Early on, in our ownership of our Road Runner, Rara Hemious Birdicus, we were excited to start repairing what we found wrong or damaged. Still, we did not forget the simple things, like maintenance and evaluating the soundness of the Hemi. We felt the 72k-mile Hemi was in good shape, but some testing would verify that.
Above: The Hemi had a set of Champion N-10Y spark plugs screwed into the heads. The plugs were nearly 40 years old, and in terrible condition. The carburetors were in poor tune, and the plugs looked carbon fouled. We corrected the carburetors, but the plugs had failed. The washers should have been removed when the plugs were installed.
Interestingly, the second owner drove the Runner 11k miles in his fifty years of ownership, and for that time, we found records for only two oil changes. One oil change was in 1980, and 10W-30 Quaker State oil was poured into the Hemi. The second oil change was in 2003, and the Hemi was filled with 10W-40 Pennzoil. A Fram PH8 filter was spun onto the engine at both oil changes.
In the past, we have used Blackstone Laboratories to evaluate the oil in our 2006 Charger. We thought this would be a great time to utilize its services to understand what was floating around in the oil. So, we ordered an oil analysis kit, which came with a container to capture a sample of oil and all the paperwork to send the oil to the lab.
Above: We have used Blackstone Laboratories in the past to evaluate our oil. The Hemi certainly was a great candidate for analysis. The oil had been changed a couple of decades ago. We collected a sample of oil from the Hemi and sent it to the lab. The results showed a few elevated metals in the oil, but they were nothing of significant concern.
When the kit arrived, we filled out the paperwork and followed the procedures to catch the oil in the container. As we captured the oil, we noted it was black rather than the amber-to-brown color like our other engines. With those engines, we tend to change the oil more frequently than every quarter of a century.
We completed the oil change without difficulty (adding seven quarts of 10W-30 Castrol and a Zinc additive). However, the oil filter spilled plenty of oil onto the K-member. Based on the dirt accumulation, the oil from the previous oil changes had not been wiped up. However, this time, we performed a painstaking cleaning.
Above: We used our oil filter cutter tool to separate the filter into two pieces. The Fram filter’s internals looked good, and there was no evidence of internal collapse. However, the oil was dirty and black in color.
While we waited for the results from Blackstone Laboratories, we used our oil filter cutter to cut open the filter and inspect what was inside. We found nothing of grave concern. As a friend stated years ago in his less-than-perfect English, ‘Glitter is good, chunks is bad.’ That means some metallic residue in the oil is normal, but large chunks could indicate severe engine damage. Well, we had some glitter but no chunks.
Above: Inside the oil filter cup were some glitter and small particles, but no “chunks” were in the filter. The filter element was free of metal debris; again, there were no large pieces of debris.
The oil results arrived via email; overall, everything looked decent. Below are the Blackstone Laboratories comments:
“A few metals assessed high in this report. Compared to universal averages, which show typical wear for this engine type after approximately 3K miles on the oil. Iron looks okay at this level considering the longer run, and aluminum doesn’t look too bad, but it might show a bit of extra piston wear. Chrome is from the rings, which seem to be wearing a bit more than they should be. Lead is probably from past use of leaded fuel, but that element can also show bearing wear. 0.5% fuel and a low viscosity are okay. If running well, check back in another 3K miles to compare.”
The results have us concerned but not alarmed. There were positive aspects to the oil analysis results, and we are optimistic about the engine’s condition. So, we will follow up with additional oil samples for Blackstone Laboratories to see if the numbers settle down with more frequent oil changes.
Above: After spinning on a new oil filter and adding fresh oil, we moved to additional tests of the Hemi. We needed a way to turn over the engine to perform the tests. We have a remote starter button that we attached a lead to the 12-volt post of the starter relay. The other lead was attached to the “S” terminal of the relay after we disconnected the yellow wire. When the button was depressed (squeezed), it connected 12 volts to the “S” terminal, which energized the starter.
The engine was last “tuned up” in the 1980s, which included lashing the valves as well as new plugs, wires, cap, and rotor. We would start our testing with compression tests of each cylinder. Following, we would perform cylinder leak-down tests, and then we would check the valve lash and adjust as needed.
In preparation for the compression test, we warmed up the engine. It was not fully hot, only lukewarm. We pulled all the plug wires. They were in poor condition and extremely brittle. The step we were most concerned about was the removal of the plugs. We hoped each would unthread and there would not be any thread damage or worse. The first plug was overly tight. When enough torque was applied, it finally popped free, and the plug threaded out without any additional difficulty.
Above Left: We used a compression tester to measure the cylinder pressure. The tester is an excellent tool for providing information about the integrity of the rings and valves. Above Right: Using the remote starter button, the engine spun over. We noted the pressure on the first pressure pulse, and after five pulses, we disengaged the remote starter button. The pressures were at the high end of spec, and the cylinder pressure variance between the cylinders was also in spec.
The other seven plugs were just as tight, but we removed each damage-free. The plugs were Champion N-10Y spark plugs, which were correct for the Hemi. Interestingly, the plugs were manufactured in the USA, which corresponds with the story we were told about the tune-up being performed in the 1980s. Champion started manufacturing plugs in Mexico beginning in the 1990s.
Above Left: Impressed with the compression test numbers, we broke out our cylinder leakage tester. Above Right: We calibrated the tester to 100 lbs. Using 100 lbs. of air pressure made the math easy, but our tester had a chart included in the case.
Above Left: To find top dead center (TDC), we threaded the cylinder leakage hose into the cylinder. We bumped over the engine until the pressure (thumb over hose) stopped. Above Right: We then plugged the hose into the gauge. If the engine had rotated, we had not found TDC. The gauge would have to be disconnected, and the process needed to be repeated. All eight cylinders had extremely low leakage numbers. For an engine with 72,000 miles on it, we were impressed with the engine’s condition.
The spark plugs’ appearance was poor. They were carbon fouled. Additionally, each plug still had its gasket washer installed. That is a mistake. The washers must be removed on the 426 Hemis. The factory shop manual states that the aluminum spark plug tubes function as the washers.
Starting on the passenger side of the Hemi, we threaded the compression tester hose into cylinder two. We connected our remote starter button to the B+ post of the starter relay and the “S” terminal (yellow wire) on the relay. With a battery charger on the battery (to maintain sufficient battery voltage), we depressed the starter button. The needle swept up quickly as the starter spun the crankshaft, and after five “puffs,” we disengaged the starter button.
Above Left: The Hemi’s valve covers had to be removed for our last adjustment. A few studs and nuts were missing, and nearly every valve cover fastener was damaged or mismatched. The valve cover gaskets had been leaking for a long time, and the loose and missing fasteners were likely the cause. Above Right: After removing the fasteners, the spark plug tubes were slipped out of the valve cover.
Above Left: The valve covers on Hemis can be challenging to remove. They are massive, but the cover is thin gauge metal. Excessive prying on the outer lip of the cover can cause it to bend. Above Right: We got the front section of the valve cover to release. After some manipulation, we freed the cover from the Hemi.
We noted the first and last pressure readings. The compression PSIg specs for our 10.25:1 compression ratio Hemi were 150-205 PSIg, with a maximum variation of 30 PSIg. After running through all eight cylinders, the compression numbers were between 185 and 205 PSIg. The variation between the lowest and highest cylinders fell into spec. The first puff, which provides information about the piston ring integrity, ranged from 115 to 135 PSIg.
Above Left: The dual-shaft rocker assembly is an engineering marvel. Everything looked good, so we proceeded to clean up the gasket. Above Right: We stuffed paper towels into each opening in the head. Using a gasket scraper, we removed the gasket material. After scraping the gasket material, we carefully removed the towels, ensuring we did not drop debris into our heads.
Above Left: We picked up a package of studs and nuts for the Hemi valve covers. The eBay listing stated they were just like the originals, and they were. Above Right: We used a stud remover/installer tool to snug each stud into the head.
Pleased with the compression test results, we moved to the cylinder leakage test. Starting with cylinder two, we threaded in the leak-tester hose and then bumped the engine over with the remote starter until we felt (with our thumb over the end of the hose) the compression pressure cease. At that point, top dead center (TDC) had been found.
Above Left: We bumped over the engine. Using a feeler gauge, we measured the lash on all the intake rockers first and then the exhaust rockers. Above Center: By loosening the jamb nut, we were able to turn the adjusting screw, set the lash, and retighten the jamb nut. Nearly every rocker needed to be adjusted. Above Right: We placed a new gasket on the cylinder head. The gasket fit perfectly over all the newly installed studs.
We attached the leakage tester to the hose while observing the harmonic balancer. If it did not rotate, we could continue. However, if it rotated, the piston was not at TDC, so we had to remove the leakage tester and bump over the engine again. The procedure must be repeated until the engine no longer rotates under pressure.
Above Left: After installing the valve cover, we threaded new nuts onto the studs. Above Center: We torqued the valve cover fasteners to the factory spec. While tightening the valve covers, we ensured the cork gasket did not slip out of place. Above Right: We cleaned the valve covers and installed the spark plug tubes. The heater core hoses were in the way when installing the valve cover. Working the valve cover onto the Hemi took just a few minutes.
When the tester was connected, we noted the engine leakage at TDC. The leakage percentages on our 57-year-old engine were phenomenal. Only two cylinders had a 6% leakage, while all the rest had 5% or less. The leakage ranged between 2 and 6%. Based on the compression and leak-down tests, the Hemi appeared quite solid.
Our last step in assessing the Hemi’s health was to check the valve lash. We also planned to install new OEM valve cover fasteners (studs and nuts) to replace the multiple studs, screws, nuts, and other fasteners that had been installed over the years.
Above Left: On the driver’s side of the engine, we lashed the valves like the passenger side. Above Center: Several of the rockers needed to be adjusted. Above Right: The valves were all lashed. Nearly all rockers required a minor adjustment, but they were last checked during Reagan’s administration, and we do not know if they were set correctly then.
We removed the air cleaner to access the upper driver’s side valve cover fasteners. When we unthreaded the fasteners, we noted some were only hand tight. Also, there were decades of evidence of oil loss around the valve covers and gaskets.
With all the fasteners removed, the valve cover would not budge. A problem with Hemi valve covers is that they are massive but have a small lip that contacts the gasket. The lip is easily bent if aggressive prying occurs. Luckily, we applied enough pressure to pop the cover loose at the top, and then we worked it free from the cylinder head.
Above Left: The driver’s side valve cover dropped onto the Hemi without difficulty. Above Center: We torqued the cover onto the engine. Above Right: Each tube fits perfectly into the valve cover.
After strategically placing paper towels throughout the cylinder head, we scraped the cork gasket remnants from the head. Once the heads were cleaned, we carefully removed the towels that had captured the cork scrapings. We installed new valve cover studs into the cylinder head. The last cleanup step was to remove the gasket material from the valve cover and spray down the inside to remove any debris.
Above: The valve cover fasteners were a mess. Several of the nuts were stuck on the studs. Others were bolts of two different hex sizes, and there was even a screw.
We reconnected the remote starter button to the starter relay. To lash cylinder #2 intake rocker, we bumped over the engine until its corresponding exhaust rocker moved about two-thirds open. One at a time, we measured the clearance (intake spec—0.028-inch cold). The lash on all four intake valves was slightly loose. We tightened them and rechecked.
To measure the exhaust lash on cylinder #2, we rotated the engine until the intake rocker arm was about two-thirds closed. Again, the lash was slightly loose (exhaust spec—0.032-inch cold), but on only three of the four rockers. After adjusting the lash, we spun over the engine and rechecked it.
Above: We removed the washers from our new Champion spark plugs. Each plug’s side electrode was centered and then the gap was set to factory specs. Because Mopar used Champion plugs for decades, we selected a set of N-12Y plugs. Based on the carbon fouling of the old N-10Y plugs, we selected a slightly hotter plug to reduce carbon build up.
With the lash set, we installed a new valve cover gasket, slipped on the valve cover, and tightened each fastener to 44in-lbs. The passenger side valve cover removal, cleanup, and lash procedures were the same. Like the driver’s side, we needed to adjust the lash on all four intake rockers. However, we only needed to adjust the exhaust lash on two of the four rockers. Again, we popped on a new gasket and installed the valve cover.
Above: The factory shop manual states to remove the washers, and the tubes will act as the washers. The washer-less spark plug will allow the tube to draw down, and the O-ring at the top will seal the valve cover and prevent an oil leak. The original plugs were Champion N-10Y, which is a colder range. Often, dealership techs installed Champion N-12Y plugs to prevent carbon fouling when the vehicle was brought in for poor running and misfiring operation.
The oil analysis, compression test, leak down test, and valve lash all pointed to an engine that is in excellent condition. With the data we collected, we will move forward with confidence that the engine is sound and will provide many years of service.
