What Head To Run

Bonanza Bryan

Bonanza Bryan

#1
#1
Building a predator 212 i have the non hemi style motor. Debating between a 18cc head that OldMiniBikes sells, a hemi head, or just run the stock non hemi head? Which should i choose?
 
ole4

ole4

#3
#3
Which head is on your motor some have 5mm stems others 5.5 also what size are your valves if they are 25mm ex and 27mm intake then you should keep the stock head and use the money to buy a flattop piston. What else are you doing to the motor?
 
OND

OND

#5
#5
Bryan if it was me I would go with the 18cc head from the OldMiniBikes it will give you more compression with out having to flat mill. Plus with that head you can run 18# or 26# springs and not worry about coil bind if you go with a bigger cam.
 
David wulf

David wulf

#7
#7
Which predator do you have , if you have the 69730 then you have one of the best head made . Look on your head and see if it's say RTC 6 or RTC 8 . If you have either then keep them have it milled and run it . The 18cc clone head is not all that , ports are not that great . If you have either head I listed then you have a big valve big port head and it's one of the best clone heads out there . Far better than the OldMiniBikes head .
I built a hemi predator and went out and bought a complete new 69730 just to get that head .
 
David wulf

David wulf

#9
#9
That's the head , with some porting and milling it will make big power . Keep it and run it .
If you don't use it I'll give you 20 dollars for it .
 
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DBMonster85

DBMonster85

New Member
#11
#11
Stock valves will work. That head uses the 5mm valve stems and the after market is 5.5 so you would have to ream them or get new ones. But port that head and mill it 60 thousands or so and it can make some good power. 26# springs.
 
OND

OND

#12
#12
I would go with the 18cc and run the 5.5mm stainless steel valves with bigger springs....sorry David but I like the 5.5mm valves theres alot more opitions for springs, retainers and keepers/locks.

^^^^ agreed 26# springs^^^^
 
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B

bdomit01

New Member
#13
#13
IMO stock valves with a black mamba cam will work fine. If you have ratio rockers and a bigger carb you'll be leaving power on the table with stock valves though.
 
B

bdomit01

New Member
#15
#15
If your putting in larger valves you will need to open up the seats. If you put a larger valve on the same size seat you will just end up hurting flow.
 
OND

OND

#18
#18
bdomit01 said:
If your putting in larger valves you will need to open up the seats. If you put a larger valve on the same size seat you will just end up hurting flow.
Click to expand...
^^^^ AGEED ^^^^
I know the hemi head is 27mm Int. and 25mm Ext. and the older heads had 25mm Int. and 24mm Exhaust.
 
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