Dyno 308 cam in Hemi Predator?

#1
Hi Everyone,

Got a little bit of an arms race going between my brothers and I in regards to our minibikes. I'm looking to add squeeze some more power out of my Hemi Predator (current set up listed below). Does anyone run a hemi predator with a Dyno 308 cam?

Mikuni 22mm carb (130 main, 125 pilot)
ARC billet rod +0.020
ARC billet fly wheel (6602-PH)
NR racing .252-611 cam
Stainless steel valves (stock sizes) + Aluminum Retainers
26lb valve springs
Chromoly push rods

I'm looking at

Dyno .308 cam
ARC - 6168 dual valve springs and retainers
Amateur porting (just clean it up a bit)

I'll have to enlarge the spring pocket diameter and possibly clearance the block or crank (which I don't mind doing), but I'm wondering how much lift I could get before coil bind? This combo would yield .320" valve lift I believe, and I've read that the hemi installed heights are shorter than the other clones.

I'd appreciate learning from some others experiences before making the investment, if possible.
 
#2
SI valves make longer valves for the hemi. you can run the single 37 lb springs if you enlarge spring pocket. Isky and nr sell the longer valves. Hemi installed heights are smaller but you should measure the retainer to spring pad height with a caliper to verify your current installed height. you may be able to use your current valves and 26 lb springs but you must check for coil bind and need at least .060 coil clearance. You should check for crank interference on the rod throw and will have to clearance block slightly. Just put the new cam in and turn it by hand and see where it hits then mark it and grind.
 
#3
Thanks! Looking that the longer valves, it looks like I'd need to do some valve seat work for the intake (I only saw a 28mm valve with the longer stem)?
 

BWL

Active Member
#6
I can't say one is better than the other. It just struck me that you already had a 252 that you'd stick with the one brand, but it doesn't matter really. I know for my application the 280 winch grind would be better, but I'm building marine outboard engines that need lots of torque on the low end..
 
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