Modular piston help!

[Jrgunn5150]

No problem bud. It seems no matter how much I repeat myself, the same misinformation get's circulated.

 

[voidfinger]

Now I don't know if I'm correct but the turbo's don't like the higher CR like the centri blowers do. I have seen many times the centri blowers like vortec and paxton run with over 10:1 CR and do it fine, I've heard from different people that I know that they know, say that root style blowers can't handle the higher CR and will detonate b/c they build more heat. Also, it would seem to reason that you would have to worry with a turbo set up b/c they are sooooo picky. I would like JR said go with the 10.0-10.5 and do around 9-10 psi on a paxton or vortec but i would also recommend the intercooler or aftercooler... thats just me. props for a nice vert. I deff. want to supercharge mine in the future but I have some trickflows calling my name

 

[Marvin97]

Well I wont run a centri blower, I just don't like them. If im gonna run all the piping and what not it'll be a HP Performance intercooled turbo setup. But for the ease of working on it, im leaning towards a KB intercooled kit. Its hard to beat the whine of that KB..

 

[voidfinger]

IMHO you don't want the compression then...

 

[MustangChris]

I never hooked a boost gauge to it, except on the dyno. How much boost I make is of little concern to me, but it was right at 10 psi, a Paxton Novi2200 on a LIvernois 5.0 stroker with VT heads and custom cams.

u like that stroker kit? ;-) thats what i want ... :-( lol

 

[CobraRed_96_GT]

Lots of misinformation in here. You wont make a big enough power increase with higher compression to warrant it's set-back. And you wont notice a fuel mileage difference, especially if you have to run a race gas mix on one.
It really depends on your goals. If you're only going for 400-430 then you dont need forged pistons and you could work around the compression although you'll need a good intercooler and a great tune while pulling timing.
Anything above that and you'll be really missing low compression.
I have stage II PI heads with a stock short block right now and im at 10.3:1 compression. Stock pi heads can be about closer to 10.4:1 - but 10.3:1 is a good estimate as well.
My forged .02 over shortblock is done and I used 18CC manley pistons which puts me at 9:1 compression and would hav been 8.9:1 without the boring over. 23cc manley's will put you at 8.5:1. 11CC is 9.55:1.
The main thing with a high compression boosted app especially with a positive displacment is the tune, because of heat. Make sure to get IAC's down low as possible and the tune needs to be pulling timing and adding fuel everywhere to keep it from detonation. Even then i doubt 93 octane will suffice for long, although the aforementioned power goals seem within reach.

 

[Marvin97]

I didn't plan on running a forged piston anyway. Im getting a set of forged rods, stock length, and was trying to decide if i needed to switch to a set of pistons from a 99-04 gt or if my current setup would suffice.

I don't understand what the difference would be in the blower, why would it be ok with a centri and not with a twin screw or a turbo setup? Im thinking its the heat, but with an intercooled setup would this still be an issue?

Also, isn't there a thicker head gasket you can use to help lower the compression? Im thinking I read about one, anybody have a link?

 

[CobraRed_96_GT]

I thought you were going to run your stock pistons, yes if you're getting new oem ones get 01-04 pistons (99/00 have even bigger dish). Might as well, same price and less compression. To my knowledge running a turbo on high compression is easier not harder, guy doing it on turbo forums on a PI swapped car. PD blowers make a lot of heat due to heat soak and some say because they cant use a air-to-air intercoolers. Plus PD blowers are a bigger strain on the bottom end. Not that i'm campaigning against them, my set-up with my forged shortblock will be using one.

 

[Marvin97]

The strain shouldn't be too much of an issue, it'll have forged rods, a cobra crank and Federal Mogul bearings. The only thing stock will be the pistons, and again I only plan on between 400-430 to the wheels, which everyone says the stock components should be able to take. Its not a daily driven car either, only sees nice weekend driving and the occasional track whooping.

 

[CobraRed_96_GT]

Why the cobra crank then? The stock cast one is good past 600hp and the cobra one is forged steel meaning it weighs more so more drivetrain loss

 

[vermilion]

iron crank isnt most peoples ideal for higher RPMs. yes it may be good up to 500 hp but if you bought it used and dont know how it was taken care of is a factor. if you break down an engine to rebuild it. its smarter and somewhat harder on pockets to upgrade especially if you have ambitions to throw some more performance mods into it for anything over 375 - 400. the rods break and pistons get squirrelly if not taken care of. most people buy the things and dont take care of it. lots of people look for magic oil..... to the OP reputable piston makers have dish sizings.

 

[Jrgunn5150]

Read alot on the internet huh? When did you run a high C/R with low boost on the street?

 

[vermilion]

i havent built anything yet. assumption? me never. ive been reading the literature and internet for comparison. plenty of books on building 4.6s.

 

[Jrgunn5150]

I wasn't refering to you. It is a proven fact however that the car with higher compression and less boost will perform better everytime.

It's hard for me to spread "misinformation" when I've actually done it. Alot of car's run the high of compression from the factory, and run just fine with added boost. LS1/LT1 are the first example that comes to mind.

There obviously comes a point when the power goals exceed what can be done with pump gas and low boost, at which point the boost needs to be turned up, and eventually that surpasses what pump gas can handle, no doubt.

I would take my 500 rwhp 10.3:1 engine running only 10 psi over a 8.5:1 running 15 any day of the week though.

Another people on the internet is is quick to spend your money. You "need" a aluminum block, and you "need" an intercooler, and you "need" a wideband in your car... All thing's I got along just fine without back in the mid 90's when they were all exotic. Are these thing's beneficial? Of course they are. Will you blow your car up in a fiery ball of death without them? Nope.

 

[iamdat]

I would take my 500 rwhp 10.3:1 engine running only 10 psi over a 8.5:1 running 15 any day of the week though.

EXACTLY! with my engine, its gonna be 10.7:1 with 10psi. thats with a dart block and all forged internals. you seem to be one of the few with sense in this thread

 

[CobraRed_96_GT]

I never said boost on high compression being a fine route as misinformation, i was talking about stock and after PI swap compression ratios being thrown around. I'm simply saying it's going to take a safer tune with more timing pulled and higher octane - but with his power goals it should be fine not worrying about thaose factors as i said. Still, if he's replacing the pistons anyways, might as well keep the stock compression ratio with 01-04 pistons.
And there's no reason to switch out to a forged crank while keeping the stock pistons, the pistons will go before the crank nearly always. I've actually never seen or heard of a cast crank fail first. MMR says they are good past 600rwhp, MPH says good past 600hp. Switching to a heavier forged crank with stock pistons doesn't make sense to me.

 

[Marvin97]

I was going to switch to the cobra crank because I have one so i thought "why not?". I didn't go out and buy it, I got it in a trade so its not like I dropped $250-$300 for it.

 

[CobraRed_96_GT]

I was going to switch to the cobra crank because I have one so i thought "why not?". I didn't go out and buy it, I got it in a trade so its not like I dropped $250-$300 for it.

That's cool. Got mine similar way. Might as well then, rods and crank specify rpm limit usually. So rev the bitch!

 

[Marvin97]

I think I may actually change my plan a little, instead of going with a KB i'm thinking now between an HP Performance turbo kit or a Hellion. I'll run less boost, and achieve about the same hp. What you guys think about that idea?

 

[voidfinger]

can't go wrong with a good turbo set up... not hard to turn up the boost also