Building Big Bird
Tom 455bird via CarCraft.com: I just bought a Pontiac 455 for my '68 Firebird. The car has its original 350, and I'm hoping to slip in the 455. I read "Junker to Thumper" in the June '03 issue-you know, '76 455, 210 hp, add headers, intake, and cam, and you get 351 hp. I love that article. Anyway, the 455 is a '72 YC code, which I believe has 250 hp, but I discovered the heads on it are '75 vintage with the 5C code and a 7.6:1-compression ratio. The heads on my original 350 are 17 code with 8.6:1 compression. Should I swap the heads? Obviously I'm an amateur, so any help would be great.
Terry McGean: The 124cc heads we used on our '76 455 for the story you referenced were indeed worthless, having the hugest chambers of any Pontiac V-8 heads, but our sources show that your 5C heads are actually from a '75 400 and that the chambers should measure 101 cc. This would make them very similar to the 6X heads used on many late-'70s 400s, and not a bad choice for a modest 455. Most Pontiac street guys look for No. 96 heads-used on '71 400 two-barrel engines-because of their 96cc chambers, which reputedly create a theoretical ideal pump-gas compression ratio of 9.5:1, something Pontiac never offered on a 455. We used a different set of factory iron 96cc heads, the No. 7K3 castings, which are less desirable because they lack the outer exhaust-manifold bolt holes and bosses. They worked for our dyno test ("New Aluminum for Pontiacs," Jan. '06), but with the stock pistons being significantly below the deck at TDC and the thick composite head gaskets we used, our compression was probably closer to 9.0:1. If we had rebuilt our 455 0.030 over and had it slightly decked, we would have easily found that half a point, if not more, particularly if our new pistons had provided a "zero deck" condition.
If you had your 5C heads cleaned up and milled slightly, you could probably get them to provide around 9.0:1 on your exist-ing engine, assuming it hasn't been rebuilt. If you're going to build it, take the time to figure out the deck height before you order pistons to get as close to zero deck as possible. As for the 350 heads, their combustion chambers are probably small enough to make more compression than you'd want on the 455 (such as over 11.0:1), plus they have the smaller 1.96/1.66-inch valves instead of the 2.11/1.77-inch valves of the big-inch Pontiacs.
Ask Anything is the portion of What's Your Problem where readers send questions for industry bigwigs, then we get the answers. So pick a hero, then come up with good questions and send them to Car Craft@primedia.com.
Steve Donnelly, Las Cruces, NM: I have a '67 Mercury Cougar that I recently acquired from a family member. It's all stock and has a 289 with a two-barrel carb and a single exhaust. I'm going to mildly upgrade the car without making major changes. The planned four-barrel, aluminum dual-plane intake and headers, and dual exhaust are no-brainer items, but I need help figuring out the ignition. I wanted to tune up the car for increased performance even before changing the hard parts.
I consulted some magazine articles and books, and most seem to agree that I need about 34-36 degrees total timing. I had a friend with a timing light check the car, and it seems to have only 6 degrees. Adding another 30 seems like a lot. In fact, when we tried to put it past 15, it started to run worse. I talked to a mechanic, and he said I needed to have the distributor recurved by a speed shop so that the weights and springs can be adjusted. I'm not sure what he means-I don't see any weights or springs in my distributor, though I have seen them in pictures in magazines. There are no speed shops around here, and I don't want to take the car apart and ship out my distributor. Also, what's the deal with vacuum advance? Some people say disconnect it; some say I have to keep it. I wanted to add an aftermarket ignition booster box, like an MSD, but I was told it can't be done with breaker points. Do I need electronic ignition? Should I forget the MSD?
Joe Pea, MSD Technical Advisor: Sounds like a good plan on the Cougar, Steve. Let's start with the ignition timing. There are a couple of different timing settings that need to be considered. Remember, one timing setting is not ideal for the variety of rpm an engine runs through. As rpm increases, the engine requires different ignition timing due to a number of changes, such as the dynamics of the air/fuel mixture entering the cylinder or the reduction in time that the mixture has to burn and combust due to increased piston speed through the combustion stroke.
To compensate for these changes, most distributors are equipped with a centrifugal (or mechanical) advance assembly to alter the timing and meet the demands of the engine. This advance system is made up of weights and springs. As the distributor spins faster, the weights overcome the strength of the springs and push out due to centrifugal force. This in turn advances the timing by moving the pickup assembly.
So when you set your timing, remember that adjusting it at idle is only part of the job. You also need to know the centrifugal amount that the distributor provides. This amount varies depending on the weights, the strength of the springs, and whether or not there is a stop bushing. The centrifugal advance that you set with your distributor will be added to this initial timing to produce your total timing. For example, if you have 10 degrees of initial timing and 21 degrees of centrifugal advance built into the distributor, the total timing will be 31 degrees.
On MSD distributors, the advance assembly is built on top to make adjustments easy (a stock Ford has the advance built under the trigger plate). To control how quickly the timing advances, MSD supplies each distributor with three pairs of advance springs. These springs hold the weights in until a point when the centrifugal force overcomes the spring tension, which controls the slope of the advance curve. Heavy springs with higher tension slow the rate of advance, while the lightweight springs allow the timing to advance rapidly with rpm.
The amount of centrifugal advance that occurs is controlled by a changeable stop bushing. These bushings feature different diameters that limit the movement of the advance plate. MSD includes four different advance stop bushings that will limit the centrifugal timing to 18 degrees, 21 degrees, 25 degrees, and 28 crankshaft degrees.
To check the total timing, you need to run the rpm of the engine up and watch the timing mark on the balancer. When it stops advancing, you'll see the total timing. Unless you have a dial-back timing light or a fully degreed balancer, you probably won't see the timing. MSD also offers a handy timing tape that easily applies to the balancer so you can set the total timing accurately. These tapes are sized for specific balancer diameters. Another thing to remember when you're checking the timing is to disconnect and plug the vacuum advance.
As far as running an external ignition control, such as an MSD 6A, you can easily connect one to a breaker-point distributor. As long as the distributor's advance and trigger are in good operating condition, running with points will work great. In fact, the points will last much, much longer because there is only a small amount of current going across the gap to trigger the MSD. Your engine will receive the benefits of MSD's powerful multiple sparks for improved throttle response, idle quality, and driveability.
MSD Ignition; El Paso, TX; 915/855-7123; msdignition.com
TPI Trouble:More Insights
Barry Dukes, Baltimore, MD: Terry McGean brought out some good points when advising Edman on the '89 Corvette misfire and surging problems (What's Your Problem, Mar. '06). He touched on checking the ignition system, and I'd like to elaborate a little bit. The distributor used in the '89 Vette is a unit with a separately mounted coil. GM used this type of distributor from '87 to about '95 on many of its V-6s and V-8s (including the 454). When the LT1 came out, these distributors were slowly phased out.
For the most part they are very dependable, but they are notorious for cracked reluctors and bad pickup coils. The reluctor is part of the distributor shaft, and the pickup coil is attached under the reluctor and connects to the ignition module. Whenever one or both go bad you get all kinds of problems, including hard cold and/or hot starting, steady misfire, intermittent misfire, surging, bucking, and so on. I'm a mechanic in a Chevrolet dealership, and back in those days we would get customer complaints like this on a daily basis.
The easiest way to check it out is to remove the distributor, then disassemble and inspect it. When it's on the bench, just knock out the roll pin that holds the gear to the bottom of the shaft, being careful not to lose the shims between the gear and housing. The shaft usually just pulls right out, but sometimes it's gummed up and won't easily come out. In that case, just spray a little carb cleaner onto the shaft and work it back and forth a bit; this should free it up so it will come right out. When the shaft is out, inspect the underside of the reluctor for cracks. Chances are there are a few cracks if it has some miles on it. Even if no cracks are seen, if it has a lot of miles on it, replace the shaft and the pickup coil. It's cheap insurance. The modules usually hold up pretty well, but if in doubt...By the way, I just worked on a customer's '89 IROC with a 5.7 TPI and a "hard start, hot" problem. Overhauled the distributor: problem fixed.Hope this helps.
Jim Randolph, somewhere in New Jersey: I have a few questions regarding an LS1 installation on my '65 LeMans. I have been doing some research on the swap and have found all the necessary mounts, fuel systems, and so on. Everyone says they fall right into place, but in all of the articles I have read (including the ones on your Web site), it shows them being installed with aftermarket pulleys, different A/C compressor and alternator mounts, and a different power-steering pump. Can I retain the original serpentine system, exhaust manifolds, and other goodies that come on a complete used setup? What about using the T56 trans? I have found that the shifter will be 6 inches or so more to the rear, and that just seems ridiculous. Hundreds of people do this swap every day, so could you shed some light?
Jeff Smith: Great question, Jim. Let's deal with the accessory drive on the engine first. There's no reason you can't use an existing factory accessory drive on a GEN III (LS1) engine. It turns out there are at least three different accessory drives for these engines, depending upon where the engine originated.
There is a truck accessory drive that extends away from the front of the engine the most, and it's also somewhat taller than the other two. The next-shorter system is the serpentine drive assembly used on F-cars, such as the Camaro and Firebird. Finally, the Corvette system is the shortest. There is also a slight variation on the system used for the GTO engine that we believe is very close to, if not the same as, the F-car system in terms of depth. What you cannot do is interchange pulleys or brackets between these systems for obvious reasons. You also cannot use an F-car-style intake manifold with a truck accessory drive since the F-car system positions the throttle body below the level of the accessory drive, thus preventing the addition of an inlet air duct to the throttle body. You should also look over the placement of the A/C pump on these accessory drives since it could be troublesome when it comes to clearing the frame and/or front crossmember. This will take some careful measurements on your part to ensure the engine will clear your Pontiac's major suspension components. Engine placement is best served by using a Camaro/Firebird oil pan. The Corvette pan is very wide, while the truck pans are extremely deep.
As for the trans, the T56 six-speed that comes behind many LS1 engines is excellent, but as you noted, the shifter is located much farther back. McLeod now offers a shifter that can be positioned in one of two different mounts on the transmission; as a result it can be located almost anywhere along the length of the transmission, both fore and aft and side to side in a very wide arc.
There's also a warning: The T56 is a very large transmission, and depending upon the height of the engine in the chassis, the trans tunnel in the early A-bodies (Chevelle, Tempest/GTO, Cutlass/442, Skylark, etc.) is somewhat narrow. This may necessitate cutting the tunnel and raising it slightly to clear the transmission. This sounds worse than it really is, but some enthusiasts do not want to put the cutting torch to their cars. If this is a concern, you may want to consider something like the Tremec TKO-500 or TKO-600 five-speed overdrive transmission as an alternative. This is a much smaller transmission, and although it is a five-speed, the overdrive selection (either 0.82:1, 0.68:1, or 0.64:1) is similar to the Fifth-gear overdrive ratio in the T56, which varies from 0.70:1 through 0.80:1 and even 0.84:1, which is only 16 percent. The Viper overdrive is 0.74:1. Of course, Sixth gear is 0.50:1--or 50 percent--and used for highway cruising. Tremec sells these transmissions direct, but they are designed to be used with an old-style Chevy or Ford application. If the TKO-500 appeals to you, for example, you could use one of McLeod's modular bellhousings to adapt the LS1 engine to the trans. You would then have the choice to use either a mechanical or hydraulic clutch linkage for this swap. The hydraulic clutch linkage might be a better choice only because you will have to make some kind of adapter off the GEN III engine to mount the mechanical-clutch-linkage Z-bar pivot on the engine. Regardless of which transmission you choose, it sounds like a fun project. Let us know how it turns out.
McLeod Industries; Placentia, CA; 714/630-2764; mcleodind.com
Transmission Technologies (Tremec); Farmington Hills, MI; 800/401-9866; tremec.com
Weighing in on Axles
Matt Sutter, via CarCraft.com: I really enjoyed your article on the budget 10-bolt buildup in the March issue. Would you happen to know how much the 8.5-inch 10-bolt rearend weighs? I think the GM 12-bolt is around 186 pounds and a Ford 9-inch is around 177 pounds. I'm trying to decide what to build.
Terry McGean: Your question got us thinking around the offices, Matt. First of all, you listed the 12-bolt as being heavier than the 9-inch, which we believed was incorrect, but then we couldn't point to a specific source to verify that, so we got out the scales.
First up was the same 10-bolt we'd built in the story you referenced. It's a stock 8.5-inch housing for a Nova/first-gen Camaro filled with an Eaton limited-slip unit and stock-type ring-and-pinion. The only significant weight increase over absolute stock probably comes from the Dutchman 30-spline axles, though the difference is probably less than 10 pounds. With axles but no brakes, our 10-bolt came in at about 160 pounds. Interestingly, when Jeff Smith weighed one of his Chevelle 12-bolts, he came up with 152 pounds, less brakes. The '64-'67 A-body rearends use the same axle length as the early-Camaro rearends, so dimensionally, these two assemblies should be nearly identical. Jeff's axles were stock, and stock 12-bolts use a 30-spline axle, so it would seem that our 30-spline 8.5-inch 10-bolt is a near match, pound for pound.
Jeff then put the 9-inch rearend assembly on the scale, also spec'd for an early Chevelle, and found that without brakes it was a portly 186 pounds. That particular rear used a cast-iron centersection as a stock Ford unit would but had an aluminum pinion support. Additionally, the Ford drum brakes that are typically paired with a 9-inch are larger than the usual 9-inch-diameter GM drums found on Camaros, Chevelles, and so on, and seem to weigh about 4-5 pounds more per pair.
It's no surprise that the Ford 9-inch is weighty; drag racers have been familiar with this penalty for years, making the sacrifice for the increased strength. Aluminum carriers can help shed some of the unwanted bulk, but probably not enough to slim it down to the weight of a 10- or 12-bolt.
Chris, via CarCraft.com: I have an '80 El Camino with a 350 and a Saginaw four-speed. It's been stuck in First gear for a while, and I'm still not sure why. Maybe linkage adjustment, broken bushings, or bad synchros...I don't know. It's not sitting on level ground, so I can't jack it up where it sits. I pushed the clutch in and my friend pulled it with his truck, but the wheels wouldn't move. I know the rearend isn't locked up. I started it up, gave it some gas, and let out the clutch; it grunted really hard, but it won't move. Any ideas? I don't know too much about transmissions, but this is my project car and that's where I need to start.
Terry McGean: Sounds like you've got it stuck in two gears, Chris, and one of them is probably Reverse. This isn't uncommon when the external shift linkage of a manual transmission gets worn. You didn't state whether this was a factory setup ('80 El Caminos were offered with four-speeds from the factory) or something that's been transplanted, but either way, you need to check the linkage. Freeing the trans is likely a simple matter of jiggling the linkage rods under the vehicle; the rods for First/Second and Reverse may actually be bound against each other, since one was probably not fully returned to Neutral before the other was engaged, again the likely result of a worn-out shifter. If you can't get underneath the car, you may be able to partially access the shift linkage from inside after removing the shifter boot.
Impersonating The Impersonator
Steve Schaffer, via CarCraft.com: How close to The Impersonator can I get with L98 heads, a Performer intake, and the same cam on my 406; would this require a different cam? I don't have the Vortec heads at this time. I'll be putting this in my '79 Camaro with a 700-R4 and 3.42:1 gears. How much horsepower and torque would this setup make?
Jeff Smith: The story Steve is referring to actually appeared in a sister magazine (Chevy High Performance, June '03). That engine was a 406ci small-block with Vortec iron heads, an Edelbrock Performer RPM Air Gap intake, a 750-cfm Holley double-pumper carb, and a mild Lunati hydraulic flat-tappet cam. The single-pattern cam spec'd out with 230 degrees of duration at 0.050-inch tappet lift, 0.480-inch lift, and a 109-degree lobe separation angle. The engine was also fitted with smaller 151/48-inch headers, and on Duttweiler's dyno it made an amazing 525 lb-ft of torque at 3,500 rpm, grunting out 471 lb-ft at 2,300. Horsepower was acceptable at 428 hp at 5,000. The limiting factor to more horsepower was two-fold with this engine. First, Vortec heads are exhaust-port limited, so using a camshaft with about 10-12 degrees more exhaust duration and a little more lift would have helped. Second, to accommodate this additional lift would require modifications to the heads, and probably better valvesprings as well
The combination you plan to assemble is not going to power up nearly as well. The Performer intake is not as good in terms of torque or horsepower as the RPM Air Gap. But the aluminum heads you suggest running are a bigger problem. The L98 heads are the aluminum 1.94/1.50-inch castings first used on the Tuned Port Injection (TPI) engines in the late-'80s Vettes and Camaros. While these heads look like they might perform, frankly, they're lame. Not only do they not flow nearly as well as even a stock old iron set of 76cc heads, but with a 58cc combustion chamber on a 406ci small-block with flat-top pistons, the compression will be somewhere around 11.75:1, which is way too steep even for aluminum heads.
You mentioned that Vortec heads are not in your current plans, but we suggest selling those weak L98 heads to some street-rod guy who doesn't care how much horsepower he makes as long as the heads look cool, then use that money toward a set of Vortec iron heads. Clearly this combination appeals to you, and the torque is flat impressive. You can purchase a pair of Vortec iron heads already modified with more retainer-to-seal clearance and better valvesprings (PN SD8060A) from Scoggin-Dickey Performance Center for $680 ready to bolt on. Granted, that's a bit of money, but if you are serious about making great power, you can probably find a way to come up with the dough.
As for the camshaft, we'd go with a flat-tappet hydraulic cam with specs of around 230/240 degrees at 0.050 with lift around 0.480/0.510 inch and a 110- to 112-degree lobe separation angle. The cam also needs to be a small-base-circle grind to clear stock-style connecting rods. This small base circle will also affect rocker geometry, which means you'll need at least 0.100-inch-longer pushrods, perhaps longer. Also remember that the Vortec heads use 64cc combustion chambers, so 22cc dished pistons will bring the compression to just under 10.0:1 with 0.040-inch head gaskets and a negative deck height of 0.020 inch. Tightening the piston-to-head clearance will improve quench, but this will also increase compression, making it tougher to be safe on 92- or 93-octane pump gas.
You really shouldn't run the L98 heads because of compression limitations unless the engine has dished pistons of around 23 cc-that makes the compression around 9.7:1. If you're still thinking of going with the Performer intake and the L98 aluminum heads, expect to make great torque, perhaps 440 lb-ft or so up to about 3,500 rpm. At this point, the heads will choke that 406 and you might make 335 hp if you're lucky. Throttle response right off idle will be excellent with this combination, but don't anticipate making much in the way of horsepower. The heads just don't flow any air.
Scoggin-Dickey Performance Center; Lubbock, TX; 800/456-0211; sdpc2000.com
Cutlass Trans Tricks
Shane Bonnie, via CarCraft.com: My cousin's got an '83 Olds Cutlass and would like to put a five-speed in it to go with the 383 I built. Any junkyard ideas on what parts can be taken to get this done?
Jeff Smith: Before we get into details on the manual trans you want to run, we should first get into clutch linkages. Some G-bodies from '78 to '81 were equipped with manual transmissions, and these cars had mechanical linkages with pedals and the entire Z-bar arrangement. To say these are rare would be an understatement, but after a quick eBay Motors search, we found a pedal assembly that did not include the rest of the linkage. It was listed for $65 with two days left on the auction, but we wouldn't be surprised if it went for $100. If you're talented, it would be possible to fabricate the rest of the linkage from heavy-wall tubing and spherical rod ends. We've also heard that a mid-'70s Cutlass Z-bar will work if you can find one. Next, the only real junkyard five-speed available that will work is a third-gen F-car (Camaro/Firebird) T5 trans, used from '83 to '92 but only with 305ci engines. The '88-and-later boxes are all World Class, which means better gear material, better synchros, and stronger parts. But these T5s are rare and also were tilted 17 degrees from horizontal, which then means you need a matching mechanical-linkage bellhousing. Our research points to only one year for that bellhousing-the '83 F-car-so again you're on the hunt for a rare part.
If you can't find the linkage and/or bellhousing setup, then you'll be forced to go with a hydraulic clutch system. Plenty of fourth-gen Camaros have hydraulic masters, but you're still going to need a pedal assembly. The Monte Carlo Mailing List Web site (Monte-list.nu) has a great rundown on a T5 trans swap that goes into far more detail than we can here. The owner also offers tips on using an F-car pedal assembly. With the trans and matching hydraulic '84-'92 F-car bellhousing, you can use all factory parts, which makes replacement parts easier to find. You will have to move the crossmember to mate up to the T5, and the driveshaft will have to be cut to fit the longer T5 trans. Obviously you will need to saw open a hole in the stock floor for the shifter. Hurst and B&M both make shifters that will bolt right in.
The nagging overall question is how well the T5 will hold up to the torque of that 383. From what we've learned, it will take abuse but will break if subjected to power shifting of any kind. We're working on an upgrade to improve the life of a Ford World Class T5; that story should appear in the next few months. G-Force offers a bunch of parts for this transmission, including gearsets, improved slider assemblies, a heavy-duty cluster support plate, and all the goodies to upgrade your T5. The upgraded gears are $1,095, while a hardened mainshaft is another $335.
G-Force Transmissions; Cleona, PA; 717/202-8367; g-forcetransmissions.com
Keisler Automotive Engineering; Knoxville, TN; 865/609-8187; keislerauto.com
|TKO-500 ||TKO-600 |
|First ||3.27:1 ||2.87:1 |
|Second ||1.98:1 ||1.89:1 |
|Third ||1.34:1 ||1.28:1 |
|Fourth ||1.00:1 ||1.00:1 |
|Fifth ||0.68:1 ||0.64:1 |