Engine failure - high speed running

[40 Deluxe]

Is the horizontal mounting that big a problem? What about all the A's and AA's that spent their lives hauling people and freight up and down steep mountain roads? Or climbing out of a gravel pit with a full load, maxed out in low gear? They rarely saw the 'official' 3 degree-to-the-rear drop! Also, many a farm harvester or industrial machine (sawmill, etc.) was powered by an A engine that barked at full power all day long, and these engines were mounted level (or "horizontal").

[Art Bjornestad]

All my A engines are set up to have the pipe going into the crankcase. Henry thought it was a good idea.

[Ron W]

This link is to a drawing of the oiling system. It shows how the oil is pumped up and forward then runs by gravity down an incline to fill the sections of the valve chamber, one after the other. Then it runs down the angled pipe on the outside of the engine to bring oil to the front again and into the front of the dipper tray. It then runs back from one dipper pocket to the next filling each, one after the other. Hope this helps. Ron W
http://www.motormayhem.net/wp-upload...ine-oiling.jpg

[ppower]

My engine has a backwards slope of less than one degree, but it does slope backwards. I am thinking about raising the front lip of the oil tray or even sealing it against the sump to ensure that all the oil coming down the oil transfer pipe has to spill backwards into every big end trough.

[40 Deluxe]

ppower, Be careful about messing with the oil tray. Each trough has to be the right distance from the dipper on the rod cap or the dipper may hit or splash too much oil out if it is too close, or not get enough oil if the tray is too low.
Plus, doesn't the oil pump feed the valve chamber from the center of the engine and then the oil flows both ways? To my way of thinking, the "backward slope" is more for driveline alignment rather than oiling.

[40 Deluxe]

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Oops! Brain fade on my part! I reviewed the cutaway drawing and was reminded that the oil indeed is pumped to front of the chamber and flows to the rear. But I still don't think that a level or near level mounting will starve #4 rod. Look at the angle of the engine mounting in a Pietenpol airplane. I believe a lot of these ran the stock oiling system.
Have you verified the oil pump is putting out enough oil?

[ppower]

The replacement engine I purchased comes with a sump in which there is no gap between the front of the oil tray and the sump, so I plan to use that sump instead of the original which had a 1/2" gap.

I notice on both engines that the casting wall between the camshaft gallery and the timing case has a weir which is lower than the first rearward weir. I therefore plan to add a plate and drill a hole at the same level as the rearward weir to allow a limited amount of oil to flow forwards.

On both engines it looks as though the casting between the camshaft gallery and the timing case has been chipped away. since I cannot see how this could have happened in service, I wonder is this is a long forgotten tweak to reduce oil consumption? Does anyone know what the original casing looked like? A photograph would be great!

[Bob C]

Originally Posted by ppower

The replacement engine I purchased comes with a sump in which there is no gap between the front of the oil tray and the sump, so I plan to use that sump instead of the original which had a 1/2" gap.

I notice on both engines that the casting wall between the camshaft gallery and the timing case has a weir which is lower than the first rearward weir. I therefore plan to add a plate and drill a hole at the same level as the rearward weir to allow a limited amount of oil to flow forwards.

On both engines it looks as though the casting between the camshaft gallery and the timing case has been chipped away. since I cannot see how this could have happened in service, I wonder is this is a long forgotten tweak to reduce oil consumption? Does anyone know what the original casing looked like? A photograph would be great!

I think you will find they are all like that.

Bob

[bdave_mcc]

Originally Posted by 40 Deluxe

Oops! Brain fade on my part! I reviewed the cutaway drawing and was reminded that the oil indeed is pumped to front of the chamber and flows to the rear. But I still don't think that a level or near level mounting will starve #4 rod. Look at the angle of the engine mounting in a Pietenpol airplane. I believe a lot of these ran the stock oiling system.
Have you verified the oil pump is putting out enough oil?

Has anyone ever tried modifying the chamber heights at all to try and get oil to the rear chamber faster? in some cases it takes a good bit of running to get oil coming down the oil return pipe. or does an amount of oil stay in the chamber after shutdown to feed the rear main between startup and oil filling the chambers? Just a thought

[dave in australia]

Originally Posted by bdave_mcc

Has anyone ever tried modifying the chamber heights at all to try and get oil to the rear chamber faster? in some cases it takes a good bit of running to get oil coming down the oil return pipe. or does an amount of oil stay in the chamber after shutdown to feed the rear main between startup and oil filling the chambers? Just a thought

It's been working for almost 90 years, why stuff with it?

[ppower]

Originally Posted by Bob C

I think you will find they are all like that.

Bob

Should the weir into the timing gear chamber really be lower that the weir into the back 2/3 of the tappet chamber?! Does anyone have a photo?

[johnneilson]

If you are really worried about this, plumb the motor for full pressure. Many examples done over the years.
The root cause of the failure was improper piston to cyl clearance.
Once the PV rating of the babbit was exceded due to excessive drag caused by above, the rod bearing failed and beat around until it broke.

I agree that the std oiling system has worked for years, when done properly it is fine.
When the motor is asked to run near the limits, it is time to improve the design.

Unless there is some reason to stay with the "A" block, since it needs replacing, it may be better to locate a "B" motor.

J

[mcorrell]

What piston to cylinder clearance should be run at 300 degrees F? If set up at .002" clearance at room temp will become .0013" at 180 F will be .0006" at 300F, assuming everything grows uniformly (it won't). Again and not to beat a dead horse, the engine was never intended to operate at or near 300 F. The coefficent of thermal expansion of aluminum is about double that of iron. If you increase the clearance at room temperature for those temperatures I am sure there will be a lot of piston slap and oil consumption at normal temperatures.
The engine creates so many BTUs of heat as a byproduct of creating power and the cooling system must dissipate that heat. Too large a radiator and it runs too cold and the engine runs poorly and is inefficient. Too small of a radiator and the engine runs hot and we have seen the results.

[Simonpie]

I've been avoiding responding because I don't have direct model A experience here, but it seems to me that a lot of 2 stroke detonation experience applies, and that I do know about. You definitely had detonation problems. Whether high temp was the cause or effect is always the question.
You can look at better cooling, but no-one has mentioned reducing heat input to the system. Consider some judicious ceramic coating. Ceramics don't really "insulate" as they are too thin, but there is a boundary between the ceramic and the cast iron, similar to a head gasket joint, that provides a real thermal barrier. I'd coat the exhaust ports from the below the valve seats down to the face of the block. Also the top of the block between the valves and the cylinder. Find a good race shop that can mask the area off properly. Consider coating all of the head that faces the flame front. You can coat pistons, but the risk is that any little detonation can blast off ceramic and then there's sand dancing in your cylinders. Use at your own risk.
You can coat the flat face of the valves, as most valve heat transfers through the seat to the block, but that's grabbing at small fry.

Lastly, consider boring into your exhaust ports and inserting a stainless or titanium ring. This is similar to the header ring that is used stock, just deeper. Both ti and stainless have very low heat transfer compared to cast iron and the interface between the ring and the block is another boundary. I haven't done this on an A, so be careful of wall thickness.
None of this helps "cooling", it reduces heat put into the block and head. It can also increase the exhaust temp, so be sure that the header system is robust.
Ceramic isn't super spendy, but the inserts are machine time for sure.

Good luck. Cool project.

[ppower]

Simonpie. Thanks for that; some interesting lateral thinking. The fitment of a Model A engine was a cheap fix when problems arose on the original engine, so I doubt I will be going down that route, but it is food for thought.

[hardtimes]

Originally Posted by ppower

Simonpie. Thanks for that; some interesting lateral thinking. The fitment of a Model A engine was a cheap fix when problems arose on the original engine, so I doubt I will be going down that route, but it is food for thought.

I just caught up on your thread here.
You originally ask the question about oiling at the engine stats that you gave. Then you gave the info that the engine is/was original Babbitt with (original) dip/splash.
I do not know if you have or have not read a book by a member here, but he builds race B engines (B Ville , etc), and he states clearly that if you are running poured Babbitt engine, as stock, then dip/splash is good/adequate for low/moderate rpm use. However, he then states that if you intend to turn a poured Babbitt engine with high rpms, then you had best build full oil pressure system into that engine to keep it properly oiled during hard use...as the originally designed dip/splash system WILL not be sufficient to protect your investment. IMO, you may have proven his experience/opinions are valid.

BTW, I am near ready to start up a B engine with poured Babbitt rods/mains. I have installed the full pressure oil system and believe that that advice and his racing experiences will keep my engine together, even when run hard

Also, for the last 10 years, I've been running a full pressure B in my '30 roadster. I have revved it a few times , more than I may should have and it keeps getting stronger with time and tuning. For all the more $ and time it costs to make an engine for 'hard use' , IMO you will never get more bang for your buck ...than a full pressure oil system in an A/B.

[bettlesr]

If you go to a full pressure system, you might need to add some baffles in the oil pan so you don't run out of oil pressure on hard right turns. I had to add them to mine.

[ppower]

To complete the story.

The car is now running again. An already owned engine had forged pistons, which look properly engineered, with relieved areas around the wrist pin and horizontal and vertical expansion slots (as compared to the pistons fitted at the time of the blow up, which were just cast cylinders), and although there was some bore wear and the rings were a little loose, it was put into service. Surprisingly there is no oil smoke in the exhaust, and the air flow out of the oil filler is no worse than before. The engine is now running on water (instead of waterless coolant)and does not overheat.

My conclusion is that the pistons were picking up in the bores, even though the clearances were loose. Eventually the piston tightened so much that the car lost power, then it seized. On the third time of seizing the big end let go- whether the thread stripped first or the stud broke is impossible to tell.

[BILL WILLIAMSON]

Ppower,
THANKS for reporting back.
Bill W.

[Flathead]

Glad to hear you are up and running, and the problems are hopefully behind you.