jeremy iroc z28

iTrader: (1)

what compression ratio should I build motor to?
heres parts so far
accel intake, runners, base all professionally ported

accel 58mm throttle body

all bells and whistles(fuelpump,pressure reg,air filters,tranny 700r4 is built,posi,b&mshifter,blah blah blah)

world sr iron heads 1.94x1.5 superduty valves 58cc smoothed to 61.5cc on all chambers and bowl blended and smoothed port matched to intake(between a felpro 1205 and 1206)

paxton sn2000 supercharger standard impeller(thinking about upgrading)

compcam 07-305-8 220-230 .510 .510 (I know its for a lt1)

I had heads and cam b4 i got supercharger was planning a 383 but since i got the sc I'm not sure if I should do a 350 or a 383 what c.r.for either?

also what is best bigstuff3 or f.a.s.t. or dfi? I havn't decided yet but am leaning towards big stuff but fast seems appealig also

any help will be greatly appreciated

myroc86

Depending on what you want to do with the vehicle, if you plan on running pump or race gas. Put your desired compression ratio into this formula and boost.

Final Compression Ratio=[(boost/14.7)+1]xCompression ratio

You'll be able to run 8 psi if you build it to 8:1 compression with the final CR of 12.3:1

jeremy iroc z28

iTrader: (1)

pump gas. so 9 to 1 is to much?if I build 383 with mahle -26cc pistons i can get8.8 to 1 is this too high for iron heads?
same piston in 355 gives 8.3 to 1
which way to go?

AC

iTrader: (3)

My last 383 was a 8.7:1 motor (dart iron eagle heads), all forged, studs everywhere. I ran 7psi without thinking about it and was aiming for 14psi. My friend has a 305, STOCK bottom end with 9.5:1 running 14psi out of a procharger D1SC. Can it be done, yes. What is your comfort level, that's the question. I would not hesitate to run 8-10 psi on a 9.8:1 motor IF, and only IF there was an intercooler for the blower. Otherwise, I wouldn't go above 6-8psi on a stock 9.5-9.8 motor.
For EFI most of us around me do our own tuning. Total cost without a laptop is low compared to anything commerically available. The BIG cost is if you have to buy a laptop.

TexasLT1

if you're only running 8psi, you can go higher than 9:1, especially if you're intercooling or going to use methanol injection. Full forged pistons like you're looking at and iron heads will help.

As far as the EFI systems, you're going to get different answers from anyone you ask as to which one is best. A lot of people get great results with any of those systems, and a lot of people have tons of problems from each of those systems. Its just a matter of getting it hooked up and setup right and having someone competent tune it. You don't need to switch to those though to run a supercharger.

jeremy iroc z28

iTrader: (1)

alright thanks so either combo is doable
no intercooler the s/c elbow has the fitting for methanol (is it worth using?)
I am still not sure wether to go with 350 or 383 id like to get some ideas about cams for both engines and the respective power and economy
I travel down south alot and it has to be dependable on long trips and am thinking a383 with s/c might be too much of a gas pig any ideas

TexasLT1

Yes, the methanol injection nozzle is mounted in the intake elbow. I'm planning on running only methanol on an F-1 supercharged 383 LT1 with approx. 10-15# of boost.

If you're doing a complete new build, a 350 and 383 rotating assembly is practically the same price....

If you're doing a supercharger in the first place, gas mileage isn't going to be a real big concern. The difference between a 350 and a 383 in that department is going to be slim.

jeremy iroc z28

iTrader: (1)

alright i am leaning towards the 355 because of uncertainty of oil prices.what do you think about the cam i have comp roller 220 230 .510 .510 112lsa will this work with either motor or should i just get a different one?

I have thought about e85 cause here in mn we can get it every where and its cheap but not sure how to do it with efi?I have heard that you need some sensor that tells the strength of the ethanol is this true?what about o2 sensor do you need a special one for alcohol?

TexasLT1

well, to run e85 correctly you'd need an aftermarket ECM where you can use a wideband O2 sensor and change the stoichiometric ratio the computer is looking for. Stoich for E85 is much lower than it is for regular gas, so you start getting into some pretty custom tuning then.

As far as the cam, I'm really not the person to ask as my experience is pretty limited in that department. I let the pro's handle cam selection.

scribbles

If it is a sn2000, it already has the upgraded impeller. That was the upgrade from the sn89 to the sn2000. Look at the blades if they are curved it is upgraded. If they are straight it the old style.

jeremy iroc z28

iTrader: (1)

yes it has curved vanes.
allright I have decided 355 it is, with above parts what would be the best comp. ratio to build motor to to?(I have iron heads)
how about fuel injector size?
and any other suggestions

scribbles

Call comp cams. Give them your specifics, and they can help you out. Sorry I cant.