Subscribe to the Free

GM Pistons, Vintage Air System & 1979 Chevy Malibu - Performance Q&A

Kevin McClelland Dec 1, 2008

Messing With My Combination
I've had the pleasure of racing with the same engine and combination for 12 years now. This engine was built back in the summer of 1996 to run in my previous '57 Chevy Super Street car. Today the engine lives in my Don Davis '27 Street Roadster. Now, more than a thousand runs later, NHRA is messing with my combination.

Last weekend Daniel and I were up at Sacramento Raceway for an NHRA National Open. At the beginning of this season, NHRA mandated the use of Lower Containment Devices to prevent oil leakage on the track in case of engine failure. This affected all classes from Super Gas up. I'm all for safety; however, putting this diaper on the bottom of my engine created a whole new set of challenges.

The ambient temperature was well over 100 degrees all three days, and I ended up driving the car around the pits to warm up the engine and head over to our tech inspection. Returning to the pits to prep for our first time run, I noticed the engine wouldn't cool down like normal. My first thought was that the water pump or the electric fan was having a problem, as the Davis car does have a very small (but highly efficient) cooling system. Everything checked out OK, so I was off for our first run. As I drove up to the staging lanes, the motor was definitely running hotter than usual. After my first time run, heading back into the pits, I went through my normal routine, checking the chassis and engine and documenting the weather conditions. Interestingly, when I was going to the back of the car to connect the battery charger, I noticed tremendous heat coming up from around the diaper! After heating 10 quarts of oil up to well over 200 degrees, there is nowhere for the heat to go except up into the water jackets of the block. This big, black, heavy canvas diaper featuring an absorbent pad on the bottom made a perfect Thermos; it didn't allow the oil to cool off between runs. You have to take into consideration that this engine was designed to run on 92-octane pump unleaded; back in early 2000, California lowered its super unleaded to 91 octane. This was my first concern. Now I have superheated oil in the oil pan not doing its job of cooling the pistons.

Daniel and I ended up having a great weekend, winning several rounds. It was a lot of work, but fortunately I was able to keep the heat under control. It just goes to show you, though, that many things can affect performance. In this instance, a safety measure produced another issue, and I may still have to make adjustments to either fuel or spark to keep the engine out of detonation. Amazing, isn't it? Also, I never thought I'd be wearing a diaper at 50 years old!

Free Slugs
Q I was wondering if you could help with an identification problem. I am attending Universal Technical Institute in Exton, Pennsylvania. We found a box full of pistons, and nobody knows what they are or where they came from. They are for a 4.00-inch bore and have coated skirts and smaller rings (thinner). On the inside, under the pin, they have "GM" cast into them with the numbers 308 and 10172839. Any info you could give would be great. The sooner the better because we want to use them in our engine build to see if we can make more power than the students using stock replacements, and we need time to have them pressed onto the rods to assemble our engine. Thanks in advance.
Victor J. Miller
Exton, PA

A Now that is a real find! A box of new pistons lying around just waiting for a new home. Sometimes it's tough to find a clean 4.00-inch bore to slap new standard pistons into. They always run a little better with an extra bit of clearance. I think we've got your pistons identified.

The numbers you gave us were casting numbers, not part numbers. Our Super GM Parts Man Ken Casey was able to find that these pistons are from '96-and-later L-31 Vortec 350 and L-35 4.3L Vortec V-6 engines. These are nicely designed cast pistons with a slight dish, four valve reliefs, a coated short skirt, and a metric ring pack. We couldn't find the specific ring pack dimensions, but we recall that they are 1.5 mm top, 1.5 mm second, with a 3.0 mm oil ring. This is a very low-tension ring pack that works very well on oil control and cylinder sealing. This piston and ring pack is a major upgrade to the standard slipper skirt, 1/16-, 1/16-, 3/16-inch ring package.

You will be very happy with the performance numbers you get with these pistons. Just make sure you don't get greedy and spray the engine with giggle gas. Beating your classmates is the objective, but the car better be running when you're done. Good luck.

Real Pony Swap
Q I'd like to start by saying that I've been a Chevy man most of my life. Recently I had the opportunity to purchase a '68 Mustang minus engine and trans extremely cheap. It has been a fad lately to drop small-block Chevys into late-model Mustangs. Does anybody make a conversion kit to put a Chevy engine and trans into these early Mustangs? Maybe something that contains headers and motor mounts? Thanks for your help.
Richard Topolewskit
Bolingbrook, IL

A Yes, one of today's more popular engine swaps out there for the Ford group is to pick up a cheap Fox-body Mustang and drop in a nasty small-block. They're lightweight and have a decent rearend and suspension, and all you have to do is drop in some power and you have a robust combination for a rather quick car.

As for the earlier Mustangs, a couple of things prevent an easy engine swap. First, the tight shock towers really make it tough, given the 9.020-inch deck height and the exhaust port and spark plug location, to squeeze in there. Next, all the early Mustangs had a front sump oil pan configuration. Even if you used an early Chevy II pan, which is a front sump, it would be tough. We couldn't find anyone with engine swap components for the early Stangs.

The Fox-bodies have much more room in the engine bay and used a rear sump oil pan, and the small-block drops right in. If any of you out there are interested in making a Mustang better-and really want to tick off the Ford lovers-check out AJE Racing for a bolt-in engine swap kit, which comes with engine mounts and headers to drop in a small-block Chevy.

Pulley Play
Q I had a Vintage Air system installed on a '66 Malibu with a 327ci. I noticed after adding the double pulley to the water pump that it now rubs on the power steering belt. I was wondering if anybody made a pulley smaller than stock that would fit my water pump. My current pulley is a stock 6-inch, and I think a 51/2-inch would work fine. What are your thoughts?
Dwayne Foland
Des Moines, IA

A Vintage Air is a very nice upgrade to any of our early Chevys. Cruising around in air-conditioned comfort is hard to be beat, especially in the hot Iowa summers. These kits are second to none and provide you with years of trouble-free service.

The '66 Malibus have a unique P/S pump mounting that elevates the pump to clear the steering box. This is probably why you're having a slight interference with the water pump pulley. One thing you may want to look at is if you decreased or increased the P/S pump belt's length is within the factory adjustability. This may change the angle of your belt enough to clear the factory double-grooved water pump pulley. If not, check with March Performance for a water pump pulley. When we looked into the factory two-groove pulley, it looks like it is 61/2 inches in diameter. The standard March pulley is the same diameter, but the billet aluminum pulley has a much steeper angle machined into the front taper of the pulley. This should help with your clearance problem. Also, you can check with March for a reduced diameter that will work with your pulley offsets. Most of the aftermarket pulleys will be a larger water pump pulley with a smaller-diameter crankshaft pulley. This is to underdrive the accessories and pick up horsepower through less parasitic loss.

Malibu Resto
Q I can't seem to find a company that sells restoration parts for my '79 Malibu. It mostly needs interior work; I'd like to change the funky green hue to black. The body doesn't need much work at all. It's got a 267 V-8 in it now, but I'm building a 383 stroker to stuff into it. If you could guide me in the direction of a company or catalog for the interior parts I would greatly appreciate it.
Steve Schlenker
Bismarck, ND

A You've chosen one of the last full-frame, rear-drive, inexpensive GM models to hot rod. The interest in the '78-88 G-bodies has grown drastically over the past couple of years. A large inventory of used models to pick up from Buick, Chevy, Olds, and Pontiac gives you any flavor you wish to hop up. Thankfully, the aftermarket is stepping up to this model.

If you've followed along at all over the past several years, you know I've built an '80 Malibu Wagon for drag racing. The interior was that nasty shade of tan with cloth seat covers. I was also interested in changing the interior over to black, and this is where Honest Charley stepped in and helped. With the depth of parts it offers (including seat covers, headliners, windshield pillar post covers, sun visors, dash covers, a carpet kit, and sill plates), we were able to freshen up the wagon's interior. A complete catalog dedicated to the '78-88 G-bodies covers interior, exterior, suspension, and engine components. Check it out online or call directly for a catalog.

Hard As A Rock
Q My '70 El Camino has minor brake issues. For starters, the car wouldn't stop rolling until the pedal was all the way to the floor, or at least that's what it felt like. I took it to get checked out by the local brake specialist, who told me that my cam was too aggressive and because of that the engine was not making enough vacuum for the booster. What I felt in the pedal wasn't the floor; it was more as if I was driving with manual brakes. I want to know if this is possible. And how do I fix it?
Angel Saldana
Via email

A Large camshafts on street vehicles will kill the engine vacuum and create havoc with power accessories, and the braking system is the first to feel the effects. You'll also see it in vehicles that have vacuum-controlled headlight doors and A/C damper doors. What you are feeling is the rock-solid pedal against the master cylinder without any power boost. If you drive the car down a hill and use the engine to help decelerate the car, you will have decent brakes for that one stop. After that, the pedal gets hard again. This is a perfect example of inadequate vacuum to support the braking system.

Several companies offer booster vacuum pumps to assist the engine vacuum with braking. Master Power Brakes offers a pump that will produce enough vacuum to operate the power brake system on its own. This heavy-duty vacuum pump kit, PN AC2724K, features a 12-volt pump that will produce a constant 18-20 inches of vacuum, and the kit includes a vacuum switch to cycle the pump when needed. We'd recommend using this pump in conjunction with the engine's manifold vacuum. You will still benefit from the engine vacuum generated during deceleration.

True Young Gun
Q I am a 13-year-old growing up with an automotive mechanic for a father. During my childhood I have learned a lot about car motors and basically know every aspect of the Chevy engine. I'm an all-time Chevy fan, and every Chevy High Performance magazine I get, I go straight to your section. You have helped me learn a lot about cars, and I think I have something you can help me decide. I recently ran across a 350 small-block that my dad will let me tinker with to help me continue my gearhead education, and I wanted to get your opinion on what I could do to cheaply create a decent-power 350 powerplant with mostly stock components. I plan to drop it into a '77 Chevy Cheyenne. I love the sound of an off-idle Chevy engine, and the truck may be taken to the track every now and then but more importantly will serve as my daily driver. Any advice will be greatly appreciated.Blake HolderHickory, KY

A Welcome to a very contagious hobby or, as in your father's case, a good living. We all got our start tinkering with anything that ran: lawn mowers, motorcycles-anything with an engine-or just the clock on the wall. They've all been pulled apart by the best of us, and some still seemed to work after we were done with them.

The best thing you can do is learn. Dig on the Internet and read as much as possible to be completely versed in what you're trying to do. To spend as little money as possible, read up on do-it-yourself cylinder head porting. There is a tremendous amount of information on the web; a couple sites have complete step-by-step instructions on how to do it. Check out the Standard Abrasives site for a full section on head porting, block preparation, gasket removal, and thinking outside the port. Yes, the company is pushing its wares, but these are very high-quality porting kits at reasonable prices. Also, Wikipedia has a great definition and explanation of porting and why you should do it. CHP has published many stories over the years in which even writers were able to make very nice gains through their first time porting cylinder heads. Get online, search "cylinder head porting," and read away.

Hopefully your dad has some tools that will give you a leg up on doing some porting. Increasing the airflow into and out of the engine is the best way to increase power. If your only expense is your time reading and doing the labor, it is basically free horsepower!

Next, since this is your very first build, stay on the conservative side; you'll be much happier with the results. Try swap meets, junk yards, and garage sales to find aluminum intake manifolds and headers. You'll need to buy a new camshaft and lifters. Again, stay away from the really nasty cams. Remember, you do want to install this engine in a heavy Chevy truck.

Welcome to a lifelong hobby or career. People will always need their cars repaired, and doing what you love for a living is the ultimate goal. Good luck.

B.C. Truck
Q I am caretaking a mint '86 Chevy C10 Shorty 2x2. It is equipped with an H-code 305 and a TH350-C transmission with a five-pin HEI, 3.73:1 posi rearend with 30-inch rubber. It has 11/2-inch ceramic headers, long. I have lightened the front end with an Edelbrock water pump, electric fans, and an aluminum rad. I've even rebuilt the Q-jet and installed an aluminum GM Q-jet manifold with EGR. I back-cut the intakes on a set of iron 1.84/1.50-inch valve heads with 1.5 roller-tip rockers with koolnuts and used the Mr. Gasket 0.028-inch-thick head gaskets.

I'm cheap and I have a new cam that I'll probably never use in anything else. It specs out at 0.390/0.410 inch max lift, 256/262 advertised duration, 194/203 degrees duration at 0.050-inch tappet lift, and is ground on 116 separation angle. This is pretty much a stock 350 cam. Do I keep the five-pin HEI with the knock sensor or go with a more common four-pin? Also, should I use a Y-pipe with a single Flowmaster 70 series or go with duals with/without an H-pipe?

I should mention I have an OTC five-gas analyzer (portable) and an Innovate wideband O2 meter that I know how to use. A steep, long hill provides the dyno. The annual sniff check for a 22-year-old truck is doable. I'm green when it doesn't cost too much, so I'll probably use a high-flow cat(s). Thanks for the help.
Ian McFarlane
Vancouver, B.C., Canada

A You're stepping over dollars to pick up pennies. However, you've put together a very tidy package of lightweight components and small efficiency increases. Just because you have that camshaft may not be enough of a reason to install it.

The stock LG4 305 camshaft specs out at 178/194 degrees duration at 0.050 inch tappet lift. I did a great deal of work with these engines back in the mid-'80s when I was at Edelbrock. We developed a camshaft that ran well with all the factory emissions controls and the electronic controls on the engine. It spec'd out at 194/214 at 0.050 inch tappet lift, 0.398/0.442 inch max lift, and was ground on 112 centers, installed at 107. We probably worked our way through 30 camshafts on both the engine dyno and in the car, an '84 Z28 Camaro. Finally, with this camshaft we saw what were sellable gains.

As for your current camshaft, I don't like the wide centers that are on 116 degrees. With the small duration you need a slight amount of overlap, and the 112 separation angle makes a big difference. If you're going to the trouble of replacing the camshaft, a better choice might be Edelbrock PN 3702.

We'd recommend sticking with the original five-pin HEI. This system will not accept the more common four-pin due to connector and wiring pin-out differences. Also, the knock sensor is a very nice feature with the quality of fuel we have today, and with the price of fuel you'll want to run on 87 octane. To round out your exhaust, we'd recommend going with a Flowmaster Y collector, PN Y250300, into a single high-flow 3-inch cat. With this collector you'll be able to build a very nice headpipe system from your headers. Then complete the system with the 70 series you mentioned. Flowmaster offers that muffler in either a single 3-inch outlet or dual 21/2-inch outlets so you could create your own dual-outlet exhaust. The single 70 has more than enough flow capacity to support your modified 305 and has great sound control. Watching your dollars in any buildup is very important. Making your money last the length of the buildup is the key. Enjoy your truck!

Cast Repeat
Q I actually have a question that was asked in the July '08 issue. It was titled "Cast in Stone" and inquired if the cast crank could withstand the author's new combination. You said the cast crank can hold up very well and that the forged cranks are better, but where do you draw the line between using a cast crank and needing the forged crank? If you intend to spray the engine, how big a shot can you use on a cast crank? I'm just looking for something to work off of before I start putting together the next engine for my vehicle.
Eddie Henselder
Via email

A The standard answer for nitrous shots on stock bottom ends is 125 hp max. Basically, this refers to a stock engine producing around 250-300 hp. When you add the nitrous, you're in the 375-425 hp range. If the engine you're planning on building is stock, go for it. However, when you say you're "looking for something to work off of," this leads me to believe you're going to wring out as much horsepower from the components you assemble. Then you're looking to add nitrous into the mix? For instance, you build a nice little 350 small-block with a hydraulic roller, a good set of aluminum heads, decent compression, and good intake, carb, and headers, you'll be knocking down 400-425 hp on motor alone. Throw the 125hp shot on top of this engine and you could be running on thin ice. As we stated in the July answer, the main problem with cast cranks is when the engine runs into detonation. Pushing the stock package up into the 400-plus horsepower range naturally aspirated is getting you there on pump gas. The massive increase in cylinder pressure when the nitrous is first applied could cause the engine to rattle and it won't take that for long. For a safe horsepower max, we recommend staying below 450 hp on the stock cast cranks.

With all the affordable aftermarket crankshafts out there from Eagle, Ohio Crank, Scat, and others, you should look to a forged crank if you're going for decent power. I've driven over a crankshaft before and it wasn't pretty. Luckily, I didn't find any guardrail, but it did kill a really nice set of Lee Shepard ported D-port aluminum heads. This happened all because I couldn't afford a four-bolt block for my big-block. It pulled the front main caps right off the block, but that's another story.

Technical questions for Kevin McClelland can be sent to him at



Connect With Us

Get Latest News and Articles. Newsletter Sign Up

sponsored links

subscribe to the magazine

get digital get print