Anthony, via CarCraft.com: Hey guys, I just read Matt King's article on the 400hp 302. I was wondering if I can do the same thing with my '69 302 or something close to it. If so, any chance of letting me know what I need to get my 302 kickin'?
Terry McGean: You just read that? We did it three years ago ("400hp With a Stock Cam," July '03), but it was a good piece. Although the power numbers were impressive, there really wasn't much trickery to Matt's combo. The real key was a set of Airflow Research (AFR) aluminum heads. The 165cc intake-port heads for the small-block Ford might sound small when compared with the 195cc and 210cc ports commonly touted for aftermarket small-block Chevy heads, but AFR intentionally kept the ports smaller to promote intake velocity. These heads still flow like mad (about 245 cfm on the intake side) and allowed the 5.0 to really wake up. One of the interesting things revealed by this experiment was that the stock cam used on '87-'93 5.0 H.O. engines is actually rather hardy for a factory EFI grind (0.445/0.445-inch lift with stock 1.6:1 rockers; duration from Ford is 276/266 at 0.006-inch lift, which is reputedly around 210 at 0.050). In fact, realizing big gains in power by changing the heads and not the cam indicates that the stock heads are the "cork" in these 5.0s, not the cam, as is often the case with factory engines. This may explain why changing only the cam on a stock 5.0 doesn't bring power up all that much. Matt did use a set of Crane/Ford Racing 1.7:1 roller rockers to gain additional lift, bringing it to 0.473/0.473-inch, but the rockers alone would not make that much difference if the cam weren't already fairly healthy.
The only major differences between your '69 302 and Matt's later version are the roller cam, which began for '85 on H.O. engines, and the piston design, though the latter is not radically different. Since the stock '69 302 heads had combustion chambers of around 63 cc that produced about 9.0:1 compression, bolting a set of the AFR heads to your engine should yield similar compression (with the 60cc chambers and a thick 0.041-inch-thick head gasket, Matt's 5.0 had a little over 9.0:1). You could use a flat-tappet cam of similar grind to replicate our efforts. Comp Cams offers a grind in its High Energy line that is similar (260H) with 212/212 duration at 0.050-inch lift and 0.447/0.447-inch lift (with 1.6:1 rockers), though like most Comp grinds, this one is on a 110 lobe-separation angle, whereas the stock 5.0 cam is said to be around 114-115. Comp describes this as "an excellent combination of torque and power; best for towing with 302 and stick trans." In other words, you can do better if you're trying to make horsepower. For instance, the Comp Xtreme Energy line features a grind with 218/224 duration at 0.050 and 0.493/0.500-inch lift that is said to be compatible with a stock converter, so the idle is probably still reasonable if that's a concern. Another concern, however, is whether this cam will cause piston-to-valve conflicts. Matt figured his late-model pistons could handle up to 0.220 at 0.050 without a problem, and your valve reliefs may be deeper, but you'll have to verify that and remember that the big (relative to factory spec) 1.90/1.60-inch valves of the AFR heads will need more room than stockers.
The other option would be to convert your early small-block to accept the later factory roller cam and lifters. It's actually not that difficult. Comp offers a retrofit kit (PN 31-1000) that includes a factory-style retainer to hold the lifter guides (also included) in place; you just have to drill and tap two holes in the lifter valley as per the instructions. Ford-style roller lifters (also available from Comp) are intended to be used with this kit and will drop right into the lifter bores in your '69 block. Make sure to use the roller-specific camshaft thrust plate and not the original one from your engine if you opt to go with the roller-the early nonroller piece is not hardened and will be galled by the steel roller cam. If you perform the conversion, you can slip in a stock 5.0 H.O. roller cam or step up to an even stouter grind, such as Ford Racing's E303. Just remember to check that piston-to-valve clearance.
Are All Valvesprings Created Equal?
Keith Tolleson, Bowling Green, KY: I'm in the process of acquiring parts for a 454ci big-block Chevy that I intend to put in my '92 Chevy pickup. I want to use a hydraulic roller cam (I'm looking at Crane's PN139021 with 0.610/0.632-inch lift and 234/242 duration at 0.050-inch lift), but I think there are specific valvespring requirements for rollers. Recently, I came across a set of AFR 265cc oval-port Magnum heads. Will I be able to use the springs on these heads or will I have to buy the Crane-recommended springs (PN 99896)?
Urik Ulick, Crane Cams Phone Tech: When considering springs for any application (and especially for hydraulic roller cams), seat pressure is critical. Proper seat pressure is necessary to ensure the hydraulic mechanism does not pump up and create a slight internal vacuum leak due to the valves not seating at the proper time. Higher seat pressures are also necessary on hydraulic rollers as compared with hydraulic flat tappets because the hydraulic roller lifters are heavier and generate much more inertia.
Crane specifies a seat pressure of 150 pounds for the cam you have chosen. Air Flow Research builds these heads with springs installed at 140 pounds of pressure. The 10 pounds probably will not make much difference on the street, but to maximize performance, you might want to install a 0.015-inch valvespring shim under each spring to bring the pressure close to 150 pounds. Any competent machine shop should be able to remove the springs, check the installed seat pressure, and shim them as necessary to achieve the 150-pound recommended pressure. Be sure to check that coil-bind does not occur before maximum lift. At full lift, there should be a minimum of 0.060-inch extra travel in the spring before coil-bind occurs. Also, check to make sure you have adequate retainer-to-seal (guide) clearance at max valve lift; proper clearance is 0.100-inch minimum. If necessary, you might have to have the guides cut down slightly to ensure this clearance.
Finally, check your valvespring open pressure at max lift. Crane calls for 460-480 pounds of open pressure with this cam. Most hydraulic roller cams are made of induction-hardened or carburized steel. Spring pressures up to 550 pounds/open are safe with induction-hardened steel cams; carburized steel cams (usually identified by copper between the lobes) can handle much higher open pressures. Your cam will generate around 480 pounds at max lift. If the springs on your AFR heads can be shimmed to the correct seat pressure and have enough travel to handle the 0.632-inch lift, use them. If they do not measure up to any of these requirements, buy the springs recommended by Crane.
One final thought: Cast-iron, flat-tappet camshafts cannot tolerate the high valvespring pressures required for roller cams. Maximum open pressure for flat-tappet cams should be kept under 330 pounds (after break-in) for adequate long-term life.
Rocker Ratio Redux?
Frederic Giroux, somewhere in French Canada: I am the proud owner of a '67 Dodge Dart GT equipped with a '69 340 engine. The engine is 0.030-inch overbored, and for the goodies, it has a Mopar Performance cam (PN P4452992; 280/280, 0.474/0.474-inch lift, 110-lobe separation). It also has an Edelbrock Performer RPM intake topped with a Holley 750-cfm vacuum-secondary (which needs a total tune-up), TTI step headers, MSD 6AL ignition (6,000 rpm cutoff), and a Proform electric fan. The rest of the engine remains stock. The tranny is a 727 equipped with a B&M Transpack and a 2,500-rpm stall converter. The 831/44 differential runs an Auburn Gear LSD Pro series with a 3.55:1 gear.
The car runs 13.74 at 103 mph with some old, crushed Hooker headers (the TTI headers are brand-new), street tires (BFG Radial T/A), and steel wheels. The car is intended for street and strip performance (80 percent street, 20 percent strip). My objective is to run 13 flat in the quarter on street tires and street trim.
I plan to do a complete head job (port and polish with intake port-match and bigger valves), and I want to change the old rockers for some brand-new roller rockers. A friend told me I should use 1.6:1 rockers on the exhaust side and 1.5:1 rockers on the intake side to "stimulate" my cam a little bit and to make more power. Does it make sense or should I go with another formula? Which rockers are best for my application?
Terry McGean: Your friend is suggesting a way for you to offset the grind of your cam without actually changing the cam. Your MP cam has the same specs on both the intake and exhaust sides, which was standard practice for performance cam grinders for many years. But the intake valves and ports on your engine are not the same size as those on the exhaust side-they're larger, which is typical of American V-8s. For that reason, many modern cam grinds have additional lift and duration on the exhaust as a means of crutching the exhaust side to make up for the reduced flow.
Using the 1.6:1 rockers on the exhaust side of your engine would turn your 0.474-inch lift to 0.505-inch; duration would be increased by a very slight and insignificant amount. If you really want more cam timing, consider swapping the cam itself. The MP grind you're using is good, but you could step up to a split-pattern grind with a little more profile to get even more of the benefits your friend is trying to get for you with the offset rockers.
You said you were planning to port those heads, but be careful-an inexperienced porter can easily make heads, even old stock castings, worse. Simply making the ports larger isn't necessarily the path to increased power. Look into techniques for reshaping and blending the bowls just under the valve job-that's where most of the power is hiding. The old gasket-match usually doesn't yield gains on par with the amount of effort it requires, and again, you could screw the castings up.
Ed Tucker, Bel Alton, MD: Let me say that I am not what you would call experienced in auto mechanics. I can do more than the average person these days, but I'm not the total-rebuild kind of guy...yet. That's one of the reasons I like your magazine; it gives step-by-step instructions to dummies like me so even we can make things happen!
I have a '73 Mustang Mach I with a 351 Cleveland engine that is in very good shape-it has fewer than 60,000 original miles, and I have had to do very few repairs on it-it's a real numbers-matching car. The problem is the carburetor. Over the years, the gaskets and other parts have worn out or dried and cracked so that the carb leaks fuel onto the intake. This is not good, especially since my wife is the primary driver of this car. No one seems to know what carb I can replace the old one with. This is the factory Ford carb, and I would like to replace it with a Holley or Edelbrock carb that will be a simple swap. I'm thinking around 650 cfm. I have called all over the states talking to Ford techs and lots of auto-part and dealership people, and no one can tell me what to replace the old carb with. I really want to get this ride back on the street. Can you please tell me what carb will replace the original factory four-barrel?
Jeff Smith: We did a little digging, and it appears that your engine came equipped with an Autolite 4300 version carburetor of 600-cfm capacity, but this carb could be either a square-flange or a spreadbore design (like a Q-jet style). We're going to assume that your difficulty in finding a replacement is because you have the spreadbore style of the Autolite carb.
According to our pal Sean Murphy at Sean Murphy Induction, there is no Holley carb that will directly replace the stock spreadbore unit that also incorporates the kick-down linkage for the automatic transmission (we're assuming also that this is an automatic). While you could use an adapter between the intake and a standard-flange Holley, that might stuff the air cleaner into the hood.
Murphy says he won't even attempt to rebuild those original Autolite carbs because they warp and leak very easily and are basically "a crappy design." His suggestion is to yank the original intake and carb and replace it with an Edelbrock Performer for the Cleveland 4V (PN 2665, $184.88 summitracing.com). This allows using the much more popular square-flange Holley carburetor, but the manifold is drilled for both carburetor bolt patterns. If you choose to stick with Edelbrock for the carburetor, the Performer 600-cfm electric choke version (PN 1406, $264.95, summitracing.com) is a great choice. You will also need the Edelbrock throttle add-on adapter for the automatic transmission (PN 1483, $14.88 summitracing.com).
If you would rather go with a Holley universal-replacement carburetor, the company offers the 0-80457S 4160-style, vacuum-secondary carb with the Ford linkage and an electric choke that's a great fit for the Cleveland. We found it for $269.99 at gofastparts.com. Several more Holley square-flange carbs are available all the way down to the universal 0-1850-style carb with a manual choke. Of course, if all this is a bit more money than you wanted to spend, you could search the swap meets and eBay for a used intake. A used vacuum-secondary 600-cfm Holley should be easy to find. Good luck.
Nitrous Fuel Pressure
Rich Schuler, via CarCraft.com: I have a question about your article I just finished reading ("Nitrous-plate Shootout," Nov. '05). It states you used a common 0.063 nitrous jet with 6 psi of fuel pressure and let the company figure out the best fuel jet for its tune-up. My question is, how did you get 6 psi of fuel pressure? Was it flowing? If so, what size jet was it flowing through? I hope it was flowing the 6 psi through the jet the company supplied, but it is not stated and would make a big difference in the tune-up.
Jeff Smith: That's a valid question, Rich. It also brings up a good point about dynamic versus static fuel pressure. We were at the track the other day and ran across a guy fiddling with fuel pressure on a typical "dead-head" fuel system. A dead-head system utilizes either an electric or manual fuel pump that plumbs one line directly from the fuel tank, through the pump, and up to the carburetor, perhaps through a pressure regulator. To accurately determine fuel pressure, this type of delivery system must be monitored under load, such as at wide-open throttle (WOT) down the dragstrip. At rest, this system will indicate a higher fuel pressure because there is very little fuel being used compared with WOT on the dragstrip, which demands much more fuel.
A full-flow, or return system uses a pump and a regulator but is designed to allow any fuel not used by the engine to be returned to the tank. If you are using an electric fuel pump in a return-type system, merely energize the pump, set the pressure at the regulator, and you're done. The pressure regulator will automatically compensate for any additional fuel used and maintain the fuel pressure very close to where you set it.
We used a full return-style system on our nitrous test so that fuel pressure was always maintained at the 6 psi limit for all the different fuel jets used. Had we been using a dead-head system, this would have required minor changes to the dynamic fuel pressure to maintain that 6 psi nitrous fuel pressure. If you want more information on designing a full-flow fuel system, we covered this topic in the Dec. '05 issue ("Fuel Delivery System"). In a dead-head system, changes to the fuel-jet size would change the fuel pressure dynamically. Realistically, however, these changes would probably be minimal. On a full-flow system, changes in the fuel jet would not affect fuel pressure unless the jet was so large that the delivery system could not maintain the pressure.
SSG Michael Ascott, U.S. Army: I am looking for anyone who can give me some advice on what to do about the lack of handling with my ride. I have a '64 LeMans post model. I have replaced the stock powerplant with a strong 455 and TH400. I didn't think the weight difference would cause that many problems for me because of the fiberglass Goat hood, but it drives like a bus. I just upgraded to a 12-bolt rear out of a '69 4-4-2 and added the rear sway bar and a set of springs from a station wagon, so I think the rear is where I want it. I have a variable-ratio power steering box that I will install as soon as I can find a pump and bracket in the boneyard. My question is, what can I do to stiffen up the frontend that won't require stripping everything to the frame and make me feel every pebble in the road? Also, by swapping to disc brakes from a '70 A-body (I think it changed the location of the wheels) and the 12-bolt that was 1-inch wider, did I ruin any chance of this car ever handling correctly?
Jeff Smith: Sounds like you've got the makings of a great machine Michael, it just needs some simple suspension tweaks. You're right that the later-model 12-bolt is 1-inch wider in the rear, with each side adding half an inch. This does not affect handling, but it does change the type of backspacing required to fit wider wheels in the rear wheelwell. With that additional half inch of width, you will need to add an additional half inch or more of backspacing. The idea is to place the wheel where it offers the most clearance. Your Pontiac might be able to accommodate as much as 6 inches of backspacing, such as a 17x911/42-inch wheel with a 275/40ZR17 tire. Taller tires, such as a 60-series on a 15-inch wheel, may not be able to clear the frame as well because of sidewall clearance, but this is a good place to start.
As for the rear suspension components, our experience with A-bodies is that those spindly, stamped-steel lower rear control arms are terrible. Even boxed, they're not much better. If you plan to run a large tire and wheel that will produce less clearance, definitely go with tubular lower control arms, such as the ones from Global West. The Global bar is offered in two configurations. The best unit uses a spherical bearing in the front to allow the bar to articulate, which prevents binding in normal street situations, such as negotiating steep driveways at an angle. Global also offers this same tubular steel arm with polyurethane bushings at a reduced price. Global doesn't recommend poly bushings because the company feels these pieces eventually begin to squeak and can cause problems. For now, leave the upper control arms stock. This is important because under body roll in a corner, Global says the arm must be allowed to twist to prevent binding the rear suspension. This has happened to us, and it causes all sorts of evil handling problems that defy diagnosis.
For the front, we're assuming from your letter that you've swapped to a '70 disc-brake setup. The quickest, inexpensive way to improve handling would be to add a large-diameter front sway bar, such as a 111/416-inch- or 111/48-inch-diameter bar. These bars can be purchased brand-new, but the smart move is to find a front sway bar from a '70 through '81 Camaro or Firebird/Trans Am. These cars used these large front bars, and the cost is minimal. You will have to measure the bars you find, as several sizes were used on second-generation cars; the biggest bars come from '78-'81 Trans Ams. The next step would be stiffer front springs. On our road-course '65 Chevelle, we are currently running 850 lb-in front springs with an aluminum-headed small-block that weighs much less than your Pontiac engine, so this is a good spring rate for your car as well. These springs are also available through Global.
Shocks are another very important consideration. Shock-absorber valving is the main component that dictates ride quality, not necessarily spring rate. Everyone thinks that a very stiff spring will ride like a piece of solid steel between the body and the tires, but shocks play a big part in that as well. A set of stiff shocks with stock springs can ride much worse than stiff springs and properly valved shocks for the street. Ideally, to improve handling, a set of adjustable shocks from Koni would greatly improve ride and handling and allow you to tune each depending upon your requirements. The single-adjustable Koni traditional shocks (PN 8040-1087 front and 8040-1088 rear) are not too expensive at around $215 per pair from koni-na.com. Bilstein also makes shocks for your car (BE3-2972 front and AK-2080 rear) and from Summit these go for $79.95 apiece or roughly $320 for all four. If this is too steep a price, there are brand-new low-pressure hydraulic shocks available from Monroe and Gabriel that are going for as little as around $14 each on eBay.
The biggest hurdle to good handling with stock A-bodies is the front camber curve. As the body rolls, the top of the outside loaded tire (such as the right front on a left turn) will roll with excessive positive camber. This induces massive understeer or "push." The best way to fix this is with a 1-inch-taller '77-'96 B-body spindle and a custom tubular upper control arm from either Global West or Hotchkis. The tubular upper arm from Global, for example, alters the camber curve to roll negative camber, which is exactly what you want to improve handling. If you do this, you'll need to run the lightest rear coil springs you can find. Otherwise, the car will instantly oversteer in the corners very easily, and that can be shocking the first time it happens. You can call Global West for more details on how this works, but we can tell you that our '65 Chevelle track car with gumball 275/40ZR17 Kumho tires can pull more than 1 g on a skidpad with these exact Global West pieces. For a first move, we'd suggest a stiffer front sway bar and better shocks to see if that improves your Pontiac's prowess in the corners.
14102 Stowe Dr.
530 Fentress Blvd.
2700 California St.
Global West Suspension Components
12035 Burke St., Ste. 13
Santa Fe Springs
Ford Racing Parts
15021 Commerce Drive South, Suite 200