smietana

https://classicoldsmobile.com/forums...-ring-set.html


Tried to find information on these pistons, with no luck. I figure I would post here to see if anyone could shed some light on them. Was told they are forged, but they look like stock pistons.
Thanks Tom

64Rocket

Great set of pistons. They are very old pistons. I've had two set over the years. Be sure to use .005 piston to wall clearance.
My opinion, a little pricey.

Gene

smietana

Thanks Gene, so are they considered a stock style pistons? My machine shop was planning on adapt a modern piston to my 425 block.
Thanks Tom

cutlassefi

Have your machine shop check these out. Much better material, better ring pack and a whole bunch lighter. They're only .017 shorter than originals and the Pontiac valve arrangement and wrist pin size is the same as an Olds.
Mill the block a little and use a shim gasket and you're there. With an 80cc head, this dish and 12cc in deck and gasket you're at 9.6:1. Sounds like a plan to me!!
https://www.uempistons.com/index.php...40af81e5d3ec07

A lot cheaper here;
http://www.cnc-motorsports.com/pisto...-150-bore.html

Need a cam?! Lol!

smietana

Thanks Mark, that's exactly what he was talking about. Will be ordering them. As soon as this part is complete, will send you the info so I can order a cam. This has been a much longer process than I planned.
Thanks

cutlassefi

Thank you. The Olds hobby is challenging enough. We could all use a bit of help from time to time.

Fun71

Thanks for this info! I have a pile of 400E and 455 parts that I was planning to build into a long rod, short stroke 425 engine, but pistons were the one thing that was hard to decide upon.
Any recommendation on rings to go along with those pistons for street use?


Minor detail (0.002" worth, to be precise), but aren't those .020" shorter than factory Olds pistons? I thought the SBO and early 400/425 compression height was 1.615" per the Olds blueprint spec.

smietana

Mark, has helped me quite a bit. We talked for almost 45mins on the phone about my build. He is wealth of knowledge when it comes to engine building. When I am through building the short block, I will be buying a roller cam from him. He is on this site giving great info(and his time) for novice like myself.

orange442

These are my pistons and they are forged. My question is, when and why is a piston, specifically made for an Olds 425, no longer a good piston to use in a 425? You then instead buy a more expensive Pontiac piston and make it work in an Olds application? Just does not make since to me, more cost and not application specific?

cutlassefi

Pretty simple really.
The piston you have is a much older design with a fatter ring pack. Plus they're much heavier.
Anytime you can use a thinner ring, lighter piston yet one with sturdier construction you're ahead of the game.
Kenneth - I've seen the original pistons listed as 1.612-1.615. You're right, a good decking of the block and the proper gasket and it'll be fine.

orange442

Ok, I did not realize he was building a race motor. And, thanks for talking him out of buying my pistons and basically telling everybody they are worthless.

MDchanic

It's not Mark's job to hustle your pistons for you.
The OP asked a question and Mark answered it, and pointed out the best piston currently available for his build.
The fact that your pistons (which all agreed are great pistons) are not as good as those newer pistons, which cost the same amount, is not his fault.
Perhaps your price is a bit high.

Take your hissy fit elsewhere.

- Eric

cutlassefi

Please show me where I said they were "worthless".
Please show me where that Icon piston is a "race" piston.
Where does it say he was going to buy them before I told him they were "worthless". Those are your words, not mine.
Last time I checked he's allowed to make his own decision in this country.
If they ARE such a great deal, why haven't you sold them already? Especially since 425 pistons are harder to come by. Hmmmmmm

Maybe your price is higher than the market will bear for that style of piston. Ever think of that? 64 Rocket said they were "a little pricey". Why don't you jump all over him?

Don't shoot the messenger.

smietana

No one talked me out of buying your pistons, my machine shop suggested adapting a modern piston first. Basically posed the question about stock style pistons, and seems everyone who has built more than one engine suggest going with a modern piston. For the reasons Mark explained.
If I am unsure about something with my Oldsmobile, I can ask on this site and get honest answers. That's the great part about be part of CO. Sorry the answers didn't fit to sell your pistons. Good luck with your sale.

orange442

Eric, I should go elsewhere? This is about my pistons and you insert yourself into a thread that has absolutely nothing to do with you and make negative comments and I am the one throwing a fit? You need to check in the mirror on that one. I know Mark is more than capable of a reply on his own. Also, the OP, as you say, was specifically asking about my pistons for sale, not what options are out there instead. Mark came directly on about the Pontiac pistons and never even made a comment about the original question about my pistons. That is where I inserted Marks lack of a comment as him considering them useless. If he considered them to be a good piston, I am sure he would have said so instead of just posting the Pontiac pistons. I wish Tom the best with his build and hopefully in the future people can stick to the specific subject of the post.

MDchanic

This is a public forum.

All members can read and post here.

Neither Mark, nor anyone else here has any obligation to further your sale, or any other economic interest of yours, in any way.
He gave his honest (and very knowledgeable) opinion, as he was asked to.

The forum has a (loosely enforced) rule that we are not supposed to post critical information on people's "For Sale" threads.
This is not your "For Sale" thread.

- Eric

cutlassefi

Well put Eric. Thank you.

Boldsmobile

Cost to install the same?

smietana

the installation cost is the same, may have a little machining cost. My guy can get me those pistons even cheaper. Overall cost might be 100-150 more but will be worth it.

MDchanic

Well, let's see:

• The older pistons are .030" over, so we are ASSuming a bore for either set (you'd be likely to bore the block any time you install new pistons, wouldn't you?).
• Both types use the same wrist pin and can be used with the same rods, so no difference there.
• There is a 0.017" compression height difference, but most people rebuilding are going to do at least a "clean-up cut" of the head sealing surfaces - taking a few thousandths more will add minimal to no extra cost.
• The new pistons don't come with rings, while the older pistons do, but the OP says that his machine shop can get the new pistons even cheaper for him, so they will cost only slightly more, including the rings.

So, to anyone but an accountant, the cost to buy and install is about the same.

- Eric

Boldsmobile

Wtf is that supposed to mean?

MDchanic

It's supposed to mean that to the normal person, on a job costing several thousand dollars, fifty or a hundred bucks one way or another isn't going to be worth discussing, but to a bean counter, yes, the cost may be slightly more.

What it actually means is open to about five pages of interpretation, since this is the Internet.

WTF are you, an accountant?

- Eric

Boldsmobile

I was looking to see the difference in pure dollars and cents as quoted from a builder. OP acknowledged more which means you can not state it as the same.

How about breakdown side by side of parts and labor? Or you just rather bestow your opinion? If you dont want to be bothered with an itemized list than why bother taking the time to throw a dart? To prove you are smarter? Im not going to stack up what i know or what i have done because i could care less what you know about me.

Why not just say, its likely a wash in a non arrogant manner?

On to the non-subject matter comments in your threads:

Implying i am not a normal person. Implying that i cant calculate the difference.

Starting with "well lets see".

Take your smug , condescending, snotty attitude and save it for someone who cant detect a jerk hiding behind words.

You post a lot of replies here trying to help people, it doesnt give you a bye to be a jerk.

So much for CO being a friendly place.

This forum does not have loosely enforced rules for behavior. Just because you are being crafty and subtle with your behavior doesnt make it appropriate.

Perhaps you should check your behavior at log in.

MDchanic

I don't need your permission to be a jerk, and I don't recall asking for it either.

I've spent over half a century honing my arrogant, condescending personality (I'd hesitate to say "smug"), and I doubt that a day goes by when I don't have a chance to inflict it on some defenseless soul, not just on the interwebs, but in person, as well.

I'll take your defensive, euphemistically profane "WTF" response as evidence that you find arrogant know-it-all jerks threatening (for reasons that I cannot understand). Look within.

- Eric

Hawghead

Pete, dude,

Take a pill, sit back have a cold one, your getting way too wound up. I read Eric's post several times and I came away with that he was just trying to say the difference in cost, if any, would be insignificant when you figure the cost of doing a whole engine build. The problem with the written word is you don't know what the tone of the writer is or his/her inflection. As a result we often add our own tone or inflection and misinterpret what the writer is saying.

Eric, I'm LMAO, that's priceless. When I was in the Navy my Weapons Officer would say to me "Chief your gonna give yourself an ulcer." I'd give him my best FU look and say "Lieutenant, I don't get ulcers I give em!"

Now everyone settle down or liberty is secured until moral improves!

Scott

smietana

Ok, I have the Pontiac pistons at the machine shop. But now my machinists saw the lifter bore, and said he had issues with a 400 that had the same .921 lifters. Saying that it was filling the top of the heads with to much oil. Because of how the lifters internal valve was operating. Also with less choices at .921 size lifters. They fixed the issue in the 400 by using comp cams internals from a smaller lifter. I think I am correct that the internals from my 425 will fit in a 455 block? I have a 455 block, advantage the smaller lifter bore. The rotating assemble of the 425 has been machined. My question is I have a choice of blocks, use the 455?
Thanks Tom

Fun71

Yes, the 425 internals will fit into a 455 block (that's a build I am planning).

How about just using a set of restricted push rods instead?

smietana

He said they tried the oil restrictor kit, all different types lifters, (will ask about the push rods) but the newly valve lifter solved the issue. I think it comes down to having very few options in a .921 lifter.

MDchanic

Funny, those lifters never caused "over-oiling" problems in millions of miles of service when they were made.

- Eric

smietana

Think that's the point, can't buy the original GM lifters.

cutlassefi

The ones I have available have new valving. That coupled with restricted pushrods will more than handle the issue.
This new lifter has only been available for less than two years.

MDchanic

Mark knows whereof he speaks. Get the information he has about the new-design lifters and give it to your rebuilder.

- Eric

smietana

Are they the ones that were coming with the cam we spoke about?

64Rocket

Putting the internals in a 455 block is a great idea. I have done a couple and work out great.
easy to get lifters and cam. A roller cam would work perfect.
With those pistons, your machinist can deck the block enough to get the compression you want along with the "CC's" in the head. easy job.

Gene

steverw

Do all 425's use the .921 lifter?

steve walker

nope some have the smaller size

64Rocket

if you have the .921 lifters you have the 39 degree cam bank angle.
If you have the .842 lifters you have the 45 degree cam bank angle.

Gene

cutlassefi

Yes. However if you use the 455 block then you can do the roller if you want.

walkerkj

Not true. I have a. ‘67 425 with 39 degree valve bank angle and .842 lifters.

64Rocket

'67 is the only year that is the diff

otherwise it apply's to all others even some '67's