3.0L Piston options?

[AdellAdam]

pistons for the 3.0L are outrageously expensive! is there any other options? I heard someone say that the 350 pistons would work, but I'm hesitant to buy some to find out they don't. My pistons are a bit worn and I need new rings and probably a clean-up bore (.010 or so). I just don't feel like spending $100+ per piston! If it comes down to it, I'll just make my own pistons and use 350 rings. Yes, I can make my own pistons. It would just take me a week to make them and there goes all my spare time...

 

[rodbolt]

Re: 3.0L Piston options?

carefully measure your old ones, there were some piston pin height and skirt changes over the years.

 

[45Auto]

Re: 3.0L Piston options?

They're pretty easy to find all over the internet for less than $50 each. You'll have to decide how much a week of your time is worth.

 

[zbnutcase]

Re: 3.0L Piston options?

And no, 350 pistons won't work due to compression height differences

 

[AdellAdam]

Re: 3.0L Piston options?

I have an 86 which seems to be the last year of the 140 from what I can tell. I'll check them next time the engine is apart.

Where are you finding them for $50? The cheapest I found was $80 each. I don't seem to do much these days so a week of my time isn't worth a whole lot anymore

And no, 350 pistons won't work due to compression height differences

That's kind of what I was figuring. But at least the rings will work. That makes part of this easy.

 

[moparmatt]

Re: 3.0L Piston options?

How about these?? They are less than 50 each They also have a set of rings for 32.00 . Great prices

http://www.ebasicpower.com/pc/FEDH896CP/MER6U-IB/Piston, GM 181 CID 3.0L 4 Cylinder.html

 

[JustJason]

Re: 3.0L Piston options?

Unless your pistons have detonation or mechanical damage on them i'd just re-use them.

 

[AdellAdam]

Re: 3.0L Piston options?

one piston is missing a part of the skirt and the cylinder walls seem to be a bit heat-tempered in once cylinder. There was water in the oil when I bought the boat (i could never find the cause of it) so i'm thinking that the water was the cause of the cylinder wall heat damage.

Thanks for the link. I might just go with those. They appear to be Sealed Power Hyperutectic pistons which are actually great pistons.

 

[Howard Sterndrive]

Re: 3.0L Piston options?

ok, I'll bite....

homemade pistons?

you can cast pistons? you know how to make the right alloy with the proper silicate dispersal? And you know how to design it to compensate for thermal expansion in the pin bores?

and yet, you work for less than $200/week?

 

[AdellAdam]

Re: 3.0L Piston options?

I'm a tool and die maker and a CNC machinist. I don't cast, i'll make billet ones. Probably out of 2024. So not "homemade" but custom machined. I do this for a living, so it's just an extention of my regular day. I don't make any pistons, but I do make molds for investment castings out of aluminum.

I'm single and I spend most of my time at home cuz I'm broke (divorced...). So if I'm sitting at home or I'm at the shop it won't make a difference. That's why my time isn't worth anything. Time I have, money I don't.

 

[gbeltran]

Re: 3.0L Piston options?

Well, since it sounds like you have access to some nice machines. You could pick up a set of 327 chevy pistons and mill .050 or so off the top, they have a 4 inch bore and close to the same pin height, as well as the same pin size, dont know if they come in any kind of dished style so you would have to figure out a way to keep the compression down, maybe mill a little more off? Just a thought. (350 pistons will not work, they have a pin height almost a tenth of an inch shorter)

 

[Howard Sterndrive]

Re: 3.0L Piston options?

neat... I wish I could do that stuff...

My one boat project helped me a lot after my divorce. I'll keep that boat forever. It gave me a goal and a focus... same deal... I had little money but lots of time.

 

[AdellAdam]

Re: 3.0L Piston options?

.050" is quite a bit to mill off a cast piston like that. I'd be afraid that it would get too thin at the top. I'd have to look at one to be sure there's enough stock on the bottom side. And putting a dish in is not a big deal, just add in a pocket cycle and profile with a ball end mill and i have a dish. I could just run flat top and go with 93 octane as long as there won't be any interferrence. The dish on my pistons is actually pretty shallow and they go right to the top of the bore, but it says to use 88 octane and set the timing at 6* BTDC. But that would be the best option if it works. Those are $20 each for standard cast ones. So for $100 I'll have pistons and rings. I can do the clean-up bore at my shop. I could even re-sleeve if I need to. And as long as I'm working on that I'll just port and polish the head.

There is still the possiblity that I'll be doing a 4.3L swap because I'm unsure of this block with the water in the oil earlier. I have been running it as-is and I haven't seen any water in there yet, but I don't want to rebuild this and see it surface after it's all back together. But I do need to get new rod bearings in it. Those are rattling like a snake. I haven't run it since they started rattling and I'm hoping the crank is okay. I might have to get (or make) a new cam, too. It was a little worn. I guess this thing won't see water again this year...

I just want to go fast! *pouts*