The Mains Are The Priority: Priority Oiling
Mike O'Brien; via CarCraft.com: I was looking at an old issue of Car Craft and reading Jeff Smith's reply to a fellow on the LS oiling system. In the accompanying diagram, the oil system appears to furnish oil first to the valvetrain. Is there a way to make this a priority main system?
Jeff Smith: The short answer to your question, Mike, is yes, but not by modifying the existing block. It would be far too difficult and costly to convert the priority oiling of a production block over to priority main. If main bearing lubrication is a concern, the easiest solution is to purchase an aftermarket block. But before we get into that, it's worth noting that the original small-block Chevy and now the LS engine both use a similar system and neither really has a main bearing lubrication problem, even at elevated horsepower levels. For example, we ran a Horsepower! feature on a turbocharged LS engine that routinely makes more than 2,000 hp using an ERL-modified aluminum production block. Even with that kind of cylinder pressure pushing down on the main journals, the engine is happy and has no lubrication issues.
However, if priority main-style lubrication priority oiling is a necessity, you do have a couple of options. Among the iron block avenues would be the GM Performance Parts LSX Bow Tie block. This fully CNC-machined casting features much thicker cylinder walls that can accommodate up to a 4.200-inch bore, which is useful for increased airflow. The block is also machined for six head bolts per cylinder as opposed to the standard four along with a host of other features. Perhaps its biggest drawback is the weight penalty of additional iron that tags the LSX at 225 pounds, which is 20 pounds more than a production iron block (205 pounds) and roughly 125 pounds more than a production aluminum casting (100 pounds). The LSX standard deck height block is PN 19213964 and goes for $2,185.95 from Scoggin-Dickey.
RHS now offers a relatively new aluminum aftermarket LS block that is also a priority oiling main design. The RHS block is available with most of the features you would expect from a well-designed casting like this. A standard deck height block, bored and finished honed to a 4.165-inch size is PN 54902, and we found it on Summit's website at $4,615.95. Certainly, this is not cheap, but you also have, with a 4.165-inch bore and a conservative 4.00-inch stroke, a 436ci inch monster that normally aspirated has the potential to make more than 700 hp with a carburetor or fuel injection. Because airflow potential is so fantastic with the LS-series engines, you can make this power without a radical camshaft, making this engine completely streetable. Plus, you're looking at an all-aluminum block that only weighs 110 to 120 pounds (depending on configuration) and 100 pounds less than a production iron block.
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Solution For LT1 Ignition Woes
Charles Nel; George, AK: I am planning on fitting an LT1 and a six-speed to a mini-truck and gradually hot-rod it as the money allows. I see on some Internet sites that the Opti-Spark is considered unreliable. Is it possible to replace it with a "normal" distributor, and how would one go about this? Or are the sites wrong, in your valued opinion?
This is the EFI Connection optional billet timing cover on an LT1 engine at the Tuned Port
Jeff Smith: The LT1 engine is considered the Gen II small-block Chevy with quite a few differences between it and its older Gen I cousin. The most significant difference is the Opti-Spark ignition system. While this ignition is much maligned, there are several ways to address its shortcomings. GM engineers relocated the distributor from the back of the engine to underneath the water pump to drive it directly off the front of the camshaft. It appears that crossfiring and misfires are the most common problem and are attributed to moisture trapped inside the distributor housing. There were actually two versions of the Opti-Spark, with the early '92 to '94 version having the most difficulties. This is partly due to the lack of ventilation that allowed moisture to collect inside the cap area and also that the system wasn't sealed properly with an electrical connection located on the top that allowed dirt, oil, and moisture to enter the cap area. The optical sensor system used to trigger the ignition is actually quite accurate, with a 360-tooth wheel that doesn't suffer from issues such as cam walk and the tolerance stack-up that results from driving a rear-mounted distributor. One of the Opti-Spark's biggest problems is access, as the cap and rotor are buried behind the water pump, requiring removal of the pump and a portion of the front accessory drive. In essence, most of the problems associated with the Opti-Spark system can be traced back to the presence of high-voltage arcing within the distributor body. So it would stand to reason that any upgrade that would remove the high voltage would dramatically increase ignition system durability.
We priced a stock replacement cap and rotor for a '94 LT1 at Rock Auto and were surprised to find the least expensive kit was $189.00; a second kit from a different manufacturer was $257.00. Then we priced an MSD replacement cap-and-rotor kit from Summit Racing and discovered that both the early design ('93 to '94, PN 8481) and the later model ('94 to '97, PN 84811) were priced at $144.95. Not only are the MSD caps better, but they're less expensive, too. MSD also makes a complete Pro Billet replacement distributor (early PN 8381 and late 83811-both at under $500.00, Summit Racing). While pricey, this distributor offers a billet aluminum body, improvements on the optical encoder, and a different optical pickup compared with OE models. Perhaps its best feature is its ability to manually adjust ignition timing plus or minus 6 degrees with a small adjustment screw on the distributor. There is also another company, Dynaspark, building a replacement distributor that costs $599.00.
This is what the 24x EFI Connection reluctor wheel looks like mounted on the crankshaft.
Rather than convert to a rear-mounted distributor, which would require a different intake manifold, we've been investigating a far more creative way to eliminate the LT1's Achilles heel. There are a couple of companies that have taken innovative approaches to converting to a distributorless ignition system (DIS). The first from Bailey Engineering retains the original LT1 distributor and optical sensor. This sends a mere trigger signal to a microprocessor and wiring harness setup. The system connects to a set of LS coil packs that you adapt either to the valve covers, like an LS1 or relocate to a remote location and run slightly longer plug wires. The Bailey LTC-1 sells for $399.00 and includes both a rev limiter and an adjustable timing retard. While the system does not employ a cam sensor, the 720-degree system (a 360-tooth wheel turning at half engine speed) can extrapolate proper engine position so that all eight individual coils fire sequentially, just like on a stock LS1 ignition.
The second approach is by EFI Connection. This company also uses the LS engine coil packs, added a cam sensor, and applied it to LT1/LT4 engines. The first step is to eliminate the entire LT1/LT4 Opti-Spark distributor from the engine. Removing the front timing cover, you add an EFI Connection 24x reluctor wheel that slips over the crankshaft (you have to do some minor hub milling to compensate for the thickness of the reluctor) that fits under the stock timing cover and integrates with a GM 24x crank sensor. Next, the company supplies an LS1-style cam sensor that bolts to the front of the stock LT timing cover. This creates crank and cam position sensor inputs that are used with an LS1 computer to drive the eight separate LS-style ignition coils. You have to figure out where to mount these eight individual coils, and obviously, you need a separate, stand-alone computer wiring harness that will control the fuel as well as the spark on your LT1/LT4 engine. All this isn't exactly bargain-basement stuff; the base 24x hard parts are $525.00, an LS1 computer is $100.00, the EFI Connection custom wiring harness is $650.00, plus the cost of eight coils and other small parts. All this adds up to between $1,200.00 and $1,500.00, but you get the decided advantage of far better computer control. It will also require custom tuning to get your LT1 engine to run properly with the LS1 computer. EFI Connection suggests either HPTuners or one of the other aftermarket LS engine controller software programs that will allow you to customize your particular setup. EFI Connection offers a limited number of free program downloads that you can try at your own risk. One additional advantage is that the stock LS1 computer can also control an electronically controlled automatic such as the 4L60E trans. This eliminates the expense of a separate control box for the electronic overdrive transmissions like the 4L60E and 4L80E. This EFI Connection system can be used on a Gen I small-block Chevy engine as well, which presents the advantage of controlling an early small-block with a very sophisticated EFI system. Imagine the questions you'll get from dumbfounded onlookers when they see a small-block Chevy in your engine compartment with hidden coil packs and no distributor in the back of the engine. That alone might be worth the price of admission.
We'll leave you with a teaser that adding a DIS ignition system with eight individual coils creates much stronger spark energy at higher engine speeds, especially when used on large-displacement engines with strong cylinder pressures. The greater spark energy from eight individual coils just might pump up the peak horsepower by a measurable amount. We've got a test lined up on a normally aspirated LT1, and as soon as the smoke clears we'll bring it to you.
We saw this under the hood of an early Nash. Any clue what it is?
Autotronic Controls Corp. (MSD)
El Paso, TX
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Ft. Wayne, IN
Tuned Port Induction Specialties (TPIS)
We were invited to the launch of Ford's new Police Intercepto
Of Flywheels And Flexplates
Jake Dingman; via CarCraft.com: I have a 283 Chevy motor with the original flywheel and 10 1/2-inch clutch for a passenger car. A friend gave me a larger flywheel and 11-inch clutch out of a '78 Chevy truck. Will the larger flywheel cause an imbalance condition in my motor? Or will there be a loss of power and torque having to turn the larger-diameter flywheel? I do have a bellhousing that will work with either setup.
The small-diameter, 153-tooth flywheels required the straight-across bolt pattern (left) w
Jeff Smith: Wow, it's been a while since I've answered a question about the 283ci small-block Chevy. These are great little engines with a 3.875-inch bore and a short 3.00-inch stroke. Because they are displacement challenged, they don't make much in the way of low-speed torque. Most of these engines were backed by a Powerglide two-speed automatic, with a few manual transmission applications. This is an internally balanced engine, meaning that the flywheel, regardless of diameter, is a zero balance. All production small-block Chevys with a two-piece rear main seal, except for the 400ci small-block, were internally balanced engines. So given that, you can easily add a larger flywheel to a 283 without a balance issue. There are two basic small-block Chevy flywheel diameters, identified as either 153-tooth or 168-tooth. The smaller 153-tooth wheel typically used a 10.5-inch-diameter clutch disc, while the larger, 168-tooth wheel utilized an 11-inch-diameter clutch disc. The two flywheels (or flexplates when used with automatics) also require two different starter motor bolt patterns. The simple way to identify the starter motors is to look at the bolt patterns that attach the starter to the block. The starter motor intended for use with the smaller, 153-tooth flywheel will have two boltholes in parallel. The larger, 168-tooth flywheel starter motor pattern will use offset boltholes.
There are two things that will affect the use of a larger flywheel. First is the bellhousing size. Most small-block Chevy bellhousings we've run across are designed to be used only with the smaller, 153-tooth flywheel. There are factory bellhousings intended for small-block use with a 168-tooth flywheel, but they are relatively rare. You mentioned that you already have a larger bellhousing, so that shouldn't be an issue. The other potential problem is that since the 283 never came from the factory with a 168-tooth flywheel, it's likely the block will be drilled only for the parallel starter motor bolt pattern. The solution is to either drill the block for the offset bolt pattern or use an aftermarket gear reduction starter motor. Of those two solutions, the least expensive is to drill the block. If you are going that route, make sure the starter motor gear is properly lined up with the flywheel. The best way to do that is to remove the solenoid from the starter and engage the starter drive teeth with the flywheel to ensure the teeth line up. Then mark the hole with a transfer punch and drill and tap. This is much easier if the engine is not in the car, but it can be done in the vehicle if you are careful. You may even want to use an old starter motor nose piece as a drill guide.
What may be the biggest consideration is overall weight of the flywheel and clutch assembly. Keep in mind that your 283 doesn't make a lot of torque. In the small-cubic-inch gasser days, one way to get those little motors to launch was to fit them with a heavy flywheel, rev them to the moon on the starting line, and use the inertia force of all that spinning mass to help launch the car. We're not saying this was an efficient way of doing things, but it was fun to watch! This is hardly a practical way to drive a car on the street, which means a heavier flywheel will not accelerate as quickly as a lighter unit. You need some kind of compromise between too heavy and too light because an overly light system (like an aluminum flywheel) will accelerate very nicely but is a major pain to drive on the street because it lacks sufficient weight to store enough energy to move the car from a dead stop. So some compromise between papa bear at too heavy and baby bear at too light is what you need. A typical 10 1/2-inch flywheel, clutch, and pressure plate will weigh around 40 to 45 pounds. An 11-inch flywheel probably won't weigh significantly more, but it's worth weighing both just to make sure.
A Regal Small-Block
Tom Jackson; Buffalo, MO: I have an '85 Buick Regal with a 350 SBC, stock bore, crank, and pistons. It has the stock iron 882 heads with a three-angle valve job with Z/28 springs and the ports cleaned up. It also has a Summit racing cam with 0.465/0.488-inch lift and an Edelbrock Performer intake and Jet Performance Q-jet carb. The trans is a 700-R4 with a shift improver kit and 2,000 stall, and the rear is a 7.5-inch with a posi and 3.73:1 gears. I need better heads. I can get a set of Procomp street/strip Pro-series aluminum heads with 190cc runners, 64cc chambers, and 2.02/1.60-inch valves. My big question is, do the heads flow well and are they worth the trouble? I am on a pretty tight budget, and I'm not building a strip car, just a toy. If the parts are all right, I'd like to add an Edelbrock Performer RPM intake and change to a Summit Racing 0.488/0.510-inch lift cam. I'm hoping to add 100 horses. What do you think?
Uh-oh, custom vans are coming back.
Jeff Smith: Your choices are well thought out and should add power over a set of stock 882 heads. The Procomp 190cc intake ports are as-cast, and the company claims flow numbers of 227 cfm on the intake at 0.500-inch lift and 180 cfm at the same lift on the exhaust side. In this age of 300-plus-cfm flow numbers for rec-port LS engines, these flow numbers are a bit tame, as there are many aftermarket heads with 10 percent (or more) better flow numbers in the midrange valve lift area. The midrange flow numbers are of critical importance for your application because your cam does not reach 0.500 inch lift. This means that flow numbers in the 0.300- and 0.400-inch valve lift range are of far greater importance. The only price we could find on these heads was for bare castings at $312.99 each at Jegs. This makes a bare pair at $624.98. The assembled price will obviously be much higher, but it's doubtful you could assemble them yourself for less than the assembled price. One other point of improvement is that the 64cc chambers will bump the static compression over the iron-head, 76cc chambers. Estimating the deck height and head gasket thickness, it appears that this change alone is worth moving the static compression from 8.75:1 to 9.9:1. With one point of compression worth roughly 3 to 4 percent power, just increasing the compression should be worth as much as 14 horsepower as well as a similar percentage increase in torque.
The camshaft you selected is a Summit flat-tappet hydraulic with 234/244 degrees of duration at 0.050-inch tappet lift with the aforementioned 0.488/0.510-inch lift numbers ground on a lobe-separation angle of 114 degrees (PN 1107). This 114-degree angle between the lobes will reduce the overlap and improve the idle slightly, but it will still be somewhat lumpy. This is an increase in duration of 10 degrees over your current cam. I'd be tempted to swap the heads and intake first and see how much power these components will deliver before changing the cam. The thought behind this is that your current cam has less duration, which means it will help create more torque in the midrange where your car spends most of its time when accelerating. The longer cam will make more peak horsepower but might contribute to a slower e.t. on the dragstrip or less responsive acceleration on the street in the engine speed range you probably do most of your driving. As to your 100hp goal, it's a bit optimistic. We ran a similar test several years ago on a 350 Chevy with aftermarket heads offering similar flow numbers and gained 50-plus horsepower over a set of 441 iron heads. Your engine enjoys the advantage of a slightly bigger camshaft with more lift, and the Edelbrock Performer RPM intake could also contribute another 10 to perhaps 15 hp when combined with these heads. Your combo may deliver 65 to 70 hp over the stock iron heads, but that's about all you should expect. Since the heads continue to show a flow increase at 0.500-plus-inch lift, you might consider a set of 1.6:1 rocker arms to bump the lift. An increase from 1.5:1 to 1.6:1 generally will deliver an additional 0.030 inch of additional valve lift, which puts your smaller cam right around 0.500-inch lift, and with the bigger cam, you'll gain a little more.
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