if you have access to a lathe or a machine shop that can whip a sender out for you. If you cannot pull that off, install the sender up in the intake. If all else fails, check out the bell reducer. You should be able to use one of these options. Good luck, and keep a cool head.

Tranny Mate

Q. I have a 4L60E out of an ’07 Silverado that I want to mate to a ’78 Gen I small-block 350. The torque converter bolts don’t align with the holes in the flexplate. I get conflicting info on a solution. One person told me I had to run a 700-R4 converter. Another told me just to elongate the holes and bolt it up. I can’t find any listings for a Gen I two-piece rear main seal flexplate to fit the stock converter. I purchased a TCI Automotive FAST EZ-TCU to control it but need to get the trans coupled first! It’s going in a ’58 International A100 Golden Jubilee pickup and can’t wait for the rpm to be under 3,000 on the highway. Any information on this swap would be appreciated.

Mike Wheeler
Great Bend, KS

A. As we’ve mentioned several times in the past, the Gen I small-blocks and Gen III small-blocks have a different distance between the rear of block face and the crankshaft flange. Usually people are trying to put Gen I transmissions behind Gen III engines. This requires a spacer on the end of the crankshaft for the converter to register into. The crankshaft flange on the Gen III engines is forward 0.400 inch compared with the Gen I engine. Inversely, you’ve installed a Gen III–style transmission behind a Gen I small-block. This puts the crankshaft flange 0.400-inch closer to the torque converter. The ’07 4L60E has a shorter bellhousing than the earlier Gen I 4L60Es. We’re surprised you’ve been able to mount the trans to the back of the early small-block and still turn the torque converter that it’s not buried into the front pump of the trans. If the converter turns freely and you can slide the converter front and back at least 1/8 inch, you should be OK.

If you don’t have any endplay and the converter just turns, you will run into trouble when everything gets hot and the flexplate does its job and flexes! If you don’t have enough clearance, you could purchase a simple 1/8-inch scatter-shield block plant and mount it between the trans and engine. These block plates are used on manual clutch applications to prevent block damage when you have a clutch failure. This will give you the clearance needed to prevent the converter and pump from getting happy with each other. Check out Jeg’s for a Quick Time block plate (PN 698-RM-6011). Simply cut the lower section from the block plate that extends below the block.

Back to your converter bolthole alignment. We recommend elongating the holes in the flexplate with a high-speed grinder. You should have two bolt circle diameters on your Gen I flexplate. Pick the ones closest to your Gen III converter and open up the holes. The 4L60Es used four different diameter converters based on the engine and application. The smallest came in at 245 mm (9.65 inches) for most of the four- and six-cylinder applications. Then we have 280 mm (11.02 inches), 298 mm (11.73 inches), and 300 mm (11.81 inches). Based on the original application of your trans in a Chevy truck, it’s either the 298mm or 300mm variant. These would have the largest bolt circle.

The Gen III transmissions used a different length bellhousing, converter, and input shaft. If you ensure that you have the proper engagement of the torque converter into the transmission, and the proper clearance between the converter and front pump as mentioned above, you should have no problem. Enjoy those low revs during your highway cruising.


Drum Spindles

Q. My dad has a ’68 Camaro that he bought brand new and it came originally with drum brakes. A few years ago he found company called ECI that makes front disc brake kits that work with the original drum spindles without any modification. The kit number is EC723ACK. He would like to drop the front of the Camaro about 2 inches and was wondering if anyone makes a drop spindle for drums so that he doesn’t have to change his whole setup.

Jared Johnson
Rexburg, ID

A. Your dad is in luck. When modifying the front spindles of either an early Camaro or Chevelle to install ’69-and-up disc brakes, all you have to do is cut down the pad for the drum brake reaction pin. This threaded hole in the spindle must be milled down approximately 0.200 inch to line up with the factory disc brake bracket. We searched for ECI and were able to find a picture of the kit. It uses the factory-style, single-piston OEM caliper with a retrofit adapter bracket bolting to the drum brake spindle.

Digging through the drop spindles offered for first-generation Camaros we found that most of the manufacturers eliminate the bolt-on caliper bracket and forge a caliper mount integrally into the drop spindle. Also, most of them wanted you to use the later-model metric-type caliper, and 10.5-inch rotors used on the later-model F- and G-bodies. Heidts offers a factory-style 2-inch drop spindle that retains the bolt-on-style caliper bracket. Also, the upper ball joint mount is only lowered by 11/2 inches. This helps with handling by giving you a better camber gain curve as the suspension travels through its arc.

Finally, again, when installing factory disc brake on early drum spindles, you must machine off around 0.200 inch from the reaction pin pad. Since these spindles are for disc brakes, you will need to pick up a spacer to bolt between your ECI brake kit caliper bracket and the Heidts drop spindle. This should take care of any bolt-up issues. Enjoy your new stance and the handling the spindles have to offer.


Peanut Plugs

Q. I have a ’72 LT-1 short-block with a 350hp hydraulic cam from GM. The engine has 2.02-angle plug heads from 1972 as well. Which spark plug should I use? The engine is in my street-driven ’69 Camaro. Thank you in advance for your answer! I have six different answers from five different GM sources, including one who says they don’t answer tech questions any longer.

Jim Shelton
Gilbert, AZ

A. Opinions on spark plug heat ranges will vary greatly based on the application and mindset of the expert. Many advisers with racing experience will err on the colder side, and OE-type mechanics will tell you to run whatever the factory recommended. When you start bolting together non-stock engine packages, the plug heat range really doesn’t move that much unless you’re using forced induction or nitrous oxide.

Back in the day, the ’72 LT-1 was a very de-tuned original LT-1. It was equipped with flat-top pistons and 76cc combustion chambers, dropping the compression down to a smog-friendly 9:1 range. The original ’70 LT-1 was equipped with domed pistons and 64cc combustion chambers yielding 11:1 compression! The factory plug for the ’70 LT-1 was an AC 44TS, which was a nonresistor, projected-tip, tapered-seat peanut plug. You said the heads are around a ’72 2.02-inch intake valve, angle-plug cylinder head; those should be the “292” casting “Turbo” head. These were the high-performance, over-the-counter GM heads back in the day. They were all we had to work with to make power. The 350hp hydraulic camshaft was the 350hp 327 camshaft used in many of the ’66 and ’67 high-performance small-block applications.

Now for your seventh opinion. Based on the information you have given us, we’d use a plug very close to the AC R44TS. This heat range is a pretty cold street plug, with most of GM’s applications coming in at a R45TS heat range for small-block applications. The 44 heat range converts to a Champion RV12YC, Autolite 26, and a NGK UR4. Between these four choices, you should be able to find a plug you prefer.

If you get a wild hair and decide to pressurize the induction system on your Camaro or install nitrous, we would recommend going one to two heat ranges colder, based on the power you’re adding to your engine. Remember, power equals heat. The more power you produce the more heat you’re extracting out of the fuel. This heat is transferred directly to the spark plug, and if you overheat the plug it turns into a glow plug. Then nasty stuff starts to happen. Also, not all cars and applications are race cars! Enjoy your street-driven Camaro.

Imp Tires

Q. I want to upgrade the wheels and tires on my ’58 Impala. I plan to use stock-style steel wheels made by Wheel Vintiques (PN 62-573 4044). These are a 15x7 with 4.25-inch backspacing. The wheel openings and suspension are stock. I need to go to a 15-inch wheel because I plan to install power disc brakes on the front. I want to keep the old-school look with a painted steel wheel and dog-dish hubcaps.

My problem is trying to determine just how big a tire I can install without clearance problems. I tried looking for complete 15-inch tire and wheel packages to get an idea. Either the sites did not go back far enough on years, only listed Corvette, or had nothing but huge wheels. I looked up the specs (diameter and cross-section) for some of the recommended 16- and 17-inch tires, then looked up 15-inch tires with the same dimensions.

It looks as though I can install a BFGoodrich Radial T/A 225/60R15. The diameter is 25.6 and cross-section 9.0 when mounted on a 6.5-inch rim. Your thoughts and recommendations will be very helpful. Thanks.

Dave Toles
Via email

A. Boy, now we’re going on the way-back machine. At Flowmaster, we supported the lowrider crowd and built several different exhaust systems for the ’58-64 Impalas. These cars are very unique with their X-frame, which crossed directly under the center of the vehicle. This required the exhaust to be routed to the outside of the framerails. So what the heck does this have to do with your wheels and tires? In the rear, the tire and wheel must share space with the tailpipe, which runs through the rear wheelhouse as well! This is the most limiting factor for rear tire selection.

Your 15x7 wheels and 225/60R15 tires will fit fine in the rear with factory exhaust. One of the more popular exhaust exits is right in front of the rear tires, which opens up quite a bit of room in the rear for more rubber. When we designed the tailpipes, we moved them up and as close as we dared to the wheelhouse to give you the most tire and wheel clearance.

Upgrade your tire combo with confidence; they will fit with no problem. Also, get those brakes changed. Your ’58 isn’t a lightweight and it needs all the help it can get to be slowed down. Good luck.


Pickup in the Sandbox

Q. I have a ’76 Chevy C10 shortbed truck, “The Puzzle”, that I would like to do a budget build on. It currently has a 5.7L 350 four-bolt main with a TH350 transmission that’s all stock. Even though it’s the last year for emissions, I still needed to get it registered under my name so I revived it by doing a basic tune-up and carburetor replacement and passed California emissions with flying colors.

I would like to have the stock block rebuilt with Vortec heads, a Vortec intake for the Q-Jet 750 carburetor, and a COMP Cams camshaft. On the exhaust side, long-tube headers with Magnaflow dual mufflers and an X-Pipe. I would like to see maybe getting close to 375 for both power and torque, but I do have some questions: Is the Vortec intake manifold gasket shaped different than a regular intake gasket? Would a Fel-Pro 0.015-inch-thick rubber-coated shim gasket bump up the compression? Is there much of a difference between the 262 and 268 camshafts? Would you recommend I use a 1.6:1 rolled tipped rocker? Can I use the stock Vortec springs for the COMP Cams camshaft or purchase it as a set? I read somewhere to use black rubber press-on seals with white Teflon inner liners and to stay away from the all-white Teflon seals. Is there any truth in that? On the transmission side of things, would I have to change the stall converter for the particular camshaft or would you recommend I go ahead and see about getting the transmission replaced for a 700-R4, since the truck will see occasional daily use? How much of a difference do 13/4- or 15/8-inch long-tube headers make?

I know my questions sound elementary, but when you’re floating around looking for pirates, you don’t have too many resources. This will be my first engine build, and I’d certainly appreciate any guidance you can provide. I’m no expert but certainly know my way around a garage. Thank you for a great magazine! Keep up the great work.

CWO2 Isai C. Palacios
USS Green Bay
Deployed to the Sandbox

A. There are no elementary questions when it comes to the specifics of an engine build. You must get it right the first time or pay the price later. Let’s see if we can answer some of these important questions.

A Vortec upgrade to your stock ’76 short-block is a good foundation for the power level you’re shooting for. Yes, the Vortec intake gaskets differ from a standard Gen I small-block port and bolt pattern. The factory Vortec gaskets are plastic framed with silicone rubber-sealing O-rings built into them. We’d go with the Fel-Pro Print-o-seal gasket for the Vortec application (sold under Fel-Pro PN Z1255 and can be picked up from Summit Racing under PN FPP-1255). As for the 0.015-inch-thick head gaskets, they are only slightly thinner than the factory 0.018 steel-shim head gaskets that are originally used on your small-block. The main increase in compression is going to be from the combustion chamber reduction from 76 to 64 cc of the Vortec heads. Even the rubber-coated steel-shim Fel-Pros are very unforgiving to deck surface imperfections. If you wish to run a thin head gasket we’d recommend a factory GM composition 0.028-inch head gasket (PN 10105117). These gaskets were used on the iron-headed late-model Gen I small-blocks. Using the factory ’76 dished piston, these head gaskets, and the Vortec heads, you will have right around 9.0:1 compression. This will work very well with your build and pulling around your truck.

Moving onto your camshaft selection, we’d stick with the Xtreme Energy 262 over the 268. The 268 only has several more degrees duration over the relatively short 262, but it will build more torque to move your pickup and give you better driveability. You will still achieve your power goals with the shorter camshaft. It’s been our experience with the Xtreme Energy camshafts that COMP has pushed the valvetrain dynamics to the limit with a 1.5 ratio rocker. Going to a 1.6 only excites the valvetrain in the higher rpm, where you would expect to see a power gain from the increased ratio. Stick with the 1.5 ratio and go roller if you wish. It’s not necessary with your camshaft selection. When you set up your engine, use the complete camshaft package from COMP, with its hydraulic lifters, springs, and retainers. This matched package will give you trouble-free performance. The factory Vortec springs will not control the valvetrain with the Xtreme Energy camshafts acceleration rates. We’ve run Teflon valve seals for years with no issues. There are lower priced Viton seals with a Teflon insert that we’ve seen the Teflon come out of the seal. This happens when builders don’t check the retainer-to-seal clearance at max lift and the retainer runs into the seals. The best seals for street use are the OE-style Viton seals. They let just enough oil past the seal to lube the valveguide for long life.

On the transmission side of things, it depends how much money you have left after your engine rebuild. Yes, going with a 700-R4 would be great for an all-around cruiser/performance build. The stock converter in your TH350 trans will work with the Xtreme Energy 262 camshaft. This is where the 15/8- versus 13/4-inch primary tubes come into play. The 15/8-inch long-tube primaries will build more slow-speed torque below torque peak to get your truck moving. If you see any penalty at higher engines speeds it would only be a few ponies. Go with the 15/8-inch headers.

Again, thanks to you and your fellow Navy enlistees for keeping us safe and free, and hope you’re in the States soon. CHP


Hen’s Teeth

Q. I have a ’69 Chevelle. It had auto tranny shift on the column, and I recently converted to a floor-shift automatic. Can you help me find a place where I can purchase a sleeve to put over the column to go over where the original pin was? Thanks for your help.

Ray Samot
Via email

A. Surely, you’ve heard the term “rarer than hen’s teeth”? Well, 10 years ago you may have been able to find an N.O.S. shift collar for a floor-shifted ’69-72 A-body GM product. Those days are long gone. Just for giggles, we checked eBay and found one going for $40, which was a bargain! We also read that many people have hacksawed off the shifter spud on the collar and Bondo’d up the hole. They sanded and finished off the collar and painted it to the color of choice. No one was the wiser.

If you wish to step up to a very nice drop-in tilt-column, Flaming River has tooled up to reproduce the ’69-72 A-body tilt column for both column- and floor-shifted applications. Check out the mill-finished 33-inch tilt column (PN FR 30001), which comes complete with an ignition switch cylinder, the ignition switch, and a turn signal switch. This column is offered in mill finish, black powdercoated, and polished stainless.

Unless you have found that hen with teeth, we’d search eBay for a while and see if one pops up. If not, you have a couple of choices based on your budget. Enjoy your Chevelle!




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