Z06FRC

I own a 99 Corvette FRC which is my daily summer car. I go drag racing with it once ever month or so, but I'd like to keep it street legal. Patriot 64cc Heads seem to be the right choice considering my car is mainly for street and I like to keep it that way. But could I get away with using the 59cc version without lowering my chances of failing emission tests, breaking any laws or turning my car into a street/strip machine. I'm looking for something for the streets but to go drag racing once in awhile.

brad8266

iTrader: (23)

The car will be even more efficient with the smaller chambered heads. I have 57cc heads and if I had a normal cam and cats I could pass emissions.

What are your other mods?

Gregory

iTrader: (4)

I don't think you'll have any problems. No scientific basis for my answer, but I do own a set of Patriot Stage II 59cc heads. No emissions tests to substantiate this. My static compression is 11.17:1.

Good luck!

allthrotle

iTrader: (2)

Im running patriot 59cc, and my car is DD with no problems.

TheLS1Kid

iTrader: (12)

Me too...

Z06FRC

Can I still run 91 octane fuel if I chose 59cc heads?

TheLS1Kid

iTrader: (12)

I don't see 91 here in Florida.

We have 93 here, which is what I use.

I'd ask around just to make sure 91 is ok.

hammertime

iTrader: (1)

Are you still running the stock cam? I would think you may be on the ragged edge of detonation with such small chambers.

Assuming you already have an LS6, you could push your static compression as high as 11.3:1 or more. That territory is better if you are running a larger cam, but not with a stock LS6 or mild performance cam.

ArrestMeRed99Z28

iTrader: (1)

I'd jump on the phone with Gunnar at Patriot and discuss with him what you'd like. More compression in an otherwise equal set up will always make more power HOWEVER milling the heads decreases the flow of the cylinder head slightly. You can read up on why that is if it interests you. Since you seem to be more concerned with low speed driveability and low end trq I'd mill them as much as possible with out causing detonation and use a .040 gasket instead of a stock .053 GM one so you can leave an extra .013 on the head, loosing less flow and decreasing quench while still acheiving the desired compression.

AJ

brad8266

iTrader: (23)

Patriots heads are not milled down, they weld the chambers to achieve desired chamber size so flow numbers due to milling are irrelevant in this case. The head deck will be the same in patriots head regardless of the chamber size.

Z06FRC

Well if I have to run a higher octane fuel with the 59cc, then I'll chose the 64cc version or maybe the Dart Pro LS1 62cc Heads. Which is better?

Gunnar@Patriot

iTrader: (20)

Our 59cc heads will be milled to reach the smaller chamber. We now use 243 castings for all of our LS6 "style" heads. We would suggest a set of our 64cc 243 heads with a .040" gasket. This will give you around 10.8-1 compression and should work well with 91 octane. If you have anymore questions, please let us know.

Z06FRC

Thanks Gunnar, I feel that the 64cc heads will be more street friendly then the 59cc version. I heard that you have to run 93 or higher octane fuel if you were to go for the 59cc heads. Also I heard that you need to have the pistons machined in order to have proper clearance with the 59cc heads. 64cc heads sounds like the perfect choice for my needs. I just want something mainly for the street, but I can take it to the drag strip once in awhile. 10.8-1 compression is perfect but I hope I won't have any clearance issues with them. Which Intake Valve Diameter do you recommend 2.020 in., 2.080 in. or 2.055 in?

PREDATOR-Z

On a stock cube, depending on cam, I would use either 2.02 or 2.055.
2.055 will require aftermarket seats.
What cam are you planning on?

Gunnar@Patriot

iTrader: (20)

Like Predator said, what cam are you leaning towards?

Z06FRC

Comp Cams Xtreme RPM High #54-424-11

Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,500-6,800 RPM
Intake Duration at 050 inch Lift: 212
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 212 int./218 exh.
Advertised Intake Duration: 265
Advertised Exhaust Duration: 271
Advertised Duration: 265 int./271 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.558 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.563 in.
Valve Lift with Factory Rocker Arm Ratio: 0.558 int./0.563 exh. lift
Lobe Separation (degrees): 115

GuitsBoy

iTrader: (4)

59cc ???, assuming your DCR is not outrageous...

Full-Force

iTrader: (11)

Why did you stop making the 6.0 heads with welded chambers? That was gonna be my choice of heads because I wanted the compression with stock ptv clearance.

aero_ub

A lot of people seem to be missing the fact or not understanding that your static compression ratio due to running 59cc heads doesn't mean much at all when determining if you can run them on 91 or 93 octane. You could have an engine with a 12:1 static CR that runs fine on 91 and another with a 10.5:1 static CR that needs race gas to not get detonation (you get the idea). What matters is your Dynamic CR. That is determined by when your intake valve closes on the compression stroke (degrees ABDC) and that is determined by your cam. The cam is what’s important here.

So, how many people here running the 59cc heads actually calculated or know what their dynamic compression ratio is with their specific cam? Where is your DCR and what octane are you running?

My issue right now with making my H/C selection and calcs is that I do not really know at what DCR does running on 93 octane because an issue? What is a reasonably safe DCR to run on an LS1? I know that once you get in the area 8.5:1 and up you better start paying attention. But, there are many aspects of an engine/head design that effect and determine when you are going to get into a dangerous area.

aero

Gregory

iTrader: (4)

There is a formula used to compute your Static and Dynamic compression ratios.
What is needed to compute this is:

Bore:
Stroke:
Rod Length:
Number of Cylinders:
Deck Height (Pistons out of the hole by .00x")
Piston Dome or Dish in cc:
Compressed head gasket thickness:
Cylinder head chamber volume:

We now know the camshaft information.
212/218 .558/.563 115