I'm pinned?
Comments
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My understanding is that holding the rings in one position would result in their wearing in to more intimate contact with the cylinder wall surface, thus creating a better compression seal. That's probably true, but a pretty fine point engineering-wise, and in my view not worth the problems it creates. Such as the risk of breaking a ring when you're installing a ring compressor during assembly. It's really easy for a ring to shift and get over the pin, then when you tighten down on the compressor the ring will break. And on the 8s, they noted that you can remove and install the piston and rod assembly from the bottom, but reinstalling one while keeping the rings aligned is a real challenge, based on my one "at the side of the road" experience way back when. And I agree with 308 ... the rest of the industry's gotten along just fine without this feature.0
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Pinned rings work fine in two stroke engines without coming loose, they keep the rings from spinning and getting the free ends into the ports. I'm not sure how a pin could come loose and get into the combustion chamber, that would mean the rings are coming all the way into the chamber, that high and the whole ring should come loose and break when the pistion goes back down, much worse than just the pin floating around.
Harry0 -
Harry, from your post I think you're picturing something other than the way these Hudson ring pins are installed. They're simply a small diameter (.040?) pin, pressed into a hole in the top of the piston above the top 3 ring grooves, and long enough to extend down through the third ring groove. Evidentally if the press fit isn't tight enough, it's possible for the pin to work its way up and out of the piston (The pin for the fourth ring, below the wrist pin, is inserted from the bottom side of the piston). As for doing away with the pin, in theory one can machine or saw the pin segment in each ring groove, but it's difficult to do without scarring up the bottom surface of the ring groove. Then the ring doesn't seal properly against the ring groove and you get serious blow-by and burning of the piston in that area (If it sounds like I'm talking from experience, you're right! LOL).0
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Why would you go with Kanter when you have genuine Hudson people you can purchase through right here. I went with Randy Maas and with the teething problems that took place building my motor,it was a good thing to have someone that really knows Hudsons. Good luck finding that at Kanter.0
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If needed, I can mill the rings for the pin. Did a set for Gus Souza on .040 hornet pistons he had but could not find a (pinned) set of rings.
Randy0 -
When I was a small child I had a friend that had his ears pinned back but I guess thats a story for another forum ???0
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Don't know how Randy feels about it 308, but the question of 3 vs. 4 rings reminded me of my most recent ring purchase, via a friend who had been a piston and ring engineer at Hastings. He recommended running just 3 rings, saying that modern ring design does such a better job of oil control that you don't need a 4th ring. So I'm running my Hornet with the 4th ring groove empty. No problems, no smoke, no abnormal oil consumption.0
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Allow me to furnish my never to be humble opinion, but, I bought all new pistons unmachined, ballanced them before and after machining, did a close tollerence line bore, polished everything, built my pistons for the ports and machined new slotted rings for the pistons. Held all the tollerences tight and finished it off. I did a lot more, but that is enough for the piston question. With the advanced machining available, I would not have been happy with anything else...0
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FYI
Go with the 3 ring Pistons when rebuilding. I have used ring pistons since the 60's regardless whether street or comp motor.
Currently I try to utilize Dale Cooper or Randy Maas for as many motor parts as possible since they specializing in Hudson parts to help us enthusiasts .....0 -
I would not buy from Kanters when there are REAL Hudson people here who know Hudson motors like the back of their hand. I look at the Kanters catalog for fun only, some of their prices are alittle crazy.0
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(partially)... It's really easy for a ring to shift and get over the pin, then when you tighten down on the compressor the ring will break.
The problem is, that the top and bottom pins are not aligned but are about 1/3 of a revolution off.
I insert pinned rings in 2 stages.
1. Compress the bottom ring with a hose clamp that has some of the excess ground off the bottom of the worm housing. That way, you can keep the clamp against the ends of the ring as it's tightened, and prevent it from getting over the pin.
2. After the bottom ring is in, use the ring compresser as normal, again keeping it against the pin to prevent the rings from getting over it0 -
I know a HET person who put the pinned pistons in a lathe chuck, and mounted an angle grinder on the tool post. He then cut through the pin in the ring groove without damaging the piston, then would tap the pin down for another cut and eventually removing most of the pin. He would then have the pin hole on top of the piston welded up. He was retired so he had a lot of time to do this. I bought a car from him, and one day when I remove the head I will find out if he did this to my 37T. Many years ago his truck broke down in a remote part of Australia and he diagnosed it was the distributor condensor. He carefully pulled it to bits, found where the spark had shorted thru the paper in the condensor, cut the section out and somehow taped it all together and got the truck going again. A very clever man. Regards, Barry0
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Thanks guys for all your advice. I will be calling Dale Cooper tonight and order two 308 rebuild kits, one for my 55 and another for a club member for his 57 6cyl. I have looked at dales website and was impressed on what he has on offer.
And for my number two piston, I had found hundreds of indentations on top of the piston and along with the missing pin which found it's way past the exhaust valve and it got stuck next to the valve stem.
Would this have caused my blow-by problems that the motor was experiencing?
The standard sized pistons I pulled out were like new underneth. I guess the motor was done not long before I bought the car in early 2000.0 -
Yes, this does cause blow-by, as the hole that is left in the piston top allows compression to blow through behind the rings, throgh the oil drain holes, into the carnkcase. This happened on my Jet, twice. Driving along, and all of a suden a loud temporary clattering, until thepin disappears out the exhaust, and then an uneven idle, and oil fumes. If you lift the oil filler cap when the engine is idling, you will hear a fizz-fizz-fizz- every time the engine fires on that cylinder. Eventually the hole fills with carbon, but there is always some compression leaks down there. I have non-pinned rings in the current engine my Jet, with chrome top ring, and stainless expanding oil rings. I don't know whether they changed the spcification of the casting material in '54, but the Specifications for that year stipulate chrome top rings for the 308 and 202 motors. This goes against all the previous theories of never using chrome rings in a chrome bore. I know Jack Clifford supplied chrome rings for the Hornets, and rubbished the idea of pinned rings. they have certainly workde in my case, as the engine now consumes no oil, and the oil in the sump stays clean, whereas before I was using a quart every 200 miles, and it would turn black in very short time. Plus economy and performance is improved as well.
Geoff.0 -
I guess I'm really confused now. How can you put a pin in from the top and have the three rings staggered around the piston? I know on two strokes the pins go into the side of the groove. If all three rings are aligned wouldn't that contribute to blow by? If the pin goes in from the top it's no wonder they worked their way out. How is it with all of Hudsons great design features this continued for so long? I'm pretty sure when I rebuild my engine I'll do without the pinned rings. As long is there a viable alternative.
Harry0 -
Harry, the top three rings are not staggered; that's what makes the Hudson practice somewhat intriguing. Actually the gaps are staggered very slightly, as the notch in the rings isn't centered. The top ring has the notch offset a little to one side, the 2d ring has it offset in the other direction, and the third (I think) isn't offset. So the gaps are staggered by a distance less than the diameter of the pin. Big whoop, huh? But back to the basic idea, Hudson evidently thought the improved seating of the rings if held in one place would more than make up for a little potential blowby at the ring gaps. And apparently the Rolls Royce folks agreed.0
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I was told that siamesed blocks, cylinders joined together so water doesn't surround the cylinder, wear into an oval shape because of uneven cooling. The pin kept the rings from rotating do they would wear to match the cylinder. The GM 454 and the Hudson have siamesed blocks. The 454 did not have pinned rings and were notorious oil burners after about 60,000 miles.0
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Here is an article that Bernie Siegfried wrote for the Nov/Dec 1987 WTN.
Hudson's Pinned Rings
by Bernie Siegfried
As I remember it, from the Hudson archives, someone in Hudson engineering when planning for the 1924 Essex Six, the forth coming replacement for the Essex four cylinder engine, wanted the engine designed as light as possible, the crankshaft throws as close together as possible for rigidity and the main bearing journals at the minimum of three. It had long been realized in the automobile industry that a cylinder bore, particularly in an L-head type engine could not be cooled uniformly. Consequently the cylinder bores when heated by a running engine were no longer round when hot, but the piston rings were. This condition added to oil consumption by oil passing the rings on the inlet cycle and to additional blowby on the power cycle.
Many years ago when Rolls-Royce automotive engines were of the L-head (side valve) type and being the perfec-tionist they were, they overcame the out of round bore condition by having the piston rings remain in a fixed position on the piston and not free to rotate as was normally done, To permanently fix the rings, a small hole was drilled down through the outer edge of the piston, said hole passing through the ring land grooves. A hardened pin (needle bearing) was pressed into the hole and the hole top staked to prevent the pin coming out. The piston ring open ends were milled semi circular to close over the pin diameter so that the closed ring outer edges had normal clearances. With the rings in a fixed position they would wear in the shape of the heated bore. A marked improvement in oil consumption was achieved.
The proposed design of the Essex Six cylinder engine would magnify the out--of-round heated bore condition. In order to achieve the goal of a short light block and crank, a small bore long stroke was chosen. In addition the three cylinders on either side of the center main were closed together (siamesed) and no cooling water could pass between them. So Hudson engineering adopted the Rolls-Royce solution and pinned the piston rings. As Hudson history reveals, the pinned rings remained a Hudson trade-mark to the end. Further development of the Essex Six engine for the Terraplane lead to the inclusion of the Ricardo type swirl chamber in the cylinder head. Hudson called it their "Power Dome" head. The pinned piston rings and Ricardo head chamber were included in the development of the Hudson straight eight. I suspect these features along with the fluid clutch; the unique front suspension and the relatively low price were prime factors in Mr. Railtons choosing Hudson chassis for his car. For years Hudson engines were among the leaders in HP per cubic inch in the automotive field. The small bore long stroke design lead to Hudson advertising slogans touting their lighter smaller but more powerful engines. However the pinned ring feature, besides being expensive to manufacture, pre-sented problems at initial assembly and at later engine repair. When installing the piston and ring assemblies at the factory it required the use of a slotted upper portion tapered sleeve to visually insure proper alignment of the rings ends to the pin to prevent ring breakage by having a ring end over the pin. Reringing a Hudson engine presented even more problems unless the cylinders were bored oversize and new pistons installed. The fixed aligned upper ring ends left a raised ridge in the upper section of the cylinder bores that had to be removed before new rings would fit properly. Also it was difficult to remove the carbon from the piston ring lands as the ring pin presented an obstacle to the land cleaner. When the 308 engine was introduced in 1951, early field reports indicated that the ring pins were coming out of the piston tops on these 313/16 dia. pistons. At that time Hudson had changed to the cam ground type piston from the earlier T-slot type, so on all engines built from then on, the pistons were turned 180° so the ring pin was farther from the hot exhaust valve. While this move did not completely cure the problem it apparently lowered it to acceptable levels, at least while Hudson still existed. Over the years during which I have overhauled, rebuilt or repaired many Hudson engines, the only engines showing evidence of rings pin loss or near loss were the 308's. On the 308's at least 25% showed evidence on one or two pistons of either a loose or missing ring pin. While in an overhead valve engine bore distortion was not a problem, the advent of the development of the steel vent flexible rings during WWII made these rings more than acceptable in L-head engines, even with Siamese bores.0 -
with the long stroke of a 308, i believe that the 4th ring would be an aid in keeping the piston steady in the bore, it sure would yank around as the rod journal crosses its centreline0
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I have the utmost respect for the late Bernie Sigfreid, who was with the Hudson engineering department, but he is wrong in his recollection of the development of siamesed bores. The Essex Six had water-jacketed separate cylinders, and non pinned rings. The bore size increased over the years from 2-5/8" to 2-11/16", 2-3/4', 2-7/8", and 2-15/16". The bores were not in fact siamesed until 1934, when the cylinder bores were increased to 3", and there was no physical room for a water jacket. Oil consumption was a problem with these engines, which also had four rings above the piston. This was overcome by shifting the fourth ring to the skirt, below the piston pin, and leaving a heavier section at the top, as less compression and heat was applied to the top ring. This also allowed fitment of the ring-locating pin in this "meatier" top section. holding the rings in position allowed them to wear in comformity to the bores, and thus hold the oil consumption. With the advancement of piston ring design, the necessity for pinning them in position was eliminated, but Hudson in their peculiar obstinacy, continued. I understand that Mr. Siegfried had some rather heated exchanges with his superiors on their engineering practices. As an aside, there was also a rather oddball engine produced for the British market, which had a R.A.C. rating of 16.9 . h.p. to bring it down to an acceptable figure for taxation purposes, which was based purely on bore size. These 6 cylinder engines looked like a standard Terraplane engine, but had non-siamesed bores of 2-13/32", and a stroke of 5", and were fitted as an option to all six cylinder Hudson and Terraplanes supplied in G.B. They also had pinned rings!
Geoff.0
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