We are off the original topic but some interesting other topics have been introduced.
I am using Driven Racing Oil(R) 10W-30 in our black Cobra with VERY original engine. Beyond the zinc compounds required* for pre-2006 engines the maker claims it is formulated to help protect engines that go through any storage periods. Very original includes all the valve train from camshaft up Ford Motor Company installed in the engine plant in February 1964. I will still run up to 7,000 rpm with it.
https://drivenracingoil.com/i-30497803-hr2-10w-30-conventional-hot-rod-oil.htmlBrad Penn(R) 10W-30 is used in red Cobra with 1965 specification racing engine on the recommendation of the person that builds engines for top tier GT40 MKI and MKII restorations and their unreplaceably rare engines. It took decades to gather parts for this engine and I sure could not replace anything broken as parts are just not available anymore.
https://penngrade1.com/products/high-performance-oils/penngrade-1-partial-synthetic-high-performance-oil-sae-10w-30/*Zinc compounds. In 1960s engines the camshaft and lifter contact points are not the only concerns. The metallurgy and clearances of everything with a sliding element contact was designed with zinc anti-scuff compounds in their engine oil. In 2003, we bought a car with HP289 engine that had 3,700 mile on it since a rebuild. The owner used a synthetic oil without zinc that the maker advised be used only in modern engines. I have never seen a HP289 engine so worn. Every ferrous metal interface that had sliding motion (timing chain and gears, rocker arms, push rods, cam, lifters, and distributor drive gear come to mind) were extremely worn. The engine was hard to start and sluggish. I put a timing light on and the timing was super erratic, the worst I every tested. That prompted a tear down. The timing gears and chain were so worn I could almost slip the chain over the teeth with oily fingers and I could with a little probe. Long block wise, I kept the block, crankshaft, and rods. I discarded an oil drum full of worn parts and sold the messed up cylinder heads for $100. The person that had the engine built and then used inappropriate oil did not suffer extra expense but we did. I have seen abused 170,000 mile 289 engines in better condition.
We use Castrol(R) SRF(R) hydraulic fluid. Not all modern fluids are compatible with 1960s hydraulic system rubber parts. When researching fluids the top restorers of million dollar plus old race cars were using it, cars still capable in the case of GT40 MKIIs of running down straights at over 200 mph. Dependable brakes are critical. Back when I investigated it I read that its "wet" boiling point was higher that the "dry" boiling points 1960s cars once had. It will absorb water and not let it puddle in brake calipers or other little spaces.
Yes, I tried full silicone type hydraulic fluids. I tried two brands. I tried in 1965 MUSTANG GT350 SFM5S142 TWICE and 1964 Cobra CSX2310 TWICE. In each car every bolt on piece was removed cleaned and new rubber installed. Steel lines on chassis were pressure solvent washed and force air dried. The silicone fluid started leaking somewhere instantly, especially in the GT350 at the brake proportioning valve. I pulled each down and did the whole process again. Same results and the Mustang valve was still the biggest problem. Before giving up I installed a new old stock valve on the Mustang, same results leaked. Third complete tear down per car. This time I did not replace the rubber just installed a day ago. I did remove all rubber parts and remove the silicone based fluid form them. I put them back together and put conventional fluid in, no leaks. That was in the 1980s. We sold the GT350. The Cobra we still use and it does not leak hydraulic fluid.
Worth noting, but 1960s cars had hydraulic system designs that planned for brake fluid to induce a slight amount of swelling in the rubber components that get wetted. That part of the design plan was real important in disc brake calipers. When the first silicone based compounds were introduced they did the opposite as rubber tended to shrink a little or at best not move. (Trivia. The rubber compounds in the quad rings of your spin on engine oil filters are designed to swell slightly in use. That is why filters seem to get "tighter" in use.)
Remember the car we bought in 2003 with engine worn out in 3,700 miles. The prior owner used silicone based hydraulic fluid. The brakes at one corner were the only brakes it had that did anything. There were fluid leaks at master cylinders and at every corner of the car. Silicone brake fluid coated the entire underside of the car. When dismantled, every piece of rubber exposed to the silicone fluid had hardened and shrunk. Some rubber pieces broke into little chunks during removal. On the rebuild I used the Castrol material described above.
