N4cer

iTrader: (11)

Here's the Cliff Notes version of the background:
I decided to build a short block while I could afford it. I built a 408, but am still using everything else from my stock cube shortblock. I didn't expect it to be much stronger, and the dyno says it's not much stronger.

That said, it's time to plan for the upgrades of the power-making parts. Top-end basically. Heads, cam, intake, and exhaust. I'm definitely on a tight budget right now, so let's consider that before starting to recommend the most expensive options. Here's what I need help on, and would like some knowledgable, preferably experienced assistance.

THIS CAR NEEDS TO BREATHE but I don't know how to tell if it is the intake side or exhaust side or both. I mean, I'm sure it's both, but what to do first is the issue.

Exhaust: I can't see me paying $1k for a set of Kooks. Sorry. I'm thinking running my Pacesetters with open headers for now will be okay until I buy Kooks later next year if at all.

H/C/I: I have Livernois Stage 2 243 heads, G5X3 cam on a 112 LSA, and using my LS6 intake (if I remember correctly it fed the Cannibal car to over 500rwhp). Since my heads are 59cc, I ran dished pistons to make up for it, and maybe run boost later in its life. So whatever heads I get have to be able to be milled to 59cc chambers to allow me the proper dynamic compression. That's what kinda ruins the L92 setup for me. Could I just have my current heads worked over to be good enough for this motor?
And I'm thinking have the cam matched to whatever heads I get of course.

Beaflag VonRathburg

iTrader: (176)

First off what are you planning on doing with this setup? What dish are your pistons? You need to decide if you want to go high or low compression first. Answer those questions and I'll be able to help you from there.

N4cer

iTrader: (11)

I already know where I'd go if I decide to go FI. Just seems like a LOT of trouble, although I know it's the best way to go if I want good times, plain and simple. The car is daily drivable but I'm willing to strip it to get good times later on, whether I stay motor or FI.

Let's discuss what to do if I went NA high compression 93 octane (11.3:1 compression):
408ci
15cc dish Diamond pistons (which is why my 59cc chambers work right now)

moeZ28

iTrader: (7)

Well, after talking to Phil (Bluecat) earlier, I am so disappointed in the situation. I really expected much more, as did Phil, and I just cant believe your heads and intake are killing you that much!! That should be plenty of cam to make nice power in a 408. Dont worry, we'll get you all lined out and get that thing running like you deserve to have it run!!

Beaflag VonRathburg

iTrader: (176)

Then you might as well contemplate switching pistons while you're at it. When I plugged in the L92 head's combustion chamber size of 69.8cc with a -15cc piston and a gm .52 compressed thickness MLS gasket you get 9.92:1 compression ratio.

My best advice to you is half assed = half fast. Do things right the first time unless you have some major sort of mechanical failure I'd wait and save for the right items. You could probably sell your top end setup and buy most of the L92 stuff. I'm not a large fan of the L92 heads to begin with, but they are your best option if you're on a major budget.

Here's how I'd do it if I were in your shoes.
-Your 408 with -2cc off the shelf 1.125 compression height pistons cut for L92 sized valve reliefs
-Stock L92 heads maybe with some port work done to them if you have the extra money
-Patrick G cam
-Stock L92 intake and 90mm tb
-Save up for some 1 7/8 longtubes and what ever other bolt ons you need

I always use this compression ratio calculator. http://www.csgnetwork.com/compcalc.html I used the following values in this order to calculate your compression:
4
4.03
4
4.065
.052
69.8
-2
-.010

Those values give you a 11.35:1 compression ratio and a .042 quench.

N4cer

iTrader: (11)

No, I wasn't clear. I'm not pulling the bottom end apart again. So piston swap won't happen. The plan all along was to use small chamber and more dish. I discussed this with some speed shops and with Bo White, and it was agreed to be a good idea. So as I said, I'm asking about what heads that flow good enough and are able to be milled to 59cc chambers.

The good news is after crunching the data all day with my tuner, it seems the problem may be just exhaust-based. The car is sucking in way more air than on the 346, but is running way richer while commanding lower duty cycle. It makes no sense other than the exhaust isn't getting out and is causing an incomplete burn. Sound feasible? We used 2 different widebands on 2 different computers at the same time, and they correlated.

moeZ28

iTrader: (7)

Soooo.......is there a chance you may follow in my footsteps and run dual cutouts right off the headers...worked great for me...as you saw!!!

Bo White

iTrader: (59)

I got your PM N4cer and returned it

Beaflag VonRathburg

iTrader: (176)

Ok, I'm confused. Is that still your old sig or are you back to not porting again?

N4cer

iTrader: (11)

Didn't help me much. Maybe 5ft-lbs.

Bo White

iTrader: (59)

I have just recently quit again, another baby on the way and have to get things in order here for his birth.....thats right, his

slow trap

iTrader: (22)

an 1 3/4 tube header is more capable than what alot of people think. i make 517/493 (cutout open) with them. a ported 90/90 will probably pick you up 20 rw or more but ofcourse that is quite a bit of coin to drop. the heads may be hurting you also but i don't know anything about livernois heads so.........
can you pm me the numbers it put down ?