OH NO :O Wrong rings?

[NiftyFifty]

Well gents,

I've been waiting on this motor for probably a month now to have the machining work finished, and today I finally get it back so I dive right in and I'm stopped before I really started.

I just went to install the rings that I purchased on e-bay that said they were for this chrys 251 and all the other engines with the same bore, but they don't fit my pistons at all?

Does anyone out there know of a different set or what am I missing here? I took some pics, the oil ring looed right, but the stock was slightly bigger but the new one's had spacers....but the flex ring that lays under the oil ring is way different and way to thick...then I just checked top and 2nd and their too thick too.

I looked to see if they were like my 218 pistons, but they have 4 rings vs. my 251 wich only has 3

Any help out there...looks like another stall in this truck...and another summer without it! :@

[Young Ed]

Where did you get the pistons? I've never seen a flathead piston with only 3 rings.

[PatS....]

My worn out Canadian 251 pistons with rings in place. I think the 251's are the same in the US except for the heads on the Chrysler engines.

[mechresto]

4MULA

It appears that either you have either mis-identified your engine as a 251,

OR you have the pistons from a '52 Chrysler C51-1 or C51-2 265 in your 251, or you have a 254.

The pistons from the '52 C51-1 and C51-2 engines are the only ones that I have found that came with a three ring pistons.(Chiltons auto repair manual 1953 pp414) There could be other years but my books don't show anything.

the bore diameter is correct at 3 7/16 and the wrist pin diameter is useable at .8594 which is only .0001 larger than the normal 4 ring piston.

There is another reference, here it is -- "Dodge TR. '49-'53 using replacement engine 254". (Hollander 23rd ed, sect 7 pp37 col 1) To me that means if the stock engine was replaced with a factory supplied engine,you recieved a 254 with 3 ring pistons.

Another reference: Note: "Dodge shows that late '54-'56 used a piston of a different part number from the late '53 thru early '54, but replacement parts manufacturers sell the late '53-early '54 piston for the late '54 - '56 jobs. Compare these pistonscarefully before interchanging." (Hollander 23 ed, sect 7 pp36 col 3)

There is one more difference in the application that may or may not have anything to do with your situation. The stroke from the C51 engines is 1/4 inch longer, 251 @ 4 1/2 inches 265 @ 4 3/4 inches, where the referenced 254 falls with it's stroke is anyone's guess as I have nothing that lists the 254 engine. Is the wristpin to piston top dimension different than that of a 251 or 265? Is the 254 merely a 251 with the C51 265 pistons in it?

Is Don Coatney reading this? Don perhaps you can shed some light??

Bryan

Edited July 10, 2011 by mechresto
missing info

[NiftyFifty]

4MULA

It appears that either you have either mis-identified your engine as a 251,

OR you have the pistons from a '52 Chrysler C51-1 or C51-2 265 in your 251, or you have a 254.

The pistons from the '52 C51-1 and C51-2 engines are the only ones that I have found that came with a three ring pistons.(Chiltons auto repair manual 1953 pp414) There could be other years but my books don't show anything.

the bore diameter is correct at 3 7/16 and the wrist pin diameter is useable at .8594 which is only .0001 larger than the normal 4 ring piston.

There is another reference, here it is -- "Dodge TR. '49-'53 using replacement engine 254". (Hollander 23rd ed, sect 7 pp37 col 1) To me that means if the stock engine was replaced with a factory supplied engine,you recieved a 254 with 3 ring pistons.

Another reference: Note: "Dodge shows that late '54-'56 used a piston of a different part number from the late '53 thru early '54, but replacement parts manufacturers sell the late '53-early '54 piston for the late '54 - '56 jobs. Compare these pistonscarefully before interchanging." (Hollander 23 ed, sect 7 pp36 col 3)

There is one more difference in the application that may or may not have anything to do with your situation. The stroke from the C51 engines is 1/4 inch longer, 251 @ 4 1/2 inches 265 @ 4 3/4 inches, where the referenced 254 falls with it's stroke is anyone's guess as I have nothing that lists the 254 engine. Is the wristpin to piston top dimension different than that of a 251 or 265? Is the 254 merely a 251 with the C51 265 pistons in it?

Is Don Coatney reading this? Don perhaps you can shed some light??

Bryan

When I was first trying to identify the engine I was on here and had pics etc of the engine numbering and the rebuild tag, which with the math worked the engine out to be a 251. It had been rebuilt in Winnipeg,MB Canada and was in a Massey 90 Combine, so it wouldn't be under any light vehicle category. I'm wondering if the original IND line of engines used a different piston? Every other 251 part I ordered including valves was bang on, so this has been the only bump on the road.

Here is a piston pic....I'm thinking a new set of 251 pistons and I'm back in biz...I hope!

[Don Coatney]

I was not aware of the 3 ring 4 ring difference between the 251 and the 265 engines and my MoTors manual does not make mention of it that I could find. As has been mentioned the bore (3 7/16") is the same for both engines. Per my MoTors manual the ring gap on the compression and oil ring on a 251 is .007. On a 265 the ring gap on both oil and compression is .011 so there must be a difference somewhere. The ring clearance in the groove for both engine sizes is .001 to .0025. Both engine pistons use a floating type wrist pin held in place by snap rings with a push fit in piston and rod with the piston heated.

Looking at the picture of your 3 ring piston I would recommend replacement. Have you actually checked the stroke to find out what engine you have? If you find that you have a 251 then I would suggest you buy the correct pistons for it. And if you find you have a 265 buy the correct pistons and rings for it.

[NiftyFifty]

I was not aware of the 3 ring 4 ring difference between the 251 and the 265 engines and my MoTors manual does not make mention of it that I could find. As has been mentioned the bore (3 7/16") is the same for both engines. Per my MoTors manual the ring gap on the compression and oil ring on a 251 is .007. On a 265 the ring gap on both oil and compression is .011 so there must be a difference somewhere. The ring clearance in the groove for both engine sizes is .001 to .0025. Both engine pistons use a floating type wrist pin held in place by snap rings with a push fit in piston and rod with the piston heated.

Looking at the picture of your 3 ring piston I would recommend replacement. Have you actually checked the stroke to find out what engine you have? If you find that you have a 251 then I would suggest you buy the correct pistons for it. And if you find you have a 265 buy the correct pistons and rings for it.

Yes I measured the stroke, and as stated below was the 4 1/2"'s as I was hoping I got a 265 when I started this engine job. The pistons in the pics are "original" of course so who knows what was going on at the time of the factory rebuild. I'll do some looking again today, but I'm not thinking I have a 254....that would have been pretty uncommon in a combine from what I've been told.

[Dodgeb4ya]

I have both 251's and 265's that I own a have rebuilt-both are/were 4 ring piston engines. I also have sets of NOS MoPar 3-7/16" pistons with the rings factory installed on them -all 4 ring. Never have seen 3 ring MoPar flathead pistons!

Learn something every day.

Bob

[NiftyFifty]

I have both 251's and 265's that I own a have rebuilt-both are/were 4 ring piston engines. I also have sets of NOS MoPar 3-7/16" pistons with the rings factory installed on them -all 4 ring. Never have seen 3 ring MoPar flathead pistons!

Learn something every day.

Bob

Well then....TODAY ONLY!!! Great deal on VERY RARE MOPAR PISTONS!! $1,000 each OBO....

WEll I hope my ebay guy can set me up with a set ASAP....I think today I'll keep moving ahead and do the crank etc.

[Don Coatney]

If I were looking for engine parts eBay is the last place I would look. I dont like to buy things that others have rejected. In my opinion you are better to buy from a known quality vendor.

I have had good luck with.....

Terrill Machine 254-893-2610 (TX)

There are several other vendors listed under the links section of the main web page supporting this forum.

http://www40.addr.com/~merc583/mopar/framesets/linksframeset.html

[Merle Coggins]

Since it was rebuilt once before it's possible that some aftermarket pistons were used. When I got the machining done on my engine the guy doing the work was telling me stories from "back in the day" when they would use Continental pistons in Chrysler engines and vice versa depending on availability at the time. Apparently they were close enough to work in a pinch. Maybe that's what you have.

What machine work did you have done? Apparently not a bore job or you'd be needing new pistons anyway.

Merle

[NiftyFifty]

Since it was rebuilt once before it's possible that some aftermarket pistons were used. When I got the machining done on my engine the guy doing the work was telling me stories from "back in the day" when they would use Continental pistons in Chrysler engines and vice versa depending on availability at the time. Apparently they were close enough to work in a pinch. Maybe that's what you have.

What machine work did you have done? Apparently not a bore job or you'd be needing new pistons anyway.

Merle

Had to have new seats cut for the valves, due to some rust/pitting issues, new guides, got new cam bearings and a tank dunk....the cyl's probably should have been done, but they cleaned up pretty decent and with the ridge ream they will be fine.

NOW....here's my newest quandry...does that flimsy ring in my OP actually make up a ring grove alone with the 2 spacer rings? I've never seen one like that before...lots of the flimsy spacers that fit behind oil rings...but nothing like that one in the pic as a whole ring? The 218 pistons have 2 of those heavy thick gapped rings then 2 compression rings...the 251 piston must have one heavy..that flimsy one..then 2 compression? This flathead stuff is all new too me...spent too much time on 80's+ stuff I guess, amd sled motors.

As for ebay...honestly...nobody could come close to touching the prices these guys have on some stuff, and it's the same brand and part numbers as local jobbers here for a 1/4 the price...clevite is good stuff in my books (most times) and thats who makes the ring set...and sealed power etc for my bearings..and as I say...jobber was like $300+ for mains...I got them for $70 with some shipping...not even comparable.

[Dave72dt]

NOW....here's my newest quandry...does that flimsy ring in my OP actually make up a ring grove alone with the 2 spacer rings? I've never seen one like that before..

Yes, very common. I don't know how many I've put together that are that style. Make sure the flimsy ring doesn't overlap on the ends where they meet. Start a spacer ring about an inch from that meeting point and wrap it around the piston to go over that end joint, then the other spacer goes on starting about an inch the other side of the flimsy ring's end points. Done correctly the spacer rings will be staggerd equally on each side of the flimsy ring's end gap.

A quick look at that flimsy ring, (for want of a better description), shows a small protruding edge on each side. The spacer rings will sit on this edge when installed. They're actually scraper rings and the flimsy ring is the expander ring

[NiftyFifty]

My parts guy is saying he has a listing for 3 ring 251 pistons....maybe their not completely uncommon???

[OLD DODGE]

These pics are something I posted for someone on the 39-47 forum. It doesn't specifically apply to your engine but it does show that the factory made changes. That it why it was so important to identify the exact engine to get the correct parts.

The factory replacement engines and rebuild kits started out using the displacement for the model number, so a 230 cubic inch motor was a Model 230. As they added changes/improvements to them they had to change the model number accordingly to insure that customers could get exact replacement parts. So the next generation became the Model 231 and so on. The displacement did not change, just the model number.

So the Model 254 replacement engine is not 254 cubic inches, but a 4th generation replacement 251 engine.

[NiftyFifty]

I've decided to just order a set of STD 251 4 ring pistons....I can get a great deal if it wasn't for the darn shipping...so much for our "free trade"