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Inside A 440-Cubed 400 Part IPart I: Engine autopsy--Does dyno testing really cause accelerated engine wear?Let's find out From the January, 2009 issue of High Performance Pontiac
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There is an adage heard 'round the racing community that says, "One pull on a dyno is equal to five trips down the strip." Or something like that. (Note to self: Stop inhaling VP fumes.) We know that many of you don't care to dyno an engine because it is perceived that an extraordinary amount of wear occurs while doing so. Others feel that such abuse is worth it, as your motor's actual horsepower and torque numbers are revealed on the dyno graph. And let's not forget about the invaluable tuning that can be done there before setting your Poncho loose on the blacktop. Your humble servants at HPP have always wondered about the extent of an engine's abuse while it produces the numbers, so when contributing editor Jim Taylor made 15 dyno runs with a newly assembled motor, and decided to break it open to inspect it for any signs of wear, we tagged along. Ready to sacrifice its mechanicals for this knowledge was a 1968 400 block with ported '68 heads and a few other goodies. This particular example also wore a Holley Street Dominator manifold that had been worked and massaged by Taylor to perform well with a 4150-series carb. This motor was built solely for those Second-Gen. T/As with all of the amenities--T-Tops, A/C, electric windows and the sort. Such frilly options provided a pleasurable driving experience for the owner, but made for a behemoth of a car--can you say 'two tons'? Taylor uses a roller cam setup for these instances, but before you shirk in fear at the idea of dropping a roller into your street ride, know that this 509-horsepower bullet produces plenty of vacuum at idle. As such, this combo makes for great driveability and fits under the shaker hood. You can tune in to Part II in this issue to get specific information on the buildup, but for now, let's see how it held up! Conclusion
After this thorough inspection it's clear that, in this instance anyway, no harm is done to dynoed motors. All of the indicators point to the beginning of engine break-in after the runs, not the beginning of the end. In part 2 we will delve into the parts necessary to build this torquey motor.  1. Our 400 after returning...  1. Our 400 after returning from the dyno. This block is from 1968 and wore 16-casting cylinder heads, which would have been installed on either 400- or 428-cu.-in. motors back then.  2. Though it looks like your...  2. Though it looks like your basic Pontiac engine, this one has a secret. Read on, to find out what it is.  3. Here is the casting number...  3. Here is the casting number for the '68 heads. The 1968 16-code heads indicates that they were used for 400- and 428-cubic-inch motors with stock 2.11 intake, 1.77 exhaust valves and 72cc combustion chambers.  4. With the valve covers and...  4. With the valve covers and intake removed, we get our first peek inside of the dyno-flogged mill. The Crower roller lifters show no unusual signs of wear, just slight evidence of use in the form of minute surface scratches. If there was a real problem, such as excessive lifter bore diameter, there would be a particular wear pattern on the lifter body. No rev-induced carnage yet.  5. After the heads were pulled,...  5. After the heads were pulled, the combustion chambers were inspected for anything unusual. There will usually be a ton of assembly lube in the combustion chamber on a fresh motor--this is from the initial lube of the valve stems and guides. From a wear standpoint, both the heads and the valves were fine, but they were a little too clean and the valves were light-colored, indicating a lean condition. Since this motor dynoed with 108-octane fuel, it appears that the mixture needs adjusting. Erney also pulled the valve springs and checked for lost pressure after the dyno runs. The Crower springs were accurate to their 187-lb. installed pressure before they went on. They now measure 180 lbs. after the dyno session, indicating an expected seven-pound loss on this engine, which is normal.  6. The harmonic balancer and...  6. The harmonic balancer and water pump and timing cover were removed next, with the Hamburger Rollmaster timing chain and gears following soon after. The timing chain showed no sign of excessive stretch.  7. After getting to the bottom...  7. After getting to the bottom of things, we discover that our dyno mill houses a 428 crank! Taylor was looking for more torque for these heavy cars, and with the 4-inch stroke and 4.188-inch bore, we're looking at a 440-cubic inch engine! Upon closer inspection, you can see the location on the block where it was relieved to accommodate the crank's throw. Once the pistons and rods were taken out, the crank was inspected for signs of abuse. Searching for any sign of contamination, an unusual wear pattern, or insufficient oiling, Jim says, "The journals look beautiful." We say, "I'll bet the dyno graph does, too!"  8. The TFX solid roller cam...  8. The TFX solid roller cam features 250o intake, 256o exhaust duration at .050 with a 112o lobe separation angle. Net lift is a .520-inch. It is used along with the MSD Pro Billet distributor incorporating a bronze gear. The cam's pattern starts where valve lash goes away.  The noticeable pattern on...  The noticeable pattern on the cam lobes is from the roller lifters, which is normal. Since a roller cam is made with such hard material, it is difficult to tell if there's a problem. Look for marks on the cam from the roller lifter's wheel edge; this would indicate uneven lifter roller-to-camshaft contact. As far as the distributor gear is concerned, there was an indication of a normal wear pattern.  9. Our pistons, rods, wrist...  9. Our pistons, rods, wrist pins and bearings after removal. Fine scratches can be seen on the piston skirts, and the initial wear pattern on the wrist pins (like a polish) can be seen as well. Big scratches on the piston skirt should raise a red flag. Taylor was anxious about the possibility of detonation, so he checked the condition of the top rod bearings since the engine ran a little lean on its pulls. Thankfully, no specific pattern indicating a real problem was found. He will re-torque the big end of each connecting rod and measure in four or five places to verify that each is still perfectly round.  10. The stock windage tray...  10. The stock windage tray utilizes bigger return holes, and it attaches with studs and nuts as opposed to the original bolts. This is because torquing the bolts would have crushed the fiber washer and insulator pads Taylor used to quell vibration.  11. The motor was turned over...  11. The motor was turned over to inspect for normal cylinder wall wear, which won't look too much different from the crosshatch made by the honing stone. This close-up of the #2 cylinder shows the minor polishing that accompanies the beginning of ring seal, but a wear pattern that occurs longitudinal of the cross hatch will tell you something's gone away.
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 | Part II: Engine autopsy--Does dyno testing really cause accelerated engine wear? |
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