I found this article about upgrading a worn 79 wagon with a 305 and it had a lot in common with my truck so I thought I would share for anyone with a similar vehicle:
http://www.chevyhiperformance.com/techarticles/148_0312_wizened_305_engine_bolt_on_mods/index.htmlProject 3-Oh-Why?
Bolt-On Mods for a Wizened 305
So your daily driver is a lame-duck 305 crippled by miles of vacuum lines and a compression ratio lower than a worm's belly, and topped off with an odometer that rolled over 10,000 miles ago. Sure, the easy thing to do would be to find a crate motor and dump it in. You'd be motoring happily along with plenty of power in no time. Easy enough, we'd say.
But we say a lot of things. Not everyone can plunk down a couple grand on crate performance. Sometimes those of us writing and wrenching on project cars and hanging around dynos may lose touch with reality. Not everyone has access to the information, tools, places, and parts that we often take for granted. So we stepped back and asked what we would do if we relied solely on one vehicle, didn't have much experience under the hood, and lacked a lot of tools--or even a place to do the swap.
Our '79 Malibu was still tugging along with its original 305. We wanted to make the thing a little peppier to cruise around in, but we knew right off that this was never going to turn into a 14-second ride, especially with the 2.41 gears out back. Our goal was simply to bolt on a few parts that would give the car enough guts for us to pull out into traffic without fearing for our lives.
We'll be the first to admit that a stock 305 is far from a powerhouse, or even a mouse's house of performance for that matter. But sometimes you have to work with what you're dealt, and since this is a daily driver, that's exactly what we planned to do.A slim minority will declare this engine worthy of a complete build-up, and we're sure to hear from all 10 of 'em. But our plan has one major advantage: It's a Chevy small-block, so any parts we buy can be transferred to another engine down the road.
After treating our Malibu to a fresh set of plugs and an oil change, we went to the track to get some baseline numbers. We left just off idle and let the trans shift by itself (mainly because the column mechanism isn't in prime operating condition anymore). The result was a stoic 20.27 at 69 mph. The only thing slower on the strip that day was a VW Bug. We tried a couple of different launch techniques, and even shifted by hand, but we couldn't crack the 20-second barrier. The answer was simple--one of the oldest schools of thought in racing--make it lighter. We didn't go import and yank the seats and door panels, but we did dump the spare, jack, road tools, and related junk, and proceeded to break into the 19s with a solid 19.98.
Under a maze of cracked vacuum lines and grime lies the dim beat of a feeble 305. It's not a street terror by any stretch, but with the help of a few bolt-ons and a weekend of wrenching in your garage, the slug can produce a little more pep.Next, we opened the hood and tossed the air cleaner and filter to shave another tenth, then tweaked the timing from 4 degrees to 10 and pulled a 19.58 at just under 70 mph. We continued messing with the timing (to no avail), but at least our baseline was set.
The first thing we wanted to improve was the air and fuel delivery. Since a friend had an Edelbrock Performer RPM intake manifold, that's what we used. The RPM is a bit taller than the recommended Performer model and is generally the choice for engines that offer a little more than stock performance in the 1,500 to 5,500 rpm range. But since this engine is merely a steppingstone to its eventual replacement, we gladly used it. Before choosing an intake, you'll also need to consider what type of carburetor you'll use, or if you need an EGR valve to stay legit within the confines of local emission laws. Edelbrock offers its RPM and Performer line for Q-Jets (spreadbores) or square bores. Though most would probably rebuild the factory Q-Jet, ours was in poor shape with a stripped and leaking fuel-inlet fitting and other signs of wear. We opted for a new 525-cfm Barry Grant Road Demon Jr.
At the track, we did the ol' air-cleaner-lid flip but saw no difference, so we trashed the entire assembly. We found dead bugs and a lot of dirt in the housing.The Jr. is a new entry-level carburetor that shares many of the features found in the popular Road Demon, and it uses the same centersection. The Jr. is available in 525-, 625-, or 725-cfm sizes, and shares the Road Demon's reinforced, high-density metering blocks, which are accurate and much less porous than other material. The secondaries are vacuum operated; this is recommended for stock or mild engines with an automatic transmission. Other features include float bowls with fuel-level windows and side-hung floats. A single inlet makes it easy to attach a fuel line.
Installing an intake and carb should be no trouble for the novice wrench spinner, but you must consider the linkage, accessory brackets, fuel lines, vacuum ports, and sensor positions. Our swap required a little filing on the kick-down bracket and A/C compressor bracket, and the coolant-temperature sensor needed a new adapter. We cut the original fuel line and replaced it with a rubber one. Later we'll upgrade it to a solid or braided line.
After a couple of low-20-second passes, we jettisoned some weight. Sans the spare, jack, and miscellaneous debris, the Malibu broke out with a scorching 19.98.With the new intake system, the car definitely felt better. The Jr. was close on its dial-ins, but we played with the float level and idle screws a little. We also added 2 to 4 degrees of timing to the system as noted in the Demon instructions. After a couple of squirts around >> town, we stepped up the jet size, as the car seemed to be running too lean. We also helped airflow to the carb with an Air Inlet Systems (AIS) ram-air box.
The ram-air box is a dual-snorkel air cleaner that accepts a 14-inch filter element and allows you to plumb clean, cool air through its 4-inch inlets. AIS also supplied a dropped base that allowed the setup to fit beneath the stock hood. We routed some 4-inch ductwork to the radiator support, into a fender, and then downward to channel the cool air. In many cases, a hole in the radiator support would lend the best results, but we weren't ready to relocate the battery to the trunk just yet.
Next on our tuning list was the timing. The lack of compression seemed to allow for about 12-14 degrees initial, which brought the e.t. down to 19.73. It was all we could muster from the 305.Our next consideration was a free-flowing exhaust system. The 305 exhaust manifolds, inefficient catalytic converter, and dinky single exhaust hampered even this low-performance putz. Hedman Hedders recently introduced its Tork-Step headers. These shorties improve clearance underneath the car and are stepped from 1 ½-inch to 15/8-inch tubes, which is good for midrange torque. We were surprised by how easily the stock manifolds came off and even more amazed at the simple installation of the Tork-Steps, which dropped in from the top. We'd recommend installing fresh spark plugs first. Once in place, the primary tubes for cylinder Nos. 6 and 8 severely limit access.
Another new Hedman piece is the X-Treme Crossover kit, complete with the necessary pipe and an X-shaped crossover to join both banks of the dual-exhaust system. The crossover eliminates backpressure caused by firing order variations between the two engine banks. When neighboring cylinders fire next to each other on the same bank (8-4 and 5-7 on the Chevy), their exhaust pulses bang into one another as they go through the same exhaust route. This affects backpressure and scavenging, causing a loss of performance. Splitting the exhaust flow between the two banks equalizes the pressure, thus >> improving the efficiency of the exhaust flow. We were also anxious to try Hedman's free-flowing catalytic converters. They offer stainless steel shielding and flow more air due to a unique internal construction and welding design.
An oil or vacuum leak will take all the fun out of any performance gain. We were fortunate that the intake had been resealed at some point in the last couple years, so the gasket cleanup wasn't too bad. Be sure to cover the lifter valley, coolant passages, and intake runners to keep debris out of the engine. We removed all of the old gasket material from the heads and deck to achieve a proper seal.Firing up any engine with the fresh exhaust is always nice. The Hedman Turbo mufflers even coerced a slight rumble out of the 305, and the testdrive showed a big change in performance. It sounded so much better that we were sure it would run better. To prove it, we went back to the track.
Our first run netted an 18.16 at 72 mph, and one of the tires even squawked! We ran it a few more times and tweaked the timing to 12 degrees to get a best run of 17.58 at 77 mph. Our meager driveway bolt-ons did their job, and even though we're talking 17-second time slips, we're quite happy with the improvements. We did, however, have another trick to try. We lifted the Road Jr. off and sandwiched a Nitrous Works plate on the intake.
Before we hit the button, we thought it would be a good idea to check the fuel pressure for the recommended 5-psi minimum at high rpm with a small shot; good thing we did, as the pressure dropped below 2 psi. This would have caused major problems and was actually a determining factor in the car running lean prior to the nitrous. We bolted on a BG mechanical fuel pump to eliminate fuel starvation problems at higher rpm, and the increased pressure allowed us to back down a jet size from 64 to 62, but we were tilted toward the rich side just to be safe. Then we pulled out a couple degrees of timing.
When we pulled the HEI to install the intake, we found the advance mechanism in nasty shape. We replaced the weights, springs, and nylon bushings with a Moroso kit and used the lightest springs so the advance would begin just off idle.The first couple of hits were 75hp shots, but that was good enough for a 17-and-change time, and the tire (only one) was spinning pretty good off the line. We upped the system to a 125hp shot by changing to the recommended jets supplied in the kit, and headed up to the line. The tire lit up at the press of the button and actually drifted a little smoke before we pedaled it. We could tell it was a good pass until top end, where the car just fell on its face. We'd tapped our bottle of go-juice, resulting in a 16.16 at 83.5 mph instead of the solid 15-second tear we were expecting.
Sure, these numbers downright suck on paper, but the performance we gained really made a difference in the car's driveability. It's a lot more fun now. Kicking it down to pass at speed is noticeably better, jumping into traffic is less worrisome, and the exhaust rumble sounds much better while driving and idling. Next on the list are stiffer cogs. Some 3.31 or 3.42:1 gears would certainly help, so we've been scouring the local yards for a cracked-up T-type. At least we can run with most of the posers in their decal-laden imports, and this will have to keep us satisfied as we make plans for a bigger and better long-block.
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