Here’s the latest reader question, along with my reply!
Bryce asks: Should I take into my possession an older car with a flat tappet camshaft? And does it make sense to switch to a roller camshaft in light of low or no ZDDP motor oil?
My reply: Lots of variables here, but let’s leave the cam aside for a moment and consider the car. Is it sound? Is it priced fairly? Do you like the car? In other words, the same basic considerations that would apply to any used car.
Put another way: I would not want to buy a rusted out old heap with not much potential and a too-high price regardless of the type of cam in its engine. But I wouldn’t hesitate to buy a desirable car in good condition at a fair price that had an engine with a flat tappet cam.
Now, to some specifics about the cam.
Flat tappet cams aren’t bad (as in defective) cams; their chief deficit from a functional point of view is that more aggressive/performance grinds get progressively less and less “streetable” because of lobe profiles. Have a look at the pic below; the roller is on the left and the flat tappet cam is on the right. A flat tappet high-performance cam will have a lopey idle because of the steep pitch – to use a roofing analogy – of the cam lobes. Performance enthusiasts love the sound – but it can be a bear to live with in stop-and-go traffic. These types of cams also usually produce a weaker vacuum signal at idle and often do not work well with automatic transmissions.
In a nutshell, it is tougher to put together a really powerful engine with a flat tappet cam that is also a street-drivable engine. As an example, I installed Pontiac’s Ram Air III camshaft in my ’76 Trans-Am’s 455 V8. This cam is about as aggressive as I can go without compromising the car’s drivability. But it is a relatively mild cam – in terms of power production – by today’s standards.
By roller cam standards.
One of the reasons the OEMs (i.e., the car companies) switched over to roller cams – this began in the ’80s – was because they were able to (literally) ramp up more aggressive profiles in performance cars like the Mustang GT of that era while maintaining good idle quality as well as engine vacuum at low RPM for power accessories such as brake boosters, etc. Roller cams are one of the reasons (along with much better airflow through the heads) that today’s performance V8s make 400-plus horsepower easily, with Camry-like idle quality.
My TA sounds very tough but the 455 only makes about 320 horsepower – about the same as the current Mustang’s 2.3 liter four cylinder engine.
The chief deficit of flat tappet camshafts from a maintenance point of view is needing to find oil with the necessary additives, as you’ve noted. However, it is not hard to find this oil. AMSOIL sells it (see their ZRod line) and you can also buy the additive as a stand-alone and add it to any high-quality off-the-shelf oil.
The AMSOIL costs about the same as any other high-quality oil so provided you plan ahead and have the oil on hand for oil changes – which you won’t have to do as often if you use AMSOIL – it’s not much of a big deal to maintain a car with an engine that has a flat tappet cam.
So, assuming you like this car – and the price of the car is fair – I’d not hesitate to acquire it if I were you.
Finally: Yes, it makes sense to switch to a roller cam, but not because of the ZDDP. It makes sense if you want a big performance bump without sacrificing the streetability of your car.
I am planning to do this myself. The swap is pretty straightforward. If you can change out a flat tappet cam, you can install a roller cam. And if you go with a roller cam, you can go with a more aggressive profile and end up with much more power without that loose nuts and bolts rattling around in a tin can idle quality!
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