slow port velocity with a 237cc runner??
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Joined: Apr 2005
Posts: 309
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From: New Berlin Wi
slow port velocity with a 237cc runner?? I building a lq4 based motor for my daily driven 95 s10. the truck has a t56 and 373 gears. I plan on using a stock lq4 block/rotating assembly. with a custom cam, 1 3/4" lt headers and 3"duals with no cats. I want at least 10.0to1 compression. origionally I was going to use an l92 based head. after talking to my local machine shop I was told that milling the heads enough to get there I would limit my cam choices.
I picked up a nice set of cnc ported 243 heads they have 237cc runners
the flow numbers look great
intake numbers simular to l92s with much better exhaust flow.
I talked to Geoff at eps and he told me that the heads were too big for the small cammed daily driver I had planned.
My goals are around 450whp/400+rwtq with great driveability. with a cam small enough to get decent mileage when I'm not beating on it.
here is the head flow data
intake exhaust w/ pipe
.100 68.5 53.9
.200 147.4 102.9
.300 212.1 144.5
.400 271.6 184.2 195.5
.500 308.7 218.5 228.5
.550 320.6 227.1 236.6
.600 325.9 230.0 242.6
.650 332.8 231.8 247.8
.700 332.6 232.7 250.5
could a custom grind cam be ground that would allow me to reach my goals without beeing to soft on the bottm end and midrange?
Thanks for the info.
Kory
I picked up a nice set of cnc ported 243 heads they have 237cc runners
the flow numbers look great
intake numbers simular to l92s with much better exhaust flow.
I talked to Geoff at eps and he told me that the heads were too big for the small cammed daily driver I had planned.
My goals are around 450whp/400+rwtq with great driveability. with a cam small enough to get decent mileage when I'm not beating on it.
here is the head flow data
intake exhaust w/ pipe
.100 68.5 53.9
.200 147.4 102.9
.300 212.1 144.5
.400 271.6 184.2 195.5
.500 308.7 218.5 228.5
.550 320.6 227.1 236.6
.600 325.9 230.0 242.6
.650 332.8 231.8 247.8
.700 332.6 232.7 250.5
could a custom grind cam be ground that would allow me to reach my goals without beeing to soft on the bottm end and midrange?
Thanks for the info.
Kory
If you were to run a cam that didn't have a lot of overlap and wasn't huge on duration, and had high .650's lift you could keep the SCR up and keep your bottom end while taking advantage of the flow the heads offer. Only downside is it would take an extremely fast ramp rate to acheive that high lift and short duration that would make your combo work unless you used an extremely aggressive valvespring to control the violent ramp rate the lobe would have to see, which would wear out springs a lot faster than what you would probably want on a street motor.
If anyone feels this is misleading let me know, but I think it's about right.
If anyone feels this is misleading let me know, but I think it's about right.
That being said you can still make your goals I think by talking to the guys at Cammotion, Pat G, AES, Vengence, VA Speed or any of the sponsors to help you out. One person's opinion doesn't mean it will not make what you want, but it coming from who it came from it will take a little more effort in the cam timing and selection of supporting parts like headers, exhaust, intake etc.
Added: I said SCR earlier I meant DCR. If you go more conservative on the duration of the cam, and you are working with a larger chamber that is lowering your CR then you will retain some good bottom end. With that 10:1 CR you will have a margin that is smaller than the usual for over camming the motor. Now if you can live with a little less bottom and more midrange and top end then you can get around that too.
Last edited by Fbodyjunkie06; Jun 15, 2011 at 09:45 PM.
I would not be worried with those heads. Put in a cam with 220 duration and you will love it. Use good double springs so you can rev it. With your manual, 3.73 gears, and light wt vehicle you will be fine. I would make sure I port matched the intake to the heads. Pick up a used fast 90 or a new one will help also.
