eb02z06

iTrader: (18)

Hey guys just figured this question maybe better suited here but I'm going to post this in the FI section too. I have a 02 Z06 that I'm adding a A&A P1SC kit too. Car is modded but will go back to stock for the blower with the acception the headers will stay. Now since I have to pull the heads I was wondering if maybe I should go a different route? The typical 02 Z06 makes around 580-600rwhp with around 9 psi. Compression works out to be very close to 10.5 and DCR with the stock 02 cam works out to 7.65-this is with the piston sitting out of the hole by .007 and using a GM MLS gasket at .054-.055-quench at .047. Now what if we reduced the CC to 10.06 using a 317 or 035 head using a .040 Cometic gasket and giving us a nice tight quench of .033? Our DCR take a hit with the 02 Z06 cam but what if we add a comp cam spec'd at 216/224 on Xe and XER lobes so it's a 269/273 114+4. This should help give a kick in the low end while still having the top end of the LS6. This cam will now raise the DCR to 8.05. Now boost will be limited to around 9-10 lbs for safety sake since this is a stock shortblock. I'm trying to see what's a more reliable safe combo while putting out the same amount or even actually make more power under the curve? So what we have is a 10.5 CC and 7.65DCR ( 64.5 243 heads, .054 MLs gasket 02 Z06 cam) or 10.05CC and a 8.05DCR( 71.06 317 head .040 cometic comp custom grind cam)? Looking forward to your thoughts and opinions.

NO-OPTION-2002

iTrader: (2)

Well, I am by no means an expert, but here goes...

1: Higher SCR/Lower DCR/Less squish = less strong low end tq (low on the boost curve), more susceptible to detonate @ higher rpm, where your boost would be climbing towards its peak.

2: Lower SCR/Higher DCR/More squish = stronger low end tq, less susceptible to detonate @ higher rpm.

Of course, this is all theory until the engine is built, but I like #2.

Anyone else?

Adrenaline_Z

Ultimately its the DCR value that matters. Quench should be as tight as possible
for best combustion.

Only trouble with tight quench is piston to valve clearnace and piston to head
clearance.

Whomever sets up the bottom end should know their stuff and appropriate
measurements for PTV and piston to head clearance should be taken.

The torque curve is going to form according to valve timing, not necessarily
SCR/DCR compression values alone.

Higher static compression will shift the HP peak up the scale because a higher SCR
will compensate for reduced effective compression as the the VE curve "rolls off".

Having said all of that, DCR at the torque peak should be within range for the
type of fuel used and boost pressure. I don't know what a safe DCR will be
with 9 PSI and pump gas?

NO-OPTION-2002

iTrader: (2)

Agreed, with one caveat.

Does increasing DCR, assuming NO detonation, not help the lower end of the scale? I.E. before the cam fully comes "on".

Please don't take this as a flame, I'm trying to understand as well!

Adrenaline_Z

I tend to think of compression as augmenting the curve as opposed to shaping it.

Higher SCR/DCR will shift the values at each point higher. Another word to use
is offset the curve higher.

The peak points and shape of the power curves come with the tuning of the engine components and
valve timing.

eb02z06

iTrader: (18)

If we go the Hi CR route with a 243 head and the standard GM mls Gasket we get CR of 10.5 and a DCR of 7.67 with the 02 Z06 cam. piston to valve clearance is no issue with either grinds custom or stock even with the tite quench of a.040 gasket. Almost all LS1's stock piston sit out of the hole.

NO-OPTION-2002

iTrader: (2)

Adrenaline_Z, thank you for the clarification!!!

Kelly

Adrenaline_Z

10.5 SCR and 7.67 DCR seems a touch high for 9-10 PSI on pump gas.

If we're using 9 PSI as 60% theoretical cylinder filling relative to the naturally
aspirated method, I would tend to think high octane pump gas would not hold out.

If most N/A motors are shooting for 8.0-8.5 DCR on pump fuel, I would estimate
the DCR would have to come down to about 6.5:1 - 7:1 for 9 PSI.

That is something you'll want to confirm with engine tuners who specialize
with boosted applications.

peter pan

I used the Z06 04 head gaskets with my car. I believe a very good blower cam is the comps 224 581 on a 114 LSA. The most important thing is the tune at the levels you want out of your stock bottom end, it must be dead on. I would also add ECS's Alky Injection to give you more protection--you run short of fuel boom and then you will need to go forged, good luck and get a great tune

MadBill

If you're considering a non-stock cam, you should go for a blower grind: Not too much overlap, lots of exhaust lift, and a somewhat early EVO to get most of that extra exhaust out before the upstroke. (of course, a blower engine makes lots of power with the last of the stroke compared to high compression, so what you really need is big exhaust valves and great ports)

white2001s10

iTrader: (4)

IMO the SCR will not change the shape of the torque curve, but DCR by boost certainly will.

I just wanted to add a couple of things to consider here as well.

If you're running the close geared 6-speed then there isn't such a need for power below 4000 RPM. Any time the engine is down that low, it will be throttled anyway.

Detonation is less likely at the higher RPM because there is so much less time during the burn cycle for it to happen.

The nature of centrifugals are that they make their power at the upper end of your RPM range, so I'd suggest gearing everything to work best in that range since you're half-way there already.

Adrenaline_Z

I can't argue either way.

My general outlook on compression is that it will provide higher combustion
pressures (which translates to higher torque) at every RPM interval as compression
increases.

Our interpretation of "change the shape" may be totally different.

Take any torque curve.

Increase the compression by 0.5:1.

Does the profile of the curve change dramatically? Will every RPM interval
be higher in torque produced? Will HP peak slightly higher?

I say no to the first question , and yes to the following two.

As for DCR and boost, I can see what you mean. A different intake closing
will effect the torque curve easily.

When I think of dramatic torque change, I think of valve timing changes,
or changing the length of a secondary exhaust pipe.

In those examples, I can see the torque peak shifting, and the lower/upper
RPM values changing considerably.