David Kauffung 308 Chevy Small Block Rebuild - Recycled Power
This Engine Masters Challenge Competitor Took The Extreme Budget Route When He Built A Discarded 305 Into A Thrifty, Powerful Street Engine.
From the June, 2008 issue of Popular Hot Rodding
By Steve Dulcich
Photography by Johnny Hunkins
When David Kauffung, a jeweler by trade, decided to build an engine for the Engine Masters Challenge, he was decidedly pleased with the format allowing any production engine to compete at the factory bore and stroke (plus tolerance). What he had was a limited budget, and a well used 305 that had been lying around for years. The old engine even sat out in the weather, but a thick coating of grease had protected the bores since the mill was pulled from an old Nova. David says: "The heads were off, and I noticed the bores looked pretty good, so I covered them with grease for protection in case I ever wanted to use the old block one day." That day finally came when David was considering what to build for the EMC competition. The old 305 had a couple of things going for it as far as David was concerned. He tells us: "The 305 Chevy has one of the longest stroke-to-cubic-inch ratios of any engine, which is a plus for low-end, and I already had it."
Far from a spare-no-expense effort, the 305 was going to be built on a real budget. David tells us the total outlay, including the engine, was right around $2,500. Since David is not a professional engine builder, the resources going into this buildup were tight (just as it is with many of our readers) and high-end machining was going to be costly. Instead, David looked at the stock engine and decided what was still going to be serviceable. "The stock bores showed almost no wear, like less than a half a thousandth, and the crank looked really good, too. It was surprising, considering the engine had clocked a good 200,000 miles before it was pulled. Actually, even the bearings looked good enough to re-use, though I did use the new ones that came in the rebuild kit," he says. Prep on the bottom end and block was minimal, and since there was no over-boring or crank grinding, the costs were also rock-bottom.
This humble lump of overlooked...
This humble lump of overlooked Chevy 305 may not seem like the basis for a winning competition engine, but as David Kauffung proves, it can make a very nice street piece.
Even though the engine sat...
Even though the engine sat uncovered with the heads off for years, the bores on this 200,000-mile engine showed very little wear. One of the advantages of late-model fuel-injected engines is that they suffer from much less ring wear-normally a by-product of fuel wash down at cold start-up on a carbureted engine. We don't know if this core started its life as such, but when selecting a budget core, an EFI engine will typically show less bore wear than its carbureted counterpart. Despite some minor pitting, Kauffung figured there was life left, and just replaced the dished pistons with a set of budget Federal Mogul hypereutectic slugs. Bore prep was limited to a hand-scuffing with some sandpaper.
David relates: "I just took some sandpaper wrapped around my hand, and ran it up and down the bores with a twisting action to break the glaze, and that was it." A new set of Federal Mogul hypereutectic pistons replaced the dished stockers in the standard bores. Likewise, the stock rods were going to offer the best dollar effectiveness in connecting the crank to the pistons, so they were simply reconditioned and fitted with ARP bolts for strength. This rod and piston combination relies on OEM press-fit pin retention, as opposed to the floating pins found on most performance or race engines. This was good enough for GM in millions of production small-blocks, and good enough for this economical 305 buildup. The seal was provided by a set of Speed-Pro moly rings. The 5/64-inch compression rings are far thicker than the race-type thin ring sets of many competitors, but again, it was the cost-conscious alternative, considering the other components that made up the parts selection.
Looking to squeeze a little more power out of the stock cast-iron crank, David spent time profiling the counterweights and cleaning up the casting, though the process was definitely not high-tech. Dave told us: "I smoothed the crank and streamlined it using an autobody sander." The objective here was to make the crank less prone to parasitic windage losses that soak up horsepower. From a practical standpoint, cutting down on power losses is just as productive as making more power in the first place, and when using low-tech stock parts there are usually areas where improvements can be found.
Of course, a major part of an engine's power combination is the airflow system, and here Kauffung knew that the stock iron 305 smog heads were not going to offer the required flow. Looking for an alternative, the choice was made to use the GMPP aluminum Fast Burn Vortec heads. These heads are known for a very efficient combustion chamber and quite a flow improvement over factory iron. The heads were treated to detail work, but not an all-out porting, keeping most of the work confined to the bowls and valves. David, having limited specialized cylinder head machinery, improvised with a bit of handy work on some of the operations. As he explains: "I don't have a valve grinding machine, so to do the back-cuts I used a drill press to spin the valves and detail them with a hand file, putting a nice radius in to improve the airflow. I did some similar work around the valve seats, and also worked on the 'guide boss, though I probably could have narrowed it some more." The result of the effort was an improvement in airflow from around 240 to 265 cfm on the intake port.
Downstairs, there seemed to...
Downstairs, there seemed to be no reason to toss out a perfectly serviceable stock Chevy 305 crank. The journals looked good enough to re-use that piece without a regrind.
Downstairs, the prep was limited...
Downstairs, the prep was limited to some hand-profiling of the crank with a body grinder to make it more streamlined, and a low-cost windage tray. The factory fasteners secure the main caps, except for the studs at the windage tray mounting points.
Here, the basic street stuff...
Here, the basic street stuff is evident: a set of stock rods with ARP bolts. The Federal Mogul bearings, however, are the premium-coated pieces for extra insurance.
The complimentary intake manifold is GMPP's high-rise Vortec single-plane. The manifold, like the heads, did not receive extensive porting, but just some cleanup at the top of the runner entrance and removal of some casting flash. One area that did show a decent gain when tested was a custom-built plenum divider. The divider slots into the manifold, and can be easily installed and removed. On the dyno, David indicates there was about 20 lb-ft of torque to be gained with the divider in place. Topping the manifold is a familiar OEM carb-a spreadbore Quadrajet. One of the attractions to this type of carb was of course cost, and when looking at available cfm of flow per dollar, a used stock carb of 800-cfm capacity represents quite a value. A four-hole spacer was added between the carb and the intake to increase torque. Although the OEM carb worked well, David stated that he is not opposed to an aftermarket carb. "A Holley squarebore may have added some more power, and it's something I'd like to try if I was to test this engine again."
As important as the airflow system is, the cam and valvetrain must work in harmony to achieve a good performance engine. Here, Kauffung went with a COMP solid flat-tappet with rather conservative specifications. With an intake duration of 229 degrees (at .050), and 238 degrees on the exhaust, the cam is anything but radical. Combined with a 112-degree lobe-separation angle, the overall result can almost be called mild. The engine had a smooth idle and high manifold vacuum, making the combination a very good setup for street use. Kauffung admits that the cam could have been a little more aggressive, particularly in the lobe separation. "Looking back, I probably should have gone with something a little narrower. Actually, after reading about some testing in Engine Masters magazine, I knew I missed on that," David says. Even with the rather short-duration specs, the lift at the valves was substantial, thanks to the 1.65:1 ratio of the PRW rocker arms, providing .538-/.553-inch lift on the intake and exhaust valves, respectively. COMP beehive springs were also an integral part of the package, offering light weight and excellent control for high-rpm stability.
The stock oil pump was plenty...
The stock oil pump was plenty for the 6,500 rpm the engine would run. The only mod here is fitting the matching pick-up tube for the Milodon oil pan.
Closer scrutiny shows nothing...
Closer scrutiny shows nothing exotic, with thick, 5/64-inch stock-width compression rings, a Speed-Pro set with a moly top, taper-faced iron second, and standard Speed-Pro oil rings. No full-floaters here; note the press-fit piston pin style.
Up top, the stock 305 heads...
Up top, the stock 305 heads were not going to offer much performance, so a set of GMPP aluminum Fast Burn Vortec heads were substituted. These Vortecs are a moderate head choice, but should amply supply a 305 with the needed airflow.
Overall, the engine built by David Kauffung is not a piece that will pose a serious threat to an all-out drag racing engine, but it illustrates several notable points. It goes to show what can be done with a combination retaining a majority of OEM parts, on an everyday budget-even when the subject is the generally neglected 305 Chevy. With nearly 400 hp and a good street idle, this engine shows the potential few realize in the 305. The fact that these results were achieved with a fairly mild assortment of readily available parts makes it even better.
305 SMALL-BLOCK CHEVY
||COMP solid flat-tappet
||229/238 degrees at .050 inch tappet rise
|Cam lobe lift:
Filling out the heads are...
Filling out the heads are relatively small 2.00-inch intake valves, and 1.55-inch exhaust valves, though the size was plenty for a 305's small 3.736-inch bore. The valvetrain was stepped up with COMP's No. 918 beehive springs, PRW 1.65:1 self-guiding rockers, and PRW pushrods. Lifters are COMP No. 2900 solid flat-tappets.
Very little rework went into...
Very little rework went into the GMPP Vortec single-plane intake manifold. Kauffung selected it based on testing comparisons with other intakes, and reserved the modifications to a little cleanup of the casting flash, and blending at the runner tops.
A modest amount of port work...
A modest amount of port work went into the heads, concentrating on the bowl area and valveguide bosses, as well as some hand detail work to the seats and valves themselves. The result is about 265 cfm of peak intake flow.
||Speed-Pro 5/64-inch moly
|Top ring gap:
|Second ring gap:
||Federal Mogul hypereutectic flat-top
||stock GM 305
||stock GM 305, 5.7 inch
|Main bearing clearance:
|Rod bearing clearance:
||GM Fast Burn No. 12464298
|Peak intake flow:
|Intake valve diameter:
|Exhaust valve diameter:
||GM Vortec Eliminator
||stock GM 8-inch
The valvetrain geometry is...
The valvetrain geometry is an important consideration, and the selected parts showed good characteristics. Quality components and the right pushrod length are the key factors here.
This particular carb model...
This particular carb model may be more at home on a pickup truck than a race car, but these GM Quadrajet carbs are said to offer 800 cfm from the small-primary/large-secondary arrangement.
One of the unusual modifications...
One of the unusual modifications made to the intake manifold was the addition of a plenum divider, which Kauffung (a jeweler) made himself. Kauffung indicates the mod was worth 20 lb-ft of torque in his abbreviated dyno test session.
|ON THE DYNO
TESTED AT UNIVERSITY OF NORTHWESTERN
Providing the spark is a discount...
Providing the spark is a discount Pro Comp brand aftermarket distributor working an MSD 6AL box and Pro Comp wires.
Continuing with the low-buck...
Continuing with the low-buck theme, the front of the engine consists of a Jegs electric water pump, and a stock Chevy 8-inch crank damper.
A used set of small-tube Hedman...
A used set of small-tube Hedman Street Hedders provide the necessary relief of spent gasses, and are actually borrowed from a buddy's car. Real street stuff here.