Nathan Seabaugh, Northern Illinois: I am building an engine for my '89 Chevy K2500. This is my daily driver/tow rig/off-road truck. I was hoping for about 300 hp while still retaining the factory TBI setup. I am flexible with going to a carb setup but would still like to use the stock heads. I have a good standard-bore, two-bolt-main 350 to start with that is assembled with a factory lower end and cam. I also have the carb intake to match the factory TBI heads if needed and a set of long-tube 15/8-inch headers. I know I need to swap out the cam to make some power, but what can I realistically expect while using stock Chevy K2500 heads and TBI? This Chevy K2500 engine is going to be in front of an NV3500 trans, an NP241 transfer case, and factory 4:10:1 gears. Can I make that much power with a $1,500 budget and the parts I already have? Or should I save a little more money and get a set of Vortec heads and a new intake manifold?
Jeff Smith: There are several ways to go about your Chevy K2500 setup, Nathan, by remaining with the original throttle body injection (TBI) system. To make 300 hp with TBI, the goal is to systematically eliminate breathing restrictions, but we have to say it will be tough with a relatively stock throttle body. Even on a Q-jet-equipped, small-block, 350 Chevy, the exhaust is the most critical point. You've addressed that perfectly with the 15/8-inch headers. Just be sure to include a 21/2-inch dual-exhaust system or a 3-inch single-exhaust and that part of the system will be acceptable.
Before we get to the electronic side of things, it sounds like you have a new engine ready to go into the truck. The best approach would be to go with a stock camshaft and a set of Vortec iron heads. These heads flow very well and would be a good choice to make 300 hp with a mild camshaft. However, the Vortec heads use a different intake bolt pattern that does not match up to the TBI intake manifold. There are ways around that by using a GM Performance Parts aluminum intake that bolts to the Vortec heads and features a stock mount for the TBI. The intake is PN 12496821 ($370 from Scoggin-Dickey). This gets expensive because you still have to purchase a set of Vortec heads, so we'll concentrate on retaining the stock heads for budget reasons. To keep the price down, have your machine shop perform a 30-degree back cut to the intake and exhaust valves. Stock cams produce relatively low lift, so the back cut will improve flow in that area. If you want to do more, spend about two hours opening up the exhaust valve throat to 90 percent of the exhaust valve diameter (1.5 x 0.90 = 1.35-inch diameter). This will help horsepower above 4,000 rpm or so.
The next restriction is the actual TBI unit. Stock small-block throttle bodies only flow around 500 cfm (compared with a stock Q-jet that flows 750 cfm). It's possible to make around 275 hp with a stock TBI unit, so rather than go nuts on a heavily modified TBI, I'd suggest you start by making sure the existing TBI unit and injectors are in good shape. The actual throttle plate diameters for the 4.3/5.0/5.7L TBI units are all the same at 111/16 inches (big-block TBIs are 2 inches). The difference is the injector flow rates. The 5.0L injectors flow 40 to 45 lb/hr, the 5.7 ones are 50 to 55 lb/hr, and the big-block injectors flow around 75 lb/hr. We would suggest sticking with the stock 5.7L injectors to begin your testing.
The big variable is fuel pressure. These late-'80s and early-'90s TBI injectors are intended to run at between 11 and 13 psi, although it's typical to see the pressure down around 10 psi. Generally, a 1-psi change in fuel pressure from 11 to 12 psi, for example, can be worth roughly an additional 4 percent fuel flow. That doesn't sound like much, but from 50 to 52 lb/hr can be enough fuel to make another 8 to 10 hp.
"That's $18,000? In that condition?"
One of the easiest ways to increase fuel flow is with an adjustable fuel pressure regulator. Companies such as JET, Turbo City, and CFM Technologies sell adjustable pressure regulators. The price hovers around $90 depending on the source. The approach is to first measure the existing fuel pressure. If the pump in your truck is already delivering 13 psi at the TBI, consider yourself lucky and don't bother with the adjustable piece. More likely, the fuel pressure will read 10 to 11 psi. Mount the new regulator and bump the pressure to 13 psi. You won't be able to go much higher because stock pumps generally can't generate more than 14 or 15 psi. Keep in mind that raising the fuel pressure increases fuel delivery across the entire engine operating range. At part-throttle, this additional fuel isn't needed, but the oxygen sensor should sense a rich mixture and reduce the injector on time (pulse width), which will lean the mixture back to the ideal 14.7:1 air/fuel ratio. At wide-open throttle, the computer switches to its base fuel map and the additional fuel pressure will increase fuel flow and (assuming the engine needs the additional fuel) will increase power. You should test any fuel pressure change with a WOT acceleration run in Second gear from about 30 to 60 mph. If the truck accelerates to 60 in less time, the engine is making more power.
Another simple trick we've tested that works well is the PowerCharger, (we call it the soup bowl) from Hypertech. This is a simple radius adapter shaped like a bowl and placed between the truck air cleaner and throttle body. Summit sells these adapters for $37.25 (PN 4001). We tested the PowerCharger on our TBI 350-powered Jake truck buildup ("Project Jake, Part II," July '04) and discovered it was worth 8 lb-ft and 8 hp. If you want more, multiple companies make swirl-inducing TBI spacer plates. CFM Tech-nologies, Trans-Dapt, AirAid, JET, and many others manufacture spacers that, while we've never actually tested them, appear to be worth some torque. Expect to pay anywhere from $50 to $100 for one of these spacers.
You also mentioned camshaft requirements. The stock camshaft for your application is pretty mild. We found the specs for an '81 to '87 computer-controlled flat-tappet hydraulic cam that specs out at 194/202 degrees at 0.050 with 0.384/ 0.403-inch lift. Adding a longer-duration camshaft with more lift will drastically improve airflow and increase power at a higher engine speed. The problem is that it will require additional fuel that will mean changes to the base fuel map in the computer. We'll get to that in a moment. If reprogramming the computer isn't a deterrent, consider a cam like the Edelbrock Performer-Plus flat-tappet hydraulic camshaft and lifter package (PN 3702, $127.95, Summit Racing). This cam is designed specifically for the TBI 350 small-block and specs at 194/214 degrees of duration at 0.050-inch tappet lift with 0.398/0.442-inch lift. As you can tell, it doesn't deliver much of an increase in lift. The advantage is the additional duration that will move up the power curve slightly. The downside to this cam is that for a tow vehicle, it may hurt the low-speed torque slightly, which might not be a bad thing. The idle quality should still be close to stock.
Here's what happens when an incompressible liquid finds its way into the cyl
Here's where it gets tricky. The GM TBI is a speed-density system, which assumes the engine ingests a given amount of air at wide-open throttle (WOT). Mass airflow systems measure the air entering the engine, but speed density systems like those used on these TBI engines do not. Instead, they assume a stock airflow value based on throttle position and manifold absolute pressure (MAP) sensor readings. The fuel requirements at part- and full-throttle are established by the factory based on the engine's air and fuel demands. Increasing airflow with a better intake, heads, camshaft, and/or exhaust increases the airflow through the engine and demands a change to the stock computer base fuel and spark maps. These TBI injection systems are controlled by GM computers equipped with chips that are burned or electronically imprinted with the necessary information. Later GM computers use erasable EE-PROMS that can easily be reprogrammed while still in the vehicle. However, the chips in the TBI trucks and cars have to be removed and a new chip is burned with the new information. This can get time consuming and pricey if you have to make multiple changes to improve driveability. If you plan to do this, call one of the companies such as JET or CFM Technologies to find out about a complete package it offers. These companies can supply the parts and a compatible chip as a package that has a much better chance to be correct on the first try. These systems cost a little more than what you could put together on your own, but that's because you're paying for their experience and tuning expertise. Trust us, it's worth the investment.
JET Performance Products
Huntington Beach, CA
Scoggin-Dickey Parts Center
The beauty of the Olds motors is that within the 350/ 403/455 engine displacements, extern
Olds Rocket Science
Nolan Malone, River Falls, WI: I have a few questions about building an Olds 350 Rocket. The engine is a second-generation motor from my '72 Cutlass. Do you know how far I could bore it out and how great a stroke I could get? Can you tell me a few companies that make aluminum cylinder heads besides Edelbrock? A list of performance parts and where to find them would also be extremely helpful. I'm only 16 and all I really know is Chevy (I have a 355 SBC in the Olds right now). It's hard to find good forged cranks/rods/pistons and nice heads. All the websites I seem to find look sketchy. Can you point me in a good direction for building a naturally aspirated engine that makes 400 to maybe 500 lb-ft (that may be pushing it without a longer stroke)? I don't care much for big horsepower numbers because this will be mainly a street engine. If you know of a good cam to help with that torque, I would love that, too. I have been reading Car Craft for almost three years, and I love every issue.
Jeff Smith: I particularly enjoy receiving tech letters from younger readers. They are the next generation car crafters who will keep this whole industry going. Since you're only 16 years old, Nolan, I'll assume this is a budget project, which means you probably can't afford stroker cranks, aftermarket heads, and all the rest of that expensive stuff that we all would love to build. I called Dick Miller at Dick Miller Racing (DMR) to get his take on your request. Dick's first question mirrored mine: "Why doesn't he just build a bigger motor? A 403 Olds will bolt right in to that Cutlass, and even the brackets for the alternator and power steering are the same." Dick's point is that the easiest way to make more torque and horsepower is with a larger-displacement engine. He gave us an example of a pump gas 403 he built for a customer with fully ported factory iron heads and a 240/246 degrees at 0.050-inch tappet lift cam with 0.541/0.544-inch valve lift that made 476 lb-ft at 4,200 rpm and 482 hp at 6,000. This was with an Edelbrock Performer RPM intake manifold and a 780-cfm Holley Street Avenger carburetor. Another point worth considering is that buying a camshaft or cylinder heads for a smaller engine like the 350 costs the same as for a 403, but the potential to make more power will always be with the larger engine. The 403 sports a massive 4.351-inch bore and a relatively short 3.385-inch stroke. The 350 uses a much smaller 4.057-inch bore and the same 3.385-inch stroke. If there is one limit to the 403, it has to be that it was available only in GM passenger cars between '77 and '79 and some motorhomes and other applications. That limits the number of engines that are out there for retrieval.
Since you asked about the 350, Dick also gave us some specs on one of his engines that made 431 hp at 5,700 rpm and 434 lb-ft at 4,900 rpm. It was equipped with production No. 5 iron heads that he ported and fitted with larger 2.07/1.71-inch stainless valves. Compression was 10.25:1 using a set of forged, flat-top TRW pistons. The camshaft Dick used was a DMR-1441 hydraulic roller with 236/240 degrees of duration installed 5 degrees advanced and produces 0.553/0.544-inch lift.
Dick says your '72 350 is probably fitted with a set of No. 7 heads, which are just as good as the heads he used on his customer's engine, but you will need to use a flat-top piston to create more compression because stock, your engine is rated at 8.5:1. This is a good step, as porting the heads may be more than you can afford, but that can wait as long as the short-block is in good shape. As a budget alternative to the hydraulic roller setup, he offers a similar-spec flat-tappet hydraulic camshaft (PN DMR-1530) with specs of 230/236 degrees of duration at 0.050-inch tappet lift with 0.522/0.522-inch lift. Combine that with an Edelbrock Performer RPM dual-plane intake and a good 750-cfm carburetor and you're on your way. If your engine is still equipped with the stock Quadrajet, that's a great carburetor for this engine. Rebuild it (if it needs it) and learn how to tune it because it will offer outstanding part-throttle response. Did you know a stock Q-jet will flow at least 750 cfm? Most guys don't realize that.
Here's our take on this: If you can find a 403 motor, we'd suggest going that route instead of the Olds 350. It will make more power. But if you want to get going, you can always buy bolt-on parts for the Olds 350 like headers, an intake, a cam, and even cylinder heads, and then if you find a 403 at a later date, you can use those parts on the new 403.
Ted Toki's '55 Gasser featured in the Jan. '10 has tape rolls hanging in the
You also asked about aluminum heads other than the Edelbrock castings. Gene Knowlton did the design work with help from pattern maker Gary Brown, and the heads are available through Lynn Wellfringer's Mondello Performance Products in Paso Robles, California. These hard-core Olds guys have developed a big-port head that they claim flows 329 cfm on the intake at 0.500-inch lift. This is a bunch more than the Edelbrock head, which Dick says flows around 240 cfm on the intake. Gene also claims his head will flow a maximum of 400 cfm at 0.800-inch lift. While impressive, these heads would be overkill for your 350 or even a mild 403 street engine. These heads are really intended for the hard-core drag racer looking for maximum flow for an Olds engine.
Dick Miller Racing
Paso Robles, CA
An excellent place to start a suspension upgrade is with a larger front sway bar. This is
Monte Carlos Forever
Andrew Carter, Bedford, IN: I have been subscribing to Car Craft for almost three years, and all I hear about are Chevelles, Novas, Camaros, and El Caminos. I am just asking, but do you think you guys could do a couple of articles on the first-generation Monte Carlos? I personally have a '70 Monte. It looks like hell but runs like a beast if it decides to run at all. Chevelle articles help, but the Monte is a whole other animal in itself. Even if you don't, I still love the rag and will keep subscribing.
Jeff Smith: For the sake of those who may not be aware of it, while Chevy calls this car a Monte Carlo, it's really a Chevelle with a long snout. What that means is while the body and interior are completely different, the mechanical underpinnings for a '70 to '72 Monte are exactly the same as the '68 to '72 Chevelles. That means that a set of Hedman headers for a '70 Chevelle will bolt right on a '70 Monte Carlo. Since headers are virtually the only engine component that is body-style specific (with a few intake manifold exceptions), inductive reasoning points us to the idea that any small- or big-block Chevy engine buildup will have direct applications to any '70 to '72 Monte Carlo. Transmission applications fall under the same situation. So let's say you want to convert your Monte's TH350 automatic to a Muncie four-speed. The factory bellhousing, clutch, pressure plate, and linkage from a '68 to '72 Chevelle will bolt right in. For example, Year One offers a clutch linkage Z-bar for these cars (PN RZ19) for $39.95, and the pedals will drop right in as well. One step further, if you found a 12-bolt out of a '70 big-block Chevelle, it would bolt right in that '70 Monte.
This Chevelle interchangeability also applies to suspension parts, which means any aftermarket component such as shocks, springs, sway bars, control arms, and trailing arms designed for a '68 to '72 Chevelle will bolt right on to a '70 Monte. This means Global West, Hotchkis, QA1, RideTech, and the dozens of other suspension-related companies all offer parts for your Monte. So if you see a story in Car Craft on how to upgrade a '69 Chevelle suspension, for example, any recommendations for that car would automatically carry over to your '70 Monte. Specific chassis tuning ideas might change a little because of the Monte's massive front nose length and the added weight the front suspension would have to deal with, but the basic components would remain the same. In other words, a front, lower ball joint for a '70 Chevelle will be the exact same piece for a '70 Monte Carlo.
The Monte's extended hood line also creates that huge distance between the engine and radiator. This was before the days of electric radiator cooling fans, demanding instead that wind tunnel-like fan shroud that spanned the distance between the engine-driven fan and the radiator. That huge shroud can be eliminated with the use of a pair of efficient electric fans mounted directly behind the radiator. In fact, all that room in front of the radiator just begs for a centrifugal supercharger that can be easily mounted on the front of the engine.
As we said, the body panels are completely different, but the many different sheetmetal companies such as Year One, Goodmark, Original Parts Group, and many others offer tons of good stuff like hoods, quarter-panels, floorpans, rocker panels, bumpers, and just about anything else you might need. So you can see, Andrew, that while we may not specifically mention the Monte Carlo in our tech stories, we are very much involved with showing you how to build your car. You just have to learn to read between the lines.
Global West Suspension Components
San Bernardino, CA
Santa Fe Springs, CA
Original Parts Group (OPG)
Seal Beach, CA
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Car Craft Mag
831 S. Douglas St.
El Segundo, CA 90245
This is a cutaway of a monstrous R-4360 Pratt & Whitney radial engine. Nicknamed The Corncob because of the helical arrangement of the 28 cylinders, the designation refers to 4,360 ci. Eight of these engines were used in Howard Hughes' famous Spruce Goose transport plane. Let's see, eight engines with 28 cylinders and two valves per cylinder. How'd you like to be the guy who had to set the valve lash?