boost and stock compression.

[ADRENLN]

guys im thinking about my future performance mods. some of you might know from other posts that i want to run a novi 2000 with a built motor.

i have some questions though. i was wondering how much boost can be run on stock compression? i am getting a built engine but i really dont want the compression dropped too low, because i dont want to lose a ton of power na.

i will most likely have to get block shipped over here and installed na for a while while i save for a blower. i dont want the car to feel like a slug during that time.

my next problem is i have stage 2 heads and miled blower cams. from what i understand my comprssion might be raised now a bit? so is there a piston that will lower the compression back around stock maybe a little lower? again i dont want it too low.

if i cant run 14psi on the stock compression then these other questions dont really matter. i will just have to save enough money to do it all in one shot then. either way it is going to take me 2 yrs to get this kind of cash saved. i just want to know what i have to do and what im shooting for, so it can motivate me to save. maybe then it could happen sooner.

sorry so long, thanks for anything you know.

i think i will get the short block built by mph and will probably buy his novi 2000 kit with a/a intercooler too.

i will be running the car on pump gas (93-94 oct.) if this makes any difference in some things i asked about.

 

[Kilgore Trout]

I'm confused... What would the stock compression spec have to do with your built motor? You need to find out from the motor builder what the compression of that motor is don't you? What does stock compression have to do with your situation?

 

[ADRENLN]

sorry its a little hard to explain.

basically i want to run a blower on a stock compression car.

i want my built motor to be stock compression, if i can run 14 psi on stock compression.

problem lies here. if i get a motor built with stock compression i will end up with higher compression once my ported heads go on top. that would be bad with a blower and 14 psi.

so i need some type of pistons in the motor that will decrease compression only slightly under stock compression.

i dont want to use the pistons that titally drop compression because then my car will slow down while i save for the blower.

is that any better?

 

[hognutz]

well I know I have seen it done. I would talk to who you want to buy the novi from and see what they say. I don't think 14psi is to high but i would pretend to be an expert.

I would just email tim and MPH as that is who I would buy the novi from.

 

[RedGTvert]

You'll be fine with stock compression. You can still run plenty of boost with 9.0:1.

If you plan on serious power, then drop to 8.5:1, but it will be a dog in N/A mode.

 

[sgarlic]

I'm probably too drunk to be posting this, but I don't see how porting your heads would raise compression. The porting occurs within the ports right? It's opening the size of the ports... I mean, on the compression stroke, both valves are closed, so wouldn't only the shape of the piston top affect compression?

The only downside I see to running stock compression with a blower is not being able to advance the crap out of the timing on pump gas.

 

[DropTopPony]

I did alot of research on this recently while i was deciding on what blower to get. With a Roots/Twin Screw its optimal to lower the compression to @8.5 to 1 when running higher boost levels because the power is almost instant. With the Centi's its good to have alittle compression to assist in the lower RPM range so the stock 9.3 to 1 compression with be fine with your forged shortblock. I'm gonna go with a @ 9.0 to 1 compression with my roots blower since i'll never be over 9psi with it.

 

[tomustang]

raising or lowering your compress for the build shortblock should be decided with what type of boost you want to run. One of the things your builder will ask you is what boost/supercharger/turbo/NA are you trying to accomplish with your build.

Call Jim @ VT engines and he'll take some time out to answer you

 

[ADRENLN]

first off, thanks for the replys. they help somewhat.

about the heads and cams, i dont know i always heard that they up my compression just a little bit for some reason, maybe its not true.

so stock compression should be fine to run the novi 2000 at 14 psi from what im understanding. i will also probably have to run a 16psi pully to see 14 psi because of the heads and cams. however that shouldnt effect anything, in the end its 14 psi, right?

so ok i guess everything sounds good i guess there is a piston that can bring me down just a tad like droptop mentioned.

one more thing. droptop you said stocg compression is 9.3 to 1 and red gt said its 9.0 to 1. i always thought it was 9.0, but which is it? or is it because you have different year cars?

 

[ADRENLN]

i was actually hoping to find a way to get a little bit out of the engine despite having a drop in compression.

i dont know anything about bores and strokes, but if one of them is not a major pita. and wouldnt cause any problems with the setup im running then maybe that is an option.

i dont like what i hear about the stroker kits, seems like alot of trouble. if i did get a bore, i would only want a tiny one, just to have a slight advantave over another gt with a regular built block. i wouldnt want an all out heavy bore. dont they create alot of heat or somthing? what are some down sides?

i also understand that all built blucks come with a tiny bore anyway, i want just a tad bit more to make a little power.

if not i was also considering the aluminium block for some weight savings. i know some things have to be changed, but i was told my builder could take care all of that. what do you guys think?