Konrad

Ah, Metrology. If using the dial indicator make sure it is tangent to the rocker arc. You want to avoid as much cosine error as possible. I always tried to leave a witness mark on the rockers I reworked, or any surface that would not be built back up. This was to show that the minimum of material was removed. If the wear had passed through the case hardening it was done in service, not on my grinder. It is a good idea to talk to your machinist and ask that he try to leave a witness marks. Also ask him to hit the MMC (Most Material Condition). Most machinists try to hit the mean tolerance. These two requests will tell him, he is dealing with a guy that is more than your average customer. Wiseman, Neil. I'm sure I'm just showing my prejudice against exhaust systems.😖 As you might recall the two areas I hate to work on, when working on cars, is under the dash work and exhaust systems. It won't be long before this is a real nice daily driver!

I thought this project was on hold pending approval from SWMBO. Love the OEM Y and flex joint. Are you going to do the work? Or are you going to take her to a shop to deal with the inevitable adjustment (hint)?

That was also my concern with the lifter issue early on. But I'm happy to report the lifter and valve are following the cam profile just fine!

It was brought to my attention that the push rod never bent. (I've removed that ref. in yesterday's 9:07 post. In the March 28th post I did accurately state that we did not bend a push rod) So, we didn't have the classic late opening early closing valve one would expect with a newly bent push rod. The failure mode was that the adjuster was perched on the edge of the push rod bucket. When the coil bound the bucket split allowing the push rod to escape and bind against the rocker and tower. This bind allowed the exhaust valve to stay open with the subsequent flame path through the carbs. 5K hour mechanics are hard to find? That's only 2.5 man years on the job.

I too have to laugh at some of the tuning errors I see with modern equipment. I recall that the stop watch was one of the main diagnostic tools we had to find the "tune" (seat of our pants). Another tool that is lost to the pages of time is reading the spark plug. From my aviation background and time on the dyno I fail to understand this rich setting. Lean of peak is a well proven tuning state. This is for engines that run at much higher duty cycles than our cars. But yes, many of these older fuel system are rather limited in their capacity. As demands for performance, reliability and tractability increased so did the sophistication of the fuel metering system. Can you tell us what was the final finding on the engine that took multiple tear downs to find? I too have had some engines that were a bear to get right. I'm think of some that just had stubborn vibration issues that were out of specification. In the end this was traced to a soft curvic coupling allowing the shaft to flex too much.

Yep, these old machines weren't "turn key" devices. Even some "modern" engines have high oil consumption. I recall the 1979 Porsche 901 (911) engine with aluminum cylinders (Alusil) burned a quart/ 1K miles.

Balance is the key concept here. I've seen many an engine with burned valves. Exhaust valves cracked to the point I wondered how the engine even ran as it wasn't making any kind of seal. Pistons seized to the point the rods failed. And the common issues is overheating! This is the prominent failure mode with industrial engines as they often are run at over 80% duty cycle. The VW was an engine notorious for burned valves as the heads often had the cooling fins blocked. And being undersized often were run at full power for a long periods up long grades. The Chrysler IND flat six engine is the same engine you are familiar with. Chrysler made a "Winnebago" engine It was some long stroke big block 419 cid with sodium filled exhaust valves. As difficult as it was for me to understand the exhaust valve is responsible for getting approximately 80% of the combustion chamber heat into the water jacket. I saw lot of engines with soft bronze valve seats ranging from Cosworth to Datsun. Also saw a lot hard Stellite seats. It is fun to see what concerns the engineers had in what application. But on a dyno I never saw where a rich mixture was used to cool. As I recall the fuel mixtures were kept between 15:1 to 13:1 by mass. 1 being the gasoline. Yikes, did these engines with the operator adjustable mixture have any EGT feedback? Tractability is a good way to stay safe as long as the operator is paying attention. But how many times have we seen engines run out of oil were the driver said "It was just making engine noises"! I love these old engines. I like to see how the engineers and bean counters tried to solve the problem they confronted. *I only go back 45 to 50 years as I worked my way through school as an "automotive machinist and engine builder". I saw a lot of distressed metal, especially at harvest time!

Understood. I just need access to the car.

My experience is as an industrial mechanic in my youth. Later I had a hand in some Porsche based race teams. But most of my professional experience is with turbine engines. So while I know my way around a combination wrench. I yield to the hands on knowledge of guys like you and Don when it come to these engines. I have countless hours building/rebuilding the Chrysler Industrial (Ind) flat head six cylinder engines. I have never seen a gasoline engine damaged by too lean a tune. Yes, I've seen burned valves and holed piston when things fail like the jets get blocked (dirty fuel). Or the fuel metering orifice falls out off the fuel injector return line. So yes it is possible to damage an engine by going over lean. But you have to go way over lean. I've never seen using fuel as a combustion chamber coolant actually work*. In fact I've seen this cause accelerated cylinder wear from the washing off of the cylinder oil film. These were on high duty cycle industrial engines. Is there any documentation from the SAE, OEM or other credible source to give credence to the idea of using fuel to cool the combustion chamber to add life (safety margins). * With super charged direct injection engines I have seen the non fuel ladened inlet charge allowed to flow past the exhaust valve during valve over lap to cool the valve. Later after the exhaust valve closes fuel in introduced into the inlet charge.

@Grimythank you for your insight! I think you are on to something here. While I think I saw the advance moving when the throttle was goosed. Next time I see the car I'll pay more attention to the behavior of the advance curve. I'm thinking the advance maybe frozen as Neil is reporting gross mileage numbers. I have a question about setting the mixture. My understanding of the mixture screws is to allow for production tolerances and wear when setting stoichiometric mixture strength at idle. If so, finding the lean mixture highest RPM has the same result regardless of the energy density of the fuel or oxygen content of the fuel. This means there is no need to run the engine richer than peak rpm regardless of the fuel. True, fuels with a higher oxygen content or lower BTU content will have higher flow rates at peak rpm (idle mixture screw will be out more). I see no reason to add to this flow value by richen the engine even further. This is true for steady state conditions. Is the rich setting to deal with off idle surges, lean transition ports? Now if tuning for dynamic conditions (acceleration) with carbs set up (manufactured) for higher energy density fuel, things can get complicated when using alcohol fuels with the undersized acceleration pumps, power valves, emulsion tubes and transition ports. These are tractability issue with flat spots in the throttle response. Richening the main metering jet and idle mixture may mask this issues. But I like to first try to lengthen the acceleration pump stroke (volume) and speed (jet size) when tuning a carb to run on fuels that carry oxygen. Full disclosure; I'm a big proponent of lean of peak tuning. I learned of this with the Allison and Packard aircraft engines, of WW2, thanks to Lindbergh's long distance work. Don't confuse this with overly lean engines and associated burned engine components!

I'd like to add my thanks for Don's gracious assistance and access to his shop. This project got a bit out of hand with the failed push rod, ignition timing and carb adjustments. We basically lost all the base lines. But with Don's knowledge and tooling we got Neil's car back to being the smooth machine she was prior to pulling the head. I feared that with the pushrod issue the valve might have tapped the domed piston. I wanted to make sure that the engine was mechanically sound before doing any more "tuning work". As Don has a leak down tester we drove Neil's car down to his shop. I was pleasantly surprised at just how good a shape the engine is in, mechanically. The leak down showed 15% leakage and even after the rings dried was still above 20%. All the leakage was past the rings. (This is a good sign, it means the rings aren't so tight as to be adding too much drag). This was the first time I was in the car after taking off the head. On the drive down. I noticed that the carbs would sneeze under trailing throttle, The car bucked at low speed in stop and go traffic. But I didn't notice any pinging when accelerating. All these symptoms could be signs of there being an open valve or too much ignition timing (other than the lack of a knock). On the drive down I was getting more and more depressed talking myself into thinking that the valve was bent. At Don's place we shut down Neil's car and played a bit of a shell game moving some other cars around. When Neil tried to restart the warmed up engine the starter protested. Both Don and myself knew what the issue was. I was feeling much better! But since we had made the trip down we went ahead with the leak down test. If for no other reason than to eliminate any lingering doubt. So what was the issue? Well, too much ignition advance! This brought up an issue I was having earlier in that I couldn't find the timing marks on the flywheel. Changing the distributor one tooth had it's own issues. We will need to look into these ignition issue a bit more in detail. But for now the engine is a smooth as we have ever seen her. But she is running a bit retarded. We synced carbs at idle and adjusted the carb idle mixture. Mainly because Don had a Uni-Syn. (Hint: If you guys have multi carbs make sure all are flowing at idle so as to keep the fuel circuits purged and ready to flow when you demand it [step on it]. Far too many folks think the stumble is from too much fuel when the second carb opens up. When in fact it is the lack of fuel from the second carb while it purges the vapor lock). So how did the push rod fail if the valve didn't hit the piston? With the effectively longer push rod from the rocker sitting on the edge of the bucket the valve spring became overly compressed and coil bound. With the coil bound solid, something had to fail. Luckily the push rod bucket failed with no secondary damage. The car still needs some fine tuning but that's for another day.

In San Francisco we have a lot of clutch burner hills. 😒 The grades are so steep that even 90 weight oil will slosh. Are there any silicone compounds that are suitable for oil emersion? Despite what I read on the Permatex package, I find form a gasket to show signs of deterioration in less than a year when exposed to petroleum distillates.

Yikes, this process was by the same engineers that had us torque the head using the periphery method. It works, but I see no benefit and it actually is rather difficult. I did learn that it is possible to adjust an engine with solid lifters while running. It's not a process I'm likely to repeat. But I did learn a new process.

WOW, that looks like doing it the hard way! To those that advocate adjusting the valves with the engine running what is to be gained? How is the precision and the how accurate are you to the spec value? From here it looks like a good process to strip the locking nut and may even break the adjuster screw. I hope nobody is going to tell me that it helps with the exhaust stem expansion. (I'd think at idle the EGT is so low as to have little effect worth addressing this way. Many high powered engine have a clearance spec larger for the exhaust valve even with an engine at operating temps, as the valve stem does grow based on the power setting ).

First I need to apologize to Neil. As pilot in command it was my responsibility to make sure this kind of rookie mistake didn't happen. I failed to make sure all the push rods were seated in the rocker arm before torquing down the rocker towers. As the cup is very thin and we didn't bend any push rods I think the damage may be limited to the push rod and adjuster screw. As to the torque I couldn't get a crowsfoot to work as I had less than 60° free movement. (A 12 point crows foot might have worked but I don't have any of those in in the bay area). So we pulled the rocker shaft. The head needed to be re torqued! Generally the cold side bolts had a break a way torque of about 10 ft/lb less than what I had torqued the bolts to originally. Re-torquing these bolts I wound up on average adding another 1/4 turn (some more some less). The hot side of the head had the break a way torque about 15 ft/lb less than what I had torqued the bolts to originally. Retorquing these bolts I wound up on average adding about another 1/2 plus turn (some more some less).