stockA4

I'm building pump gas iron 6.0 short block for good average tq from idle to 6000rpm or more if it wants to, 3700lbs vehicle daily driver, and I'm down to choosing the right pistons for it. They will be at least a 0.030 overbore though.

I'll be using box stock 706 heads with blue springs and a comp 212/218 .558/.563 115 LSA camshaft.

Breathing will be done through stock LS6 intake, injectors, and 2002 fbody exhaust manifolds for now.

I've been comparing +6.7cc dish and +0cc flat tops with a good calculator and playing with the dynamic compression numbers from there.

static compression should be somewhere around 10.5 with the dish and 11.4 with the flat tops.

The 212 cam closes the intake valve at 41° @ 0.050 and 67.5° @ 0.006 when installed on a 115 intake centerline

​​​​​​if I move the cam around (up to 4 degrees in either direction ) I can achieve roughly the same calculated dynamic compression numbers ( about 8.5 ) with both the dish and the flat top pistons however, the intake could be closing as much as 8 degrees later with flat tops which could be less efficient down low ?

soooo......

do I do dish pistons and advance the cam or flat tops and retard it for the most power on 93 pump gas from idle on up and how much power are we really talking about here?

Also, Would a dished piston with the cam a few degrees retarded tuned for 87 octane really be that far behind?

Darth_V8r

iTrader: (4)

Given its a 3700 pound vehicle, I think you'll benefit more from keeping the cam straight up and running the dished pistons, assuming you're dead set on that cam. I think retardingt he cam will be counter productive, even with increased compression. My $0.02

stockA4

that sounds like what I want to hear and I think that's what I will do for now. I wouldn't be opposed to more cam, but not much more.

A.R. Shale Targa

iTrader: (2)

I’d try that 224 BTR truck cam that works with the blue springs and go flat tops

stockA4

that sounds a little rowdy! That's a 224/230 111+2!

G Atsma

I tend to agree, but there are those here who regard such cams as "mild baby cams". Sounds like macho BS to me...

Bspeck82

Cam is fine. Get 799 heads to bump compression up a bit and use flat tops. Will make great torque and should have dcr close to where you need it.

stockA4

which Cam? My 212/218 or the 224/230? My 706#s will bump the compression more than 799#s and I already have them so I'm going to use them.

stockA4

I think about it this way ;-) I would rather lose a race to a car with a rougher more radical idle than mine than get beat by a car that idles smoother than mine does.
​​​​​

Bspeck82

You want your dynamic compression ratio around 8.25-8.5. I don't know exactly what you want for a cam but I would assume you are not towing. Find out when your Intake and heads will restrict you from making more rpm (which will probably be around 6400) and choose a cam that will make peak power right around that point. For more torque I'd suggest a single pattern cam (i.e 224/224) because those will ALWAYS have more torque. Which is important to move the heavy tank. If you bias the overlap towards the Intake you will have better low end response and less top end but this may not be necessary so long as the events are correct. This is me trying to be very basic without overcomplicating the process (it's complicated). The 212/218 is a bit small I wouldn't bother. That's more for the guys that want a small bump in power and will tow. I would talk to Preston at lunati and go through this with him. He is great to deal with and loves to educate. As for the heads, you may benefit from bigger valves, as well as of course head work. Call up Frankenstein and see what they think because like lunati they love to answer questions and the gains from head work can be yuuuuuge.

Bspeck82

I think I'd personally run a 228/228 112 (.600/.600) cam with heads worked over by Frankenstein. 3600 converter and 3.7x gears. Get those longtubes as well they will help tons. Get static compression to 11:1 which should give you a DCR around 8.3 which is a safe margin for pump and shouldn't worry too much about premature air/fuel detonation and melting pistons in high heat bad gas environments.

I'd also run double springs and steel retainers for piece of mind.

HioSSilver

iTrader: (8)

Whats your goal op? Hp....et...1/4 trap?? Kinda need to mention all of them.

what car is it goin in? What gears....what trans....how tall tire. All that needs to be takin into account or you may end up with a giant turd. Because right now I'm leaning towards you putting the engine in it stock.

stockA4

https://ls1tech.com/forums/drag-racing-results/1894529-completely-stock-z28-a4-4-8-long-block-swap.html

HioSSilver

iTrader: (8)

That answered very few of my questions.

I mean this is a fail from the beginning if you're gonna leave the stock gear and converter in it.

what are your goals?

stockA4

sorry if I've confused anyone. My goal is useable torque right off idle but I'm really just having fun with used parts on a tight budget.

the car is already great with the 4.8 in it for a full weight year round reliable daily that can be played with at the drag strip without breaking down. It's still faster than an 02 mustang gt. It's even a few mph faster than my old m6 Lt1 was with some bolt ons already so I can't see how using the stock 706 heads and 212/218 cam from the great running 4.8 I already have in the car to make a really mild 6.0 would make it any worse, especially with the stock verter and 2.73's still in place. This is a St.Louis car that's daily driven, she sees all kinds of hot, cold, and bad weather and needs to have "truck like" reliability.

back to my original posting and given the parts I already have, I just wanted to know what pistons to use and what center line to install the cam on for the best average power from idle to Ls6 intake on 87-93 pump gas.

​​​​​​

HioSSilver

iTrader: (8)

If you're on a budget the pest thing you can do is put that 6.0 together with a stock cam and some 1.9 rockers with ls6 valvesprings if off idle midrange tq is your goal using what you have.

especially being the cammed 4.8 didn't really run that well. Someone on here made it to the bottom 13s with a stock 4.8 and soso bolt ons.

about the best thing you coukd do at the moment is stop worrying about the motor and put you some 3.73s or 3.90s in that car.

stockA4

I've got a 1721, 0965, or the comp 212/218 to put on the 6.0L with the 706#s from the the 4.8. I'll have the 4.8 for a spare then. I've been contemplating doing the crank out of the 4.8 in the 6.0 as well just to be weird. Then I could definitely try the big flatops with the 706#s Not interested in anything but free rockers. I have enough stock spares and I'm not scared to rev the **** out of them.

Think about this and do the math. my 4.8 runs great for what it is. 293Ci is powering a high mileage heavier optioned 4th gen with the most restricted drive train option available in the car stock. The car itself is completely stock, only a old used whisper lid and a new magnaflow 12267 welded in by me. With the car taking the LS1 > LR4 penalty It has trapped as high as 104mph. That's good enough for guys to get higher 12's with the right 60' at the track I run at. My Ls1 z28 was trapping 110mph at the same track in similar circumstances with less weight, 3.73's, longtubes and real tuning.

face it, your all jealous of my j/y sourced, Craigslist cammed 4.8 camaro that cost me less than the price of a new refrigerator to build and you want to see what gears and a converter will let it do before I throw it away for a 6.0 just like everyone else does.

Darth_V8r

iTrader: (4)

Yup you are right. Who in their right mind would want a LS7 when they could do a JY 4.8 swap for the same amount of work? I could just kick myself

Ok I had my fun. In your case, less is more. If you already have the 212 cam, run it. Not like it'll blow up the world or anything if you don't like it. Ls6 cam with rockers is an interesting idea if you don't have the cam already purchased. Otherwise a 227/235-112+3 will run nicely as well.

Bspeck82

Why so much exh duration? Your just bleeding off torque for the sake of carrying peak power a little farther. There is a whole lot more power and that can be used before peak than after. (For a street car) Not to mention egts can be higher because unburned fuel is entering the exhaust port and into the header. Explain your way of thinking to me I'm curious.

Darth_V8r

iTrader: (4)

I guess what I was thinking is 52 degrees isn't really that early of a EVO. I find moving the IVC early does more for torque than almost any amount of EVO. For example, when you advance a cam to gain torque, you open EV earlier. So I figure EVO is under 55 should be fine.

If anything that cam is a bit overlap biased, but I figure a 6.0 will "absorb" it. I expect that cam would peak around 6200 and really fall fast over 6500. Mainly due to that 42 degree IVC.

Anyway, that's what I was thinking. Strong midrange.