A day on engine dyno..

Today at work, it was boring as hell as not much business was going around, bosses spend most of the time prepping a Chrysler V8 engine for a customer's Dodge Challenger.

Anyway, the V8 engine if not mistaken is a 565 cubic inch or 8.7 liter carburetted OHV engine. Prior to today's testing the engine wasn't going more then 5200rpm and later discovered cracked valve retainers were the culprit. After later dismantling the valve retainers the customer subsequently found out that one of the lifters weren't pushing on the push rod as it should be.

Typically, an OHV (Over Head Valve) configuration engine is an engine with the camshaft on the middle of the engine, as opposed to the Over Head Cam, which have camshaft on the top of the engine. It opens and closes valves via the operation of the Lifter, Push Rod and Rocker Arm.

A lifter, oso called hydraulic tappet, is a device use to maintain a zero-gap between the camshaft lobe and the push rod. The push rod is then attached to the lifter on one end, and to the rocker arm at the other end. Thus when the cam lobe rise over, it will pushes the lifter - push rod - rocker arm, before the rocker arm converts an upward motion into a downward motion and presses down on the valve. The lifter have Hydraulic and Solid type. In which the main difference is that Hydraulic lifter doesn't need adjustments while Solid does. Should theres no lifter in the process, the push rod would not have follow up with the motion of the fast rotating motion of the cam lobe, and thus will result in the valves not opening and closing properly.
















The Red square marks the lifters while the Green marks the push rod, while the rocker arm is Yellow.

What happen before hand is that one of the lifter on one of the engine have failed and therefore the customer re-ordered a brand new sets of lifters from America's top brand Crowers. Before this he was using Crane, which is also a top brand. After bolting everything back on smoothly it went on the dyno today. And for everyone that knows or seen how to basically operate a chassis dyno, engine dyno is 10x more difficult.

At first i thought i was looking at some hugely complicated equations and numbers followed by numbers that all seem to be pointing to something but not to my understanding. It is as complicated as piloting a jet fighter, and there is ton of information being shown on the screen, and there are page 2, 3, 4 and so on, so theres almost 4 page full of information displayed that you can extract out of. And this is just from a carburetor engine, imagine a fully computerized EFI engine.....

Some of the 'normal' ones i can get was RPM, Torque, A/F left A/F right ( i assume is air fuel ratio for the left bank and right bank, oil pressure and temp and a little bit more, but wat i learn today, was the term Brake Specific Fuel Consumption. It is actually a measurement for the fuel consumption vs the power being outputted by the engine itself, aka the calculator for fuel efficiency. And in terms of generating big horsepower, everything have to be balance, as the carburetor is a four barrel type and uses two fuel bowl, both the fuel bowl's output volume must balance to a fine tolerance . In this case of the Chrysler engine, the difference between the 2 bowls are just +/- 1. And after just a a few runs, the car was making 650bhp at a increased 6000rpm and a staggering 701 nm of torque from 5100rpm onwards. This is proven to be a heck of a result as this car was meant to be a street car ! With just normal manifold and mild performance oriented parts this prove to be big big success.

But after finish the dyno, my boss suggest that we take the valve cover off to have a look, everyone was still joking about theres crack on the retainers, but then, my boss found something, the new lifters were fucked again ! This time 3 of them.....my boss suspect its something within the oil valley as when we start the engine up it was idling at perfection, but just might be that after the engine was turn off the oil starve up on the lifter.........

Such a shame things like this happens, but in all the bad scenario that it could happen, it happen here on the work shop, so it was a blessing in disguise actually. The customer was relatively positive bout it, stating that now that he knows theres a problem, when he fixed the problem, there will be a horsepower rise for sure !