Recommendations to repair-not rebuild-a Model A Engine

[Bud]

I just recently acquired a diamond block Model A engine. I removed the head to see what I bought and found the bores only .040 over. The bores look very nice, but the engine, head and spark plugs look fairly black with soot and oily. I have not looked at the head and block surfaces yet, nor have I inspected the main and rod bearings for clearance.
The thought has crossed my mind that if the block and head look good visually, perhaps I could do some service work to this engine without sending it to a rebuilder. I could perhaps regrind the valves, install new valve springs and cam gear (if it needs it), install all new gaskets, generally clean it up and have a good engine as a spare without a big investment.
My question is: what do you recommend in evaluating this engine and repairing short of rebuilding it?
Can I re-use the pistons and put new rings on? How do I determine if the rings really need replacing? Same with the valves. I am interested in your recommendations. Thanks in advance.

[J Franklin]

You can do a lot to improve an engine if the cylinders and bearings are not worn excessively. Rings, take up bearings, lap the valves, & Etc. that's how things were done during the depression (1930's).

[BRENT in 10-uh-C]

Bud, any competent engine machinist can use bore gauges to check the cylinder walls for taper or out-of-round. A good Model-A machinist can advise you based on what he sees regarding type of valve composition, type of guides, camshaft, and the Babbitt appearance. He will also be able to look at the pistons and install a ring to see how much tension is there.

My personal feeling is you need to determine exactly what your plans are first. If you are only looking for a parade-type engine, it may be perfectly fine as-is. If longevity & reliability are of utmost priority, you may want to explore rebuilding anyway. Since it is a spare, I would not waste the money on rebuilding it at this time unless this engine would become your good powerplant and the one presently in your A becomes the spare.

[Synchro909]

Originally Posted by BRENT in 10-uh-C

Bud, any competent engine machinist can use bore gauges to check the cylinder walls for taper or out-of-round. A good Model-A machinist can advise you based on what he sees regarding type of valve composition, type of guides, camshaft, and the Babbitt appearance. He will also be able to look at the pistons and install a ring to see how much tension is there.

My personal feeling is you need to determine exactly what your plans are first. If you are only looking for a parade-type engine, it may be perfectly fine as-is. If longevity & reliability are of utmost priority, you may want to explore rebuilding anyway. Since it is a spare, I would not waste the money on rebuilding it at this time unless this engine would become your good powerplant and the one presently in your A becomes the spare.

Brent talks sense.

[hardtimes]

Originally Posted by Bud

I just recently acquired a diamond block Model A engine. I removed the head to see what I bought and found the bores only .040 over. The bores look very nice, but the engine, head and spark plugs look fairly black with soot and oily. I have not looked at the head and block surfaces yet, nor have I inspected the main and rod bearings for clearance.
The thought has crossed my mind that if the block and head look good visually, perhaps I could do some service work to this engine without sending it to a rebuilder. I could perhaps regrind the valves, install new valve springs and cam gear (if it needs it), install all new gaskets, generally clean it up and have a good engine as a spare without a big investment.
My question is: what do you recommend in evaluating this engine and repairing short of rebuilding it?
Can I re-use the pistons and put new rings on? How do I determine if the rings really need replacing? Same with the valves. I am interested in your recommendations. Thanks in advance.

Hey Bud,
If you strip block down bare for exam and/or rebuilding, PRESSURE TEST it !

[Bud]

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I would like to explore what I can do myself without incurring all the time and cost at a rebuilder. Ideally that would be the way to go. But I suspect this engine is not at the rebuild stage. My understanding is this: I can check the mains and rods with plastigage and mike the crank. I can check the cylinder bores with a bore gauge. I can examine the valves (recommendations?) and perhaps hand re-grind them (which I have never done). I like the idea of a pressure test (but I don't have the $250+ test kit). I can visually inspect parts, clean up the engine in general, etc. I wonder if I have to go to new pistons: can I evaluate the ring grooves, mike the rings???; go with new rings/old pistons; use feeler blades between the rings and cylinder walls? I can take up the mains and rods if necessary. I would like to know what I can do. I want to learn more about the process. Yes the most reliable way is to turn it over to someone else and write a check, but I learn nothing that way. Another alternative is to let the motor sit until I need it (or until it is sold from my estate someday). I am looking for a middle ground between a total rebuild and just gasket replacement. If I discover some problems at least I know what I have and can always go the rebuild route. So any other ideas out there? Thanks again for your input.

[jeep44]

A few hints if you decide to have a look inside that engine: First, get the Model A-specific engine stand mount, that fits in the four-wheeled Harbor Freight engine stand-then you can swing the engine around. Get a paint pen, and mark every bearing cap with a number, and a line that will tell you the proper way to put them back on. Do the same with every piston-number it, and paint a line from the cap to the lower part, so you don't get the bearing caps turned around or on the wrong piston. Get a piece of cardboard, and as you remove each valve, number it and put it in a numbered hole in the cardboard, along with the valve guides, keepers and springs, each set in a seperate, numbered baggie. The idea is that you want every part to go back in the same place, and the same orientation as it came out. As you clean the valves off (I wire-wheel them) you will lose your paint marks, but do them one at a time, and re-do the marks before you put them back in the right place in the cardboard holder.
I re-cut my valves with a hand-cutter ( one of the very useful tools I've found at swap meets), and re-grind them by hand with grinding compound. Not difficult, but tedious.

[H. L. Chauvin]

Hi Bud,

You probably know this already; however, just in general, and as simple as this may appear:

1. It is amazing what one can find out about the "history" of a vintage engine by asking the previous owner(s) questions, only ......... "IF" ....... this is possible.

2. "IF" possible, questions asked the seller "after" the seller is paid, the answers are usually answered very accurately and can provide most helpful historical information.

3. A few possible questions asked could be if there were any past engine problems when the engine was running, like maybe noisy valves, oil burning and/or blow-by, engine knocks, piston slaps, water leaks, oil leaks, water in oil; and ask about types of oil used like detergent/non-detergent; how about, did it every get overheated; and maybe, when was the last rebuild and/or repair, etc., etc.

4. Depending on former use, oil change intervals, my guess is that "IF" you demand utmost cleanliness inside an engine, this engine could very possibly need a thorough cleaning.

5. When dismantling, tag parts such as pistons & connecting rods 1, 2, 3, & 4; valves and valve guides 1 through 8, all tagged with tags or similar identification like placing in numbered boxes ...... and be observant of direction of scoop on bottoms of connecting rods ...... if not very familiar with a Model A engine, cell phone photos never hurt.

6. A book could be written on what you are asking; however, as a general rule if engine was used say over 5,000 miles, as a minimum, I usually install new rings, (less than $100.00); re-seat valves and adjust valve clearance; check Babbitt and adjust if necessary; and thoroughly clean everything inside.

[700rpm]

Henry, did you mean lap valves, or do you really reseat them? That is, install new seats?

[H. L. Chauvin]

Hi Ray,

Thanks.

Nationwide, in many different mechanic shops in many different States, I also have heard the verbs lap valves and reseat valves used interchangeably as well as reseat meaning installing new seats ..... which can bring up questions.

Per paragraph 6. in reply #8 above, I would just remove all existing valves, clean same, get valve grinding compound, and lap/reseat them with first coarse, and then fine grit valve grinding compound until one sees a clean uniform circular valve to valve seat contact area.

Next I would check gaps at ends of valve stems below and set clearances at 0.011" intake & 0.013" exhaust; and if possible maintain original tappets rather than go to adjustable lifters.

Hardened valve seats are still advertised in Model A parts catalogs as being necessary while using lead free gas; however, prior to 1923, leaded gas was not available,
and from 1909 until 1923 all Model T and humteen other car engine valves and valve seats did absolutely great with no lead ..... in the 1950's and 1960's I only used lead free Amoco gas in my Model A with no absolutely harmful results.

Vintage fishermen always looked for unleaded gas which they referred to as "White" gas because with their 2 cycle outboard motors and inboard hit and miss 2 cycle motors, both with gas mixed with oil 16:1, there was far less carbon buildup around valves, in piston ring grooves, and on spark plugs with much cleaner burning lead free gas.

In my opinion, I would never install new Model A valve seats when the originals are still serviceable.

I think Bud is going to really enjoy digging into his newly acquired Model A engine.

[Chuck Kuntz]

If you do not have access to a bore gauge you can measure the end gap of a piston ring at several points in the cylinder bore. You can use a piston to square the ring in the bore.

[Bud]

Thank you all for your comments. I appreciate your taking the time to respond. I need to decide what steps I want to take. Thanks again.

[H. L. Chauvin]

Hi Bud,

Thanks to Mr. Kuntz for reply no. 11.

Like the utmost simplicity expressed by Mr. Kuntz in above reply #11, there are so many different vintage ways to rebuild vintage engines with exact precision ..... without having access to today's digital technology engine rebuilding equipment.


Today, nobody even mentions or attempts to write about precision vintage rebuilds of vintage engines or the procedures of how this was done successfully with such simple inexpensive tools found in one's shop.

Years ago we removed vintage cylinder ridges without a ridge cutting tool; our heads and tops of blocks were made flat without electrical resurfacing equipment; Babbitt bearings were precisely and far more quickly adjusted for over 50 years without aluminum foil & Plastigage; (e.g. plastigage was not developed by the U.K. Navy until the 1950's); we adjusted gaps at bottoms of valve stems to be used with "original" tappets rather than using phonky adjustable Model A tappets that historically has caused so many problems for current Forum members today.

Do it once, and you will never forget how it "was" done.

Hope this helps.

[Mitch//pa]

The first thing I would have done before removing anything is a leak down test which would have helped me make a decision

[BRENT in 10-uh-C]

Originally Posted by Chuck Kuntz

If you do not have access to a bore gauge you can measure the end gap of a piston ring at several points in the cylinder bore. You can use a piston to square the ring in the bore.

Chuck, how accurate are you thinking this will be, ...and with what would you use for measuring the gap?

Personally, I am not sure I would not waste the effort trying to do it that way simply because what info someone might garner could easily be skewed by a couple of thousandths. In theory I think your idea sounds great however my dial bore gauge will pick-up the 1 ten-thousandths ( 0.0001 ) differences where I am not sure you could maintain .003-.004 accuracy. Imagine someone misreading the end gap thinking they had .005" taper and decided to rebore when in reality it was .001" Or, imagine if the numbers were reversed!

Stuff costs too much today, and time is too valuable to take a chance these days. Again, I think Bud should find someone who is willing to sell him 30 minutes of their time giving a professional evaluation of what he has. If that is too expensive, I sent him a PM with another offer.

[Bruce Adams]

I purchased a "Spare Engine" some years ago, then I thought, "Why have a "Spare"? I then replaced my former engine one December since I figured WHEN it finally broke it would probably be July 3, or some other time where it would be an emergency replacement.
Having a newly rebuilt engine is a lot more relaxing than an "older" one.

[1955cj5]

I went through a similar process last summer....the engine was old and worn but I wanted to learn what I could, and hoped to reduce the crank end play with a bronze rear main thrust washer from Bert's (A-6336). Unfortunately the rear babbitt bearing was loose in the block so I did not try to install the bronze washer.

I did set up the bearings and it ran well until removed and replaced with a rebuilt engine in November.

I learned a lot and enjoyed doing it. I may never get another opportunity.

https://www.fordbarn.com/forum/showthread.php?t=174324

[Bud]

Hi Fellows,
The reason I bought this engine was that I have a Model B motor that I probably have 1000 miles on that has 3 cracks in the valve seats. It is currently at the original rebuilder having the cracks stitched. I am hedging my bet this motor may not hang in there for the long run.
If I can evaluate my recently purchased engine, then I am better prepared to make the decision on how to rebuild it--if I need to rebuild it all.
Thanks for any and all suggestions.

[Chuck Kuntz]

Well, that's exactly why I will not volunteer none high tech solutions to again. I wonder how you check the end gap on new rings except with a feeler gauge.

[H. L. Chauvin]

Hi Bud,

Just one opinion:

If you learn how to prepare your ground, and prepare your ground by yourself, and cultivate just one (1) crop of tomatoes ........... you will learn meticulous agricultural details you never thought existed in life.

If you continue to buy tomatoes or anything grown ...... in your store ...... you will question the details of how anything grows on earth for the rest of your life.

All of our very young grandkids today are teaching us how to use computers and cell phones ..... in my opinion ...... this is mainly because they do not have some disgruntled old fart warning them what they "cannot" do.

Please take your engine apart, learn, and rebuild it yourself like I did as a young teenager ...... believe me ....... you may fail ....... you may succeed ....... so what ....... it works just like our kids today with cell phones and just like trying to grow your first tomato crop ........ have fun with the challenge.

Hope this helps.