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Old 01-23-2009, 07:57 AM
donraye's Avatar
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Join Date: May 2008
Location: Waikoloa, HI
Cobra Make, Engine: Street Beast "Grabber Orange"/Silver stripe w/418W 520HP full roller, T5. and: Backdraft #814 RT3B "Black Label" "Magic Black"/Sterling Grey stripe, 408W, full roller, 475HP, T5
Posts: 165
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Default Another "Different Cam?" Question about my 418 build.

Well here's the short block I have now ended up with and is being assembled as I write this, so it can no longer be changed. But the CAM still could be if really need be.
I may have to change the cam as the valve intake and exhaust timing seems very odd to me but I'm an idiot about stroker cams and that's why I will probably have to call Comp Cams tomorrow and get them to give me some expert advice, unless I can get what I need here.
The JE 17cc dish pistons I bought will give me 10.125:1 with my 67cc (actual) heads and an .039 gasket. The quench height will be either the 039 used to figure that compression (or could also be .040-.045 depending on which gasket I end up choosing if there's a good reason to change)
Now: The Cam I already have:
The valve timing on this cam @ .050 is:
Intake: open: 14 BTDC close: 42 ABDC
Exhaust: open: 53 BBDC close: 9 ATDC
Gross lift .555 and .576
Advertised duration @ .060 tappet: 287 and 293
With cam installed at 104 intake centerline:
Duration @ .050: 236 and 242
Lobe seperation 108
Lift @ .050 .347 and .360

The BIG question is can I use the above cam with it's valve timing and the 10.125:1 static comprassion ratio the short block with my heads have?

When I try to use some of the calculators like the one at KB Pistons it tell me the dynamic compression will be a little above the 8.5:1(which is not a good thing for pump fuel I've heard?).
But I have also been told by several people that that calculator is all wet and they ended up with considerably lower real world dynamic compressions than that calculator told them they would have, So...
I know it is nat the best calculator because my builder has a much more sophistocated desktop dyno the he uses and it calculated the static compression to be different from the KB calculator and I know his is correct as it had a lot more info used to do the calculation and his agreed with my other machinist's calculations as well..
Does anyone out there FOR SURE know if the above (cam,static compression,(rod length,stroke,etc.) combination will be OK or not? I know it will be far from "ideal" to many of you who would like to see a much larger cam for more high end power, but this is a 100% street motor and I am just wanting this set-up to work with pump gas and make good (not maximum) power.
The cam was chosen by Keith Craft for me BUT, it was back when I was originally building a 408 (not the 418 it has now become).
It became a 418 because the 408 internal balance cranks were backordered and my short block builder HAD the 418 crank in stock so I had him switch to it rather than hold up the build for a couple of weeks or more.
Will this cam (above)work for me or should I order a new one to get it right?
Don
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