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Old 12-22-2009, 05:18 AM
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Cam choice for 11:1 400sbc

Hi
Im trying to work out if i need to change the cam in a 400sbc as i think the Dynamic Compression will be to high
heres some info
4 bolt 400 sbc 30 thou over
speed pro hyper flat tops standard rods and crank
041 heads 1.94 1.5 valves ported flow around 194cfm
port matched victor jnr manifold 750dp
current cam isky z25 201025
adv dur 278
dur @50 240
480 lift
using 100 octain fuel
I found a comp calc at http://www.kb-silvolite.com/calc.php?action=comp

and worked out static at 10.8 and dynamic at 9.6
Do you think i can get away with the current cam or will i have problems???

Heres a dyno2000 file
http://www.4shared.com/file/178699146/d03837cd/400.html
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Old 12-22-2009, 05:43 AM
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With 100 octane fuel you will be fine, anything less than 96 octane will probably be a problem.

You didn't ask, but the 194 cfm head flow # is pretty poor if it was taken at 28 inches depression. If port work is decent it should make 230 cfm @ 28 in..
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Old 12-22-2009, 06:02 AM
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Yeah im not to sure on the flow as i tested them using my home made flow bench so it could be more.
The heads are the small valve version, they are pocket ported fairly well and a clean up of the runners, looks like the valve guids have been cut down a bit. Theres no work done in the chambers in regards to valve shrouding.
I can only compare them to a set of fully ported 186's and they flow about 10% more and alot more after 500 lift.
I dont think i can do much more to the 041's other than go up in valve size.
Added some pics, i could remove some from around the vavles but i dont think its worth the trouble.




Last edited by slr6000; 12-22-2009 at 06:55 AM.
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Old 12-22-2009, 09:41 AM
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The valves look to be sunken pretty good, this will account for some flow losses, especially low lift. You might consider going to 2.02" x 1.60" valves just to get them 'on top' of the chamber. You can use a head gasket to scribe a line that is safely inside the gasket's circumference to unshroud the valves a bit.

The port work is hard to make out- but doesn't really look too good, does it? You might want to spend some time just smoothing and blending what's been done, w/o actually changing the port shape any more than already done.
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Old 12-22-2009, 09:58 AM
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pics of some basic port smoothing with 80grit cartridge rolls. different heads, but you get the idea.
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