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Discussion Starter · #1 · (Edited)
Someone said "ported C5R heads is undoubtly better than ported LS7 heads"....

I wonder if I should infer from the statement above if, with further racing development on the LS7 heads, the C5R heads would still yield better results?

Your thoughts on this?

Quantifiable information for a method of explanation would be appreciated.

Hope this isnt a repost.
 

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Thats the stupidest thing I have ever heard. Thats like saying a modded Z will beat a modded camaro.

What modds right?

What porting?

Bowl work, gasket match, Valve relocation, Raised floor; point being what does the term ported mean!

Any head when ported and be moddified to out perform another. Dumb question.
 

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The LS7 head was designed from and based on a C5R head. But it is NOT an evolution of the C5R head to a better design. The LS7 head is still a street head on a smogger engine. It's potential is larger than an LS1/LS2/LS6 head but not quite that of a C5R head.

The biggest difference between the heads are the combustion chamber size; 70cc on the LS7 and 30-38cc on the C5R, so the C5R head will yield a higher CR and thus more HP, is probably a faster burn and has a larger quench area. No amount of porting and polishing can REDUCE the chamber size.

The LS7 valve angle at 12 degrees approaches the C5R's 11 degrees from the LS1/LS2/LS6 15 degrees, but not quite.

In addition the intake ports of the C5R head are still slightly larger and may have a slightly higher placement resulting in better overall flow and a straighter shot to the chambers. The C5R's intake ports are probably shorter.

Both are CNC'd. The LS7's combustion chambers are already optimized whereas the C5R head comes in one finished version and 2 unfinished versions for optimization.

I think we will see some minor aftermarket porting & polishing on the LS7 head, extrude honing, optimizing the valve seat angle, basically "cleaning it up". The biggest improvements will come from shaving the head to decrease the chamber volume and increase the CR AND improving the valve train.
 

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DJWorm....now that is the proper way to answer someones question....thanks for squelching previous remarks.
 

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C5 CU,

I was not refering to your question as stupid, but rather, what "someone had said". I still think that it is still stupid.

Yes DJ listed differences in the heads, but not the answer to what you originally refered too. Was which ported head is better.

Far as chamber volume in CC's the LS7 is more desirable for turbo and s/c motors. In N/A cars the C5R head will yeild more power due to higher compression. Though a custom piston could accomplish the same thing. Obviously the flatter the piston the better, so when designing a motor from scratch that is not turbo/S/C you look for comp. You originally refered to porting.

Now the change in 1 degree in valve angle would probably be meaningless in comparing modified heads. Porting is such a general term that it is impossible to compare two heads unless looking at the results of the finished head porter. That is why I said that the comment that "someone said" was stupid.

The real factors that matter in heads is CFM, port velocity,swirl, and port volume. They all play a vital role. Unless you have the specific data of a modified head it is impossible to compare the two.

At Wilson Manifolds we use a Superflow 1020 bench that have a velocity probe as well as a swirl meter.

The C5R's intake runners maybe shorter, I'm not sure. If so that does not really mean better. In a class of racing where modification is not allowed, the head may have been cast to acheive a desired runner volume and velocity to yeild the best results with in the intended RPM.

So, even with the differences in the design of the two, its still hard to compare unless knowing the intended purpose. Now throw in Porting and it is really impossible.

Randy

PS DJ have you personally had a C5R head on a 1020 bench. I'm curious what the velocity and CFM was. Not a 600 bench. They are to inconsistant. When we compared Dart's heads on our bench we are usually with in +/- 2-3 cfm. When we compare 600 benches I've seen +/- upto 30cfm.
 

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Randy, That's a lot of error on your SF600. I didn't know they had that kind of problem. Did you compare two benches or were you seeing that kind of error on one bench? Were you guys using the Flow Com System with motor controller?

Thanks, D.J.
 

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Its hard to answer this questions since no one has seen the LS7 head let alone port and polish it to the nth degree. As we all know heads are a tool used to reach a specific objective, some heads are made for high compression, others for forced induction etc. Therefore i think its safe to assume that a RACE STYLE head like the C5R will outperform the LS7 head with the works 99% of the time. The C6Z06 will not have anything that is better than the C6R.
 

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Discussion Starter · #9 ·
Guys thanks for the responses that is what I was looking for.

RandyN, not trying to attack you (although it sounded earlier that you were attacking me), but it was I that did the thread and asked the question not C5 CU (just to clear things up). Thanks for providing useful information unlike your first reply. I appreciate that.
 

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We seen differences in comparing a 600 to our 1020. The 1020 is computerized and self calibrates before each session. The 600 is calibrated manally. We have seen tuners advertise certain numbers than we put the heads on our bench and get 30-40 cfm less.

Alot of people will also use a much larger bore plate and get false, well lets just say, not as accurate. If you put a 4.500 bore plate and compare to a previous session with a 4.000 diam you will see almost 30 cfm in some cases.

One example is some "CNC heads of FL^%$%^" LS1 cnc heads. They were supposed to flow 300+. Best we got is 272. Swirl, well none since the swirl vane was removed and the velocity was down as well since ithe port was basically just made bigger. Thats why good porters start at the bowl and short turn, then change volume to match cubic inche and RPM. Funny thing is when we flow Dart heads against what they say, we get the similar number.
 

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To answer my own question:

I checked out the 2005 GM High Performance Catalog and they show the C5R Racing Cylinder Head as being a ported LS6 head. Part # 12480090

They also show a CNC Ported C5R Racing Cylinder Head (Part # 88958609.) This must be the one you guys are talking about.....the [email protected] inspired head. 11 degree valve angle.

HOWEVER, the description says this head WILL NOT accomodate an LS6 intake manifold.

Next question, with this head, what intake will fit? I'm assuming my F.A.S.T. intake won't fit either. The part description says a Kinsler fuel injection manifold will fit.

Has anybody had experience with the Kinsler manifold??

Now guys, don't make me find the answer myself :rofl:
 

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LS6 vs. LS7 vs. C5R Head

Comparison of Production LS6 vs. Ported LS6 vs. LS7 vs. C5R Heads.

C5R heads are NOT improved LS6 heads. There are in fact 4 different part numbers for a C5R head in various stages of preperation

12564824 Production LS6
88958665 CNC Ported LS6
88958622 ASA LS6
XXXXXXX LS7 (not yet avalable)
12480090 C5R (38cc)
12480005 C5R (30-38cc)
12480025 C5R (30-38cc)
88958690 CNC Prepped C5R

Spec/LS6/CNCLS6/ASALS6/LS7/C5R/CNCC5R

CombChamVol/65/65/60.9/70/38/30-38

Intake Runner/210/210/250/nya/118*/xxx

IntakeFlow**/278/314/350/360/450/480

Intake Valve/2.00/2.00/2.18/2.20/2.15/2.15

IValveMat./HSS/HSS/HSS/TiA/TiA/TiA

ValveAngle/15/15/15/12/11/11

ExhaustPortVol/75/75/85/nya/???/xxx

ExhaustFlow**/??/??/??/210/??/??

Exhaust Valve/1.55/1.55/1.625/1.61/1.60/1.60

EValveMat/HSSNaF/HSSNaF/HSSNaF/HSSNaF/HSSNaF/HSSNaF

IntakeRunnerPos/xxx/xxx/xxx/Raised/Raised/Raised

Comp.Ratio/10.1/10.5/11.2/11.0/12/12-14

Max.Lift/0.525/0.525/0.525/0.591/0.600-0.700/0.0600-0.700

RockerRatio/1.7/1.7/1.7/1.8/1.85/1.85

C5R blocks have larger machined valve spring seats at 1.630"

*C5R Intake runners have larger area than LS6/LS7 but are shorter, so Volume is reduced but Max. Flow is increased.

**28" H2O STP (normalized to 0.600 Max Lift)

HSS = Hollow Stainless Steel Stems

TiA = Titanium Alloy

HSSNaF = Hollow Stainless Steel Sodium Filled
 

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The description in the 2005 Catologue indicating that the C5R head is a ported LS6 head is a TYPO.

The C5R heads have a different intake port pattern that only fits a Kinsler FI Manifold or a custom sheetmetal drag racing Manifold such as a Wilson or the new Harrop Manifold from Australia. The LS7 will also have an intake port pattern similar to the C5R.

This will prevent the interchange of heads and manifolds between LS6 Catedral type intake ports and the LS7.

Wether or not the LS7 Manifold will fir C5R heads is yet to be answered.
 
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