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When I bought my car I was told to never use a synthetic in my Fontana so I usually use the ordinary Castrol GTX 20w50 (mineral oil) in my Fontana Aluminum engines, but just now noticed this Castrol Classic stuff apparently with high zinc and prosperous. Im thinking may not be great for and aluminum engine from some discussions I have seen. Just curious what others think?



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Zinc and phosphorus are the main ingredients in ZDDP.  If your engine has a flat tappet cam then you pretty much have to use oil with ZDDP to prevent wear on the tappets and/or cam lobes.  In the 1970's all oil had zinc for this reason.  Then catalytic converters came along and zinc had to go because it fouls the cats.  Detroit switched to roller cams at the same time zinc was left out of most engine oils.  If your Fontana engine is flat tappet then zinc (ZDDP) would need to be added to the Castrol GTX 20/50.  Valvoline VR1 has always retained its zinc content and that is what I have been running in my flat tappet engines.  It is good to know that Valvoline VR1 has some competition now.

Last edited by stevebuchanan

I have a Fontana block with a hydraulic roller camshaft. The engine builder told me to use high Zinc oil because of the load that is put on the distributor gear. I am also using a high pressure oil pump, which can increase the load on that gear. There are several different brands of oil that offer high Zinc content for older engines and they are not hard to find. In my opinion, it is better to stay safe and use the high Zinc oil rather than gain an advantage with higher temperature capability of a synthetic oil.

@does200 posted:

Interesting replies, thanks. I'm just not sure what is in my engine builds, I bought the cars with a 427 Fontana and the other 417.

Jan, you might be able to figure out the type of lifters (solid or hydraulic) and the type of cam without pulling the intake manifold on the engines.  Take a valve cover off and try to wiggle each of the eight rockers up and down.  Four or five will be unloaded (on the cam base, not the lobe).  If the lifters are solid then you will feel the .020" valve lash (gap) on the unloaded valves.  If there is no gap on any of the lifters then it is a hydraulic setup.

Determining if the setup is roller or flat tappet is more involved.  Take off one of the rockers and then take out its pushrod as well.  Use a flashlight to look down the pushrod bore.  Or better yet use a borescope since they are now cheap, as low as $20.  If it is a roller setup you will see the retaining system for lifters (either bars on lifter pairs or a big spider clamp with dog bone retainers on the lifters).  If you don't see a retaining system for the lifters then it is flat tappet.  When you reinstall the pushrod and rocker, that valve will have to be adjusted.

DE5EC751-ADC0-4745-9969-1FCEC2EC4AD26FD25CF1-D529-485A-887B-A23D766469B9Regardless what type of Cam, the Best oil for a Fontana based engine is PennGrade 1 20w50 Partial Synthetic Motor Oil. Contains High Levels of Zinc and Phosphorus. That’s what I use on my 427 Fontana Engine with hydraulic roller lifters. Best Oil in MHO. Running Eight Stacks EFI. 520 RWHP and 500 Lbs of Torque at the Wheels at 6200 RPM.


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