How about just Pistons for my 383

[Yellow Submarine]

I have posted about my deli a with a rebuilt 383 but with low compression Pistons. The previous owner had the driveline rebuilt in 94' along with other work but stopped the project. I have looked inside the bores with a medical scope which also allows me to look back at the valve. Everything looks as the paperwork indicates, basically unused. The engine and 727 run great but I want more power but don't have resources to stroke it , get a 440 etc. as it appears the engine is barely broken does it make sense to take it apart, have the cylinders ehoned and buy decent compression Pistons? The current ones are all very close at 120 psi with comp check. Have gone through the thumper cam discussion but not sure if I want a real lumpy cam in this car. Cutting heads or changing to closed shambered ones is not appealing. I just want to get to a little more power than a stock magnum while keeping costs down. What do you think??
John

[Racer57]

What are you calling low compression ? Stock ?

[Yellow Submarine]

Rebuild Pistons that give 120psi.

[1 Wild R/T]

Cylinder pressure is a function of compression ratio & cam selection plus a few other variables like altitude & power adders... You could have 11-1 C/R but a big cam that at cranking speed only makes 120psi but at 4000 rpm the cylinder pressure could be 250+... Probably not the case but without measuring it's a guessing game... But being a 383 & with the dismal piston availability your likely spot on...  Problem is while there are better piston choices there aren't any great piston choices so honestly it's a wasted effort..... those 88-92 cc chambers are just to big for a short stroke engine like a 383... I'd still look at either a set of 915 or 516 heads to swap.... On my 383 I went from a 7.9-1 C/R to a 9.4-1 C/R by taking off my 906's & bolting on a set of milled 915's with steel shim gaskets.... Seriously woke my 383 up....

I know someones gonna say stealth heads or Edelbrocks, or TF's.. But Aluminum heads don't like steel head gaskets & that extra .020 for a comp style gasket eliminates the potential for quench  so I'd avoid going that way..

[Yellow Submarine]

Rt, They are not high comp Pistons and the cam is very mild. Not sure if it's even a magnum grind. What did it cost to buy and rebuild a set of 915s. All my valve gear is basically new.

[1 Wild R/T]

Well I traded a forged 440 crank for the head cores & I rebuilt a couple steering columns and a front suspension in exchange for the machining of the heads... I supplied valves, guides, springs & hardened seats all purchased through Summit... So my cost won't be like your cost.... But honestly good pistons & machine work would likely cost more....

[Yellow Submarine]

Through summit I came up with $390 for Kbps hyper Pistons, about $100 for rings, then a gasket set and honing the cylinders. I would do all assembly and everything is new or rebuilt.
John

[1 Wild R/T]

You can do that but

Using Keith Black KB-162 pistons (5cc dish with stock compression distance of 1.908 puts compression at 7.69:1

Using Keith Black KB-400 pistons (6cc dome with stock compression distance of 1.908 puts compression at 8.37:1

Neither of those options is very exciting...

[Yellow Submarine]

So does anyone make the correct compression pistons anymore. Seems like a simple thing to me . Its funnybecase so many build up articles tout how good the bore size stroke etc are but nobody makes high comp pistons???

[1 Wild R/T]

In order to raise the compression ratio with a 383 with open chambered heads you need a domed piston to fill the chamber volume...
Dome pistons adversely effect flame travel so it's best not to use domed pistons...

And FWIW even in 1970 there were no pistons with flat tops that could raise the compression ratio on a 383 with open chambered heads...  Smaller chamber volume....

[Yellow Submarine]

Ok rt thanks for the help with this. At some point I would really like more displacement and aluminum heads. Maybe Ill just wait till then.

[1 Wild R/T]

Probably your best choice..