What's up guys new to this Fourm and to karting but not engines I'm a mechanic and work on engines on a daily basisso I'm familiar with the concept so trying to figure out where I need to go with my build I'm building a predator block the reason I'm using it because it has a stock bore of 2.75 using an arc billet stroker (.175) and rod wisco piston and a 320 cam plan on running an alky 28mm minkuni so I'm looking for a head what size valves do you guys recommend I'm looking to turn around 8500 rpm's any sujestions ?
Stroker build info needed!!!!
- Thread starter Danny
- Start date
youngengines
Member
It depends on what rpm drop it will have in the corners. I don't know what that carb flows, but I would do at least a 28.5 intake valve..and possibly a 32mm if the carb will flow enough.
Ok what rpm drop am I looking for? These parts I got from a guy who builds the same engine and dropped a valve in trying not to have that issue again he said he was turning in the 10s so I'm shire the carb was flowing pretty good to get that kind of rpms looking in to getting some titainium valves if possible or do you think it's over kill ? I will be running 55# springs with Rollers 1.1 ratio
alvin l nunley
Site Supporter
I've never understood this idea that a intake valve could be too big! Oh, if it got so big it was being shrouded by the head, maybe.
Ambient air pressure is pushing air into the engine, the bigger it is the more air can get pushed in. The exhaust is getting pushed out by the compression of the piston, bigger is not proportionately more advantageous.
Ambient air pressure is pushing air into the engine, the bigger it is the more air can get pushed in. The exhaust is getting pushed out by the compression of the piston, bigger is not proportionately more advantageous.
What size do you recommend? What's the strongest or better built head core to start with
alvin l nunley
Site Supporter
I'll leave that to the more experienced people in the sport.
Why are you using 55lb dual springs with a 320 lift cam? 32lb or 37lb single springs should be fine for that, you may or may not have to have the spring pockets cut for them. Stainless valves with good retainers and split locks will do the job and keep you from dropping a valve. As far as getting a head, Barry Young (youngengines) has been doing some of the best heads out there lately and can get you exactly what you need for your engine, id highly reccomend him. You can tell Barry the details of your engine, track size you plan to race on, and let him build the head and carb for you so you just bolt it on and go...he can put springs, valves and all in it for you so its ready to go
You want to choose a head that is going to flow what your carb is capable of flowing. I suggest sending your carb to Young so he can flow it and build you a head to match your carb perfectly. You could either send him a head you already have or have him choose one for you and build it from there, your choice
My opinion if you are wanting to do it yourself, get a head that has been ported and has a 28.5mm intake with 25mm exhaust valve, use stainless steel valves and good retainers/keepers, 37lb springs with the spring pockets cut and the .320 cam with your choice of rockers. A set of champion rockers would work nicely, in a predator RTC-8 or RTC-9 head
modifiedman
Member
Jmo but get your self a set of green strip dual springs and just use the outer spring they are 32lb will still have to cut pockets but thats more then enough for that cam.I run the 356 cam and only use the outer.