piston and ring package

[steve cowan]

a buddy of mine wants a freshen up on a 383 sbc (4.030 x 3.75) early 010 block
motor is 10 years old and tired
scat rotating with H beams 5.7 rod JE flat tops with 1/16 - 1/16 - 3/16 rings
still has moderate cranking compression 175 psi hot
but has a lot of leakdown and starting to have a lot of blowby
i will disassemble block and get it sonic checked and i hope it will go to 0.040'' over
we are talking about going to a 6'' I beam rod -i have a new set of scat pro comp I beams at home here that i have previously measured
they look good and i will mic up the pin end and deal with as required when i get some pistons
my buddy wants to run a gapless top ring but i dont really want to as i have never used them before. The block will be bored and torque plate honed as required
there is a huge choice of piston and ring packages available and it be a bit overwhelming with choosing something
can you guys give me some suggestions
my next question is -
he is talking about a 100 shot of gas down the track
on my personal N2O engines i always open the ring end gap
do you think i can get away with 0.004'' ring gap per inch of bore on a small 100 shot of course i dont want the rings to butt because cylinder heat etc
this a streeter engine might make 480hp pump gas 10.4:comp
dart pro 1 s 215
comp roller 254-260 630 lift 106 lsa in at 102 ICL
6800-7200 max rpm
3 speed auo 4500 rpm converter
9 inch 4.1:1 rear gears
255/60/15 drag radial
any help with pistons and ring set appriciated

steve c

[engineguyBill]

CP Pistons with 1.2mm, 1.2mm, 3.0mm ring package. Steel top ring, cast (Napier) 2nd ring and standard tension oil ring assembly. Gap the top ring at .0045" per inch of bore and the second ring at .0055" per inch of bore.
Most late model engines, both domestic and import, are going to metric thickness rings, it's the wave of the future . . . . . . .

[wyrmrider]

agree with enginguybill
KISS
reciprocating weight will be less so re-balance
B4 you pull the pistons check the deck heights at all 4 corners and the block deck with a quality straightedge
you want to know if you need to clean up the deck or adjust your quench B4 you order pistons
ask if you need to change your hone technique with those rings IDK
do you hang and align your pistons or just put them together?

[statsystems]

Use the gapless top

[wyrmrider]

old school 1/16 is 1.5875 mm so 1.2mm is quite a difference
oil is different, pistons cams are different today too so rethink your clearances
let us know what you come up with- this has to be a common happening and all to many just slap in the parts they are used to
often guilty here

[steve cowan]

hi guys,
thanks for your responses
i dont have the engine apart yet,if i remember correctly the engine block was zero decked
i spent a few hours yesterday seeing what was available out of the box
there is not much for a 0.040''
JE pistons #181913, 4.040 bore
3.75 stroke
6'' rod
9'' deck
1.125 CH
11.1:1 comp with 64 cc chamber
-5cc valve reliefs
394 gr
1/16'' x 1/16'' x 3mm rings

i think a 1.2 mm ring package is a custom piston
i have never ordered a custom set of pistons before,there will be alot of measuring before i purchase
our first street points meeting is in february
trying to get machine work done in a reasonable time frame is a sonabitch
any more information or ideas appriciated

steve c

[statsystems]

hi guys,
thanks for your responses
i dont have the engine apart yet,if i remember correctly the engine block was zero decked
i spent a few hours yesterday seeing what was available out of the box
there is not much for a 0.040''
JE pistons #181913, 4.040 bore
3.75 stroke
6'' rod
9'' deck
1.125 CH
11.1:1 comp with 64 cc chamber
-5cc valve reliefs
394 gr
1/16'' x 1/16'' x 3mm rings

i think a 1.2 mm ring package is a custom piston
i have never ordered a custom set of pistons before,there will be alot of measuring before i purchase
our first street points meeting is in february
trying to get machine work done in a reasonable time frame is a sonabitch
any more information or ideas appriciated

steve c

If you want to make a points race in February and you don't have Pistons, and you need a custom piston, you are in the shit. I doubt you can get them in less than 8 weeks.

[steve cowan]

LOL statsystem,

you would be 100% correct
i want this rebuild to take 1 month and not one year
i have ordered custom cams from comp and being here in australia
there is a time frame process with corespondence via email etc
i am confident i can match piston to ring package to block prep to suit the application
remember this a basic tough street engine and we are not looking for every last ft/lb
thanks for your input

steve c

[wyrmrider]

I hope it is square and 0 decked already but you need to know the crank centerline to deck height are there notes anywhere?

(I usually used 9.015 except where I couldn't which was way too often)
so you may have to do the quick check before pulling down the motor then checking your existing pistons
are the rods may have been rebuilt shorter than stock- etc so measure B$ ordering pistons even if you are changing rod length
If the shelf pistons you can get are off a little it's easy to offset bush the rods a little does not take 8 weeks -
1/16 rings will be fine for your application- it's not a perfect world

[steve cowan]

hi wyrmrider,

i will check deck height when i take heads off
i do sort of remember when they went to deck block,the deck face was rolled from say left front to right rear and they had no meat to play with
the best thing for me is hopefullly machine shop can help out and i think they will have to line hone the crank to start with,there will be a rebalence as engine bill said earlier
there is no quick fix-old block as well so i hope we can get one more go at it
like everyone i dont want a $3500 freshen up ending up being $10000
we will see i guess
thanks for your advice

steve c

[DCal]

I'm reasonably sure that CP has what you need in the Bullet series, just not sure if they have 4.040 or 4.045 bore. They have 1.5, 1.5, 3mm rings. Info on ring end gap is on the website.

[steve cowan]

Dcal,

you are correct
CP pistons
6 '' rod BC1025-040-8

5.7'' rod BC1026-040-8

BC1026-045-8

ALL RING SETS 1.5MM X 1.5MM X 3 MM ALL FLAT TOPS WITH -6.8CC VALVE RELIEFS
DONE SOME RESEARCH LAST NITE .down loaded there piston catalogue

[runawy9]

Mahle power pak piston and ring package.
Part# MAHSBC1250040F05
I have used it in my 385 with a 200 shot.
Very good pistons!