rebuilding an old school 383 conversion...

[joe dirt]

so i got my hands on a 72 camaro 4 bolt 010 block that was advertised as a healthy stroker with aluminum heads...it was just a long block when i got it....pulled the heads and found 030 4 valve relief flat tops....one cylinder had a bit of scarring....rest where just glazed...tur. it over and removed the pan to find its a 4 bolt! yay!......it has a factory 400 crank turned to 350 mains...factory 5.565 400 rods and i believe the pistons are 350...i didnt see any grinding on the skirts......so to get going...its going to need an overbore to 040....new pistons and rings...im thinking about using the 350 pistons with the short rods.....the heads are cheapo pro comp heads 64cc.......id like to keep the cr around 9.8:1 or 10;1.......i picked up this block for $300...so im cool with putting a few dollars in it...plan to run an xe284h cam with performer rpm air gap and 750 dp
this will be going into my 61 c10 with stock sm420 4speed and eaton 390 rea end untill i can get a 12bolt under it with 308 gears.....manual breaks and steering...so vacume not needed as much
what pistions and rings should i be buying to achieve my goals?...id like 400hp.....find a stock 400 dampner or a aftermarket one?.....same goes for the flywheel.....stock or aftermarket....

any input is appreciated....this will be my first build...thanks

[Marv D]

Probably the least deseriable way to build a 383, but for $300 you did good if the block really cleans up ar +.040. Myself I'd not mess with it if it needs more. There is too many 0010 blocks out there to mess with thin cylinder walls.

That said,
Because the rest of the motor is somewhat low-end I wouldn't invest a buttload in a high end piston. BUT be cautious and realistic about what your doing too. MANY of the builders pistons, and KB pistons have a reduced compression height and will leave you wishing for compression.

While the block is at the machine shop have it cut to 9.000 deck, and IF your never going to hit the motor with boost or nitrous and are willing to spend the time to get it in tune (carb AND timing curve) so you don't have ANy detonation issues,,, I'd do a SpeedPro hypereutectic and a set of GOOD Plasma Moly FILE FIT rings . Ring seal and longivity is worth the extra cost over a set of cheap cast / ductile rings.

IF your thinking of stepping on it at all with RPM or boost,, do yourself a favor and do a quality forged piston (SRP / JE is my weapon of choice)

You didn't say what cc those heads are (intake runner or chamber) so piston dome / dish and cam, intake and such is WAY up in the air to comment on

[joe dirt]

marv...these are the heads...i know they arnt the best...but its what i have...lol

[Marv D]

With a 64cc chamber, You need to determine if the block has been decked (is the stamping still on the ID pad in front of #2 cylinder?)

IF it's been zero decked you will want a piston with a 22cc dish.

If it's a near stock 9.025" deck you want a 12cc "D" dish. (much preferred)

With those heads and a 0.041 gasket, and flat top piston with 3-5cc eyebrow valve reliefs your looking at ~10.5:1,, if it's been zero decked yor over 11:1.

Yes aluminum heads will tolerate a little more compression than it's iron counterpart. But in a mild cam cruising application I still like to stick around 9.6:1 even with aluminum heads.

[joe dirt]

currently is stock deck height,..any way to tell if one piston has a shorter skirt than another? also you think the xe284h cam would be a good match for this setup...the 10:5:1 cr would be my goal...I don't mind a rowdy idle,...its not a daily driver and has manual everything

thx

[joe dirt]

pulled a piston tonight to check out the bearings.and crank...is this too bad of grooves on the crank?...the mains are std bearings and the rods have 010 bearings in them...

[Marv D]

WOW, she had a bunch of trash go through those bearings hu!!! This is what a motor looks like when it looses a cam and they think they can just change the cam and oil and it's good to go. The debris just embeds in the bearings and grinds away at the crank (and every other moving part) until someone takes tit apart!

I suspect it's going to need another 0.010 off the crank, and you'll just have to see how bad the bottom of the bores are .

BUT these are ?s only your machinist can answer positively.

[GASoline71]

I thought the exact same thing with the wasted cam trash going through the engine. People think I'm nuts when I tell them a wiped out flat tappet cam means a complete teardown to remove all the metal out of the engine. This looks like it is exactly as Marv described it.

Gary

[joe dirt]

check out the lobes on the cam...

[MySons68C20]

Please post some close up pics

[GASoline71]

Looks like some flat ones!

Gary