I have a 1915 Coupelet which went on its maiden tour to Nebraska and melted the babbitt out of the no. 2 connecting rod. I need some advice on piston clearances and ring end gap clearances.
I measured the no. 2 bore & piston last night just to make sure before I order new rings.
bore size 3.747 Piston size 3.748 !!!!! yikes
My measuring probably is not totally accurate as the piston does fit in the bore but there is virtually no clearance. Kinda fits like a piston pin.
The block has been sleeved back to standard.
If found this post on piston clearance from 1923 -
Piston clearance not less than .003" nor more than .004"
Is this correct?
Then I put a few rings in the bore and checked the ring end gap clearance. Which one of these do you think fit in the gap.
All of them !!!! I think it adds up to 0.042 !!!! yikes again
From the Ford shop manual:
The ring gap clearance is .008" to .012" for the top ring, .006" to .008" for the middle ring, and .004" to .006" for the bottom ring.
Is this correct?
The MTFCA engine book gives the same ring gap numbers, so I guess those are the ones to go with unless someone comes up with a good argument for something else.
Dial calipers are not accurate enough for bore measurements. The surface where it contacts the cylinder bore is flat giving you a false reading.
I don't recommend feeler gages either.
You need a dial bore gage or telescoping gages to find the dimension accurately.
This from a fellow Coupelet owner.
Philip
Didn't say that in the post but I did use a telescopic gauge and measured that with the dial indicator above. Another club member has a direct read bore gauge, I plan to make some more accurate measurements.
Also another thought came to mind. Since the pistons and bores seem to be standard size it would make sense that the rings that they used were standard size, is it possible that the standard rings came with that much end gap?
I doubt it. It could be the previous assembler made use of old rings. (He used old pistons.) I also wouldn't use dial calipers to make decisions on the size of the pistons or bores. Also, the bore should be measured at a Minimum of six locations.
Back when an overhaul cost $15, measurements accurate to .002" or more were common. So was traveling at 10-20 MPH maximum. Do yourself a favor and build it right with accurate tools. It could save you from more melted babbitt.
Ok, I'll give you a pass on this one. As a guy who has been in machining for over 25 years, calipers are only good for taking out slivers from your fingers.
Let us know the outcome because I'm starting to assemble the engine for my coupelet in a few months.
Philip
First of all I would toss the cast iron pistons in the trash. They limit your top speed to perhaps 30 MPH. More than that and you will pound out the rod bearings.
Cast iron pistons are required for some model T race they have in the USA so do not throw them away, If you replace them sell them on ebay instead.
Really? Which one?
Montana 500?
As the car is being driven, the outside circumference of the rings rub against the cylinder walls each time the piston moves up and down. Since there is much less surface on the ring than on the cylinder, the rings will get more wear than the cylinder, but both will receive some wear. As the outside edge of the ring wears it will expand outward toward the cylinder wall, hence the gap increases with wear. Your measurement indicates that the rings are worn out and need to be replaced. Order a set of standard rings. Even if the gap were to be within limits, the rings should still be replaced because you will not get them in exactly the same configuration to the cylinder wall and they will not seat properly after being used for many miles.
What do you mean be "maiden tour"? Certainly the car has been driven before during it's 97 year lifetime. It was either rebuilt incorrectly, or it has many miles since rebuilt. I am guessing that the pistons are OK but it needs rings and bearings poured. If it were mine, I would be more concerned with the condition of the crankshaft than of the cylinders.
Norm
Montana 500 allows aluminum pistons. Wrong.
Norman, about maiden tour.
I purchased the Coupelet a couple of years ago, with a nearly completed restoration. As with most things it took a couple of years to get the few remaining items completed. For instance it arrived without a windshield. I do not know who rebuilt the engine, it was not me.
It has a Nov 1915 block which has been sleeved back to standard. I think I am going to keep the cast iron pistons in this car. I have 4 other Ts.
I can understand using the stock standard size pistons but can't believe someone would put the used rings back in, I certainly would not.
Cash Iron Piston clearance not less than .003" nor more than .004"
Is this correct?
Nobody has chimed in on this.
That's what it says in the service manual, paragraph 404.
I've re-used piston rings when they've gone back on the same pistons in the same cylinders, lightly honed the cylinders and lightly sanded the outer face of the rings. Works for me, your mileage may vary.
Chris,
I have some NOS ring sets for cast iron pistons. If you are really going to use them I will give them to you if I have the size you need.
Thanks Royce, I will contact you offline.
With 42 thousandths ring end gap, reusing the rings will not fix the problem.
Norm
Pig and ford races i think.
http://www.mtfca.com/discus/messages/29/33948.html?1186752744
A while back a guy was asking on here how to use some cast iron pistons and you all kept telling him he should use aluminum until he explained it is against the rules.
If anyone expected me to install cast iron pistons for any reason I wouldn't. For the 120 bucks it costs for a set of good Egge pistons the performance and longevity difference is easily worth it. If Chris can use these rings he is welcome to them I would never have used them, and have considered many times throwing them in the trash.
So, tell me Kep, do they X ray the engines at the pig - n - Ford race or how exactly would they tell? Does the pig have to be a certain breed too?
I agree with Royce. Toss or sell the cast iron pistons and install a good set of aluminum pistons. The cast iron pistons add a lot of stress to the crank and, in my opinion, can lead to a broken crank.
Because the cast iron pistons have the same coefficient of expansion as the cast iron block, less clearance is needed than with aluminum pistons. The pistons do get hotter than the block, so some clearance is needed.
Neil
I guess Henry did make 15,000,000 sets of defective pistons afterall. How woulda thunk. Just joshin' you Royce.
No idea i never went to the races. They must remove the cylinder head and test it with a magnet.
Cast iron has its place. It makes a wonderful block. It is dimensionally stable and gets a nice smooth surface when properly broken in. The little platelets of graphite in the iron is what gives it the smooth surface. I guess that is why early engines had cast iron pistons too.
Didn't Ford go to aluminum pistons in the improved Model T?
Neil
FWIW: To determine if the pistons are iron or aluminum you need simply go through the spark plug hole with a small magnet on a flexible extension.
I think everyone involved in this particular discussion knows the difference, but I want to clear up a source of potential confusion for any lurkers that might misunderstand. We are talking about two different clearances here. The .003 to .004 is the clearance between the piston and the wall of the cylinder. The .042 (WAY excessive) is Chris's current end gap where the two ends of the ring come together with the ring installed in the cylinder.
Another bit of info. I weighed an aluminum and cast iron piston-rod set.
1430 g aluminum
1730 g cast iron
Piston, rings, rod, pin, bolt
An update on my progress.
I balanced the pistons to within 1 gram.
This is what I started with
Piston | Rod | Rings | |
+ Pin | |||
962 | 639 | 1601 | |
953 | |||
941 | 637 | 1578 | |
956 | 639 | 1595 | |
23 | |||
Piston | Rod | Rings | Total |
+ Pin | |||
933 | 638 | 119 | 1690 |
933 | 638 | 120 | 1691 |
933 | 637 | 120 | 1690 |
932 | 638 | 120 | 1690 |
Then I put all the rings in the bores and measured the end gap at the top, middle and bottom of the bores.
Piston 1
1st | 2nd | Oil | ||
0.016 | -- | 0.016 | -- | |
0.019 | -- | 0.018 | -- | 0.020 |
0.020 | -- | 0.019 | -- | 0.020 |
1st | 2nd | Oil | ||
0.017 | -- | 0.017 | -- | |
0.020 | -- | 0.019 | -- | 0.020 |
0.020 | -- | 0.020 | -- | 0.020 |
1st | 2nd | Oil | ||
0.017 | -- | 0.017 | -- | |
0.020 | -- | 0.020 | -- | 0.022 |
0.020 | -- | 0.020 | -- | 0.022 |
1st | 2nd | Oil | ||
0.016 | -- | 0.016 | -- | |
0.019 | -- | 0.019 | -- | 0.022 |
0.020 | -- | 0.020 | -- | 0.023 |
Chris, the way you drilled the pistons on the sides, made the oil ring useless. It is going to smoke when you put it back together!
Joe, I kinda wondered about that myself. There sure isn't much to stop the oil from splashing above the oil ring through the holes in the piston. So now Chris will get his aluminum pistons. Here's another question, why aren't the entire piston, rod, wrist pin, rod cap and rings weighed and balanced as an assembly. I would think by weighing the components separately would create the opportunity to "stack" the differences.
Also, please use telescoping gauges with a micrometer (not a caliper) to measure bore, and a micrometer to measure the pistons. If you've got a bore gauge and some sort of set master that is set with gauge (joe) blocks use it. As far as setting ring gap, I don't see how you have any choice but using feeler gauges and for what your doing they will get you way close enough. Somebody said using an indicator to check ring gap but I noticed they didn't say how to make it work.
I went back and read Phillip's post and apparently I read it wrong. He's not suggesting an indicator for ring clearance. But I still have to say that feeler gauges are about it for measuring ring gap, which by the way is supposed to be measured at the bottom of the bore. And the pistons are to be measured at the bottom of the skirts.
Chris, I think you just decided to order new aluminum pistons, right? Where did the idea come from to drill holes in pistons? We can find all kinds of reasons not to do that. It's just plain wrong!! So when you get new pistons, or replace with some good used cast iron, your original question was clearance. Ford said .003 to .004 on cast pistons. Note also that cast pistons were round and should be round. Aluminum pistons should be cam ground and you will need to measure and fit them per the piston manufacturer's instructions. Most measure 90 degree from the pin on the skirt about 1/2 inch from the bottom. This is important. Don't be afraid to use feeler gauges. They won't lie to you or let you make a mistake in reading. Thats how they measured in the day, and it still works. When I rebuilt the green t I read the forum and was warned to clearance my new pistons from .005 to.007 because someone had scored a piston. The manufacturer (from snyders) said .002 to.003, so the machine shop set mine at .0025. I double checked that, put it together, and it's still running fine. I hear some piston pins are tight on the new ones, and that can cause the piston to score, so be sure and check and hone out or use some timesaver to fit them. Rings if new are supposed to fit. If the gap is too large, the cylinder is probably too large, or the ring is too small, but you can't change it. If the gap is too small, then file it to spec or it can also cause seizure and scoring. Good luck, hope to see you on tour some time. Lloyde
The idea came from a couple of pistons that came from Stan Reynolds in Wetaskiwin. He was a racer in Alberta in the 40s & 50s. We figured he did it to lighten the pistons to go faster.
Drilling pistons like that was a common practice with racing cars back when. I have drilled pistons to even the balance, but have kept it under the bottom ring. I do worry about pistons breaking if they are drilled too much (it has to weaken them somewhat). Sometimes I think I should build a speedster just to drill pistons and rods and more. Just so I can drive it as fast as I can to see how long it would last. I have put quite a few miles on engines with cast iron pistons. Just not drilled that much.
Drive carefully, and enjoy, W2
I have know of T owners driving their T over 50MPH with cast iron pistons. they are not that much heavier than aluminum when they have the pin & rings & the pinch bolt in them compared to an aluminum piston with all that stuff added on.
The Chevrolet 6 had babbit rods & cast iron pistons well through the 40's.
There is usually plenty of meat to take out of a cast iron piston without drilling holes into the skirt. As I have said before, I ran cast-iron pistons in the Montana 500 and did very well (second place). I've had my cast-iron motored T up over 70 mph and nothing bad happened.
The last T I have purchased, has been running very happy on cast iron pistons for 86 years, original engine and still STD, a Rajo head and 3/1 diff, since the 1960's, last owner since 1953 (uncle before that from new, tolled me he even sat on 50+ for some 800 miles to complete the last day of a 3 day trip.
Its going to smoke pretty badly with all those holes above the oil ring. I would buy a new set of pistons.
Different ways to skin a cat. I balanced cast iron pistons by pressing in different lengths of rod into the wrist pin hole. I found the shank of head bolts to be the right diameter. I made sure they were a good press fit and I used sleeve retainer for good measure. You loose the ability to tighten the wrist pin bolts by placing a rod thru the hole. A piston vise solves that problem. The pins will expand a tiny bit but not enough to keep them from entering the pistons.
I wanted to keep the car original for historical reasons so my rebuild was different and in some ways more difficult.
Chris, I have a set of used standard size CI pistons, w/rings and wrist pins if you need them.