Car 5.0 Not H.o.

Check the firing order. The HO firing order needs to work with an HO computer. A Non HO firing order needs to work with a non HO computer.

This doesn’t prove that the block is a HO block. Some trucks evidently use a HO firing order
with a low lift cam. However, it will definitely prove that a block can’t be HO because the firing order is wrong.

Remove the #1 & #3 spark plugs. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Slowly turn the engine until the TDC mark and the timing pointer line up. Mark TDC on the balancer with chalk or paint. Put your finger in #3 spark plug hole and crank the engine 90 degrees. You should feel pressure trying to blow past your finger. If you do not feel pressure, repeat the process again. If you feel pressure, it is a HO engine.

No pressure the second time, remove spark plug #5. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Put your finger in #5 spark plug hole and crank the engine 90 degrees. If you feel pressure now, the engine is not a HO model, no matter what it says on the engine.

Using a small carpenter or machinist square to mark the harmonic balancer off into 90 degree sections may be helpful here.

A 15/16 deep socket & breaker bar or ratchet may be used to turn the engine.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

The stock roller cam will probably be better that any flat tappet cam that isn't really wild. The reason is the roller cam opens and closes the valves very quickly. This gives more valve lift and more effective duration.



Roller cams have a different lobe profile from a flat tappet cam. A roller cam has a lobe shape like an inverted "U". and will reach maximum lift quicker and stay near maximum lift longer because of the shape of the lobe. The valve accelerates from closed to full open in a much shorter period of time than a flat tappet cam. the profile plotted on a graph would look something like this:

----- Full lift
/ \
___/ \_____ Zero lift

. Roller cams will typically develop more power and have better street manners than flat tappet cams with the same amount of duration. It increases engine efficiency and reduces air pollution, which is the reason Ford switched to a roller cam design for the 5.0.. The down side of using a roller cam is that the rapid acceleration of the valve train requires good springs and close attention to the design of the valve train.

A flat tappet cam has a shape lie an inverted "V". It will reach maximum lift slowly because the side of the cam has a slope to it to keep from overstressing the flat lifter. The valve reaches maximum opening and stays there for a shorter period of time. The valve takes more time to accelerate from closed to full open than a roller tappet cam. The profile plotted on a graph would look something like this:

-- Full lift
/ \
___/ \______ Zero lift

The down side of flat tappet cams is that the wilder the cam, the more the engine loses power at low speeds. It is more trouble to drive on the streets because of the loss of low end torque. However, the valve springs don't have to be as good, and the valvetrain design is simpler and lighter.