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

[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.

[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