Balance Of Power :Decision '07

Balance Of Power :Decision '07
http://images.highperformancepontiac...check_list.jpgLike most election fodder, many issues that lead to poor consequences with engines stem from small details and missed opportunities. In our case, a $7 thermostat caused the failure of a 40-cent freeze plug on the back of the block (inside the bell housing) and toasted an otherwise perfectly serviceable L-98 350 TPI engine in our '88 Trans Am. Since we were destined to either replace or rebuild the smoldering remains of our engine, we needed to research all of our candidates' qualifications, sorting through so many campaign promises for the hard information before we elected an engine combination that we could live with in the long-term. We weighed the major party platforms, which included cut our losses and rebuild stock, go with a crate engine, or do a complete performance build. We chose the latter.
Since making these choices can be a daunting task, we decided to take the reader through our decision-making process and offer solutions for many situations that hobbyists may face while taking into account price and fitment issues specific to the L98 powerplant.
The first step for making these complicated decisions is to list priorities, and thus the options begin to sort themselves out according to your wants and needs. As with political candidates, you must do some digging to find the important details.
Soon, a number of pitfalls and obscure fitment issues hinging on the intake manifold/heads arose to repudiate our original budget limit, thus requiring an increase of financial and other resources we had not intended. Follow along as our detours lead us to a more expensive and hopefully much more fruitful plan and build up.
The priority going in was to see if we could find 350 rwhp while not exceeding $5,000 total on the entire package. Though we have a few decent solutions that could bring those results, they would come at a compromise to the quality of parts in the bottom end, which wasn't acceptable.
Our other objective was to try and improve efficiency, as our previous exhaust upgrade had delivered just over 200 rwhp but at a marginal 16 mpg. We wanted to squeeze closer to 20 mpg out of the old girl. This will be a challenge with the 700-R4 automatic transmission, so our priorities rank exactly in that order: power, budget, then mileage.
The Incumbent
Our '88 Pontiac GTA's 350 TPI engine has been tinkered with during several previous HPP fact-finding missions, and we found a lot to like and dislike about this candidate. Powered by the first major redesign of the venerable Chevy 350, this is a one-piece rear main-seal block and has longer lifter bores and cast-in mounting bosses for the hydraulic-roller cam spider, so the block and crank don't interchange with older small-block Chevy units.
This incarnation also includes heads with center-mount bolts for the valve covers, and the center two bolts on the intake manifold to cylinder head are at a 72-degree angle (as opposed to 90 degrees for all earlier heads). Although this is a distinction of the '87-'95 engines, an earlier head can be used on this block with an earlier manifold, or the later '96-'02 Vortec heads will also bolt on with a Vortec-pattern intake manifold. So, even though we have a small-block Chevy to work with, in reality, there are just enough differences that most of the key components won't interchange.
Although the L98 was regarded as a performance engine in it's day, GM missed the boat on a performance head by a wide margin. Unlike the Corvette L98's aluminum heads, the F-bodies came with cast-iron heads featuring press-in rocker-arm studs and no guideplates. They instead employed machined slots to guide the pushrods, resulting in pushrod interference with any rocker arms over about 1.60:1, even with the stock cam. These iron L-98 heads have only adequate ports and Fred Flintstone-era combustion chambers.
Since our estimate for upgraded valves, springs, and related hardware; a three-angle valve job; and a port and polish of these heads came in at approximately $900, it seemed logical to push the budget and ditch the incumbents for some state-of-the-art performance heads that would give us substantially more power. However, this will require the replacement of the also-restrictive TPI manifold base-not just because it becomes the power bottleneck, but it also won't fit most of the good cylinder heads due to the strange 72-degree angle of the center two intake-to-head bolts on either side.
The block is a decent part and will hold up fine at our target power rating of about 420 flywheel horsepower without needing any special treatment apart from some girdling of the main area, so it will be retained. Though the nodular-iron crank would also be adequate for our power target range, upon evaluation of our other options, we found that we can upgrade to a new 3.75-inch cast stroker crank (stock is 3.480 inches) for this application quite economically. We would put about $50 into the stocker in machining anyway, so it's hard to argue against an additional 28 ci for about $150-$370, depending on the crank selection.
It's money well spent from a power/torque standpoint, but this will substantially increase the load on the bottom end and increase piston speed. The bargain crank, rebuilt stock rods, and cast pistons would be OK if we can keep the rpm down, but higher rpm is what we need to make power, so we'll need to upgrade in this area as well. Since the parts we are considering seem to be headed over our budget, we considered swapping in a decent crate motor.
A Turnkey Candidate
A quick search on the Internet gave us a new candidate: the Golen Engine Service 383ci/405hp TPI long-block (www.golenengineservice.com). This package is designed to replace a 305 or 350 engine under the TPI induction system and carries a price of $5,199 for the long-block (not including intake, water pump, distributor, and so on). Rated at a healthy 405 hp and 495 lb-ft of torque, it's almost double the power of the stock 350.
The component choices in this crate engine are aimed at an efficient and powerful daily driver or street car, and the use of HD performance cast pistons and crank is a logical choice to make if the engine won't be raced regularly or fed significant doses of nitrous.
Golen definitely went top-drawer with its choice of Air Flow Research 195-L98 pattern heads and the Comp Cams 112-degree-lobe-separation cam (the stock one is 117), spending money where it will be of most benefit to power production. The dyno chart on the site has the engine running with a smog-legal TPIS base and runners and a 52mm throttle body, so don't expect these figures with your stone-stock intake. Golen Engine Service recommends PCM's for less to supply a tuned chip for your individual combo, and if all external smog components are present and functional, it should pass smog.
Shipping an entire engine from Hudson, New Hampshire, ranges from about $250 to New Jersey up to about $450 to California. Although we are going to see what we can come up with on our own, the Golen engine would be a great value to readers in similar situations.
Budget Bullet Building Block
On the tight budget side of things, to restore the engine to health with minimum fuss and expense, we vote for the GM Performance Parts 12556121 350 Partial Engine. This short-block is brand new and features hypereutectic pistons, powdered metal rods, and a nodular-cast crank in a four-bolt main block with all bearings and brass freeze plugs installed. It lists for $1,153.95 from Jim Pace Pontiac, and that price includes shipping!
To bring our 350 back to health (or upgrade a 305-powered car), we could have purchased a new oil pump, gasket set, and a performance camshaft and timing set. The stock heads could have either been rebuilt or replaced with iron Vortecs (with caveats, see Heads of State below). With 64cc chamber heads, this engine will yield a compression ratio of 9.1:1.
If your intention is to just build a stout 350 for daily use, this would be an excellent core to build on as all ancillary items down to the hydraulic roller lifters and spider from your engine can be reused in this block.
As value for dollar goes, this one is a hands-down winner. You can see more and order direct from the Jim Pace Web site, www.paceperformance.com. Though this choice is tempting, we will still build our own.
Heads Of State And An Intake
Our choice of cylinder heads will be critical to the power output. We evaluated a number of heads, and the consequences of ditching the stock L-98 heads requires a change of lower intake as well, adding another $400 to the equation. (This cost is not included in the Golen engine. It uses heads compatible with the restrictive stock intake.)
On a cost/value scale, we've heard many times that the Air Flow Research heads are not in the bargain-basement range but are among the best for making power. AFR makes both the SBC- and Vortec-pattern heads, and both list at the same price ($1,399 a pair) for 180cc intake-runner volumes. Although we feel confident these 180cc intake heads would produce good power numbers for our planned 383, we would probably opt for the larger-volume 195cc AFRs for the same price, although they are only available in the older SBC intake-port design.
One of the early, popular front-runner candidates for the office of cylinder heads is the venerable iron Vortec (truck) heads by GM. These heads are very well respected for their performance potential. Very good low-lift flow and highly efficient combustion chambers offer excellent power potential. However, as built by GM, these heads were intended for pickups and SUVs, so they aren't designed for higher-lift cams (the spring pockets must be machined for any cam that will give more than about 0.460 valve lift). Add to this that they come with press-in studs and will need guideplates, and the price of disassembly, machine work, and the hardware goodies moves what would have been the most cost-effective heads into the $1,000 range. In addition, they require a Vortec-pattern manifold. Although still several hundred dollars cheaper than any of the aluminum heads, they just don't seem as good a deal when we factor the results of the upgrades into the price.
We also looked into the Avenger and Edelbrock E-Tec heads. The Avengers are fully CNC-ported, aluminum heads, similar to the AFRs, at $1,299 a pair, and advertise similar airflow numbers. We only know of two engines built with these heads, and they have reported surprisingly strong power figures. They look good and seem to perform well, but there is the "unknown" factor working against them, and they don't include guideplates, which we need for our Harland Sharp roller rockers. If you root for the underdog-especially one that has been extensively modified and developed-check out the Chevy Avenger heads at www.avengerheads.com
Since we have accepted the fact that we will need to replace our intake base no matter what heads we use, why not go with the newer Vortec pattern but in a modern aluminum head designed for performance valve-lift numbers? This led us to the Edelbrock E-Tec series heads, which are not CNC-machined but otherwise carry the modern centrally placed spark plug, big valves, screw-in studs, and guideplates, all installed and ready to go. Edelbrock offers the E-Tec series in both a 170cc intake-runner design and a 200cc version. Since we are looking at upgrading to the 383-cid version of our small-block, we decided to opt for the 200s and the matching Edelbrock Vortec TPI intake.
Pistons And Rings
The pistons don't receive a lot of attention from horsepower junkies, but professional engine builders spend considerable time and effort on them. Perhaps most critical for power, weight saved on the piston causes a cascade effect throughout the engine as the connecting rod can now be lighter, the crank pins can be smaller, everything is less stressed, and the engine can spin higher with less energy expended.
Another consideration that pays dividends in both performance and economy is ring seal. Remember, the rings seal on the cylinder wall and against the piston ring lands as well. Our research brought us three distinct options in price. Since we will be making enough power and our strokers' piston speed will be punishing to our candidates, we set our sights pretty high for this critical component.
Coming in at a great deal for a set of pistons and rings are the venerable KB hypereutectics. The term hypereuctectic refers to an excess of silicon in the aluminum alloy that forms crystals, giving the pistons better thermal properties, allowing tighter tolerances and keeping the heat in the top of the piston. A full set runs about $260 including pins and rings. Although they're cast pistons, they have proven to be durable and efficient.
Our next level of pistons is the Mahle power pack. These are a fully detailed forging with many expensive options and a Formula One pedigree. The technology used to attain better ring seal and lighter yet stronger pistons is quite impressive. As we learned more, we appreciated where the extra money goes for these. We chose a fully matched set that runs about $600 with rings, pins, and locks.
The final level is represented by Ross Racing Pistons. If you are a serious racer and are committed to the optimum combo, Ross pistons are custom-made to order, and the company has computer maps of most high-performance head's combustion chambers to be able to deliver the maximum compression ratio or valve clearance for any combination you want. These pistons are designed specifically for the application, so there are no "shelf" pistons for our use. While we just can't justify space shuttle technology for our TPI Trans Am, it's nice to know where it is if we need it. Prices vary substantially with different designs and features, but if you are looking for big horsepower-adder pistons that need to hold up to racing abuse, Ross Pistons would be the obvious choice.
Spare The Rod, Spoil The Engine
The rods really should be considered along with the crank, but frankly, there are a lot more options here than we could possibly deal with in the scope of this story. This is one of the places where the part is 100 percent interchangeable with a small-block Chevy, whereas the crank is specific to only a few corporate blocks, so our options on the connecting rods are plentiful and reasonably priced. We won't split hairs here by offering even a fraction of the choices before you, but we would like to go with a rod that is as long, strong, and light as practical at around $350 for the set.
As this is such a critical component in the longevity of the build, we were wary of low prices. We consulted with our friendly engine builder, Troy Bowen at Pacific Performance Products. He cleared the air by recommending an RPM International forged crank and either its I-beam or H-beam, 6-inch, forged connecting rods. Since RPM International doesn't sell direct, we placed our order through Pacific Performance Products, which went with H-beams for their twist resistance and clearance for the stroker combination in the block.
Crank Shaft
As we intended to sack our incumbent 3.45-inch-stroke cast crank in favor of a 3.75 stroker, we selected several candidates for evaluation such as the budget-minded Ohio Crankshaft 3.75-inch-stroke, nodular-iron cast crank with a 1pc rear main seal ($195) and a Scat "lightweight"-cast, 3.75-inch stroker crank ($231). Each would give us a substantial increase in torque, and since the 383-cid stroke version of the SBC has enjoyed so much development, we have a lot of information on what to use with this combination.
Our next option is to upgrade to a forged-5140-steel, 3.75-inch stroker crankshaft from RPM International ($369, which we ultimately chose) or a Scat 4130 forged-steel, 3.75-inch stroker crank ($630), and on up to the beautiful Callies CompStar 4340 forged-steel crank ($730). Obviously, there are significant differences in the quality and finish of these cranks, the most important being the quality of the forging, consistency and accuracy of heat treat, quality and detail in machining (which often creates a substantially lighter crank), and optional coatings.
For a show or strictly street-performance car, the cast crank will be fine for your needs, as we've been told that a good pearlitic iron-cast crank can support well over 500 hp. Keeping in mind that cast-iron and lesser steels are also more brittle materials, and when it does let go, it comes apart with gusto, we emphatically recommend that for all-out racing, a builder will never regret spending the extra money on the high-quality forging. Know your needs and cast (or forge) your vote.
Camshaft
At long last, we get to perhaps the most critical key of this combination besides the heads: the camshaft. Our stock cam is a power killer, even in this wimpy-headed engine. Its lobe-separation angle is 117 degrees, which the factory decided was necessary to pass smog requirements, but there is such little overlap that it kills all high midrange-and-up power potential. Troy suggested we go with a Comp or Crane camshaft, and spec'd it for our combination at 225/228 degrees of duration at 0.050 with 0.560 net lift using 1.6-ratio rockers. He also emphasized that we needed about 112 degrees of lobe-separation angle to both pass smog and also enable our combo to rev a bit.
The Cabinet
Since we have the "big" parts out of the way, all that is left is the smaller necessities that make the package work and pretty much blow our budget out of the water. We will probably swap out the included springs on the Edelbrock heads for the proper Comp Cams parts.
Since Pacific Performance Products is a complete machine shop as well as cylinder-head development shop, when we get the E-Tecs apart, we want to put a professional eyeball to them and see if there are any easy gains to be had. Jay, Pacific Performance Products' cylinder-head guru, stated that a racing valve job and a little detail around the bowls can often bring easy gains even on well-developed production heads.
We will also use an oil pump from Dynamic Performance, a Pro Gear timing set, one of Pacific Performance Products' main girdles, a Milodon oil pan to make room for it, Harland Sharp roller rockers, Comp Cams pushrods, stock-style lifters, Fel-Pro Gaskets, and Michigan Racing bearings.
HPP Proposed L98 Buildup
We cannot bring ourselves to cast our vote for the safe, smart easy way of doing things, as we would certainly not be pushing the envelope of info-tainment that our courtship with performance disaster all too frequency brings us. No, our target is to try and beat the power output of the Golen crate engine while building a much stronger bottom end. Unfortunately, Golen has spent its money wisely on Air Flow Research heads and has lost little to no power in the bottom end and thereby saving enough cash to pay for those AFR heads. So we are prepared to be beaten in cost per horsepower, but we have a bottom end that can withstand a dose of giggle gas in case our evil intentions get the better of our already questionable judgement.
In retrospect it would have only cost about another $150 to upgrade to the fully CNC-ported 190 Air Flow Research heads, but we just had to stop somewhere, and that money offset the additional cost of the forged crankshaft over the cast, and upgraded rods, as well.
Any of the other heads would also have been a good choice, but we had decided to go with the taller-port, Vortec-style E-Tec heads after seeing the performance numbers of both iron Vortecs and of the yet-taller-port LS series engines.
The chart below lists the parts and adds up the approximate cost, and it sure added up fast. We just lost our morning trip to Starbucks for the next few years, but we think it'll be worth it. Now we have to start collecting this stuff for a future buildup.
L98-BUILDUP PRELIMINARY PARTS LIST

DESCRIPTIONCOSTSOURCENOTESGM iron L-98 blockN/AN/AStock original engine blockEdelbrock E-Tec 200s$1,140 SummitRequires Vortec-pattern manifoldEdelbrock Vortec TPI$450 SummitHi-flow to adapt Vortec-style heads5140 forged crank$369 RPM Inter./PPFillets on bearing surfaces requires race bearingsForged H-beam rods$369 RPM Inter./PP6-inch, forged-steel rodsMahle forged pistons$550 Pacific Perf. Prod.Double-coated, includes pins and ringsMichigan bearings$100 Pacific Perf. Prod.Special racing bearings for fillet-machined cranksFel-Pro gaskets$80 Pacific Perf. Prod.Not the place to save money-trust meCamshaft$290 Comp CamsHydraulic roller cam1.60:1 roller rockers$210 SummitHarland Sharp true rollersBalancer/damper$53 Pacific Perf. Prod.ProGrearDynamic oil pump$80 Car Shop, IncCheap insurance!Milodon 7-quart pan$270 SummitIncludes pickupMain cap girdle$170 Pacific Perf. Prod.Build it onceMachining and assembly$1,200 Pacific Perf. Prod.If you assemble it yourself, deduct about $600Total$5,330
Remember, engine parts are heavy, so shipping can be expensive. If you buy mail-order, you must include this in your budget as well. Keep in mind a local shop will be paying your shipping for you when they quote you a price, and returns or problems are much easier to deal with.

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