343 pistons in 360, don't fit...

[PaintedRat]

NOTE: For those using this for search info, the Egge 343 pistons are listed on their site under Rambler, and are slightly shorter than listed. These will provide CR over 10, but quench isn't perfect, read for details.

I tried install my pistons into my block today. The bore is fine, and the rings fit. The counterweights on the 360 crank contact the piston skirts at the bottom of the stroke. What do I do now?

I'm thinking the easiest would be to have the counterweights taken down, then rebalanced, but I don't know if you can do that. One suggestion was to machine the pistons, but that sounds like it would take more effort and money.

[jeepsr4ever]

This is common when your fitting a custom set of pistons. You will need to cut the skirts either grind them or mill them doesnt matter.

[PaintedRat]

Is this something I can do with a dremel and file or should it go to a shop? How much clearance do I need? Can it be done on the rods, and should I remove the rings (both for the purpose of not trapping debris in bad places)? During removal/reinstall of rings, I'm afraid I'll break another ring and have to order new ones.

http://www.geocities.com/thepaintedrat/4x4/engine/enginenew2.jpg

[jeepsr4ever]

at least .035 of relief...you can use a dremel. How bad is it?

[PaintedRat]

It is solid contact, but at the very bottom of the stroke. I think a hair off and it will pass. I will try to do this today on the first piston and see if I have any trouble.

Oh, and I see a lot of orange/red, blue, and black blocks, so I thought the green shown above would be a fun color for my first engine build.

[jeepsr4ever]

Sweet looks like AMX Big Bad Green :t:

[AMX69PHATTY]

Interesting.
I have a stock 343 4V piston sitting here beside
a TRW replacement cast 360 piston.
On the TRW 360 piston, the part of the skirt that goes
from the side of narrow part farthest down on the skirt 90* from the pin
to the cresent shaped flat surface 90* away, below the pin
is what differs from the stock 343 piston.
On the 360 piston this area comes down almost flush with the cresnt shaped flat.
Looks like on each 343 Piston, in ( 4 ) places, you would need to blend / grind this area
so the skirt transition from the 2 skirt "tips" becomes almost, but not quite,
flush to the cresent shaped flat area above the pin.
May I ask if you have 360 pistons to sit besdie and compare to the 343's ?

[PaintedRat]

I had the machine shop chuck the 360 pistons after they were removed from the rods, so no side by side comparison. I'll try to get a pic of the 343. I don't know what brand they are, they were bought through the machine shop.

[AMX69PHATTY]

Not the greatest pictures, but the camera I have is really old.

http://mywebpage.netscape.com/SketchKT/AMC+343+vs+360+Pistons.jpg

[73hornut]

I would have them rebalanced afterward. Your going to change the weight of each piston.

[PaintedRat]

It is hitting the area below the wrist pin marked in the pic. Should I take material off both sides of the piston, or just the side that contacts the crank?

If I can get away without rebalancing, I would prefer not to spend the money. I'm pretty much pushing my budget to finish this motor as it is.

http://www.geocities.com/thepaintedrat/hosted/343piston.jpg

[AMX69PHATTY]

Wow, I don't know. That area does look thicker in your pic.
That ledge is about .20 thick on the ones I have.
From piston top to that surface is about 2.40 on the 360, 2.45 on the 343.
Guess this is over my head and I'd better drop out and let the proffesionals.

[Goose]

Well I am not sure on the clearance issues but I can tell you 2 things to keep in mind.. Rods stretch and shrink.. so If you are going to clearance the pistons.. make sure you have a little extra clearance, cause at operating speeds that piston is really moving when it hits the top and bottom of the stroke.. and what looks like enough now, won't be.. (as to the amount.. beats me maybe MC and the fast guys know..) but the second is.. If you grind material off those pistons.. spend the bucks.. rebalance. balancing an engine is the single best dollar you can spend.. It will increase power and longevity more than any other money spent on a bottom end..

[jeepsr4ever]

How much is hitting? If you have to take off a small amount I wouldnt worry about re-balancing. Your not going to hit and hold 7500+rpm are you?

[PaintedRat]

I didn't have a good mic handy at the time. I don't think it is much material, but I'll put one rod/piston on the crank after work to measure before I do anything to the piston. Too much drama yesterday to do anything more than paint the tins (and my hands).

I hope to never hit 7500 RPM. This is an offroad rockcrawler that I will be driving to trail this season, trailering starting next year. It will be idling a lot, and staying in the lower RPM range, but it'll run higher compression if it matters.

BTW guys, I appreciate the input. My book shows the steps, but not what to do if things don't fit. If not for Bulltear I would have already smashed everything.

[ironman_gq]

you'll probably be fine if you try to take the same amount off of all the pistons.

[1980_Cj7]

http://www.geocities.com/thepaintedrat/hosted/engineblock1.jpg

Wow, if we put that in our engine compartment...you wouldn't be able to see it, ha, ha. It would be camouflaged, or however you spell in French.

https://home.comcast.net/~rwsr50/ComcastOnlineStorage/401homecoming_026.jpg

[jeepsr4ever]

Frank is goona flip! Hey Pat remember when we stole Frank's jeep after the shots of Icehole? Doesnt that stuff lead to trouble :?:

[Mudrat]

OMG!!! (In a pseudo California Girl Voice)
Yeah I remember dragging Frank outta the rack (tent?) to fire up his truck, grab the trailer and come salvage his ride. What was it 12:30 ... 1AM when we finally made it back to camp?? :mrgreen:

That engine would DEFFINATELY get lost with the same color has his Jeep.

Frank, remember, GREASE is your friend - use more of it :wink: :?
And remember the spelling grEAse, not to be confused with gOOse . While he may be a friend, he won't keep your hubs from sparking and melting #-o

[jeepsr4ever]

:?:

Anyways, love the color!

[PaintedRat]

Grr, too late for power tools in my apartment, so I did some measuring. Looks like .040in needs to come off to clear, plus min .035 as recommended before. Taking .075+ off the skirt for either side of the piston. The piston measures just as 343 measurments stated earlier. 2.45in from skirt to face, and ledge about .21in thick at narrowest point.

Clear schedule tomorrow afternoon, so I'll try to escape work around 5. I'll update after I make a piston fit.

[AMX69PHATTY]

Ya sure that's a 3.44 Stroke 304/360 Crank ?
Casting number 3214724.
Rods are 5.875 center to center ?

[PaintedRat]

Took a quick look and couldn't find the casting number on the crank. Is it visible still in the engine? When I tore down, I got the distinct impression that everything inside was original. The wear on the cylinders made it impossible to remove the pistons, so original crank/rods seems likely.

I clearance one piston skirt last night by less than 1 mm, and it can now pass the crank counterweight. I don't like how much debre stuck to the piston, even after trying to clean it. I'm going by the machine shop to ask a price to remove, then later reinstall pistons. If I can afford that, I'll clearance them all myself and rebalance.

I have bad luck with piston rings, and I expect to break one during removal/reinstall. Any recommendations for a complete new set for a 343, .040 over, 11:1 compression?

[AMX69PHATTY]

Casting number is on the side of the small part of one of the counterweights. Second one from the front near the main journal. Have heard good and bad things, Maddog Racing / Fast Engine Parts seems to have good pricing, but some claim to have had shady experiences. My understanding is cast rings will seat in easier and faster than chromemoly. Do you have the info about proper ring orientation ? Are you aware that AMC pistons have an offset pin, a specific Front & Back to the piston, and should be mounted to the rod and installed in the block a certain way ? They Rods and caps should have cylinder numbers stamped into them. Install Rods so stamped numbers face outward. Other side of Rod Cap joint has a notch which serves as an oil squirter hole for cylinder lubrication. "Problem" is the rod bearings being manufactured now do NOT have a semicirular notch at the mating ends opposite the locating tabs. There are differing opinions as to if this notch and squirter are needed or not. Some say no, others notch the rod bearings by hand to allow the oil squirter hole to continue to function.

[PaintedRat]

Had the pistons facing the right way, these pistons have a mark to front. The ring set I got had directions for ring gap and orientation. Rod caps are all marked for order and orientation, but I will double check which way the stamped number on the rod faces. I know they are either all right, or all wrong. Rod beardings have the notch for oil squireter. I've got cast rings now, and if I break one, I'll get a new set of cast. My federal mogul bearings have the notch in them, and I'll be using them if I don't mar up the couple I need to take back out. Rods were installed snug, but not torqued down yet, so I think I'm ok.

EDIT: Talked to the machine shop. He said only 100 bucks to remove and reinstall the pistons, BUT, there is a danger of breaking a piston in the process (I'm just assuming during removal). I'm having them check with Eggy if a single replacement piston is available should that happen, because with my luck it always happens. If no single piston is available, I'll just clearance the piston while on the rod, and clean as best I can.

[PaintedRat]

After several delays, I got the pistons clearanced and installed. Found out they are Egge brand. I took down each side about 2mm to just under 61mm from face to flat part of the skirt. Each piston clears the counterweights by > .035in.

I used a 4" grinding wheel, then Dremel sanding wheel, then sandpaper to get a clean surface. I removed the oil rings, then dunked everything in gasoline and it was clean of debree. Oiled everything back up and installed. Now I can finally put in all these other parts that are lying around, like the BT toys I just got in the mail...

http://www.geocities.com/thepaintedrat/4x4/engine/enginenew3.jpghttp://www.geocities.com/thepaintedrat/4x4/engine/timingnew2.jpg

[PaintedRat]

I tossed my old intake, and cut off the fill tube to try and reuse. It doesn’t fit even after freezing. Is the oil fill tube tapered at one end, or does it just take a lot of encouragement to fit? Do I just need a new tube?

[AMX69PHATTY]

Pretty sure the oil fill tube is not tapered.
I've heated up the intake with a propane torch to get it installed.

May I ask when did you get those pistons from Egge ?
Do you have a part number ?
Everyone is looking for 343/360 pistons that are not dished
and that's what you appear to have there. They're cast ?
If Egge has those they could sell a lot of'em.

If a person want's, they can add a breather cap to a valve cover
for oil fill and put a freeze plug in the inatke oil tube hole.
Make sure though to have the sheet metal baffle for thr PCV on the itake bottom.

[PaintedRat]

They are cast. I'm afraid the numbers were in ink on the piston face. It's gone now. I ordered them in January through Decker when I ordered my gasket set and machine work. Less than $400 I think. I'll try and remember to ask part# when I go in friday.

Note: If it helps anyone, this appears to be the first rebuild on the engine, deck was surfaced, but not extra material removed. At TDC, piston face measures about .040 below deck surface.

[AMX69PHATTY]

I called EGGE to get the info on the pistons.
Thanks PaintedRat !
Those EGGE pistons are what a lotta folks have been lookin' for.
They have the "as-stock" 1.600 Compression Height rather than
the shorter 1.58 that all the others seem to have
and they're even flat tops or a 2V with a small dish.
You outta have some pretty healthy Compression in your motor.
They're hard to find on the EGGE site, they're listed under RAMBLER, not AMC.
Check out my post in the ENGINES Section here.
Told'em about the crank counterweight problem you had also.

[djaponi3]

the more I look the more I find especially this whole 343 360 piston thing thanks guys I am in the presence of mechanical geniouses excuse my spelling

[PaintedRat]

There may be genius here, but it isn't me. I just researched. I don't think I've come up with an original concept yet.

[AMX69PHATTY]

As a follow up, after contacting Egge again, they reported that the Compression Height
on the cast 343 pistons they sale as being only 1.570, which is .010 shorter
than most other aftermarket dished top 360 pistons at about 1.580,
and not 1.600 like stock pistons, but the Egge's are still flat tops
with valve reliefs, which is still better for compression than the .18 or so deep dish
in aftermarket stock replacement cast 360 pistons.

Understanding is Nick Alfano (spelling) is or will be having made and offering
flat top and small dished pistons for 360's and 401's with compression heights
closer to stock, but not sure if they're cast or forged. Not sure what his website is.
Maybe someone else here knows, or it will show up in a google search maybe.
So that's maybe another possible option now.

[djaponi3]

they look thinner in the pin area you have marked in blue

[AMX69PHATTY]

PaintedRat posted the picture with the interference area marked in blue.
Understanding is that is the area where there was a slight interference with
the crankshaft counter weights and some grinding was required.
In the thread there are some dimension values for the distance from top of piston
to that surface for the 3 different pistons, AMC 343, TRW 360, & Egge 343,
and I think the Egge 343 was a little bit bigger in that area.
Here is the picture that is now missing on page 1 of this thread.
The image host I was using, Netscape, was closed down and went away.
I myself do not have Egge pistons on hand to do anything with.
Understanding is PaintedRat used the Egge #L2336 343 4V pistons pictured.

Dimension info from top of piston to surface below pin.

AMX69PHATTY wrote:
From piston top to that surface is about
2.40 on the 360 by TRW
2.45 on the 343 by AMC

PaintedRat wrote:
The piston measures just as 343 measurments stated earlier.
2.45 inch from skirt to face ( 343 by egge ),
and ledge about .21 inch thick at narrowest point.

http://home.fuse.net/ckthomas/AMC-343-vs-360-vs-Egge-Pistons.jpg

[djaponi3]

his piston does look thicker in that area than your pics and all the other pics I see maybe he got some early prototypes? I think I am going to close my eyes and just goose it with the 343 2v pistons these should keep comp tolerable for the street according to your calculations thanks again for your helpful insight

[djaponi3]

I also could have sworn somebody used these and had to install them in the block backwards something to do with offset of pin in piston? or maybe this is just a brain fart

[AMX69PHATTY]

There is an offset, pistons have notches to indicate which way to install towards the front.
Haven't heard of anyone needing to install them backwards.
About quench, or piston deck clearance, in the overall scheme of things,
at these CR levels I'm not convinced it is a big priority.
Stock type dished 360 pistons have very little quench area due to the large dish.
Only quench are on those is the thin lip around the outer rim.
True quench pistons have a dish shaped to match the head chamber afaik.
Nominal values:
9.208 deck - 1.72 throw (3.44/2) - 5.875 rod = 1.613 pin to deck
1.613 - 1.570 nominal Egge Comp Ht = .043 deck clearance
Stock AMC 343 had .060 deck clear & 360 had .012 deck clear.
The .043 deck clear can be reduced by deck milling or offset grinding the crank if so desired.
I have ran a 343 9.175 deck ht block with a 3.44 sroke 304/360 crank and and 1.580 comp ht
360 dished top cast pistons with 0.000 deck clear for about 20 years.
What has to be watched very carefully is Piston to Valve clearance depending on cam used.
Some day, would like to do a build using the Egge slugs with more deck clearance
to get same CR with more deck clear but less piston volume.
The 360 ~27cc dished pistons have to come up so far since they have the .18 deep dish
and the Egge slugs are flat top or a small ~14cc dish.
Asked PaintedRat about how his performed a couple months ago, but
he has been busy with other things and has not ran it much yet.

[djaponi3]

thanks again I have always built my stuff on the conservative side and always had regrets after they were done! as soon as I hear from my machinest on block condition and bore size I am going with the egge 2v pistons will keep all posted on progress and clearance issues and I hope to hear some time on paintedrats progress