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I was hoping someone on the forum could confirm what is the correct piston for a 1954 Packard Clipper with 327 cid engine. It is a 5401-5411 series.

Max Merritt states that the slot into which the top compression ring goes should measure from top to bottom at 3/32, for the middle ring, also compression, should measure 1/8 and the slot for oil ring measure 3/16. The pistons on my Packard the top ring is 1/8 and the middle ring 3/32 and oil ring 3/16. The pistons in my Packard all have the number 403535.

I have also measured the slots for the rings on my pistons using an inside digital caliper. Measurements are: top ring 0.108, middle ring 0.097 and oil ring .1860. The 1954 Packard shop manual states that the rings themselves, both compression rings are the same at .093 and oil ring .1860.

Another mystery is that even though the car has 60,400 documented miles it appears one or more of the pistons have been replaced.

The previous owner had replaced the head gasket yet foolishly didn't remove any carbon from the top of the cylinders and didn't even change the oil after the repair. Then with two stuck valves they allowed the car to sit for a couple of years. One cylinder/piston adjacent to the stuck valves had rusty sludge on it. That one piston is an Autothermic brand as specified in the shop manual. It was very pitted on top and the rings were rusty and deteriorated. The other 7 pistons are Permite brand and are in excellent condition. Both the 1 Autothermic and 7 Permite have the number 403535 and the slot for the top ring is the same at 1/8 and middle ring at 3/32.

I hate to throw out 7 flawless pistons and buy 8 pistons from Max Merritt so that they all have a top ring slot at 3/32 and middle ring at 1/8. Max was emphatic that my pistons are "not a Packard piston." Even if I stay with the 7 Permite pistons I still am going to need a replacement for the bad Autothermic and it will have to have a top ring slot at 1/8 and middle ring at 3/32 to conform.

I'm sorry this was so long-winded but I wanted to share all the facts. I really appreciate any advice you gentlemen can provide.

---Steve

U wrote:
"The pistons on my Packard the top ring (AS IN RING) is 1/8 and the middle ring 3/32 and oil ring 3/16. The pistons in my Packard all have the number 403535.

I have also measured the slots (AS IN SLOTS) for the rings on my pistons using an inside digital caliper. Measurements are: top ring (MEANING SLOT?) 0.108, middle ring (meaning slot?) 0.097 and oil ring (meaning slot?) .1860. "

THere is something wrong here.
In the FIRST statemnet u say that the top RING is 1/8 which is .125". But in the second statement u say that the SLOT is .108. That is impossible to have a .125 RING fitteing a .108 SLOT.

REgardless, the question u are asking is not a Packard specific question but is actualy a general engine rebuilding question.

THerfore:
What is inmortant is not the slot width but rather the MATCHING FIT of a ring to the slot regardless of the width. Look in the manual and it will most likely indicate a RING-TO-SLOT measurement clearence to be measured with a feeler gauge.

To put it another way: the ring must be fitted to the slot. Doesn't matter what the slot width is as long as the RING width is compatable for that particular slot width.

Furthermore:

There can be variations among pistons ( for ANY engine at ANY time by ANY manufacturer ANY where) depending on SUPPLIERS that can vary even in original production for the engine. Such pistons with variations may very well all ahve the same part number cast into them. This is not uncommon.

Bottom line: The RING must fit the slot according to clearence specifications of the manual. NOT actual dimensions of slots.

Quote:
"I hate to throw out 7 flawless pistons and buy 8 pistons from Max Merritt so that they all have a top ring slot at 3/32 and middle ring at 1/8. "

U only need ONE piston. MIxing pistons in the same engine is often touted as poor craftsmanship. Assuming that the piston fits and is not made of lead or some meaterial lighter than air or some other outrageous or conspicuos difference then tHere is simply no truth to it being poor craftsmanship. Perhaps not most desireable to mix pistons of course. Most desireable is to have everything matched.

***** As for your pistons "not a Packard piston" then I HAVE A QUESTION!!! How did the PAckard number 403535 get cast into the pistons????? *****

Is 403535 a PAckard number for the pistons???? I don;t know.
If it is not a Packard piston then what is it????? A Yugo piston or something????

Did Packard even make THEIR OWN pistons????? Maybe not. Maybe some piston manufacturer(s) made pistons FOR Packard.
In that case there is no such thing as a "Packard piston" to begine with. So how could ANY piston be a Packard piston???

Get the picture????

"That one piston is an Autothermic brand as specified in the shop manual. It was very pitted on top and the rings were rusty and deteriorated. "

From that description i am unable to determine if the piston is serviceable or not. Pitting on the TOP (crown) of the piston is not necessarily a reason to scrap the piston DEPENDING on how bad the pits are. I can't see the piston so i can can not make any judgement call at this point.

Or to put it another way, I've built engines using pistons where a valve guide had broken and beat alot of small nicks into the top of the piston. Otherwise the piston was good. In fact i've buuilt at least 4 such engines over the years ranging from hi performance chevy engines to HD to Indian and small lawn mower engines. They ran a long time and very well with no problems.

Desireable???? Of course not. It's not a perfect world.

As for buying just ONE piston then good luck. in most cases suppliers usualy only sell in sets.

Take a closer look at the bad piston.

From 3rd paragraph of post 1 above:
"The 1954 Packard shop manual states that the rings themselves, both compression rings are the same at .093 and oil ring .1860."

That ought to be the bible on it. Thus ANYTHING else is "not a Packard piston" either.

Quote:
FWIW, the parts manual shows different numbers applicable to the '54. I can't find a reference to 403535 in the general numeric index at all (1948-1954).

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The top slot you measured is .108. The top ring is 3/32 which is .093. That leaves .015 vertical clearance. I do not have a shop or Chilton's handy but that is far in excess of allowable wear, The up and down motion of the ring will cause them to break eventually.

That one piston is an Autothermic brand as specified in the shop manual. It was very pitted on top and the rings were rusty and deteriorated. The other 7 pistons are Permite brand

Steve - autothermic is not a brand, it's a engineering design - the Packard specifications are identifying the style or type of piston, not the maker. Permite is a trade name of a brand, like Bonalite was for Nelson.

Looking at Fred Kanter's #s, if the piston is in otherwise good condition you can have a machine shop cut the top groove oversize and fit the new ring with a spacer - pretty standard job in its day. As to different brand pistons, if they are dimensionally correct and the weight matches the others, it should be quite serviceable. Sealed Power used to sell cast pistons for those who had to replace one or more OEM autothermic pistons which had been damaged, retaining the other original pistons. They were dimensional and weight equivalents and intended for that type of service. This practice probably wouldn't be done today, but it was very common when engines were "repaired" rather than rebuilt.

Thank you to "Packard V8", "JD in KC", Fred Kanter and "Owen Dyneto" for the helpful comments.

"Packard V8"
Pointed out that if the top slot was 1/8 it would measure 0.125 with the caliper, not 0.108. How right you were. Using the "outside caliper" I got a measurement of 0.125. Must be something wrong with my caliper when using inside feature. The middle ring slot measures 0.097 so that appears to be 3/32" (I have to allow a little latitude for caliper variations.) I believe I have the "ring to slot measurement clearance" you referenced. The shop manual states, "Compression ring gap .0054 to .0207." As for the one bad piston; it's really bad. The entire top surface has a pebbled appearance, part of the top edge is rough and there's about a 1/8" hole in the center. I think it's shot. I'd have a concern about not being able to have consistent weight from piston to piston. You certainly put it in perspective when you say the manual is the bible. If it says both compression rings measure 0.093 then the pistons ought to both have comparable slots, not 1/8 on top and 3/32 in the middle. I know this is hard to believe but rings I salvaged from one of the good pistons measure 0.091, both top and middle ring. Those rings must have been slopping around in that top groove.
"Packard V8" also noted that pistons can vary within a model year. That wouldn't surprise me here because this car is a "Super Touring" which means it's sort of a freak anyway with a 1953 dash and 1953 brakes but everything else 1954.

"JD in KC"
Thank you for the reference and now we see that the pistons I have aren't even listed for 1948-1954. More proof they are likely incorrect.

Fred Kanter
Referenced my incorrect 0.108 measurement of the top ring slot and that an 0.93 ring would not fit properly. That makes sense and makes it even more bizarre that this car had rings measuring 0.091 in a slot measuring 0.125. I'm beginning to think some extremely poor mechanical work was done to this car at one time.

"Owen Dyneto"
Pointed out that Autothermic is not a brand. Thank you for clearing that up. My one bad piston had that stamped inside whereas the others did not. That one bad piston does have the brand/model Nelson Bonalite.

Digesting all of this and getting back to you with more details of what I have it sounds like I have to buy 8 new pistons all the same and with specs consistent with the shop manual. I welcome any further advice or corrections to my conclusions. I have never had this car running. I bought it 2 years ago and as time permits I have been disecting it before attempting to start it. It was kind of a mess from lack of use.

---Steve