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October 2012 Chevy High Performance Q&A

Light Fuel

Kevin McClelland Sep 4, 2012

An easy rant to get started on these days is the price of gasoline and diesel. It’s highway robbery what the oil companies and speculators are doing to our world, and hopefully someone will step up and take them on. I don’t think politicians have any desire to get this right. They have just approved another fuel in the United States that will make us lighter in the bank.

Tell me, do you want to buy fuel that will actually give you worse fuel economy, which will make you purchase more fuel? I didn’t think so! Well, we’ve been buying fuel called E10 for a couple of years now. It’s mandatory in eight states and many more states are adopting this fuel as time goes by. What E10 consists of is 10 percent anhydrous ethanol (anhydrous contains less than 1 percent moisture) and 90 percent gasoline. It is claimed that we’re doing this to get us off the dependence of imported crude oil, and to reduce emissions. Adding essentially 10 percent alcohol to our gasoline reduces the Btu content per gallon. Gasoline contains 116,090 Btu per gallon and ethanol has 76,000 Btu per gallon, so to achieve the same amount of power you must use more of this fuel blend. Late-model cars don’t have any issue with E10, as the fuel systems will handle the added corrosiveness of ethanol. Also, the EFI systems will adjust the air/fuel ratio to increase the fuel flow to run correctly. But here’s the rub: Our older, carbureted hot rods will begin to run leaner and need recalibration to run perfectly.

chp 01 O  Ocbtober 2012 Chevy High Performance Pqa 2/2

So that was E10. The EPA has now approved the use of E15 for passenger cars and light-duty trucks manufactured after 2001! The administration has set a goal to help fueling station owners install 10,000 blender pumps over the next five years. This will give stations the ability to blend levels of ethanol right at the pump. Again, this is all to get us off imported oil and reduce emissions. Well, I just read last week that since 2006 we’ve reduced the dependence on imported oil by like 20 percent! This is because we the people are parking our large trucks and SUVs and driving more economical vehicles. Also gas doubling in price over this period certainly helped change our driving habits.

Be on the lookout for fuel blend labels on your gas station’s pumps. It’s mandated by law that they post the blend of fuel you’re purchasing. Changes in your vehicle’s personality could be as simple as the swap from E7 or E8, which we’ve been running for years, to E10. It doesn’t sound like much, but when you’re on the edge of tuning, it doesn’t take much to effect the performance. Between smog checks and now blending fuels that are not compatible with our early performance vehicles, the environmentalists will get us to crush our cars if we don’t stick together. Go online, use your favorite search engine, and read up about E10 and E15. It’s all out there. Be informed.

Pump Gas Baby!

Q. I love reading your tech Q&A. I’m hoping you can help me with my car, a ’67 Nova two-door sedan that has run a best of 11.66. It has a 383 small-block with Eagle SIR rods and cast crank, KB pistons, cast-iron Pro Topline 220cc heads with 2.02/1.60-inch valves, 64cc combustion chamber, a Howards solid cam, 0.543/0.563-inch max lift with 252/260 duration at 0.050-inch tappet lift, a Super Victor intake, a Quick Fuel Q-series 750-cfm carb, an MSD Pro Billet and 6AL, and Hooker Super Comp 13/4-inch headers. The engine has 12.2:1 compression. We estimate the horsepower to be around 500. This is a street/strip car that I run 110 octane at the track, and premium with octane booster cruising around town. All the while I’m trying to keep rpm at a reasonable level. With rising gas prices I really would like this to be a pump-gas-only motor. Is it possible to do that by moving to a larger head that has larger 2.08 intake valves but keep power levels close to where they’re at? I don’t really want to lower the performance of the car and in talking to other people they act as if it’s not possible to build a 500-plus horsepower pump-gas 383. Do I need to look at a different motor combination? This is something I’ve wanted to do for a while but cannot get a straight answer whether to make my current motor work or do something new. Your help would be greatly appreciated.

Jason Ulrich
Via email

A. Tons of people out there will tell you that you can’t build good power on pump gas, and you certainly can’t run a race car on the stuff. They’ll tell you that it won’t repeat and that you’ll blow up your engine before you leave the burnout box. Well, we will have to disagree. We’ve been running race cars on straight pump gas since 1988. Many of them have been mild street engines, but three in particular have pushed cars to respectable e.t.’s and lived for years. Our first real venture into pump-gas race engines was with a Chevrolet Performance 502. Back in 1996, we took a dead-stock Mark IV Mercury Marine big-block and added a Crane roller camshaft, an Edelbrock Victor 4500 manifold, and a 1050 Dominator carb, and ported the stock cast-iron cylinder heads. This engine made 680 hp and 600 lb-ft of torque on the dyno. This was with only 8.9:1 compression! This engine ran for about 13 years and more than 1,400 runs. At this power level it produced 1.35 hp/ci—remember this number.

In the big-block world, we’re running a 524 BBC. It has some major upgrades over the original 502 with Dart Pro One cylinder heads, Dart manifold, and a slightly larger Crane camshaft that comes in at 270/276 at 0.050-inch tappet lift, 0.756/0.756-inch max lift, ground on 112 centers. With this engine we pushed the compression up to 10:1. At a mild 32 degrees of spark timing it’s producing 800 hp and almost 700 lb-ft of torque. To date this is our best power per cube at 1.52 hp.

Finally, the mild small-block in our son’s wagon is a 354 cid with a set of LT4 heads that we’ve warmed over, a Chevrolet Performance Hot camshaft, and a Chevrolet Performance LT1/LT4 dual-plane manifold. We pushed everything on this puppy and the compression is up to 11:1! This thing—with its very mild camshaft—produced 466 hp and 444 lb-ft of torque on the pump. With the very mild combination, that’s still 1.32 hp per cube.

We wouldn’t be afraid of reconfiguring your 383 to run on Chevron’s finest. I would recommend going with a slightly smaller inlet runner than the 220 cc you’re currently running. Pump-gas engines are like tractors. They like to run between 5,000 to 7,000 rpm. Tim Wusz of Rockett Brand Racing Fuels taught us years ago, when he was the chief fuel engineer at Union 76, that pump gas isn’t very stable above 7,000 rpm. We’ve always respected his advice, kept the combinations within these limits, and have been very successful. Look into a set of aluminum cylinder heads with 210cc inlet runners, and 76cc combustion chambers; these chambers will drop your current short-block’s compression ratio down to 10.5:1. You will want to keep the engine temperature under control and not run it at high loads much over 170 degrees coolant temp. Start with the total spark timing in the 28-30 degree range. After you’re comfortable and not experiencing any spark knock, you can advance the timing in 2-degree increments until you don’t gain any miles per hour at the dragstrip. We’d even recommend when you find the best mile per hour drop the timing 2 degrees for added level of safety margin.

Back to the 1.35 hp per cube. Your 383 comes in at 517 hp at 1.35 per cube. If you take the LT4 small-block at 1.32 you’re still producing 505 ponies. Again, this shouldn’t be a problem. Good luck with your little Chevy II and let us know how it comes out.


Plug It

Q. I am trying to find the right spark plugs for my car. It is a ’69 Nova 307, bored 0.030 inch over, with a Torker intake with a Holley 750 and headers. The cam is just a little above stock, and the heads are ’80-85 305, cast number 14014416. Can you help me with this?

Bert Oglesby
Via email

A. The production AC spark plug for your small-block with the later-model cylinder heads would be an R45TS. This is a moderately hot plug that will keep clean and shouldn’t give you any issues with your mild build. If you wish to run a slightly colder-range plug that would be a R44TS. Again, these are ACDelco spark plug numbers. You can convert these plugs into any flavor you wish. We’re partial to NGK plugs as they are relatively inexpensive yet very well made. The NGK cross-reference for the R45TS and the R44TS is covered by one plug: an NGK UR4. You can pick these up at any of your local chain auto parts stores. If you watch the Sunday paper for ads you’ll find one of the big boxes with them on sale. Happy hunting.


Totally Tubular

Q. I just read the header shootout from the Feb. ’09 issue. I am building a 0.030-inch-over 400 small-block for 5,500 rpm and below, with Edelbrock E200 heads, an RPM Air-Gap intake, a 650HP Holley DP carb, a COMP Cams 264H hydraulic roller cam, and 1.6 roller rockers. This will be backed up with a 700-R4 trans with a 2,600- to 2,800-stall vigilante lockup converter. I bought the 11/2-inch Flowtech mid-length headers but am having second thoughts that the diameter and collector are too small. Any new thoughts since the article? Do you have any thoughts on header selection?

Mark Hutch
Augusta, GA

A. I agree with you that the 11/2-inch primary mid-length headers wouldn’t be the best choice for your engine build. The mild 400 small-block builds we’ve been involved with always ran the best with 15/8-inch primary long-tube headers. You really need to have a pretty substantial build before the 13/4-inch primary tube headers give you enough horsepower gain upstairs to make up for the torque gains made in the meat of the torque curve with the 15/8-inch headers.

Not knowing the chassis you’re dropping your small-block in, please go and check out the Holley/Flowtech website and pick out a set of long-tubes for your build. You’ll be much happier with the finished product.


Greetings from Finland

Q. I have a problem with my boat engine backfiring upon acceleration. A broker bought the ’97 Sea Ray from England, and it appears the engine had been swapped at some point, and is now a ’98 Mercruiser 250hp 5.7L (type 4311025LS). It was a pleasant surprise, as the ’98 got Vortec heads, Thunderbolt V ignition with a knock sensor, and hydraulic roller cam. The boat only has 240 hours on the odometer, but the engine might have more hours on tap. It sometimes backfires at cold start, or when accelerating from idle, again usually cold. I suspected a vacuum leak but couldn’t find any. I overhauled the two-barrel Merc carb, but there wasn’t anything wrong with it, and the accelerator pump worked fine. Ignition timing is spot-on, 10 degrees with the timing lead grounded. I browsed through the documents that followed the boat, and found a service report stating the intake manifold gaskets had been replaced because of a suspected vacuum leak. Obviously, that didn’t cure the backfire. What else should I look for that would be causing the backfire? Also, the idle quality is not as good as I’m use to. Could this be spark related? Kind regards.

Jyrki Pykari

A. GM built some very special engines for Mercury Marine over the years, offering some very cool small- and big-blocks. The engine you have in your boat is a mix of truck parts, special Marine hydraulic roller, and carbureted technology. We believe you have a lean condition causing your backfiring at cold start and accelerating from low engine speeds while cold. What type of choke control does your carb employ? Is it electrically controlled by heating a coil that unwinds as it heats up and opens the choke blade or does it use some other type of external heat to open the choke? As you know, the Vortec heads do not have an exhaust crossover, so we suspect it’s an electric choke arrangement. Your backfire could be related to the choke and how quickly it’s opening after cold start. Also, if you have the ignition on for a period before starting the engine, it could be preheating the choke coil, causing the choke to be out of time for the temperature of the engine. Also, we’re sure Mercury uses some type of vacuum-assisted choke pull-off. This could be out of adjustment, causing the choke to be pulled open too far when the engine starts. This will also give you lean bog, or backfire when pushing into the throttle.

You also mentioned that the idle quality isn’t up to snuff. Yes, this could be a vacuum leak, or that the carburetor idle circuit is adjusted too lean. Most of the later-model carburetors had either plastic caps or stainless covers placed over the idle fuel screws to prevent adjustment. Remove whatever is preventing you from adjustment and set the idle fuel of the engine hot with a vacuum gauge. Connect a vacuum gauge to a manifold vacuum source and adjust the idle fuel screws with the engine at operating temperature until you can achieve the highest idle vacuum. These adjustments are identical to what we’d recommend for both the choke and idle circuit on any carburetor.

Finally, you could have a vacuum leak at the intake manifold gaskets. We’d re-torque the intake manifold bolts and try adjusting the choke and idle fuel screws. If you cannot bring the idle quality in line with the idle fuel screws, you’ll need to dig deeper to find your vacuum leak. Good luck, and happy boating!

Drive Like Granny

Q. I just picked up a ’71 Chevelle Malibu with 41,213 miles. It was an older woman’s car, used for church and local errands. It has the 307 with a Powerglide trans, A/C, P/S, and power drum brakes. I have a distributor out of an ’83 Camaro Z28 305 engine. I was thinking of getting rid of the points distributor; I am not positive if that would work or I should invest in an MSD unit. Also, is it worth it to change the intake and carb if it runs great? This would be in the future, since money is tight. I also have a 350 with four-bolt mains. I forget the exact year, but it is a one-piece rear main seal and would also be a consideration on the intake and carb for a future build.

Also what size wheel and tire combos fit? This is not my first Chevelle—I’ve had about 15! I think I remember having 15x8 Corvette Rallys all around with 235/60-15 tires. I was thinking of going with old-school Cragars with 15x8 all around, or 15x7 just in front. Thanks for your help.

Jim Mangano
Via email

A. Fifteen Chevelles? That must be some kind of record for one guy! Which one did you like the best, and what would you do to get it back?

At its age, with only 41,000 miles on the clock, it probably rarely got up to operating temperature, and we’re sure it has quite a ridge at the top of the cylinder wall from the wear of the top piston ring. The first time you really want to air this thing out, the pistons are going to travel into uncharted territory at the top of the cylinder and break the ring lands on the piston. I’m sure that it will run forever if you drive it like its past 41 years. If you want to hot-rod your 307, make sure you’re ready to swap out the 350 you have in the garage.

Swapping out to a later HEI distributor isn’t that big of a deal. First, you will need to make sure you have a non-computer–controlled HEI. The ’83 Camaro was the second year of Electronic Spark Control (ESC), and the computer controlled the spark timing. It’s very easy to identify if you have an ESC distributor, since it doesn’t have a vacuum advance canister, and will have a wiring pigtail coming from it with a four-pin weather pack connector. If you have a standard mechanical advance HEI with vacuum advance, it will drop right into your 307. The only mod you’ll need to do to your wiring is to remove the resistance wire from the engine harness and replace it with a standard 12-gauge wire. This resistance wire is in the engine harness from the firewall bulkhead to the coil positive terminal and is used to reduce the voltage delivered to the points ignition. It will be the cloth-wrapped wire in the harness. You will need to remove the spade connector from the bulkhead connector and solder the new 12-gauge wire to the connector. Then, reinstall it into the bulkhead. This wire will then feed a full 12 V to the HEI with a full 12 V.

Finally, 15x8s will fit all the way around your Chevelle with ease. Also, they will drop right on with the standard 4-inch backspacing from the 15x8 Corvette Rallys. If we were buying a set of Cragars for your ride we’d go for a little more backspacing to give you more clearance for the front tires. They will get a little tight on turns with the on-center backspacing. Cragar offers the 15x8 SSs in a 4.25-inch backspacing. Also, we’ve run as large as a 255/60-15 tires on ’70-and-up A-bodies. The wheelhouses and rear-wheel openings are larger than the ’69-and-earlier models.

Hope all this helps with your budget enjoyment. Yes, a full MSD Ignition setup would be the bomb. If you can recycle parts out of the garage for a while, you can enjoy your Chevelle while saving your pennies.


Positively Ventilated

Q. I have seen the short answers about PCV systems. I would like to hear from a professional. I think a PCV system is a must-have for evacuating acidic and moisture-rich vapors from the crankcase. On the other hand, at WOT and near 0 inch of mercury, the PCV ceases to exist and oil (crankcase vapors) emits at the breathers. I am aware of the guys who build with low-tension rings and compensate with crankcase vacuum. I think a simple solution is a remote breather that won’t puke oil on hot headers and catch fire. Or design an engine with no blow-by. What’s your take on this?

Al Caskey
Cortland, NY

A. You’re spot-on, Al. The best, for many reasons, is a no-blow-by engine. It’s amazing what the OEs have been able to do in the past decade with cylinder wall finish, piston ring design, and piston ring land configuration. When it’s right you have just about a zero blow-by engine. They had to do it for emissions regulations and they ended up benefited by increased performance and durability.

The positive crankcase ventilation system utilizes engine vacuum to evacuate crankcase vapors from the engine and ingest them with the intake air and fuel. You’re correct, as the engine vacuum drops (increase load) the PCV becomes inactive and all the ventilation is through the breather system. This is true at WOT, but we drive our cars on the street 99 percent of the time in high-vacuum conditions, which purge the crankcase of vapors through the PCV.

To reduce emissions, the vehicle manufacturers had to reduce the amount of this pressure, as it brought oil vapors from the crankcase and burned it in the combustion process. This was done by improving the cylinder wall finish in both the texture of the honed wall and the straightness and roundness of the cylinder. This made it much easier on the piston rings to follow the cylinder and seal. This allowed the ring designers to reduce the thickness and radial tension of the ring. This increased engine performance by reducing the parasitic loss of the rings dragging up and down the cylinder walls. Everything listed above was a major benefit. We’re down to production engines with 1.2mm-thick top and second rings with 3mm oil rings. To give you some idea how much of a reduction this is, a standard old-school small-block Chevy had 5/64-, 5/64-, 3/16-inch ring packages. If you convert this, a 5/64 ring equals 0.078 inch and a 1.2mm top ring equals 0.047 inch! That is a huge reduction in mass and drag.

In a performance, non-emissions application, an external breather for the crankcase is a simple solution. The main thing you need to make sure is that your engine oil reaches 212 degrees all the time to boil off the moisture that builds up in the engine oil from condensation. This is mostly where the vapor comes from on a properly sealed engine.

Yes, a zero blow-by engine is the best to keep the combustion gases from contaminating your engine oil. Total Seal top piston rings are the best we’ve come across for attempting this goal. They are great for racing engines, but for an everyday street car you may be lacking the long-term durability. Total Seal has two-piece top ring packs for just about every engine combination today. Keith Jones is a good friend who’s been at Total Seal for the past 12 years. He’s spec’d out every set we’ve used, and they do deliver on their name. Give him a call at 623.587.7400 for more information on your application, and he’ll give you the straight scoop. CHP




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