Here's the scenario. I have a 1966 GTO with less than 2000 miles on it since restoration. I had the engine pulled and looked at by my machinist, who told me the engine looked fine. New rings and bearings and throw it back together. I had him do the work. I also had him rebuild the tri-power.
When the engine was installed in the car, it didn't run right. I spent a number of hours searching out the gremlins and addressing each one of them. From poor fittings on the gas lines, sucking in air instead of gas, vaporlock, to dropped floats, stuck floats, leaking seats, etc... Once I took care of these things, the car operated great. I was actually able to take my father out in it before he passed. It was his car since 1972, and since having a stroke 18 years before, he wasn't able to do the work or drive it anymore. But, within a year after his passing, the engine spun a rod bearing.
After taking the engine apart to find a bearing had spun, I brough the parts to the machinist, and he got on my case saying I should have taken the car to a tuner and had the tripower properly tuned, because in his opinion there was gas in the oil and that's what caused the problem.
We've driven this car for 50 years prior with the set up it has and never had an issue. After we let other people mess with the engine and carburation to refreshen things, now we have a problem. So, I'm not totally convinced this is the fault of an improperly tuned carb.
So, I want to ask:
How rich would a carb have to run to cause damage to the engine?
How much gas in the oil would be required to cause it to lose its lubricity?
Is idling really all that bad for an engine?
Thanks
As Scotty says, gas in the oil can certainly wipe out a bearing but is not the only possibility.
It does sound like there were issues with the carbs. (A dropped float or leaky seat will let way too much gas through.) Did the oil smell like gas? Was black smoke coming out of the exhaust? Were the spark plugs fouled with carbon, maybe even wet?
Here are some details from a leading engine oil manufacturer. It concerns dilution from diesel fuel but the issues would be basically the same as with gasoline, though the latter may be even worse being a stronger solvent:
It would have been interesting to send a sample of the oil out for analysis.
https://testoil.com/services/oil-analysis/fuel-dilution/
This article suggests that oil should be changed if the dilution level reaches 4%:
https://www.fluidlife.com/blog-fuel-dilution-example-effects-recommendations/
Aside from oil dilution, low oil pressure alone can cause problems. Was the oil pressure checked after the engine was overhauled and installed in the car? Low oil pressure can definitely cause bearing damage.
Oil pressure was and still read 60psi at start before pulling the engine to check this problem.
The oil does smell a little gassy now.
I changed the oil after having the stuck float filling the carb up with fuel.
The leakage from the seat was only enough to cause dripping after the engine was shut off.
All those issues were fixed and the car ran well for 2 years before this problem.
Hopefully this won't be an issue again.
So any amount of gas will destroy them, I take it?
Little gas residue always makes it past the piston rings. That is called blow-by. When it becomes an issue is when there's a lot of blow-by, and you don't let it basically burn off. Worn piston rings can cause this if your engine is already hot. It's inevitable that some residue will leak past the piston rings, it doesn't create a perfect seal. The engine can deal with ordinary blow-by, if you have a PCV valve, it recirculates back into the engine to be burned again. It's when it becomes excessive that you have a problem. For instance, smelling raw gas coming out of your tailpipe is way too much gas.
Realize gasoline is very thin and if you do get gasoline in the engine oil it can wipe out bearings because of the bearings are the softest parts. They're made to be replaced after they wear for tens of thousands of miles so you can actually fix them. But the downside is they're very soft and if you get gas in the oil or any other impurities, those soft bearings can easily be destroyed
So any amount of gas will destroy them, I take it?