It seems they are the way to go...but. Is anybody running these things on the street? Any real world experience? I want this car (the ZL1) to be unique but I also want it to be reliable. Clearly the Stage III LS6 heads will be reliable and street tested whereas the C5R heads are an unknown. I just don't want to be sorry I went with the C5R heads. Are they worth the gamble?

 

that my friend is only a decision you can make but they might be a little overkill for street use like I said when we talked before. Good luck with your project and if i can help you with anything let me know

Jay Fisher

 

Seems like the combustion chambers on the C5R heads are tiny ie. huge compression.

If your builder can find you a suitable piston to bring down the compression to pump gas, I'd go for it...

It would blow folks away to see a custom intake on there and C5R heads.

I can tell you that we on here are hard to impress!

A custom intake with Kinsler fuel injection would have maximum boingyoingitude!!!!

 

and how much would those manis run???? More than the heads???? <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />

 

Yeah--I'd think a custom sheetmetal manifold would be more than the heads themselves...
Don't C5-R heads also come unported--as in they have to be ported to be used?
Anyway--sounds like a fun trip you're about to take, grb <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

Actually, the custom manifold is probably the cheapest part of this setup.(kinda scary to think about) <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> The Speed inc. manifolds are custom order so it could probably be made to work with these heads.

grb - I would not worry about reliability with these heads. They are made for endurance type racing. They have never failed on the C5R corvettes. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

The question I think you need to ask is, What do I want outta this motor/car?

These heads have huge ports so you may lose(relative term) some bottom end but, the upper rpm gains over LS6 heads will be outrageous.

They would definately make your project more unique. There are quite a few people out there with LS6 heads. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I think you should call Katech back and ask them about what the bottom end power will be like with these heads since drivability is a concern. I can't think it'll be bad though with 427ci's. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Good luck

John

 

grb,
What John just said, ditto.
There is a car in Melbourne Australia who has had them for a while, with supercharger, is proportedly putting out @ 1,000 HP. On the street.
He has driven it over larger distances. If that helps. I say get them. Just my 0.02cents worth (may cost up to 0.04cents in Australia).
Cheers. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ July 26, 2002, 01:14 AM: Message edited by: Will Race 4 Food ]</small>

 

Is Colonel running a C5R Block/Head combo on his new setup?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Will Race 4 Food:
<strong>grb,
What John just said, ditto.
There is a car in Melbourne Australia who has had them for a while, with supercharger, is proportedly putting out @ 1,000 HP. On the street.
He has driven it over larger distances. If that helps. I say get them. Just my 0.02cents worth (may cost up to 0.04cents in Australia).
Cheers. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">has that thing ever go going? Last I saw it was still in a heap of bits...

 

The heads are just part of the equation. Every single part on them is diff. from any other GM piece. TB size and tuning will become an issue. And I think the header flanges will have to be modified. I'm not too worried about low end with a 427, but reliability is important. Look at all the valve spring failures people are experiencing now. That would be less likely to happen with LS6 type heads (assumming that it is one certain spring causing the problem).

There doesn't seem to be anyway of getting around paying Katech 12 grand for the heads and taking their recomendations for the other needed parts. And maybe that's not all bad.

And yes I do want it to be impressive when I pop the hood. Even though most people around here wouldn't know a C5R from a flat head.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>Seems like the combustion chambers on the C5R heads are tiny ie. huge compression.

If your builder can find you a suitable piston to bring down the compression to pump gas, I'd go for it...
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">JE can make a set of -20cc Inverted dome pistons. With the 'normal' C5R chamber of 38cc, you would be around 58cc for about 12:1 compression. With the milled C5R head chamber of 30cc and the same pistons, you would be around 50cc and about 13.2:1 compression. Of course you can go with deeper piston and drop the compression level even more <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

just get the c5r heads and have them machined for dual springs. c5r heads last hundreds of race miles in the race motors at 15:1 compression or more. street driving at "low" 12:1 compression will be nothing.

 

The exhaust port locations are the same on the C5R heads as a production LS1/LS6. You would still be able to use a regular set of 1 7/8" headers.

I know your concerned with reliability but, what heads you go with has nothing to do with valve spring reliability. The C5R heads are already milled to accept big double springs so as long as you keep the camshaft reasonable there shouldn't be any problems. Think about the Corvette C5R's at the 24hours endurance races. Think of the abuse they put the valvetrain thru. Those two cars have some of the most powerful and reliable engines out there. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I know I'm trying to steer you towards the C5R heads <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" /> but, the LS6 heads will make for some nice power also. The LS6 headed big cube motors have put out over 500rwhp at rpms under 6500 where the C5R heads may put out 650+rwhp at 8000+rpm's.

Personally, I'd be happy and wouldn't worry about either setup. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

If you do the C5R heads I wonder if you could run a 20cc dished piston like ls1290 said and just clean the combustion chambers up a bit to get a reasonable compression ratio. I just don't understand how Katech can get a price of $12,000 dollars to setup and port these heads. That works out to be alot of money for port work because the parts don't come anywhere close to that number. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Maybe you should call ARE or MTI. Katech isn't the only place that has dealt with the C5R heads.

Good luck with whatever route you take. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

John

 

C5R heads + intake will be a lot more money, like maybe $10K more maybe even more than that.

Good luck either way. I like the sound of those inverted dome pistons!

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong> I like the sound of those inverted dome pistons!</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Definately go with the inverted dome pistons rather than dish ones. Inverted domes produce a more even and complete burn than dish pistons.

 

What is the diff between an inverted dome and a dished piston? They sound like the same thing.

 

The reason why the price is SO high is a combination of many things. The seats on them are ALREADY machined for a large dual spring for solid rollers. The valve train alone is 2800 from jesel. The titanium intake valves are around 140 apiece, where the exhaust valves are inconel and are consequently a little more. They most likely CNC the port, and then go and spend quite a bit of time touching them up. They would be a LOT more reliable then the LS6 heads. The CCs are very efficient, so 12.0:1 might not be so bad.

The one thing that this will require is a LOT of tuning time. Custom intake, MAF calibration, Injector sizing and tuning. If you want to keep the stock PCM, and tune that, The TB will be the next restriction.

This is surely a nice project, and I wish you well.

Louis

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by grb:
<strong>What is the diff between an inverted dome and a dished piston? They sound like the same thing.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">A dished piston refers to one that the entire head of the piston has a dish. Most inexpensive cast and forged pistons are made this way. An inverted dome refers to a piston that has a dish where a dome would normally be. This dish is made to complement the combustion chamber shape and design, just as the dome would be if it were a domed piston. The advantage of the inverted dome is that the piston retains the flat-top portion where the quench area is located. This design has a much better combustion effeciency than a piston with a dish on the entire head of the piston.

 

Louis - Thanks for the breakdown on some of the prices for parts. I guess I can start to see how the expenses add up. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

John

 

Is there a formula or whatever to compare the power output of maxed out LS6 heads vs. C5R heads at various RPMs all other things being equal?