"What I Learned Today" With Jeff Smith — Keeping Water And Oil Apart

“What I Learned Today” With Jeff Smith — Keeping Water And Oil Apart

We learned the hard way about sealing small- and big-block Chevys when a friend built a 454ci big-block that found its way into a pleasure boat. The owner bolted the engine in the boat and hooked up a water outlet at his house to test-fire the engine. At first, the engine ran fine. But, soon suffered from hydraulic lifter clatter so the owner shut the engine down. That’s when he discovered water in the oil.

The initial diagnosis was that the head gaskets had failed, but that seemed doubtful because the engine builder had used Fel-Pro quality composition head gaskets and the engine was fitted with a new set of TFS aluminum heads. We were asked to diagnose the problem, so the engine ended up in our shop. We drained the milkshake oil from the pan and replaced the filter and then decided to pull the heads. After only the third or fourth head bolt, we noticed that the threads had no sealant, and there was a substantial amount of water still clinging to the unthreaded portion of the bolts. We found the smoking gun.

All Gen-I and Gen-II small-block and Mk IV big-block Chevy engines are machined with the head bolt holes in the block drilled straight through to the water jackets. This demands a sealer on the head bolt threads to prevent pressure in the water jackets from pushing coolant past the threads in the block and entering the crankcase area.

We used ARP Thread Sealer on all head bolts that intrude into the water jacket. Also, make sure that the chamfer in the head bolt washer faces upward so it matches the radius o the backside of the head of the bolt and there is lube on the underside of the head of the bolts. This is where a majority of the friction occurs when torquing head bolts.

We decided to remove the heads anyway and replace the head gaskets just in case. This also allowed us to more closely inspect the combustion chamber and tops of the pistons. There appeared to be very light valve witness marks on the pistons, so we checked the valvetrain and discovered the “engine builder” had placed the cam gear one tooth off from the crank. We also removed the oil pan so that we could clean the remaining water out of the corners which required a new pan gasket.

We moved the cam to its proper position, re-assembled the engine, and carefully re-torqued the head bolts after using ARP thread sealer on all the head bolts and ARP Ultra-Torque between the head bolt washers and the bolt heads. We refilled the engine with oil and ran it on our test stand to ensure no more leaks. To completely eliminate the last vestiges of water required a third change of oil and filter but now the engine is healthy and running well. All this required at least 8-10 hours of work to fix the problems stemming from a hasty assembly. The original engine builder was lucky that the damage was really confined to water in the oil. It could have been much worse if the valves had hit the pistons.

Remember that head studs threaded into a small- or big-block Chevy must also be coated with thread sealer. Head studs should never be torqued into the block.

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About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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