Internal engine questions:

[TylerCharger69]

I have a 383.  The pistons in it are the "dish" type...at least that's what I think they would be called, meaning  there is a recessment on the tops of the pistons.   My question is...would I be able to install flat tops in this engine without valve interference?  And also...will this change the compression ratio, and how much?    And...would it be a better set up?   The reason I ask is because I have a set of .030 pistons that was given to me...(Wiseco)  along with the rings to go with them.   Somehow...his order got screwed up and they sent him .030 over pistons for a 383  instead of a 413.  (Good news for ME)

[firefighter3931]

Tyler, the dished factory pistons were usually in the 9:1 range. The wiesco slugs will probably increase the compression ratio if they're a true flat top and the installed height is taller than your current pistons. There should also be some valve reliefs cast into the pistons to allow for a larger camshaft. Is more compression better....usually it is...to a certain point, then it becomes problematic if you want to run pump fuel.

Bigger cams like more compression so you need to base cam selection on compression and a host of other components. Stuff like rear end gearing, stall speed, headers, exhaust, carb size and the intake manifold all come into play.

Do you have any specs on these pistons ?


Ron

[TylerCharger69]

Well...all I know is.....they are supposedly a stock replacement for a 383.   I do realize, however, that 11:1 comp ratio is about the limit on pump gas.   These pistons are .030 over as the original pistons that are in the car are still the factory ones.  Let me explain that....the car was parked in 1972 by the original owner in his backyard, and it never moved from that spot until I rescued it on Thanksgiving Day of 1995, thus explaining as to why it still kicks butt with the original pistons, so when I rebuilt it, I just cleaned it up by honing a good cross-hatch into the cylinders, and replacing all the other internals except for the connecting rods.   I'm estimating that these may bring my comp ratio up to about 10:1 to 10.5:1   I just wasn't too sure if they were going to interfere with the valves or not.   They are flat tops, with no "eyebrows" cut into them...just a ".030" stamping on the top.   I've built some Chevy engines that had the eyebrows and that's why I was asking about the interference.   The car is not really that radical on the takeoff....not bad though...but it's top speed seems to be endless.   It really kicks itself in the butt around 35 to 40 M.P.H.  and at around 100 to 110 M.P.H.   Stock tranny...other than manual valve body and shift kit, and the rear end is a 3.00 ratio out of a Ford.   Engle K54 camshaft..........electronic Mopar ignition, Eddy performer intake and 1405 carb.   If this helps....

[Chryco Psycho]

the K 54 & a flat top piston should be fine but still check the clearance to be sure
if the piston  is below deck with the open chamber heads the max compression would be 9.6:1 even with >20 steel shim gaskets , assuming the heads are not milled down   

[myk]

I thought that 10 or 10.5:1 were the limits for pump gas...

[Chryco Psycho]

10 : 1 max for Most pump gas engines with Iron heads
11:1 max with alum heads

[chrisII]

I am guessing that your 383 was origionaly a 2bbl standard engine? and these "stock replacement" pistons would be a replacement of the 383 mag piston. if so i would not expect any problems with valve clearance with your open chamber heads. pump gas shuldnt be a problem either.

[TylerCharger69]

Yes...you are correct...it was originally a 2 bbl car.  It runs fine with the Eddy intake and carb, and the Engle K54,  Electronic ignition upgrade (Mopar).   I just was curious as to how much stronger it would actually run if I was to put these in