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Confirm or deny? Comp height

jeepthrills01

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Phoenix, AZ
I read an almost 20 year old post where a very respectable member of another board said,

"1968 and 1969 383 2&4 bbl pistons shared the same Compression height...just the 2bbl were dished."

With more info available these days as our world continues to grow smaller, would anyone care to add yes or no to that statement? Yes 2 bbl were dished...most of us agree on that...but the same CH?
My reason for the inquiry pertains to my own low..LOW LOW buck 383.If your not familiar...i acquired said engine in a completely rebuilt state...it had just been sitting for 20 years wrapped up in a Phoenix garage. No surface rust...gobs of engine lube on the cam....and very inexpensive.
These dished 2 bbl pistons measure .007 below deck at the four cardinal points for all 8 cylinders...yes..32 separate measurements..all equal. And 8 center of piston depth measurements of .09
The 12cc dish is keeping me just below the 9s on CR (8.88) . Block was very carefully decked...im assuming .015 as my research states most OEM 2bbl pistons living .020 to .030 in the hole.
I already have Eddy 82cc heads, a mild Voodoo [email protected], .475 .484 cam, 1.6 rockers and 1.75 headers.
But cracking 9.7 or higher and getting some quench seems plausible with flat tops considering where the pistons currently sit. It could make the difference of a runner..or a screamer.
I know were talking about a bump of 1.1-1.6 in CR which is what..15 hp?..but the possibility of quench and efficiency (as opposed to race gas and spark knock) intrigues me.
This engines purpose would be 70-80% street...with monthly trips to the run what ya brung at the local strip.

Slap it together as is? Find pistons?
Low Buck Thoughts?
 
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There is a set of new .020 over flat top 383 pistons in the parts for sale section.
Real decent price on them.
Not sure what your rebuild bore size ended up at ?
 
2 barrel 383 is like stated around .027ish down, 69 383 magnum is like .003ish in/out of the deck. So not the same ch, not sure on the 330hp super commando? They are listed the same but mopar also listed the 440s in 68-69 compression the same and they were not. Depending on the piston upgrade be careful with the piston hitting the quench pad on the head if its decked
Below .007 you will have some quench already. Forged pistons would be a nice upgrade. That is a big dish...shouldn't be hard to upgrade. I don't believe anyone makes the exact copy of the 68,69 piston, the originals were taller then aftermarket. I don't think a magnum piston will work. Assuming its a fresh bore there should be piston options.
 
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There is a set of new .020 over flat top 383 pistons in the parts for sale section.
Real decent price on them.
Not sure what your rebuild bore size ended up at ?
that ad is over 5 years old...and machining would blow the budget.

was built 20 years ago and never fired up before i acquired it...best i can measure is 4.257 at 3 different depths.
Being low buck...and already having the above listed parts...including a performer RPM...about 500 is all I would really be willing spend parts.

Kb400s would really limit cam lift...hell im still reading in half the posts i see that Eddy 84cc (which is what these were before the clean up cut) will need notching to fit the heads...unless my micrometer is whacked there is a significant amount more than 4.25 across the combustion chamber. The exact number escapes me right now but i can remeasure if anyone is curious. I assume thats an old wives tale.
 
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Well that seems to be a standard bore block.
Leave it alone.
Dial in a good ignition set up.
Add headers if you do not have them.
 
I guess I don't understand, if your goal is low buck and it's already together with what seems like precision machine work...
 
All bearings are perfect Clevite half rounds. And the short block is still assembled.
The 500 was allocated for pistons/rings.
Im not willing to risk steel shims with aluminum heads...and the cometics .027 gaskets are about 80 bucks a piece...and was being considered over and above the piston cost. But if i find a piston that reached 0 deck or slightly above...the less expensive Felpros will save the day and save the quench..lol
 
I guess I don't understand, if your goal is low buck and it's already together with what seems like precision machine work...
I guess im looking for a unicorn. If i can manage to find the exact right piston...8.8 turns to 10.8CR...probably swap to a solid cam...375hp becomes 450+...and like i said..from a solid runner to a screamer.
 
4.257? May want to have that double checked. .007 is plenty loose for a cast or even a forged piston. A std piston can be knurled .005 over but its hard to find anyone that does it. That loose will be noisy till it warms up, and making power at 6k there is a possibility you could brake a skirt off a hyper or cast...forged would handle it better.. I don't see a std bore forged from anyone? It stinks but boring .030 w kb's or a icon looks to be the best...buy a 440 source cheap .054 if you need more piston clearance.
 
4.257? May want to have that double checked. .007 is plenty loose for a cast or even a forged piston. A std piston can be knurled .005 over but its hard to find anyone that does it. That loose will be noisy till it warms up, and making power at 6k there is a possibility you could brake a skirt off a hyper or cast...forged would handle it better.. I don't see a std bore forged from anyone? It stinks but boring .030 w kb's or a icon looks to be the best...buy a 440 source cheap .054 if you need more piston clearance.
As far as the bore goes...only answer i can come up with...is this engine was built around 1990-2001. Might have even been earlier than that....it had new "Texaco" branded green stripe sparkplugs in it when i picked it up.
Back then..using a "10 up" file fit ring was more commonplace.
I see your point though..going to have to do some more searching and pondering.
 
I'd run it. You've got very little investment in the short block. Who goes to the trouble to get the decks perfect and runs .007" additional piston to wall clearance? For what its worth we ran a 440 motorhome short block (piston at least .125" in the hole) with Eddy RPM heads, .484 purple shaft, Eddy 600, performer RPM, 3.91, street tires and a stock 11" C body converter. Went 12.90s@110 in 65 Belvedere.
Doug
 
Bore is Bore just like to make good our fathers and granfathers have figured this all out.
 
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