MTFCA Forum

Greetings all,

I find myself looking for your advice once again.

My 22 T has fundamentally a fully rebuilt engine (new aluminum pistons, rings, and plastigauge rod and main journals) with a rebuilt carb, and a new BOSCH distributor, etc. She starts up quickly and runs smoothly but after about 20 minutes of driving I get a slight knock from the engine and it begins to loose power. In more than one occurrence its even stalled and is slow to crank for a few minute. I put a digital thermometer with a thermocouple inside the top radiator hose and the temperature stays around 195-200f - unless I'm going up a steep hill (in low) or at a high speed and she climbs to 210 - where I throttle back. I don't have any sort of tachometer to judge speed -

My carburetor bushings are not the greatest, and I suspect the mixture may go lean when warm due to bypass air.

For overheating my next steps are to 1) flush all, 2) put in a 50/50 mixture of glycol and water, and 3) strip the 'hi heat paint' I have on it now and then spray it with 'radiator paint' from Eastwood. If that doesn't improve it -I may switch to an electric fan ... and go from there. (a New radiator is beyond my budget) (note: no thermostat or water pump)

All that said, my biggest worry is the knock.

So, possibly expanding cylinders with lower compression? Expanding pistons with wrist pin knock? rods need to be checked and possibly taken up?
what else?

Thank you all again - I would never have gotten this car going without this forums help.

Your engine appears to be "new" and a little bit "tight". When the aluminum pistons heat up they will expand and get tight in the bores. Don't drive it like that. Instead, run it in your driveway at a moderate idle while staying near it. When you notice it beginning to slow down a bit, shut it off, let it cool until you can hold your hand on the head, and repeat. Eventually, you'll have it broken in. The knock is most likely a piston beginning to get tight. I'll bet you're not hearing it when the engine has just been started cold??

As for your coolant temperature, it's hot, but I would not say that it's overheating. When your engine is better broken in, the heat should go down some. (Double check your timing too. Being too retarded can make heat. Being too advanced can cause knocking.)

great advice- thanks!

You might want to put a fan in front of the radiator to move air as if you were driving. This would give you longer run times between the "HOT" knock. It would most likely shorten the "wait" times between "run times" as the thermosiphon will still be happening even with the engine off.

Are you able to do the "long screwdriver" hearing test to determine which piston / where the knock is coming from? It might help to determine if the knock is high or low and/or front or rear in the engine.

It is entirely possible that the thermosyphon system used for cooling in a Model T was not designed to be used with aluminum pistons.

Been Here Before wrote: ↑

Tue Jul 09, 2024 4:11 pm

It is entirely possible that the thermosyphon system used for cooling in a Model T was not designed to be used with aluminum pistons.

It's possible the pistons were fit too tight.

Been Here Before wrote: ↑

Tue Jul 09, 2024 4:11 pm

It is entirely possible that the thermosyphon system used for cooling in a Model T was not designed to be used with aluminum pistons.

Since probably 90% of T's use aluminum pistons, and probably 75% use thermosyphon, I'm guessing this is not a problem.

What size pistons are in it? How were the bores measured? Were they bored and honed during the rebuild? Honed only? Sounds like the motor is tight. Could fix itself with a few heat cycles as it runs in, but could be a problem if it's too tight.

If it were me I'd pull the head to have a look at the bores to see if there is any scoring. If not try heat cycling the engine a few times and see if that runs it in.

I believe the original motors used cast iron pistons. Newer rebuilds introduced the aluminum.

http://www.mtfca.com/discus/messages/17 ... 1316104086

As for clearance suggestions on the aluminum pistons see:

http://www.mtfca.com/discus/messages/80 ... 1255551432

Some of the rebuilders like to have every clearance tight in a newly rebuilt T engine. Was the engine rebored? It can be that the builder didn’t leave enough clearance to allow for expansion when heating up the engine. It wont be the first time it’s happened.

John kuehn wrote: ↑

Tue Jul 09, 2024 5:18 pm

Some of the rebuilders like to have every clearance tight in a newly rebuilt T engine. Was the engine rebored? It can be that the builder didn’t leave enough clearance to allow for expansion when heating up the engine. It wont be the first time it’s happened.

Yes this is an old subject.
The root of the problem is the little sticker on the box of new pistons calling for .002" clearance.
You need to remove the sticker & tell the machine shop the clearance you want.
According to typical standards, the machine shop would give you .00375-.004"
That would work, but I prefer a little more partly because there is no cylinder water jacket on a T block.

Thermosiphon is primarily based on temperature difference, difference in elevation between the heat source and heat sink, and flow channel diameter. It doesn't really matter what materials the system is made of, as long as there is a good temperature differential, appropriate elevation differential and adequately sized flow channels.

I worked and taught on a nuclear submarine prototype propulsion and electric generation plant. This was the ONLY thermosiphon nuclear reactor at that time. It worked great. All made of Inconel (stainless steel) Quiet, excellent power profile, great coolant (water) flow. Most reactors rely on pumps to move the water. When the pumps quit, there is a potential for serious problems. With that thermosiphon reactor, if we lost pumps, we were still in fine shape. Our only limitation was 60% of full power. To go above 60%, we needed the extra flow provided by the pumps.

Addressing aluminum pistons: Do you think the pistons ADD or SUBTRACT from the amount of heat generated by the engine? I see no substantial difference between aluminum and cast iron pistons. While the aluminum pistons MAY conduct heat a bit better than cast iron, the heat would be transferred to the head, block, engine oil. The head and block would be a benefit while the oil would be a slight detriment as some of the heat in the oil would be lost to the air outside of the oil pan. I believe this small amount of "lost" heat would NOT affect the thermosiphon to any appreciable amount. I submit: How many T engines have aluminum pistons, today, and still have adequate cooling?

There is another thread about a "hot" engine. The author measured 214 degrees F at the top of the head. IF, that engine was at sea level, with just water in the system, it would have boiled as the boiling point of pure water at sea level is 212 degrees F. Add altitude, the boiling temp. goes DOWN. Here in Denver, at 5280 ft elevation, water boils about 201 degrees F. It takes an additional 10-15 minutes cook time to get to appropriate done temps. except for meats, the cook time is less as the water is boiled out quicker and the meat turns out dry if cooked for a recommended time. Thus, we have to keep antifreeze in the coolant year round, ensure our coolant systems are clean as possible, and radiators clear of leaves, cottonwood cotton, and the like. We have more episodes of boiling (gurgle) after we shut off the engine. I have yet to boil over even after a long, hard run, but it will gurgle. I know this engine has been rebuilt by a reputable man and has aluminum pistons in it.

Did they set the ring gap too tight?

Sorry if I missed this being discussed here.... but what about spark,throttle, and mixture settings?

I don't think the problem is the cooling system, you say the car starts and runs fine until it heats up, then it loses power and heats up past normal operating temperatures.
There's a big chance the problem is related to the aluminum pistons.
I think the bores are too tight relative to rhe aluminum pistons, as mentioned before ; everything is fine when cold, as the engine warms the pistons expand more than the block and cause a LOT of friction, giving the engine a hard time turning and generating a tremendous amount of heat, that in turn causes overheating your cooling system to boiling point and the extra friction results in less power at the driveshaft.
So it is sort of the other way around than what you think, my guess is that changing to smaller pistons or cast iron pistons will solve your problem. I hope the bores are not scored yet, if they are a hone-job is called for, positive is that in that case you can keep the pistons
Good luck in solving your problems.

Aluminum pistons require a different (larger) initial clearance than cast iron pistons. If they have any effect on engine cooling, they would likely improve it somewhat. Montana 500 cars probably all run aluminum pistons. Modern style aluminum pistons with modern type rings offer many advantages of the stock cast iron pistons, particularly as relates to oil control and reduced bearing loading at higher engine speeds. Engine vibration is probably reduced somewhat.

Torsional vibration is greatly reduced with aluminum pistons as well as all of the other benefits.

Art Mirtes

Thank you all for the good advice.

When the engine was rebuilt it was done by a professional, seasoned, model T expert who I trust 100%. All tolerances and specifications were met.
We did have a bit of a struggle with the number 1 piston but clearances were all measured and met spec.

I now think the 'knock' may be from detonation - (hopefully not pre-ignition) from the extra heat- and my timing being too advanced.
I think the overheating is from poor radiator efficiency at idle speeds and under heavy load.

So - next steps will be to improve heat transfer by the radiator and tune up the carb/ points and plugs to run smoother at a lower advance...

For the radiator- Going from water to a 50/50 antifreeze will raises the boiling point 3'f (from 220 to 223) at sea level - which does improve efficiency somewhat -but I think increasing the airflow with an electric fan will be a better solution, because it reduces the mechanical load on the engine (no pully, belt, fan...) and it increases the airflow over the radiator... this car did overheat on the 4th parade- and it also overheats during my hill climb home...

Just throwing this out there into the ether, about 30+40% of heat transfer in an engine is through the exhaust & cooling system and supposedly another 30+% of fuel is used in the cooling of the engine. Any chance you have an obstruction in the exhaust manifold and/or the rest of the exhaust system? Are you running too lean? Have you ever use ThermoCure or Evapo Rust in the cooling system to help clean and loosen debris in the system before a flush? Did you paint the fins on your current radiator with radiator paint or just some regular rattle can paint? Is the pitch of your fan blades correct? Just a few things to consider if you can’t drop 1k into a new radiator.
Just an aside, I have a dreaded 6.0 powerstroke crew cab & one of many issues is the delta between oil temp & water temp. My range was way past safe, my head gaskets were not blown. I read about Evapo Rust on the powerstroke forum. From that info I drained & flushed the system dry. Then added 2 gallons of Evapo Rust then topped off with distilled water (though the post said regular water) and drove it several hundred miles over several days. When I drained & flush again I couldn’t believe what came out. I then recharged the system with coolant & distilled water, Magically my temps were significantly below the concern level. The #}]^** 6.0 has been doing great since & that’s been over 4 years.

Best John

Steve Jelf has a nice video on his web page on flushing the T cooling system.

JTT3 wrote: ↑

Wed Jul 10, 2024 2:34 pm

Just throwing this out there into the ether, about 30+40% of heat transfer in an engine is through the exhaust & cooling system and supposedly another 30+% of fuel is used in the cooling of the engine. Any chance you have an obstruction in the exhaust manifold and/or the rest of the exhaust system? Are you running too lean? Have you ever use ThermoCure or Evapo Rust in the cooling system to help clean and loosen debris in the system before a flush? Did you paint the fins on your current radiator with radiator paint or just some regular rattle can paint? Is the pitch of your fan blades correct? Just a few things to consider if you can’t drop 1k into a new radiator.
Just an aside, I have a dreaded 6.0 powerstroke crew cab & one of many issues is the delta between oil temp & water temp. My range was way past safe, my head gaskets were not blown. I read about Evapo Rust on the powerstroke forum. From that info I drained & flushed the system dry. Then added 2 gallons of Evapo Rust then topped off with distilled water (though the post said regular water) and drove it several hundred miles over several days. When I drained & flush again I couldn’t believe what came out. I then recharged the system with coolant & distilled water, Magically my temps were significantly below the concern level. The #}]^** 6.0 has been doing great since & that’s been over 4 years.

Best John

Steve Jelf has a nice video on his web page on flushing the T cooling system.

good point about exhaust - and lean mix.
Exhaust is all new - stem to stern
Mixture I believe is a bit lean due to worn bushings on the butterfly valve - I can hear a whistle sometimes from the carb...

Dirt dobbers & mice really like new metal ha. Put a new muffler on a T years ago & several weeks later went for a short drive. When I stopped I kept smelling some strange type of BBQ & you know the rest of the story, ha.

JTT3 wrote: ↑

Wed Jul 10, 2024 3:16 pm

Dirt dobbers & mice really like new metal ha. Put a new muffler on a T years ago & several weeks later went for a short drive. When I stopped I kept smelling some strange type of BBQ & you know the rest of the story, ha.

I once had a hard time getting my 27 to start after a winter. Cranking, cranking, cranking, starter fluid, did all the troubleshooting couldnt find a problem anywhere.

Well, it finally started with a BOOM, the muffler split apart, and a whole bunch of straw, leaves, walnuts went everywhere

Steve Jelf wrote: ↑

Wed Jul 10, 2024 5:32 pm

I, and many others, have never needed an electric fan. By now millions of people have driven millions of perfectly stock T's millions of miles without overheating. I wonder what has happened in the last 100 years.

I do agree- but radiators do fail --- a new radiator cost over $1000- a new fan cost $50.00 ... and I happen to already have a fan from another project- If I can fix it so I can drive it for $50.00 - I'm happy -

By any chance do you have a picture of your stock fan for a T?

ElGranadaT wrote: ↑

Wed Jul 10, 2024 7:23 pm

Steve Jelf wrote: ↑

Wed Jul 10, 2024 5:32 pm

I, and many others, have never needed an electric fan. By now millions of people have driven millions of perfectly stock T's millions of miles without overheating. I wonder what has happened in the last 100 years.

I do agree- but radiators do fail --- a new radiator cost over $1000- a new fan cost $50.00 ... and I happen to already have a fan from another project- If I can fix it so I can drive it for $50.00 - I'm happy -

I don't recall you mentioning that your T has boiled. If it doesn't boil, then it's not overheating.

I do agree- but radiators do fail --- a new radiator cost over $1000- a new fan cost $50.00 ...

Did I recommend buying a new radiator? No, I did not. Granted, a recore will cost more than a fan. It will also put a stop to overheating. Will a fan? We'll see.

One last little thing. When using aluminium pistons the wrist pins need to be honed. My then recently rebuilt engine stopped suddenly after a parade and long drive, engine overheating badly all the time. Engine stuck. Next day, engine turned over but clearly something was wrong. A better rebuild discovered that one piston had begun to melt from heat caused by un-honed wrist pins. A bit late for you to check that area, but if all else fails!?!?!

Update for the day:

For the overheating:

Found an excellent radiator repair shop here in the SF Bay area - who is very experienced with T's.
I knew my radiator was not stock - but as it turns out it' has a 6.5 inch top tank - as opposed to the stock version. I gather larger tanks were made in some Canadian cars, and there was an aftermarket radiator available for warmer climates- like India, Africa and south America. (Mine came by way of Argentina)

Bottom line; the radiator was clogged- and some tubes were showing signs of leakage- so, I'm getting a new 4 tube core put into it for $800.00 . The larger top tank, and extra row should keep things much cooler-

For the knock:

Aftermarket crankshaft fan pulley was loose- shimmed it up and seems fine -

Will update after all is back together-

p.s.
Before I started this thread I didn't know there was even an option to rod out radiators or replace just a core, so a word of thanks to those who educated me -

Rebuilding radiators used to be a common practice, and most every town had one or more shops. Today, you're lucky to find a radiator shop.

I hope getting the radiator in top condition is indeed the fix.
Your description of the symptoms & their progression still leads back to a tight motor seizing.

Hello all - I wanted to update this post on the car -

Thanks to all your good advice - I managed to find a terrific radiator shop here in the SF Bay Area. Its B&M Radiator - (42450 Blacow Rd, Fremont, CA 9453) The owners name is Grant. Great ol' guy... and I was surprised when I asked if he ever did T radiators and he said dozens. I ended up with a new core - with 4 tubes - ($850 total) and she ('Juanita' the car) now idles around 195 f. as opposed to the 212 + Steam engine I had before the rebuild... While there, I also had to shim up the fan pully- which was a bit loose and I machined out a adapter to go between the top hose inlet and the head- and put a thermocouple in the water flow... So - overheating is not a problem ---

But...

The stuff nightmares are made of... <insert sad face emoji here > It still knocks enough to irritate the hell out of me - I can say its not timing, because it happens through the range of retard to hi advance- . I have yet to try the trick of disconnecting each spark plug to see if somehow it might be a connecting rod - but with my trusty mechanics stethoscope I was able to narrow it down to the front of the engine - near no. 1 main... which is where I had troubles with a loose piston wrist pin a year ago...

Now we live on a very steep - and hill climbs are typically around 5 mph in low gear for a good 3/4 mile ... and although I have a new pick up scupper / tube from the flywheel paddles to the front of the engine - oil starvation 'may' have created problems...

I am going to drop the pan and inspect all - and probably do plastigauge on the rods at least - regrettably I can't get to no. 1 main though...

More news to follow --- and I'll update the post with my findings in a few weeks ... Till then, wish me luck!

motto of the day... Perfect is the enemy of good ... (nuff)

A few thoughts regarding your recent post.

A thermostat,( if thats what you mean) like a modern motor uses will restrict the open flow needed for a "thermosyphon" system. Unless its needed to slow the rapid flow created by a water pump, which you dont have.

If you find oil flow to the front is an issue, a high volume HH mounted oiler could help. The external oiler pick up is much higher (with too much flow @ times), providing an oil flow @ a steeper grade than even a large internal funnel.

When you short out #1 plug does the knock lessen? =#1 main problem.
If your rebuilder put in a regrind cam that REQUIRED a front thrust washer setup, but didnt, your knock could be coming from the lobe digging into the front cam bearing. I found/fixed this problem on a "professionally" rebuilt motor. You can see this thru the inspection cover. Evaluate the cam gears condition & tightness @ the same time. I hope your motor builder took into account your hill driving & put some serious oil slingers on.

Why do you claim you cant get to #1 main? It can be dropped & removed thru the dipper cover. You typically have to notch the pan a little bit to remove the 2 main bolts.

I have given you more possible places to check. It aint rocket science, I am confident you will figure it out.
Best of luck.

Hi John - Thanks for the reply-

Today I did pull the plug wires and no. 1 is definitely the source of the knock ... I should have mentioned this before but the knock frequency was in sync with a single piston power stroke ...
...
about the 'adapter' between the top outlet and head- (see image). I had it machined in China for $43.00 - fits great and I put a 3mm Type K thermocouple in it - and connected it to a small digital temp readout. So, no thermostat -

...
I will definitely look into a high volume HH mounted oiler ... every bit helps -

...
About pulling no. 1 main ??? I am confused on that one - from photos and the T Manual it looks like you need to split the bottom crank case from the main engine block? If I can get to no 1 main - GREAT! what did you mean though about "notch the pan a little bit to remove the 2 main bolts"... ???

Does it knock when you accelerate, or decelerate?

Acceleration knock = main bearing
Deceleration knock = rod bearing

RE: removing #1 main .
When you remove the nuts & let the main bolts drop, they are not quite clear of the block & cap. You will note the bolt heads will rest on the inside edge of the cover hole. So , you need to grind a small amount away to clear the bolt heads, about 1/4" into the crankcase edge then the bolts will drop out. The inspection cover will still seal with this small loss of material.
Easily doable to remove #1 main with the motor still in position from the bottom side.

Thanks Jerry- Currently it knocks at idle - I will pastigaugue both rod and main and hopefully it's just a matter of removing a few shims ...

given the frequency is in time with every power stroke I am thinking rod bearing - but I can see how it could transfer the impulse to the main also
if the rod bearing is in tolerance...

on the other hand - could it also be a wrist pin?

I did have a problem with a no. 1 piston wrist pin 2 years ago - and replaced all pistons and wrist pins then. All bearings were within spe'c with shims...

completely hair brained thought - aside from the hill oil starvation issue- what else could cause one wrist pin to wear more than any of the others?
it's a splash oil system... maybe a crankshaft defect?

learning one new thing every day -but sadly forgetting two at the same time ...

If it's clearly every OTHER revolution, or power stroke, it may indicate a cam or lifter or timing gear issue. Maybe even the timer. I'd check the rod first, wiggling it and plastigauging it at TDC and BDC. Before taking the cap off, it may be a good idea to wiggle it and compare how it feels with the other 3 rods. Check all rod and main cap fasteners for looseness. Once in a while, a loose motor mount or other loose item can mimic an internal bearing knock. A tight piston might cause a light knock due to excess friction with the cylinder. Model Ts don't like thick oil. A 10W30 is a good choice in warm weather. 5W20 is fine in winter with a tight engine.

Re: wrist pin: Some repro pistons were on the market some time ago that lacked an oil hole in the pin bosses. If you have those, it might explain a wrist pin issue.

"completely hair brained thought - aside from the hill oil starvation issue- what else could cause one wrist pin to wear more than any of the others?"
Lack of oil , piston issues. All (still) points to seizing when hot. You'll be looking for a seized/galled wrist pin.
Once you get the inspection cover off & remove the rod cap, the situation will be obvious. Look for evidence of a hot pin.
Its not from being worn loose.