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Arias pistons question...

6K views 23 replies 8 participants last post by  jbird 
#1 ·
The 34 year-old high performance shop near me has sold to new (young) owners and I went by today to go over what they have as they are selling the old inventory. Alot of you guys would be drooling, stacks of dust-covered parts going back 30 years and they have no clue what most of it is.

Among the treasures are 6 sets of new, in the box Arias "Speedmaster" 454 pistons... flat-top and dome. I need a set of slugs for my build and was hoping one of you here with a long memory might have some advice or remember if they're good. They are from the late 80's, forged 2618 aluminum. He's selling them for $300 a set and I wanted to know if I should buy or not.

Thanks a bunch!
 
#5 ·
Older Arias were sort of a low-tech deal that used a lot of clearance, like .007. This will produce much more cold piston noise than people today are accustomed to. Also, you would want to verify suitability as to compression height, ring groove sizes, pin retaining method, etc. I've used a bunch of Arias pistons in oval track racing applications, seemed like there was always some little custom detail that made them like a custom built thing.
 
#6 ·
Thank you all, esp Mr. Mobley. I'm racking my brain now trying to figure out piston-valve clearance in general. I just ordered a custom cam from Harold so I guess I'll ask him for piston recommendations. If I'll have to fly cut regardless then I'll just get these and have 'em cut.

Mr. Mobley, you mentioned "always some little custom detail" with Arias...could you explain more? I'm relatively new and not sure whether thats good or bad.

Thanks again for the help.

chris
 
#7 ·
2618 material is for N2O ,so I would say yes and they may already have oversized valve reliefs.Most people who run a good hit will use a larger exhaust valve.Also ,ask Howards about them and see if you can get a part number.If they need fly cutting,be cautious.
Do some research first.It would be bad if you bought a $300.00 set of pistons you couldn't use.
 
#8 ·
I'd try calling Arias with the numbers off the box first.

One box I had, the pin retainer grooves were odd, used a lock I had a hard time finding. Another had different width ring grooves, I ended up having to buy 2 sets of rings, mix and match. Little custom things I didn't know about because I bought them from somebody who had ordered them for something and not used them. Not a deal killer, just not known about in advance.
 
#9 ·
Some of the older "special things" included "press fit rings"!! The rings grooves were super tight, and to install the top rings you had to heat the piston to install the rings. Otherwise, the ring would not fit in the groove. This feature would make pistons so equipped useless as street motor pistons.
Make sure the pistons are not of this type. Get a piston ring that should fit and see if you can slide it in the groove. If they were truely made in the 80's, I believe the "Press Fit" style was out of vogue by then.

Make sure the wrist pin isn't up into the oil groove.

A lot of the older piston skirts had a slick finnish that did hold oil very well. If the pistons are made like that, they will benefit from glass beading the thrust surfaces.
 
#10 ·
Thanks again guys. I learn more every day. FYI, I'm new to piston particulars but I did notice these pistons have horizontal grooves cut into the skirts over the entire surface of the skirt, and they also have what appear to be oil bleed holes at the tops of the skirts just under the rings. Had not seen this before and not sure what they are for. Looked kinda cool to a dummy like me though.

I will try the ring trick to make sure they accept them, thanks.
 
#11 ·
#13 ·
Sorry, one more pic. Also very curious about how the valve reliefs are cut differently in the two dome sizes. This one (smaller dome) has relief cuts for intake and exhaust. The other I posted previously has one and not the other????

http://www.putfile.com/pic.php?img=4151010
 
#14 ·
those pics, some are small block, some a BB. the ones with an angle in the middle of the dome are BB. the domed SBC are very high compression, 12.5:1 or more. the flattop SBC are machined that way with equal size valve pockets so they're interchangeable left and right. probably a race piece with no pin offset either. Those BB pistons look like a pretty big dome too. Careful, make sure you know what you want and that these will make it.
 
#15 ·
K'woodKen,

Press fit rings!!!?? I think someone is pulling your chain. Heating the pistons and hammering the rings in would make the rings totally ineffective, as far as sealing the cylinder goes. Besides, how would you compress the rings to install the pistons into the cylinders??
You're are probably just joking, but remember there are a lot of people reading these posts who might just think you are serious.
 
#16 ·
Tom,

The boxes they came from are all BB, 454 and individually wrapped slugs in plastic. I checked the numbers in the catalog at their shop and they match the codes for BB. I held the two domed next to each other to make sure and they appeared to be the same bore...454 .030 over. I may have grabbed the wrong one on the flat tops. I was gonna mention I have big hands where visable in the photos and was using a phone camera so the pics may not appear as accurate as possible. I'll double check them, though, and thanks again for all the feedback.

BTW, I'll be running them w/ 119 cc AFR 305s if that makes a difference. Just trying to make sense of final combustion ratios. If you think its a bad idea to try to work with these I'll just get some new ones from Jegs, etc.
 
#17 ·
what I think doesn't matter, what matters is if you can get accurate info from Arias on them. Bore + oversize, compression height, wristpin length and lock style, ring package, dome volume, cold clearance needed and if it's built into the piston already. All the usual suspects, IOW. Is all that stuff written on the inside flaps of the box or on a piece of paper in the box?

Are you building a race engine or a street engine?
 
#18 ·
Thanks Tom. I looked for info in the box but honestly didnt check the inside flaps, thanks for the pointer. I am building a street engine, but will see plenty of 1320 time as well. I ordered a cam from Harold (250ish @.050 and 660 lift roller) and he said it should be fine w/ most 10.1 pistons which I am shooting for but to check for clearance when I get all the parts.

I will call Arias Monday per your advice and see what they say.

Thanks again for your help.
 
#19 · (Edited)
I didn't say the rings were hammered into the ring grooves!!!

One of the piston companies, I'm thinking Arias or Venolia, made some pistons with top ring grooves that were ultra-tight in an attempt to aleviate ring flutter. The top ring groove was made the same width as the ring, .043, and the pistons were heated in boiling water to install the rings. While the piston was still hot, you put a compressor on the ring until the piston cooled off, and the ring was then held captive in the groove. When you fired the engine, the piston heated up, and the rings funtioned as normal, only with very tight clearance.

The reason I mentioned it is there is usually a reason for pistons sitting unused for long periods of time. For lack of a better term, I've used 'pressed fit rings' as one of those wierd things you don't want to find out about after you buy those bargain pistons. It's just one more of those things that were done that most people never heard of. And if you were to buy a set that were cut that way, they would be unuseable.

I'm thinking the close fit rings were tried in the late 60's or early 70's. Can't really remember for sure. I'm sure if you called Venolia or Arias, one of them could, maybe, remember such a thing if the person you talked to was old enough.

There have been a lot of things tried in the quest for HP that turned out not working or not worth the time and money. Close fit rings was probably one of them. Right now, we are going through the gapless ring marketing stage. And the Tornado Tube. ??? What will it be next? I'm still hearing talk of the "100 MPG" carburator. When you consider that the IC engine is only 20 to 30% efficient, and you consider how many BTU's are available in a pound of gas, you will quickly arrive at the conclusion that "100 MPG" out of a 3600 pound car is an unreasonable expectation. But the rumor keeps being spread by the unknowing.

Hey! There is another dyno test for DF. Find an old Fish carb and compare it to a modern FI. That should settle that argument once and for all!! Freiburger, I'm still waiting for my reply on the offset crank dyno test. I really think that with your pull, you should get Motown to cast a big block with offset cylinders. Then we could have a real apples and oranges test. (In the words of Daffy Duck:"I'd just like to see them try!")
 
#20 ·
QUOTE: I'm sure if you called Venolia or Arias, one of them could, maybe, remember such a thing if the person you talked to was old enough.

There are some pretty old guys at Arias, notably Nick Jr., and Fred Blanchard - I'll check with them.

That is an interesting concept though. Bet you would play heck getting the engine to start if the rings were that tight. I can visualize the compression being so low that the thing won't start, or worse the rings locking into the grooves so tightly that the cylinder walls are galled or the ring lands fracture.

Now, about that Tornado and 100 MPG carburetor . . . . . . .
 
#22 ·
I need to stress here: this is not MY concept. I'm only the messenger here. Just stating it because of the unusual circumstance of old pistons not being used. There is usually something funky about parts like those. Wierd rings, unusual rod length, off standard bore size, goofy pins, funny domes, etc. (I know because I've ordered pistons with all of those flaws in the same set!!!) You know; the engine with 390 AMC rods and the Divco piston rings. When every one else covers the obvious, I look for the not so obvious and it gets me in trouble every time. I'm leaning toward Nick at having the answer to the tight rings. It is a concept so strange it resist googling. Covering this subject may be an internet "first."

Second rings provide enough 'seal' for compression. My Bultaco had pentagonal rings, and it ran. Model 'T's ran with 4:1. I don't know what the minimum compression is, but I would think 4:1 is near the low limit.
 
#23 ·
The info I received on the pistons was that a customer ordered them, put a down-payment, then never came to claim them. I agree with the oddball parts idea, but in this case the guy who owned the shop made his money building race engines and simply ignored his parts stock, so there's alot of good stuff on the shelves he just simply forgot about over the years.
 
#24 ·
The picture of the domed BB piston looks like a closed chamber dome. Probably in the 36cc range would be my guess. I agree with Tom, the flat top and the other domed piston look like small blocks. The valve reliefs are lined up instead of canted.
 
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