Engine: Piston interchange

[kelmbaker]

I have looked at all the sources, and I know it is there, but I can't find the interchange pistons for a full flow 259. Make, year engine size, etc...

I don't mind an overbore and I don't mind the pistons coming up further in the block than stocker 259 pistons.

If you remember the interchanges, or can point me to the information, it would greatly appreciated.

Thanks,

KM

[Skybolt]

I know of only one that is a straight bolt in type job. The rest I have found either have piston pins too large or compression distance issues, or some strange piston head configuration. You can get custom forged or cast prisons but I also would like to know if any one has the answer. Len.

[kelmbaker]

I think piston pin holes can be enlarged (to a minor degree). The pin height has some room, because 259's are .070 down in the hole at TDC. You can lose the pinch bolt piston mounting and go to an interferance fit. That gives lots of room. The custom pistons are too rich for my blood.

What pistons were you refering to?

Thanks,

KM

[Dan White]

Is there an issue with just buying a set from one of the Stude vendors? Studebaker Intl. and others have individual and full sets for 259s

[PackardV8]

I can't find the interchange pistons for a full flow 259. Make, year engine size, etc... I don't mind an overbore and I don't mind the pistons coming up further in the block than stocker 259 pistons.

Some random thoughts:

1. Unless one owns a milling machine and a Sunnen Rod Shop, the cost of boring and honing out the small end of the rod and rebalancing the rotating assembly for the difference in reciprocating weight is far greater than the slightly lower cost of BrandX pistons.

2. Pistons with greater compression height can easily increase the compression ratio beyond the 9:1 maximum Stude V8s will reliably tolerate on regular pump gas. Having to use premium fuel has been shown to cause apoplexy in CASOs.

3. Unless one owns a rod heater, assembling press fit pins can have a steep learning curve.

Your results may vary.

jack vines

[Skybolt]

Kelly,

As you know I have a set of pistons that are .0105" over Studebaker standard 259's. These, as I have referred to before on the forum, are from an Australian Holden 186 six cylinder, 0.40" over, which was made in the sixties and millions of these engines were produced and still on the road. I will use approximates here as I am not going to go into detail. The pin is 0.8661" and Studebaker used 0.8741". So during install the pin bore is honed to fit, like any other pin bore if one is making sure and not just plugin away and amusing it all fits like the manufacture said. This means no modification to the rod. The compression distance is 1.7835" compared to 1.7344" so it sits 0.0491" further up in the bore. This puts it in the range of good squish. It will be somewhere around 9 to 9.5:1 depending on what head and what work was done to the head and gasket used. The rings used are from a Chrysler 273 0.040" over for my particular set. It is the easiest swap I know of and have used it before. I can get the pistons any where from .060" to 0.145" over Studebaker stock bore dimensions. So, that means 273 piston rings in standard to .080" over rings but the .040" is one of the easiest sets to find.

I spent a lot of time trying to find a different piston, one that was used in a US car but none were made, that I know of, that fit the bill of piston pin dimensions, compression distance and with a bore equal to or greater, withing the limits of the block, so I sourced the Australian pistons. These are made in Taiwan from an ISO 9001 and TS16949 certified company who supply pistons to Nissan, Yamaha, Honda, Subaru just to name a few. So if any one can come up with a better off the shelf piston I will buy them.

I am in the process of getting more sets so if anyone shows interest I will discuss price when availability is confirmed. The set mentioned above was deviled early this year and will be installed later in the year. The car has sat since coming back from paint, which was in April, as I am off work due to an injury, so I'm restricted to just think about the work these days. I was not going to let the cat out of the bag until I had the engine together and at one of the meets to show it off so others can see it's not magic, I will once I recover do just that. Len.

P.S. Price should be under $300 a set. Rings not included. I will know more once details from the manufacture are confirmed.

[PackardV8]

Very interesting data and you've obviously put a lot of work into the interchange.

Yes, agree gaining the extra .75 points of compression is a benefit and getting close enough to the head to have some squish is a benefit.

Yes, if one wants the maximum possible bore diameter, having .105" and larger pistons could be desirable to some.

Have you gotten any quotes for pin fitting pistons which require honing each pin bore .008"? My machinist says he'd do the first ones for $5 each and see how long it takes him, so that's another $40.

However, since these are cast pistons and thus not really suitable for racing, and since price is the same or higher than normal replacement 259" pistons, what other benefits are there to using the Holden pistons?

jack vines

[Skybolt]

Jack,

The price sounds about what I was quoted and I don't think that is excessive. I think that for the added compression height alone it's worth $40. If you had the option of for an extra $40 to raise your stock pistons that much I think you would take it. It's better than the hassle of decking the block, with all the other components that need attention afterwards, to get the same result. It is far cheaper. No work to the rods, no special rods, nothing fancy just pistons that should have been put in there instead of the stock ones.

What prices does one pay for a set of 259 pistons?

It would also appear that rings are cheaper too.

Another note: I was wrong about the sizes. I can get them all the way from stock Studebaker 3.5625" sizes all the way up to 3.705" which is 0.1425" over. As I was just mentioning the 186 pistons. The smaller bore 179 six has the same dimensions but the same bore size as the Studebaker 259.

Price... under $300? Yes, hopefully about $250 a set but depending on quantities and shipping costs it could be more but not less. I am trying to keep the cost down but still cover my costs and time. If no one wants them I don't have to do a thing. If they do I have to work as I don't sell Studebaker parts, and rarely sell used stuff, I wont be put out if I don't sell any. It was Kelly who asked about them in a PM and then on the forum. I have mentioned that these were available many times and that I have used them before so I guess at some point somebody would ask for a set. As I can't put anyone onto a retailer or distributor in the US, as there are none, I have to do the leg work myself. I've even tried to get them from Australia but that was cost prohibitive. If the exchange rate ever gets back to the 2:1 of ten years ago that might change things. I would be getting forged ones from there. But that is not the case and I have to get them from the manufacturer.

I am trying to get more information about material make up of the set I have as they do offer hypereutectic but I don't know if it is available in that item. The Si content ranges from <.6 to 24% through six different alloys. I'm trying to get these in the 18-20% alloy but that could raise the cost or that could be the alloy they are already. Most new pistons for the Australian market for these engines have a high Si content. I will have to see. I was not concerned as it was going to be for myself and they had to be better then stock. Now if I would be to sell them I want to make sure people know what they are getting. If I can I will sell nothing but the 18-20% Si content alloy pistons.

I did not get these to sell. I have them for myself and thought if any one else wants them I can save them the trouble of what I had to go through.

Len.

[PackardV8]

Agree completely. If someone asked me to build a hot street 259", I'd recommend paying an extra $100 for higher compression, squish and hypereutectic alloy.

(That's assuming they were adamant about wanting a 259" and I couldn't talk them in to spending just a little more to have a 299" or a 304.5".)

jack vines

[Skybolt]

Yeah, that is the deciding factor. I personally like the short stroke 259 but to be truthful I have not had a 289 on the road, only on the shop floor with rod bearing problems.
Most of us are not going to race our cars so they are fine for most of the use they will see. I did however give the last engine I had, built with these pistons, a hard time and had no problems. It had larger valves, stiffer springs, I pushed it up to 6000 rpm, ran it on avgas, used a carter AFB, then triple 2bbls, hot cam, many things and the pistons never had a problem. The engine is still running today, 23 years later, as my brother has it. Len.

[Skybolt]

Update on the pistons:

I am in negotiations with the manufacturer about the alloys they can produce the pistons with. They can supply them in any of the alloys in the chart, link below.

http://rides.webshots.com/photo/2684631930087432881sMckZr?vhost=rides

The pistons I have at the moment are AC8A alloy.

When more information arrives regarding cost of each alloy and delivery times I will make this known.

Len.

[Skybolt]

P.S. for clarification of AC8A(LOEX) the LOEX stands for low expansion. This is listed on the chart.

These are the standard pistons and are a eutectic material having between 11 and 13% Silicon. If you study the chart they are quite a good piston.

I may have also made a typo in some of the PM's which read "AS8A" which should have been "AC8A". Sorry for any confusion. Len.