Well....I spun a rod last night and im toying with buying a scat stroker crank (260.00) using my stock rods, new hyper pistons. Question is, how much will this affect my compression ratio? can i still run regular gas? can or should i compensate when buying the new pistons by going with dished, or can/should i use a thicker head gasket? is any of that needed? I dont plan on using a blower or anything, thought someone out there would have some ideas for me.

 

Dang dude, you aren't having much luck lately! First the overheating issue and now this.

If it were me, I'd spend the extra for forged parts (inc. pistons). That way if you ever do decide to go the FI route then the motor will be capable of handling it without much worry.

 

Buy some flat tops with valve reliefs. The compression ratio won't be too high. I actually did the Impy head gasket to push my compression up more. I ended up with 11.3:1 which is fine with 91 octane.

Heres a compression calculator:

http://www.smokemup.com/auto_math/compression_ratio.php

 

you spun a rod bearing and you are going to reuse your rods?

for what it will cost- just get new connecting rods- it will cost about the same as getting them checked and resized and such.

as far as compression-
I dont get the question. a longer stroke will create more static compression if you have the same heads and the same dish on the pistons and all else equal.
compression simply is how much you "push up" / how much space is there.

so if you have 100ccs being forced into a 10cc chamber- its 10:1 comression (i used easy numbers)

if you have 110ccs (longer stroke) and the same dish and heads- you have 11:1 compression.

just remember that if you use the same rods and a longer stroke, you cant use the same pistons so its a pretty mut point. if you use the same pistons a 383, the piston is going to shot about 1/4 inch into the head. The wrist pin needs to be about a 1/4 inch higher.
so you will need new pistons, just get the correct pistons, thats all

however i have a feeling you are asking about dynamic compresion when you brought cams into the equation????

 

no, my luck is sh*t so far!! im tryin to stay positive though the machine shop told me about 100 to recondition the rods (if possible), how much and where can i pick up some new ones in that price range? machine shop also recommended using the hypers in it for a daily driver. says those forged make alota knock, and that the hypers can run a fair amount of hp? (also a lot cheaper!) My ? on compression ratio is simply wether or not i should order pistons differently from the flat tops so that pump gas can still be run on order to compensate for a longer stroke?

 

uh........i DID get the overheating issue fixed at least!

 

assuming you are running stock heads (safe assumption?) a -20cc piston will give you a 10.5: compression ratio.

then add in whats going on when you mill the heads and all that. I think 11.2-11.5 is a healthy number to hang out around for you.

As far as forged vs hyperutectic-
Hyper pistons have tighter tolerances i believe but niether should slap. I do agree that you should get hyperutectic pistons if you dont plan on spraying the motor too heavily and you expecting moderate power output.

Forged would be a waste of money if this is the case, money better spent in the heads.

edit:

http://www.angelfire.com/fl/procrastination/motor.html
stroke fro a 383 is 3.75
a standard bore is 30 over so your piston diameter is 4.03
54 cc chambers and .039 head gasket is standard.

fiddle from there.

 

Sounds like good advice trey-and much appreciated! I ported/polished the heads, put a 3 angle valve job on them just a few weeks ago. So Im looking at ordering the new hyper pistons with the -20cc dish in them and i should be fine as fas as you know-right?

 

.....the most i am considering spraying would probably be a 100 shot. appreciate everyone's feedback-thanks guys!

 

id want a bit more compression. the only head work that will effect compression is milling the heads and messing with the combustion chambers.

 

as long as im picking your brain......what are your thoughts on making this a 383 withthe ported/polished heads and the hotcam? im thinking it will only cost me a few hundred more to go 383, so why not?? will this combo make any type of power? I was hoping to see around 340-355 rwhp (mac headers, electric water pump, cai....) can this be attained with a few more cubes-or will the cam combo fall short?

 

ported and polished is a very general term. the 383 will make more power down low because its longer stroke will "draw" in more air and in at higher velocity.

like your sig says, theres only one way to find out. one think is for sure-
if you need a new crank, there is no reason not to get a 383 crank.

Im not a big hotcam fan, id go witha larger lift cam but thats just me.

Id really like to shy away from dyno guessing, but it seems relativly atainable- especailly with good head work.

 

I understand..... didnt have the heads flowed or anything. bowl blended, removed a fair amount from the intake roofs/sides, and around guides. same thing on the exhaust ports. Dont know if it was a good job or not, but im anxious to find out......... ! looks like a decision: go 383 use reconditioned or replacement stock length rods, cast crank, hyper pistons (flat top with vavle reliefs and a different wrist pin heigth for the different stroke), hot cam and the current heads. and like you mentioned on the rest............
only one way to find out!
appreciate the input.....now off to researching engine removal from the bottom of the car...?

 

Id just like to suggest 6'' connecting rods and www.cmotorsports.com