Cam Theory ????
Cam Theory ???? OK the new heads went on and made a solid 19rwhp/19rwt over the old heads. Good right? Well at lockup with low rpm it feels like I lost some grunt.
you can definitely feel more up top though.
The cam is a 230/234 111+2 (10* overlap @ .050). I was talking to a buddy who builds motors at a local machine shop and he feels I am losing torque because the exhaust port is so efficient it is evacuating the intake charge before the combustion. The exhaust flows 87% of the intake so it is very efficient. He thinks that a single pattern cam with less overlap will get me more torque and perform better. What are you cam gurus thoughts on this. Any recomendations or thoughts are appreciated
Switched to 42# injectors too and it's using so much fuel if I didn't know better I would think my gas tank was leaking....
I am not on my computer so I can't post the flow sheet but here are the #'s
lift Intake Exhaust
100 73.3 60.6
200 138.0 128.6
300 217.1 193.0
400 272.9 245.6
500 306.4 270.2
550 315.5 277.5
600 322.9 282.7
you can definitely feel more up top though.
The cam is a 230/234 111+2 (10* overlap @ .050). I was talking to a buddy who builds motors at a local machine shop and he feels I am losing torque because the exhaust port is so efficient it is evacuating the intake charge before the combustion. The exhaust flows 87% of the intake so it is very efficient. He thinks that a single pattern cam with less overlap will get me more torque and perform better. What are you cam gurus thoughts on this. Any recomendations or thoughts are appreciated
Switched to 42# injectors too and it's using so much fuel if I didn't know better I would think my gas tank was leaking....
I am not on my computer so I can't post the flow sheet but here are the #'s
lift Intake Exhaust
100 73.3 60.6
200 138.0 128.6
300 217.1 193.0
400 272.9 245.6
500 306.4 270.2
550 315.5 277.5
600 322.9 282.7
Last edited by SOMbitch; Apr 8, 2010 at 03:37 PM.
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Sounds right, where in my case I need the split duration to makeup for my less efficient exhaust side on my ported/ milled 241s to get them to do what I need. You might also look at a tighter lsa like a 109 or even 108 on a 230/230 cam
Yeah my tuner would love me for that LOL......
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What lobes and lift on your current cam? At what RPM are you wanting more torque? Looking for higher peak numbers or more cruising torque? Compression ratio and intake manifold. Where does your current cam peak, and do you want a higher power band?
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Don't tell him....give him the valve events instead, and he'll never know the difference and just do the job instead of thinking about it.
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Wow those are some strong exhaust flow numbers even considering thats with a pipe.I'm no cam guru but with a E/I ratio like that I agree that you don't need more duration on the exhaust.I'l be interested to see what you do and the results.
How about a reverse split cam that might do it for you. Since you have such good flow numbers you don't have to worry so much about contamination and loss of power. The reverse split will ultimately give you what you are looking for on any LSA you choose.
Your exhaust to intake ratio is not as high as you think it is.
Where are the dyno graghs comparing old and new?
Assuming the same test facility and dyno that would be useful information.
Did you change anything else with the swap and did you keep the CR the same?
-Tony
Want more lowend 2.5k and under. XFI/X-ER .612/598. CR is 11.2 (heads 60.5cc). Unported 90/90. It carries right to my 6500 redline (stock 98 rodbolts). It won't let me post a dyno so I will try again later.
For now I agree with predator-z. Install the cam on a 107 ICL. If that doesn't help I can get you in touch with someone who can easily help you there. Its all a trade though is 10hp up top worth 10 ftlbs down low? How much tq @3000 rpm do you have now?
Last edited by Nitroused383; Apr 8, 2010 at 08:02 PM.
Good to know Tony. CR was bumped up about half a point to 11.2ish.
Base line dyno was done on the old heads and a couple days later the new head dyno. I will try to post the sheet tomorrow. The dyno shows a consitent 19/19 gain but the pulls started at 3.5k It is below there that I feel the lowend loss. Actually at 2500 it is like a power switch comes on and it picks up nicely but when the vertor is locked at highway speed limit speeds (1700-2200) it is not very responsive..But hell yeah it makes more eveywhere at WOT.. but that is not where I am 99% of the time...
Base line dyno was done on the old heads and a couple days later the new head dyno. I will try to post the sheet tomorrow. The dyno shows a consitent 19/19 gain but the pulls started at 3.5k It is below there that I feel the lowend loss. Actually at 2500 it is like a power switch comes on and it picks up nicely but when the vertor is locked at highway speed limit speeds (1700-2200) it is not very responsive..But hell yeah it makes more eveywhere at WOT.. but that is not where I am 99% of the time...
Last edited by SOMbitch; Apr 8, 2010 at 09:44 PM.
Good to know Tony. CR was bumped up about half a point to 11.2ish.
Base line dyno was done on the old heads and a couple days later the new head dyno. I will try to post the sheet tomorrow. The dyno shows a consitent 19/19 gain but the pulls started at 3.5k It is below there that I feel the lowend loss. Actually at 2500 it is like a power switch comes on and it picks up nicely but when the vertor is locked at highway speed limit speeds (1700-2200) it is not very responsive..But hell yeah it makes more eveywhere at WOT.. but that is not where I am 99% of the time...
Base line dyno was done on the old heads and a couple days later the new head dyno. I will try to post the sheet tomorrow. The dyno shows a consitent 19/19 gain but the pulls started at 3.5k It is below there that I feel the lowend loss. Actually at 2500 it is like a power switch comes on and it picks up nicely but when the vertor is locked at highway speed limit speeds (1700-2200) it is not very responsive..But hell yeah it makes more eveywhere at WOT.. but that is not where I am 99% of the time...
In a reasonably heavy street/strip car, the high flowing small port (high airspeed) design is ideal. Your simply getting a first hand experience and understanding of WHY. And the key is with the right small port head you can still make big power at WOT with a much more explosive curve everywhere but especially at low RPM part throttle.
This isn't a dig at your current head choice.....you would have experienced something similar with AFR 225 heads on a 346. Its just a bit large to work effectively at part throttle on that small a displacement engine....and as you witnessed....if your going racing and let the clutch out at 4500 RPM's its not a problem.
Combination is key....and big port heads and/or large duration cams always come with their fair share of compromises (unfortunately).
-Tony
