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post #1 of (permalink) Old 04-19-2019, 07:30 PM Thread Starter
Rusty_S85
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Join Date: May 2010
Posts: 136
Engine vacuum estimates

Ive been doing a bunch of reading and I am just not sure so I wanted to post here to see what others think. I started thinking on this after a guy posted about a cam hes looking at and if it would make enough vacuum in his 351w. This how ever is about my 302 build I got most parts for but got a few pieces left mainly head and camshaft so I can still make changes.

Specs so far

306 cid
9.5:1 compression
165cc AFR Renegade 58cc heads 1.90"/1.60" valves
edelbrock performer dual plane intake
1" phenolic divided spacer
600cfm summit 4V carb vac secondary
Crane Truck Max Roller cam #449541. 216/224* @ 0.050", 0.520"/0.542" lift, 112* lsa, 107* centerline, 58* overlap
1.6:1 scorpion roller rockers

If more information is needed just ask, I think I listed all information that is important for vacuum but I might have forgot something.

Way I am thinking I figure I should be around 14 or 15 inches of vacuum which should be enough for power brakes. But I am now wondering because this cam is listed by crane as "Good low-end torque and HP. Good Idle. Daily driver with economy. Towing and Off-road performance. Compression 8.75 to 10.0." but the reading I have done indicates for a truck/towing cam duration should be around 195* - 198* duration and that my duration of 216/224 falls under Street/Strip application which counters the whole description from Crane.

I am probably over thinking this but at the same time I want to understand this and know what to expect so I can make changes if I decide to. So far this is the smallest 5.0 HO roller cam I found listed under the Truck Max label. I cant go smaller than this without going to the PowerMax series of roller cams and the smallest there is 208*/216* @ 0.050" and 112* lsa. To me this cam is not much smaller than the TruckMax and that PowerMax cam is listed as working on speed density with a Green Diamond meaning it is CARB Compliant where as the one I am looking at the only TruckMax cam listed really that is a Hyd roller for a 302 HO is an amber diamond which is offroad only. Enough to make someone like me drive myself mad trying to grasp this to avoid trial and error mistakes.

Any help would be appreciated. One thing is this truck will be driven daily, axle ratio will be changed as well as a wide ratio gear set for the C6 transmission. It looks like my move might be finally happening so majority of my driving will be highway driving at 65 - 75 mph with very limited city driving.
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