V6 piston choices?

[immortality]

Yeah, my old VN and missus VS were both run without cats fitted, legally too

[vlad01]

the gemini is a race car so it doesn't matter.

just comparing the camtech and crow. the small camtech one is smaller lift that the crow stage 1, also the crow has more duration on exhaust but less on the intake than camtech.

camtech states for the little one 1500-5300 range with good torque.


then the camtech next cam is fair bit for aggressive than crow's stage 2. camtech has more lift and duration, range 1800 to 5800.

the crow stage 2 is smaller and also has more LC so I gather the crow stage 2 would be pretty smooth and lower rpm range?

[immortality]

My understanding is that more exhaust duration or forward split tends to assist the engine hold on longer at high rpm but sacrifices low rpm torque which would suit a race engine.

You could also look at throwing on some higher ratio rockers. My old s1 VN definitely liked the 1.9 rockers from MACE. The old style rockers can't be good for a performance build.

[vlad01]

we had some mace ones from ecotec. they worked well for making bit more power but there dont appear to have any hardening after mace weld and modify them. The pushrods ate into the radius rather quick.

i'd stick to stock rockers for reliability. seen over 400k and like new can't be wrong. thats the pressed metal ones not the better ecotec ones.

not sure on the exhaust duration being more. the factory cams are like that and I dont seen extra torque at higher rpm.

quick google.

"You can also pick a cam based on airflow, but not on total flow numbers. Along with compression and operating range (engine speed at cruise, often dictated by gearing and tire diameter), the difference in airflow from intake to exhaust ports offers a guide for duration figures. For example, if your exhaust ports flow 60 percent of your intakes’ cfm figures (which is pretty restrictive), then use a lot more duration on the exhaust ports, regardless of lift. This applies to many street-driven cars and suggests choosing a split-duration cam, of which there are many to choose. Similarly, most dyno tests done both by manufacturers and sanctioned by magazines use dyno headers, which give much better exhaust flow than the corresponding car’s exhaust system. A dual-pattern cam with more exhaust than intake duration can make up for some of this backpressure."

so maybe for the shit factory cast headers they did this?

[immortality]

If you have access to some sort of dynosim type software it should give you a reasonable idea what different cams will do.

I think I might have found a copy I had of dynosim. It was running on an old PC that's fairly much dead but I think I've found an old back up that might still have a copy of the software. I wonder if it will run on win 7?

I've also found a copy of the Wade cams catalogue, the one with all there cam grinds.

[vlad01]

this is what im wanting to buy.

http://www.proracingsim.com/dynosimmainpage.htm

the newer versions like this are extremely accurate a lot of people have said having used it. the older versions like dynosim 2000 and such apparently dont have friction data to add to the simulation resulting in bit more power than real life.

[immortality]

Looks like it's going to take a fair bit of time to get this old back up restored

Might have a play tonight if I can get it working.

Does anybody have any head flow numbers for a standard 3800 V6 head? Will need it to get some accurate numbers in the sim software.

[vlad01]

here ya go.

http://forums.justcommodores.com.au/v6- ... tions.html

[immortality]

Champion

[vlad01]

I'd already been looking them up for this reason so I knew where they were.