Weakest link, engine

[Terry, NJ]

In conjunction with Brent's excellent inquiry regarding lightened flywheels, I'm asking what is the weakest link in a Mod. A engine. My Saab 9000 4 cyl has 170,000 miles, My Ford E 150 V6 152,000, my VW Jetta 1.8 TDI Diesel is 110.000. All of these mileages on a mod A and it would be totally worn out. Yet those car run well. Granted some have squeezed 100K out of the Mod A. but most do not. What is the most common cause of failure? Is it wear? Or breakage?
Terry

[gweilbaker]

I would tend to think it has to do with what it was designed for, the cars you mentioned were designed differently than those of the Model A. The times and conditions are very different, a lot of experience and engineering came after the Model A. The A is a car that requires routine maintenance, including re-babbiting, it is what it is. To me the biggest failure is the distracted drivers around me.

[TomW]

I think it's as you said: "totally worn out". Today's oiling systems are better, and use filters. Even with short oil change intervals, I think that there's probably a lot of stuff in the oil that's sandpapering the engine.

[V4F]

center main seems to be the weakest point to me . to much rpm kills it ...........

[BRENT in 10-uh-C]

To me, the weakest link is the fiber timing gears. Use is detrimental however so is letting the engine set too as the gear deteriorates and starts losing teeth.

[John Stone]

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IMHO it is the person driving it. New people don't know how to manage the spark lever. They think they are behind the wheel of a modern car and expect too much out of it. Pull 'er down and go. Takes out the lower end.

[C26Pinelake]

I have 6 Model A's and I have replaced the fibre timing gear on 3 of them !
Brent has my vote !
Wayne

[H. L. Chauvin]

Terry,

Humble Opinion:

Although expensive on the long run, this would be a learning experiment to try on "all" of one's next "new" modern vehicles in order to try to find a few items that cause Model A engine wear or failure; e.g. try running the "new" engine(s) after:

1. Removing the air filter.
2. Removing the oil filter.
3. Removing the PCV valve.
4. Removing the coolant thermostat.
5. Allowing the oil filler tube to suck in unfiltered air.
6. Allowing the oil dip stick to be uncapped, &/or without a rubber grommet.
7. Operating vehicle with a partially clogged radiator similar to an 80 year old radiator with water pump grease in the tubes with no temperature gauge to monitor same.
8. Advancing the timing a little too much, as is done in some cases with a Model A high compression heads. (Adding a manual spark advance inside the "new" vehicle would help to compare apples to apples).

Then after 170,000 miles on one's new vehicle, write a report on how the "new" engine compares to the Model A engine.

Also, to add to the mix, one can try non-detergent oil for 170,000 miles in the new engine without removing the oil pan.

[juke joint johnny]

HL Chauvin makes some good points!!!

I think the Well Maintained Model A would last a very long time,
The trouble is most of them were probably not looked after for all their 80 plus years!!!
When they became known as Kid's jalopies !! or during the Depression, how many could afford to change the oil or grease anything?

It's to easy for us to forget how hard peoples lives were back then . The Model A was the workhorse that pulled them through to better times !!
John Cochran

[juke joint johnny]

The Weakest Link !!! Could that be the Loose Nut behind the Wheel???

John Cochran

[newshirt]

Weakest link: I think it's the three bearing design.

Modern engines have more bearings. With only three, I think there's too much crank shaft flex, which shakes the engine to an early death. Can you tell I want a rebuild?

[Kevin in NJ]

The Model A engine is a very robust design. The weakest part is not the engine, but people trying to rebuild the engine not understanding how it needs to be rebuilt.

Possibly the greatest asset is also it weakest point. That is its ability to run when things are just far from working right. So anyone can throw it together and make it function. There is a big difference between the engine returned to factory specs and one put together based on an "interpretation" of the specs. To be direct, there are those that feel is it just a little 4 cylinder car you do not need to be very careful in building it.

There are 3 things that one might consider weak and Ford corrected as they learned more. The camshaft, the ignition cam, and the higher compression head. The cam and the ignition cam are two big changes that happened back in 1932 with the Model B. With the advent of better gas the high compression head is nice, but not critical.

There is little comparison to getting 200,000 miles on a modern car because the A engine just can not go there. You will have to replace a lot of parts to get to the 200,000 mile mark.

Newshirt complains about the 3 bearing design. While that may not be the best design, it is very functional. I would point out the vibration issue is really a post production issue as people rebuild the engines without the necessary attention to balance details. You put 60lbs spinning .005" off center and something is going to go wrong (this is more common then you would hope). Which takes me back to my first point, it is all about understanding how the engine was built and properly rebuild it.

[Purdy Swoft]

I think that the weakest link is the fiber timing gear followed by the split skirt pistons. I've had four timing gear failures in the past 52 years. I've had two engines to drop the skirts off the pistons on the number 3 & 4 cylinders, both engines had lots of wear.

[Flathead]

I think Mr Chauvin nailed it. Let's level the playing field. One can't deny that engine design has come a long way, but simple and basic can have advantages. As for three main bearings, I think crank stiffness and journal/bearing size are more important at these HP levels. The V8 has three mains and works well in regular use.

[JoeWay]

I have read that the two main factors (by a LONG shot) which allow modern long engine life are computerized fuel injection and better oil.

Fuel injection systems turn off fuel flow at the instant the ignoition is cut, so excess fuel is not ingested to wash the oil off the cylinder walls.

Most of us can't take advantage of injection in our Model As, but all of us get the great benefit of modern oil--well, all except those who are still using single-weight non-detergent because "that's what Henry put in". And even that oil is better now than it was then.

Joe

[Mike V. Florida]

I'm with the Johns, the driver.

[CarlG]

Originally Posted by BRENT in 10-uh-C

To me, the weakest link is the fiber timing gears. Use is detrimental however so is letting the engine set too as the gear deteriorates and starts losing teeth.

I'm putting one of Dan McEachern's bronze timing gears in my engine this week (along with a matching crank gear)

[H. L. Chauvin]

A study on wear or failure for Model A marine conversion engines operating on water would also be as interesting as reply #8 above.

Model A Marine engines, as well as other gasoline engines, had flame arrestors for safety in lieu of air filters; however, being always on water with no road dust, engines never needed air filters & other boats in adjacent paths never kicked up harmful dust.

Many constantly used Model A Marine engines were "always" properly cared for & lasted over 15 years with no rebuilding. Water temperature entering the hull was always cool; but also engine coolant without radiators were temperature controlled & monitored.

Marine engine maintenance & mechanical knowledge was a "must" & had "high" priority with commercial fishermen -- stuck on the road with a vehicle, one walked for help; stuck out on the Gulf or Ocean, too far to row against a tide or a wind -- no radio or cell phone communication -- engines & components well lubricated & were kept in tip top shape at all times.

[Terry, NJ]

Thanks Guys! I think now that engine failure seems to be about 60/40 wear vs breakage with fiber cam gear failure being #1 (And I just bought a new fiber gear for a engine I'm doing.) But the solution to extending engine life is to keep it clean inside. Air and oil filters are a must.
Terry