Checking out the various vendors I see pistons from 60 to 130 dollars a set. What are the differences, any bad experiences? Looking to upgrade from cast iron and adding a stipe cam and Z head.

Ernie

Ernie,

The higher-priced ones are domed for a mild compression increase but will only work with a stock head. So, with the Z head you plan to buy you get the lower-priced ones. Ring set sold separately.

Seth

The expensive stock and high compression pistons are made by Egge Machine here in the USA. The cheaper pistons only come in stock and are made in Japan. I only sell the Egge but have not heard anything wrong with the imports except for one set that was not properly cam ground.

Get the Egge pistons.

There have been dozens of bad sets of the Chinese pistons sold that caused unending grief to a number of us who bought them. Do not buy the Chinese pistons under any circumstances.

Whatever type you buy,make sure the cylinders are bored for proper fit.

I have used many sets of the cheaper pistons with no troubles. Any piston troubles I have investigated were directly related to not enough piston clearance as Mack has mentioned.

Les is right, Aluminum pistons need 4.5-5.0 In.clearance. Egge's instructions are misleading in that they say clearance 0.0025. What they mean is total clearance all the way around the piston or 0.005 total. If you don't give them enough clearance they are sure to seize.

A fellow club member and Montana racer recently told me about the pistons available at Snyder's.
He said they are the best ones that he has ever seen. They're made in USA (ISO 9001 certified) and sold in matched sets. I ordered 2 sets and when I weighted them I found only 2 grams difference between the heaviest to lightest! At $79 bucks I think that is a unbeatably Great Deal?

Check them out

I just rebuilt a 26 engine with the snyders pistons. I kind of doubt that they are made in U. S. A., but the quality seemed o.k. and they were very close in weight. I must differ with Glen on piston clearance. I'm pretty sure that the manufacturers know how to measure and specify clearance specs. When they say .0025 thats what they mean. Mine were marked .002 to .003 and my boring machine operator set them to exactly .0025. I confirmed this with feeler guages when assembling the engine, and also confirmed ring end gap, ect. Engine runs great and cools well, after 300 miles I have not had piston seizure. The original cast iron pistons in this engine only had .005 to .006 but I certainly would not reuse them. If you set up at .005 your engine is almost worn out and the ring end gap will also be out of spec from the beginning. If for some reason pistons NEED to be set up at .005, then I think you have a problem with faulty pistons or you are not measuring properly. Respectivly submitted, LLoyde

Hi, I set my pistons up at .0025 ten years ago and never have had any problems. Pistons set at .007 will slap the walls till they warm up. So setting up new at .005 will give you very little room for wear till you start having problems. Letting the pistons slap will crack one sometime soon. Pistons are cam ground and only the bottom of the skirt fits tight. So its not like the whole piston from top to bottom all the way around touches. The tight spot is only around the size of a nickel or so. But you can do what ever you want in this country. Good luck

Glen Chaffin is "Right". Lloyde, Just because your engine has not seized yet is no guarantee your pistons are not being damaged/scored due to insufficient clearance. Glen has assembled numerous engines and is correct on this issue. I opened the clearance up to .007" (Total) on the model T engine I am presently building. The engine in our 13 T had .005" clearance and the pistons were still being scored some. I pulled them, there is no question in my mind on this issue.
My 1910 2 cyl. REO (4-3/4" Bore) was honed to .012" clearance. You are asking for problems setting model T piston clearance to modern car standards.
Respectivly submitted, Les

Think there is one point that should be made with aluminum pistons. All the cranks I have tested so far are bent with the throws in the vertical position. It takes over 300 thou to bend a crank so how the devil does a crank bend when the center main holds the crank to about 2 thou deflection?

The only way as Seth explained to me is the cast iron slugs changing direction make a hell of a stress on a crank at that point BENDING something.

So, Its a very good Idea to use aluminum to save the crank from further destruction.

AMEN brother!

Cheers, Seth

Glen and Les are "right". LOL I am pretty careful when assembling engines. I make sure the pistons are aligned in the rods. On my 12, I initially set the alumnum pistons at .0035 clearance. I tore the engine down to correct a transmission problem and noticed the cylinders and pistons were scored. I power honed the cylinders to .0055 and carefully sanded the score marks on the pistons. I assembled the pistons with new rings and ran it in the car. After less than a season I had to take the engine out to replace a bad mag coil and found no scoring. After that I became a believer in .005" clearance.
I don't experience piston slap in three cars where the clearance is set at .005-.0055. I agree .005 sounds like too much, but its worked for me.

Pistons is pistons, NOT!

No piston is pure aluminum. They are all alloys of some kind. Some foundries use old pots and pans for raw materials. Construction design varies, too. The "Improved" Audel's manuals from about 1938-47 have about 80 pages on pistons, rings, etc. If you're serious about an engine rebuild, it's a good idea to snag an Audels on tbay.

You may need .005 with Egge's, for example, and .0025 with some other make.

rdr

Richard
I first learned this the hard way back in 1978 on my '27. Similar experience to yours. The engine ran fine on the level but when I got on a big hill at full throttle for several miles it suddenly tightened up. I stopped and let everything cool and continued on the tour. When I got back from the tour I pulled the pistons, sanded the scuffs and honed out the cylinders. 25,000 miles later it is still running strong. These were the "off shore" made pistons of the '70's. Since then I have helped a couple of other guys with new engines. Most recently at the Cochrane (Calgary) national tour a guy showed up with a fresh restoration with a torn up con rod and scuffed pistons. We re did his rod in one day and we power honed about .001-.0015 and sanded the scuffs and he ran just fine for the tour.
Certainly what Ralph says about pistons being a alloy is right and there are several popular alloys for pistons. In either case they all expand at about the same rate. Certainly there are different designs in the internal ribbing and expansion cuts and cam grinding but suspect on T pistons it is as much shade tree engineering as any thing.

I am sure you're right on that Ralph, but how do you know what clearance to use on a particular set of pistons? You can't rely on what the manufacturer says. The ones in my 12 that scored at .0035 came with a recommended clearance of .002. Egge recommend .0025. BTW, I don't buy the explanation that they really mean .005. The Ford manual recommends .002 on Ford iron pistons if I recall. I know aluminum expands more than iron. So it seems that using .002 or thereabouts for aluminum pistons regardles of the makeup of the alloy is aking for trouble.

Forged pistons require even more clearance compaired to standard cast aluminum pistons. Engines running forged pistons are noisy untill they heat up sufficiently. My 2 cyl REO with .012" clearance (4-3/4" Bore) does not seem to have any piston slap noise above all the other sounds it makes. Smile!

Let's add a little to the mix: reinforced wristpins.

Clamped (semi-floating) wristpins must be reinforced, or they will bend.

Reinforced wristpins are thicker through the midsection where the rod clamps. Clamping distorts thin pins when they get hot, and they bend. That applies to the T, the 4-cyl Chevy, and to modern Ford engines. Full floating wristpins, like Model A, don't have to be reinforced. Stock T wristpins in iron pistons are thick all the way, I believe.

I came to grief with a set of Egge pistons with thin (unreinforced) wristpins. The pins bent and caused galling of the pistons. This ruined the engine, and nearly ruined our run in the 2000 Greatrace.

A few years ago I bought a Chevy crank, rods, and custom Ross pistons out of a T engine that had been put together for racing, and had thrown a rod. I bought the lot from a Model T pro. I examined the pistons just the other day, and lo and behold, they were in various states of galling, and the thin wristpins were bent.

If you have galled/scuffed pistons, check the wristpins.

rdr

In a book I have for the home piston designer/maker written by Stephen Chastain (available from Lindsay also at stephen chastain.com) he says that the coefficient of expansion for a aluminum is about .000013 and for cast iron is .0000074, so the aluminum expands at 1.75 as much. The aluminum also transmits heat much quicker so the piston generally gets hotter overall I wouldn't bank too much on this. Anyway Stephen's book is really well written with just the right amount of practical with good explanations of why.
Ralph
I have wondered about the size of the T wrist pin. As the pin is .740" outside diameter what do you think would be a good ID? Are you of the opinion that press fitting the wrist pin into the con rod is a potential problem? I am having to make some .750 wrist pins and I bought case hardened dowel pins. I need to drill them still and was considering a 1/2" hole. I plan to press fit them into the con rods.

I don't know, Les, but judging by modern Ford engines, like the 1.9 OHC in the Escort, and the 4.2 V6: bigger is better. They are .90-.93, and reinforced, because they are clamped.

The pre-'29 Chev is 0.85 reinforced.

rdr

Ricks,
Any suggestions for finding reinforced wrist pins (292 Ford Size) that will fit my bored out 28 chev. rods?

Ford V6, 3.8 to 4.2, wristpins are .905 dia. Should be close enough to your .91 pins in 292, Les.

Curiously, they are only 2.5" long, while the bore is near same as T, at about 3.8".

Escort pins should be about same size. You could buy a set of pistons on tbay and recycle the aluminium.

rdr

Listening to you guys discuss pistons and the like.....I am impressed!

I've been a mechanic for many years since the 70's, but have never worked on one of these antique babies. It must be a great hobby!

Donald

Donald
It is!! Get a model T and join the fun! It will stretch your knowledge. A good running model T needs to carefully assembled. We can help you avoid the pitfalls.