need help from my fellow engine gods

[kramer03gt]

Well guys considering you were all awesome in my suspenison question i had im poping another one at you guys, as most of you know im in the process of getting ready to start work on my gt and im just trying ot get everything lined up, i have a general knowledge of things but i like to dig a bit deeper, so this has to relove around the forged internals part of things, im going to keep the same block that i have being its allready broken in persay, but i was looking at a rotating kit from vt engines, that had crank, pistons and etc. but i was wondering what else is out there that you know of like dss racing or modular powerhouse or etc... along with other than the strength advangtages and being able to handle SC applications better... what does the forged things really do for the performance of the car as compared to the stock gt parts? and also what are the best pistons to run for a SC application ive been looking around and there are a ton.. for example what do the different CC's stand for like VT has 11, 18 and 23.. so what does that actually mean and what does it do as far as a performace engine goes.. so i guess ill take all the info i can get and once again i appreciate all of your help guys... its making this process alot easier!!

thanks again

Steve

 

[GREENBIOCH]

I'm by no means an engine guru, but as far as a rotating assembly goes, there is no performance gains from forged parts. its just able to withstand more heat the the stock parts without warping/melting for when you are pushing boost. i think compression ratio is another thing to consider when getting forged internals, you want a lower compression ratio if you are gonna be pushing boost and a higher one if your gonna push the limits NA. Thats about as technical as i get.

 

[kramer03gt]

allright cool yeah that was another area i forgot to mention was compression ratio and what that was all about, i plan on running a KB 1.7 at 14psi on forged internals

 

[GREENBIOCH]

since i have never done it i'm not one to give advice really....but i think stock compression is fine for any kind of low boost(low being prob below 12lb), but if i were you i would want room to turn the boost up a bit if you get used to the power if you know what i mean. from what i have seen i know alot of people get the compression ratio around the 8.5 to 9.0 range if there looking at a blower like you are.

i'm sure someone here who does have all the info can jump in here and let you know for sure the best route to take.

Edit: the cc # is what will change your compression ratio, it is the volume of the dish in the top of the piston. so the bigger the cc/volume the lower your compression ratio.

 

[Thundermouse]

It won't hurt to also ask these questions on the modular powerhouse forums, lots of built engine experience over there.

 

[Torinalth]

ok, lets see where i can assist.

what do the forged parts do for performance?

well, themselves they dont do anything for performance. there is a stipulation to this, i will cover it later. all the "forged" pieces do is allow for more stress. to be taken without breaking. take an aluminum can and crush it in your hand... now take a soup can and crush it in your hand. its all about strength and thats the only real reason people do this.

will the VT engines rotating asembly be good?

this is an issue. the problem comes to the point of build up. yyou said you want to use the same block... ok... but there is something to take into consideration. as your parts move in the cylinders they make grooves, pits, lag marks, etc. this will efect compression aside from the fact that the new pistons will make DIFFERENT marks.. this is bad. to correct this you will need to bore the cylinder out to .01 or .02" over stock size then hone it to make sure its ready to take the new pistons. i seriously recommend getting a new block... though honestly the price difference between building your own vs buying a new shortblock might not be worth the time... maybe a hundred bucks difference. just something to think about.

what is the piston dish mean?

dish size is just that.. dish size... its a piston that has a bowl shaped dish cut into the top. this affects how much space is in the chamber once compressed.. the deeper the dish (higher the number) the more space, and thus the lower the compression. i dont know what compression associates with what dish size, talk to who you buy it from and they can help there.

what compression do i need for my 14# KB?

stock is fine honestly. with a solid built engine stck will be just fine... however, you will have to pull more timing from the spark advance to prevent detonation. its a game at this point to shift the boost, timing, and compresion amounts to be the most optimal.. i dont plan on SCing anymore, so i really cant help there... Tim and MPH can help there.

what do you recommend?

bottom line, i'd just get an assembled shortblock and go from there. either PnP heads, or stock heads and cams... oil pan, whatever. something to note is that almost all shortblocks require the use of an 8 bolt flywheel, which may require another purchase. there is a lot that is needed when going this route... take the time to find out everything needed.... (IE talk with whoever you are buying from and ask if you have missed anything and to go over everything)

i need to run but i'll post more later.

 

[kramer03gt]

Ok cool thank for the info, now if i bore it out that .01 and .02 over stock, would the 4.6 rotating kit still work or would i have to get something different being that i am making it bigger? and besides VT and Modular Powerhouse does anybody know of anywere else to get a built short block, basically i guess i want to keep the 4.6 with forged internals is really what im looking for, or if i should go bigger what are some advantages of that besides the obvious..

thanks again